Saturday, December 26, 2015

A post-summer review of my vent fans (Seattle Summer Slicers)

Back in May, I made my first post about a set of window fans I'd built to deal with the Seattle summer weather in a rental with no whole house fan or whole house AC - these gizmos.

The fans are some high quality (ball bearing) Delta 120mm computer fans, secured with automotive trim tape (quite sticky double sided foam tape) into a frame made of aluminum L angle.  Due to their rather high RPM, they've got fan guards on the front to keep fingers, papers, ferrets noses, and other things out of them.

For those unfamiliar with why I put together such a contraption: I live in the Seattle metro area.  Houses out here generally don't have whole house attic fans or whole house air conditioning.  Window units are common enough, but window units don't work well with side-opening windows (they slide sideways, instead of up).  In previous summers, the whole upstairs just got hot, stagnant, and very uncomfortable.  This summer looked like it was going to be a really hot one.  And it was.

It's now December.  I've run them all the way through our long, hot summer, in a house I've been in for nearly 4 years - so I'm quite familiar with how hot the house was previous years.

This summer was, by far, the hottest Seattle summer I've been through.  It was also, by far, the most comfortable in the house - entirely due to these fans.  And they're rental house friendly!

The fans ran perfectly.  I had literally zero issues with them.  After a month or so of playing around, I set them up with a lamp timer.  They turned on automatically around 3PM (that's about when the upstairs started getting warmer than outside), and turned off around 7AM.  In the afternoon, they were venting hot upstairs air, and at night, they sucked cold air through most of the house.  I could adjust airflow by which windows were open, but I also set up a default path that handled the common case (cooling down the whole house).

Read on if you're interested in how things ended up.

Sunday, December 6, 2015

Cobalt Requirements for a Global Electric Vehicle Fleet

It's commonly asserted by many people and a few companies that the future of transportation is electric cars.  One thing electric cars need a lot of is battery capacity - it's what makes them electric, and sufficient battery capacity is what makes them a genuine replacement for a car powered by an internal combustion engine.

One concern often raised about electric cars is regarding the materials needed for the battery.  Lithium is frequently mentioned, but it's not actually likely to be a significant problem.

Cobalt, on the other hand, is used in basically all of the high energy battery chemistries, and is a much more limiting element for widespread electric vehicle adoption.

If you're interested, join me in a bit of a dive through the numbers of cobalt, batteries, and just how much of the world's reserves we need for electric vehicles.  If you're just here for the ebike photos... you probably won't care too much for this post.

TL;DR: Current global reserves of cobalt are 7.2 million tons.  To replace the 1 billion vehicles on the planet with NCA based electric vehicles at 60kWh per car would take 6 million metric tons of cobalt.

Friday, November 20, 2015

My wattemeter arrived! It's crap! G.T.POWER RC 130A Watt Meter and Power Analyzer High Precision LCD 60V GT-Power

Based on a post over at, I ordered a shiny wattmeter/power monitor/etc gizmo for my bike.

It measures everything you might be interested in!  Instant amperage.  Instant voltage.  Instant power (watts).  Peak watts.  Minimum voltage.  Peak amps.  Total power consumed.  It's perfect!

**sigh** So the box says.  Of course, I bought one.  And built it up into a nice system to mount on my stem, running power up from my battery pack.

Excited, I wired this up with 10 gauge wire for minimum losses (Anderson PowerPoles at the end, nice crimp connectors at the wattmeter side), mounted it on my stem (above my blob of DC converter), verified it showed a sane voltage, and set off on a trip (to collect a baby toy)!

I took a 5.8 mile ride to collect some data.  And I got the following data:
1254 Watts Peak
32.50 Amps Peak
35.06 Volts Minimum
2.694 Amp-hours Used
35.2 Watt-Hours Used

Huh.  That's odd.  For people who don't have an EE background, I'd like you to focus on the Watt-Hours Used (35.2Wh), the Amp-Hours Used (2.694Ah), and the Volts Minimum (35.06v).

Watt-hours are easily calculated.  They're watts.  Over time.

Watts are volts * amps.

Watt-hours are volts * amp-hours.

My battery is around 42V fully charged, and on this trip, dropped as low as 35.06v (as measured at the end of a fairly long run of 10 gauge).

Based on the data, my watt-hours used should have been between ~113Wh (42v) and 94.5Wh (35v).

35.2Wh is right out.  That's not even close.  It's not remotely right.  It's impossible.

The display also isn't very easy to read in most conditions.  It's OK at night, but I could not find a good position for it with sunlight.

I took some other rides, and the watt-hours reading is consistently wrong.  I don't know what's wrong with it, but it's just flat out wrong.  Period.  It's flat out impossible, given the voltage and amp-hours measured by the unit, unless you redefine most of math.

I've found other reviews mentioning the same problem with some of these units, and people generally consider them to either be very nice, or somehow broken.  They're not particularly reliable, either.

So, if you want a wattmeter for your ebike, or for anything else, I wouldn't go with this one.  Spend a little bit more on something higher quality.

At least I was able to get my money back from the seller.

Saturday, November 14, 2015

My Daily Driver Bike One Year Review: Boring and Reliable

This is my commuter ebike.  I've had it for over a year now.

I've been riding it about 9-9.5 miles/day since I built it - pretty much every weekday, rain or shine.  This, plus weekend riding and store runs, works out to about 2500 miles.

In this year, I've replaced the following things:
- Chain (stretched beyond wear limits)
- Rear freewheel (torn up by the stretched chain, partly because I mostly use the small sprockets)
- Rear brake pads (worn, replaced with KoolStop Electric Bike Pads)
- Front brake pads (same as the rear)
- Rear tube (took a huge nail, but I was able to ride home due to the slime in the tube)
- Throttle lever (the thumb bit snapped off).

None of these left me stranded, and only the front brake pads required minor side-of-road tweaking (the pistons weren't retracting properly with the pads worn out and the brakes were dragging).

In terms of maintenance required for a daily driver, this has been insanely low.  I've spent around $100 on parts, total.  And about $7 on electricity to power me these 2500 miles.

The only major additions have been more light up front (powered by a DC-DC converter I built) and a set of bike balls.

At this point, I can confidently state that this bike is exceeding all my expectations!  It's somewhat overbuilt for my needs (which was half the point - pushing limits on a daily driver is a way to have an unreliable bike), but it chews up hills easily, is cruising well under rated power, runs cool, and generally is an incredibly boring ebike - which is exactly what I wanted.  It just works.

I've got a 15-20 mile range on my current battery pack (36v, 13.3AH LiFePO4), a top speed of around 23mph on flat pavement, and while I have to pedal some to get up hills, the motor covers the bulk of my power needs.

The fenders do a very good job of keeping the wet road grit off me, though I'll still take some splash on my shoes from the front wheel if there's standing water.  The rear fender works perfectly - my backpack has zero road grime on it.

The triple layer of armored tires, heavy duty thorn resistant tubes, and slime also works exactly as I'd hoped.  I've only had one tire problem in a year of commuting, and that was a rather large nail.  Even with that, I was able to make it home riding - I consider this a huge success of my tire system.

I'm incredibly happy with this build, and would absolutely encourage anyone considering a commuter to go for the "somewhat overbuilt" approach to reliability.

Saturday, November 7, 2015

My bike balls arrived!

And they are, indeed, as overconfident as advertised!

If you've got no idea what this is, you should take a look at the Kickstarter page for the Bike Balls Bicycle Light.

It's a flashing bike light.  In the form of a set of balls.  That bounce around as you ride.

They're surprisingly firm in the hand.  And quite bright!  I'm quite happy with the purchase.  More rear light is always good.

If you want more photos, read on!

Thursday, November 5, 2015

How far can you ride an electric bike on the power it takes to produce a Model S battery pack?

A truth of modern industrial society is that it takes energy to make things.

Sometimes, that energy is better spent doing things than making the thing to save energy or "be green."

Let's consider a Tesla Model S battery pack.  The shiny new one is 90kWh.

How much energy does it take to build a 90kWh pack? makes some claims about lithium battery embodied energy.  It claims:
According to the latest LCA's, aimed at electric vehicle storage, the making of a lithium-ion battery requires between 1.4 and 1.87 MJ/wh
How much is that?  1MJ = 0.278 kWh = 278WH.

I'll be nice and use the lower end for Tesla's batteries. 1WH of lithium battery takes ~390WH to produce.

A Model S 90kWh pack, therefore, takes ~35MWh to produce. also does some math on the Tesla packs.  Their number is 472WH per WH of battery.
Based on an embodied energy of 472 kWhe per kWh of battery capacity, the Tesla's 85 kWh battery pack will have 40,120 kWhe of total embodied energy.
Well, 40MWh is within a reasonable tolerance of my numbers, so I'm happy enough with my back of the envelope calculations.

How far can that 35MWh take an electric bike?

A throttle-based ebike will consume somewhere around 35Wh/mi.  So... a million miles. :/

What if we use a pedal assist bike at 15-20Wh/mi?  Near as makes no difference, two million miles.

A typical American car travels 12k miles/yr.  If you drive for 80 years, that's 960,000 miles.

So... for the energy involved in creating one Tesla Model S battery pack, you can ride an ebike for your whole life.


Wednesday, November 4, 2015

Building a DC-DC converter to run cheap lights from pack voltage

Winter is coming.  This means dark evening commutes, and a lot of biking in the rain.  And that, of course, means I built this!

What is it?  Two DC-DC converters, waterproofed with hot glue, to power my winter lights.  Interested?  Read on!

Thursday, October 22, 2015

TEC-02 Ver 3.0 Semiconductor Battery Tester

This is the first of my semiconductor based battery testers.  It's a TEC-02 Ver 3.0 unit.

I purchased mine on eBay as a 5V Lithium Li-ion LiFePO4 NIMH Battery Capacity Tester Voltage Detector Analyzer.  $11.58 shipped - not half bad for a semiconductor based unit!

As usual, I'm going to dive into translating the manual, then do some analysis on it.

Saturday, October 10, 2015

ZB2L3 v2.0 ZHIYU battery tester

I've got another battery tester to play with!  This tester is a ZB2L3 v2.0 by ZHIYU.  It's rated for a max of 15v, 3A, and 9999AH - so you can test your 12v lead acid batteries with it, if you care.

It looks something like this:

Mine came from eBay as a 1.5v~12v Battery Capacity Meter discharge Tester 18650 li-ion lithium lead-acid.  $7.98 shipped - not half bad!

Tuesday, September 29, 2015

Chinese BTY AA3000 NiMH batteries vs Energizer Recharge: A Review

In this photo, I have a Chinese BTY brand AA battery, AA3000 series.  It's rated at 3000mAh (according to the websites selling it - it doesn't actually list capacity anywhere on the cell), and costs about $0.50 retail.

In this photo, I have an Energizer Recharge rechargeable NiMh battery.  Same physical size (AA), rated at 2300mAh, and retails for around $1.50 or $2.

Shall we dare to compare?  I think we shall!  Read on for details of how crappy the Chinese batteries are...

Sunday, September 20, 2015

Digital Lithium Li-ion NIMH Battery Capacity Tester Voltage Detector Discharger v 1.1.SP 2013/4/1

Let's say you want to measure the capacity of some sort of battery.  You've found something that looks exactly like this on a website that sells things, and want to know if it's any good - and also wouldn't mind a manual written in something that faintly resembles readable English.

Excellent!  Hopefully I can be of some use.

This post is the first of what I intend to be a series of battery testing device testing.  I've got a bunch of these things showing up, and intend to review and test them, ideally finding the best cheap battery tester for my needs.

This particular tester is a somewhat sophisticated resistor-based battery measurement device.  It dumps the battery into a resistor, and measures the current.

Mine came from eBay, and was sold as a Battery Capacity Meter discharge Tester 18650 li-ion lithium +PC online function.  I paid $14.52 shipped for it.

The instructions on the website selling it (often eBay) are some quality Google Translate jibberish.  I'm going to attempt to translate the important parts, and then try to test it out and see how it works.

If you're interested, read on.  If not, feel free to skip the next post.  This is pretty esoteric.  However, I did have an excuse to drag out my old oscilloscope, so there's some great vintage oscilloscope photos in here, if you like such things.

Monday, September 14, 2015

Schwinn Tailwind Review (in 2015)

The Schwinn Tailwind.  The name sounds powerful, fast, and sleek!  It sounds like the type of thing Snoopy might fly into combat against the Red Baron.

It's not a half bad looking bike, either!  But... is it any good?

As you've probably guessed if you read this blog frequently, you'll have to read on to find out!

Sunday, September 6, 2015

Is the bike you're looking at a toy or a tool?

You're looking at a shiny new ebike on some indiekickbay website.  Is it any good?

Good question!  That depends on what you're about to do with it!  Play with it on the weekends in the summer, or ride it to work every single day, wear it out, repair it, and keep it rolling?

My bias here is clear: I commute on an electric bike, love them for that task, and want to see more commuter-ready electric bikes on the market.

There are an awful lot of electric bikes on the market today - they cover a huge amount of ground, from little 250W assist units to things like the Stealth Bomber and a lot of homebuilt ebikes that are full on electric motorcycles with pedals.  However, some of them are better suited to commuting, and some are better suited to being weekend toys.

This is a list of things to consider when looking at an ebike, and might help you decide if it's better suited to being a toy or a daily use tool.  I'm deliberately not listing brands or specific projects here, because I expect an endless stream of these things, and I don't want to be responsible for keeping up with them.  I'd rather be riding. :)

And, don't get me wrong - there's nothing wrong with a toy.  It's fun on the weekend, and you may very well be looking for something like this - but if you try to use it as a daily commuter, you might find yourself wanting a lot more.

Interested in things to consider?  Read on!

Thursday, August 20, 2015

I Am a Backsideist.

In the United States today, we've got two primary political parties: The Democrats, and the Republicans.  They fight like cats and dogs on TV, but deep below the surface, they've both got an awful lot in common, and act more like friends than enemies.

One of the biggest core assumptions they share is regarding growth.  They both agree that Sustained Growth is the desired state of the economy, and while they disagree on which particular levers to pull to make sure Growth Returns, and maybe some aspects of the fine detailing on the lever handles, they don't dare question the Almighty Sustained Growth core of their beliefs.

What if growth is over or nearly over?  Calling THEM dirty names only accomplishes so much (none of it useful).  It would be very useful to have a political party exploring the concept, and proposing solutions that, while perhaps not along the lines everyone would like to see, are much more useful and match what people are actually dealing with in their everyday lives.

I'm calling this political party the Backsideist Party.  Because, well, I get to name the things I come up with.

Why Backsideist?

Easy.  If I'm right, we're on the backside of the story arc of western industrial civilization.  We should do something productive about this instead of insisting at the top of our collective lungs that we're still up the upswing and prosperity will return to every household if we just {whatever your preferred political party thinks the way to stimulate growth is}.

The reality in America is that the lower class is toast, the middle class is getting gutted, actual unemployment (not the gamed numbers announced on the news occasionally to great fanfare) is quite unpleasantly high, the state of infrastructure is quite sad (when was the last bridge collapse?), and if you don't count financial games played on Wall Street, there's not a huge amount of good stuff happening with regards to the GDP.  The American Consumer is out of credit, and there's not a huge amount of actual physical wealth being produced in the country right now compared to the ongoing decay.

We may as well state the facts of our current reality out in the open and do something useful, instead of pretending it's not happening.

Interested?  Read on!  This is a high level glossing over the concepts I'd like to work with, and will absolutely be expanded in many future posts.

Wednesday, August 12, 2015

Nexus 5 Bad Battery Symptoms & Replacement

You've got a Nexus 5, and over the past few months, it's gotten... sort of "quick" - and not in the good UI responsiveness way, more in the "It's done running in under 6 hours" way.  It might not make it through the day.  It might randomly shut down.  It might be super fast to charge, but never have the battery life you remembered.

A particularly common problem is the phone shutting down while taking an HDR photo - it'll take the picture, then, boom, black screen.  If you're lucky, it will power back on, and if not, you might have to plug it into a charger to get it to function - but powering on, it'll have 35% battery left!

What's up with that?

Well, it's highly likely that you've got a bad battery!

Read on for more details.

Thursday, August 6, 2015

Rebuilding a BionX 36v 9.6AH Battery Pack - upgraded to 13.5AH

A month or so ago, I posted a teardown of a BionX 36v 9.6AH battery pack.  Some of you may have guessed that I was going to rebuilt it!  You were right!

If you're here because you have a BionX battery pack you want rebuilt, please go here for information on my pack rebuilds.

As you may recall, the core of the BionX 36v battery pack is a 5x12 grid of batteries glued together.  Freed from the power wires, it looks an awful lot like this:

I'm going to build one just like that - but better!

And you absolutely want to read on to see the photos of the rebuild...

Monday, July 27, 2015

First Gen Moto X (2013) screen replacement notes

Sorry, no photos.  If you're reading this, you're probably deep inside the phone already and wondering how the screen/frame assembly on one side gets moved to the screen you purchased on the other side.

The iFixit Repair Guide is excellent, but fails to discuss the nature of moving the frame over.  They also separate the frame from the screen without removing the pins - you can do this to get things apart, but they won't go back together like this.

There are 7 very small (0.5mm x 1.5mm, maybe) pins that hold the frame into the screen assembly.

They all need to come out.  You can push them out from the inside with a SIM tool or similar.  BE CAREFUL.  They will disappear if you let them wander - they're genuinely tiny!  I found that pushing them partway out and then using tweezers to grab them is the best way to remove them.  Put them in a bowl or something so you don't lose them.

When all 7 are removed, the frame will come free of the broken screen.

Push the frame into the new screen assembly, being careful to route the cables properly (the display connector goes inside the frame, not between the frame and the plastic).  The spaces for the frame are beveled, so you have to do this before you put the pins in.

Once the frame is in place, drive the pins back in from the outside.  Again, be careful or you'll lose them - they really bounce.  Tweezers work well, and you can finish driving them in with the flat part of a Torx driver or something.

Let me know if you find this useful!

Bypassing the Schwinn Tailwind Battery Management System

You might recall one of my previous posts about the Schwinn Tailwind battery pack.  In a nutshell, it's a 24v, 4AH pack built of Toshiba SCiB lithium titanate cells.  It's really a weird pack - but that's fine, because it's on a really weird bike.  I did some analysis of it, but wasn't willing to hack it up as it wasn't my pack.  So I fixed the glitch and bought the bike.  It turns out, ebikes with bad battery packs aren't worth particularly much.  I knew this, though.

Bad BMS - Bummer!

The problem with the pack I now own is a bad BMS (or a bricked BMS that won't allow anything to happen, because the batteries drained too far - same result).  The pack won't charge, and it won't discharge.  The BMS controls the normal charge and discharge ports with a set of power semiconductors of some form or another, and it's stubbornly refusing to run them.

Except... it does charge.  The standard charge port for home use (8A charger - 2C rate... *blinks*) doesn't work, but the bulk charger (40A... 10C charge rate!!!) does, and I can charge the pack through that with an external power supply.

An inspection of the BMS shows that if I were to add a few wires to jumper current around, I could get pack voltage to the output - and get the normal charger port to charge the pack as well.

So, of course, this being an absolutely terrible idea, I set out to do it.

Lithium Titanate Chemistry

The only reason I'm considering this otherwise mostly idiotic idea is because the cells are lithium titanate.  An extensive amount of research indicates that they're a very well behaved, safe chemistry that can actually be discharged fully without damage (unlike a lot of the other lithium chemistries).  They're a low energy density chemistry as well, and I'm not too concerned about running them in light duty without a proper BMS.  I wouldn't do this with other chemistries, though.  Consider this a special case for a particularly exotic pack.

Don't Do This.  Seriously, don't do this.  And if you do, I'm not responsible.

This is a terrible idea, bypassing a BMS like I'm about to.  You shouldn't do this.  You definitely shouldn't get creative with my steps and do it better than I did.  And if you do, I'm not responsible.

Seriously.  This is battery hacking at a level that simply doesn't need to be done.  Buy a 24v battery of some other type and hook it up instead.  Don't do this.

... so read on to find out how to do this.

Friday, July 3, 2015

Schwinn Tailwind Service Manuals

If you have a Schwinn Tailwind, you might be interested in the manuals for it.

The following links are for the assorted manuals associated with this bike.  Feel free to download them - Schwinn support will send you them if you ask.

Schwinn Electric Bicycles Manual Supplement

Schwinn Electric Controller Replacement Procedure

Schwinn Ebike Tech Supplement - Fuse Replacement

Schwinn Hybrid Pedal / Electric Bicycle Dealer Service Manual

Hopefully you find this useful!  If there are any other manuals you have, please comment and let me know where to find them!

Sunday, June 28, 2015

Electric Bikes for Commuting in the Greater Seattle Metro Area

Last updated 25 June 2015

This document is intended as a somewhat living document to describe why electric bikes are awesome for commuting in the Greater Seattle Metro Area, and why you should consider one!

Yes, it's long.  There's a lot to be aware of.

I’ve linked to vendors and products here, but please don’t take them as the only options.  They’re just things I’ve personally used (or friends of mine have used) and am familiar with.  There are many, many valid options!

Also, please note that most of my suggestions are geared towards a daily commuter.  I'm not interested in building 60mph weekend toys.  I'm interested in boring, reliable, "daily driver" grade bikes that can get people around legally with a minimum of maintenance and drama.  This guide also assumes you want to build your own, though at the end I touch on a number of prebuilt bikes and things to consider.  Many of the same considerations apply to building your own and evaluating a prebuilt electric bike, though!

My Seattle Eastside Daily Driver

What is an electric bike?

It’s very much like a bicycle, except it’s electric!  More specifically, it’s a bicycle (with working pedals) that includes an electric (very specifically electric) motor.  Anything with a gas motor does not count here, and is legally something different.

Why are they awesome?

The hills around here suck to climb (in the majority opinion - some people love them), and traffic sucks.  In warm weather, you typically end up hot and sweaty, requiring a shower at both ends of a commute.  In cold weather, after bundling up enough for the cold and rain, you end up hot and sweaty inside the layers, requiring a shower at both ends.  With an electric motor, you have a vehicle that ranges somewhere between providing a light assist up hills (often referred to as a “hilltopper” setup), and one that is capable of hauling you the entire commute distance on motor/battery power alone.  I prefer the second type.

In addition, you're allowed to use bicycle lanes and pedestrian overpasses, so you can bypass the stopped traffic that is a frequent feature of this area.

Want to know more?  Dive on in!

Saturday, June 27, 2015

Nexus 4 Faulty Battery Behavior

I have no idea if this will help anyone else or not, but:

If you're replacing the battery (or a bunch of stuff) in a Nexus 4, and the phone does the following:
- Refuses to charge from USB/won't bring up the "charging" screen when powered off and plugged in
- Won't power on normally, but if you hold the power button for 10 seconds or so, flashes the red notification LED once when you let go
- Powers on normally with the recovery mode power/volume down sequence

Try a different battery.  I found a bad battery in a new batch that behaves like this, and while I have no idea what's wrong, the phone was perfectly happy with a different battery (and had been happy on the previous battery).

It took me an hour or so before I tried a different battery, so hopefully this saves someone some time!

Thursday, June 25, 2015

BionX 36v 9.6AH pack teardown

What's in it?

This is the starting point.  This is a 36v, 9.6AH BionX battery pack.  It clearly has a battery in there somewhere - so, this being a dead pack (there's a running theme in packs I deal with here - which is, "I don't tear apart working packs"), it's time to dive in and see what's inside it!

Keep reading for the teardown!

Sunday, June 21, 2015

2011 iZip Ultra Review

2011 Currie iZip Ultra Review

This new-to-me bike came stone dead (as far as the "electric" part of it was concerned).  It now lives with a freshly rebuilt battery pack!  So, that raises the question: How is it to ride?

There were a few issues for early owners of these bikes - broken spokes in the rear were a common complaint.  However, this isn't a problem on mine, because the previous owner replaced all the rear spokes.  He also replaced the cables to deal with some snagging issues, and I don't think it has slime in the tubes right now (apparently it solidifies if the wheels don't move for long enough).

I've been using this for potting around locally since I finished rebuilding the pack (for those not familiar, I rebuilt the 10AH stock pack as a ~14AH pack), and I think I've got a slight feel for the character and nature of the bike now.

Which is: This is really a cruiser style bike with road tires that happens to love climbing hills.

For more information and many more photos, keep reading.

Friday, June 19, 2015

Tesla Model S P85D C rate calculations

I don't know why this keeps coming up, but it does.

The Tesla Model S 85kwh battery pack has a 74P96S battery pack configuration (sets of 74 18650 cells in parallel, then 96 of these sets in series).

Fully charged, the Model S pack is right around 400v.  At 4.2v/cell, this should be 403v, so I'm happy to call "fully charged" 4.2v.

Nominal voltage on the cells will be around 3.7v/cell, or 355v.

The cells are each ~3AH (3000mah).

At highway cruise speeds, a Model S manages roughly 300WH/mi at 70mph - or 21kW.  For a fully charged pack, this is 52A, and at nominal voltage, 59A.  This correspond to 0.7A or 0.8A per cell, for a C rate of ~0.25C.

Peak power consumption on the P85D is about 470kW.  This corresponds to full/nominal amperages of 1175A/1324A, for a per cell current of 15.8A/17.9A, for a C-rate of 5.25C/6C (briefly - the car will hit max speed in a hurry).

The normal P85 cannot sink so much power, so peak C-rates are lower.

Ludicrous mode seems to peak around 570kW (based on Wikipedia).  This requires the 90kwh pack (or roughly 3.2AH individual cells, assuming the same pack configuration).  This corresponds to full/nominal amperages of 1415A/1605A (though I understand it's limited to 1500A).

1500A out of the P90 pack works out to a per-cell current of 20.3A, for a C-rate (on the 3.2AH cells) of 6.35C - so slightly more than the existing pack, but not by much.

Talking to some Tesla owners, the cars only accelerate "at their best" when fully charged - so the amperage being limited and acceleration being slightly worse when drained sounds like that's actually how things work.  This being, of course, utterly opposite from an internal combustion vehicle, which will accelerate best with a nearly empty tank (less weight).

Still very, very impressive!

Thursday, June 18, 2015

An open letter to Toshiba and Schwinn regarding the Tailwind Electric Bicycle

To whom it may concern:

In 2008, Toshiba and Schwinn partnered together to create one of the first lithium powered electric bikes, the Schwinn Tailwind.  Right now, many of them are sitting, waiting to be scrapped, because of dead batteries.

An advanced, pedal assist electric bike with a very fast charging lithium battery was revolutionary at the time.  Toshiba used their new SCiB technology, and Schwinn, a long recognized name in bicycles, designed the bike.

Seven years later, in 2015, there are a large number of Tailwinds sitting in garages with dead batteries, and an advanced, undocumented battery management system that nobody will admit to knowing anything about.  I've personally received calls from many people who have dead packs, and know of many additional dead packs that could be revived with the right information.

Schwinn support won't help but suggests talking to the battery manufacturer, and Toshiba suggests calling Schwinn.  The corporate finger pointing doesn't help customers who own one of these bikes and would just like to use their electric bicycle again.

There are diagnostic ports on the battery management circuit board, but nobody knows anything about interfacing with them, despite Schwinn documentation talking about how this advance will make diagnosing bad batteries easy.

If you genuinely care about sustainability, the environment, and keeping bicycles and batteries from being scrapped long before they should be, please provide information about these battery packs so those who have the packs and bikes can keep them running and repair the batteries and bicycle.

I'm currently serving as a source of information for these batteries, so please contact me about how these bikes can be kept out of the scrap heap.

Chromebook Pixel LS vs Chromebook Pixel

I've had the original Chromebook Pixel for a while.  It's been my favorite little piece of hardware, for quite a few reasons:

The keyboard is excellent.  The trackpad is excellent.  The screen is excellent.  And the overall build quality is superb.

It did, however, have a few issues.  Mostly, only 4GB of RAM.  And the heat/battery life from a somewhat older processor than it probably should have used.  That didn't stop me from carting it all over, using crouton, developing on it, and generally enjoying it immensely.

As all 15 people who use Pixels now know, Google released a new version!  And the high end version (the Pixel LS, for Ludicrous Speed) is very nice indeed.  It's fitted with a Broadwell i7 2.4ghz processor, 16GB (!!!) of RAM, and is otherwise almost identical to the first generation.

The keyboard is also different.  It's slightly softer and less crisp, but is in no way more difficult to type on.  And there are separators between the "F-key" row at the top instead of one long row.  Those are noticeably quieter and less "clicky."

The speakers, though. :/  Ouch.  What a downgrade.  They're muted and muffled.

But for a Linux development laptop (using Crouton)?  There's nothing else like it.  It's worth every penny.

Sunday, June 7, 2015

Schwinn Tailwind Battery Pack Teardown and Analysis

Schwinn Tailwind.  The name rolls off the tongue.  The bike... well, we'll get there.  But in 2015, it probably doesn't roll at all, because it probably has a dead battery pack.  An incredibly built, radically over-engineered, insanely beautiful battery pack.

It's one of the earliest lithium powered electric bikes out there, and it was reasonably expensive - $3200, in early 2009!  It was also one of the earliest uses of the Toshiba SCiB (Super Charge ion Battery) technology - a very fancy Lithium Titanate battery, capable of some truly impressive recharge rates - 6C charge rates were well within it's capability (a 10 minute recharge time)!

The battery pack is removable, and slips easily into the back of the bike.  That's what I'm tearing apart today.

Keep going if you want to see inside.  After the teardown, there's more information, including some attempts to revive it.  And some complaints about Schwinn & Toshiba.

Sunday, May 31, 2015

Koolstop Electric Bike Brake Pads: Are they any good?

Koolstop makes brake pads specifically for electric bikes.

According to
Our E-Bike disc pads are produced with a ceramic barrier between the organic friction material and the steel backing plate to reduce heat transfer into the brake caliper causing brake fade. With the heavier design and quick speeds of Electric bikes, they require a compound that will hold up and provide consistent braking power.
Are they any good?  I couldn't find any reviews, so of course, I bought a set for my disc brakes (specifically, Kool Stop Deore M525 Disc Brake Pads for Electric Bikes).

Yes, they are very good.

I was making one of my normal "Lots of downhill" runs (to get beer, of course!), and decided that, with the ebike compound in the rear, I'd skip the use of the front brake until I faded the rear.  Normally, I fade the rear if I'm using it alone by the bottom of the first hill.  These kept going solid, and held my speed nicely down several more steep hills (about 300' of descent combined, all fairly steep).

My rear rotor is shades of blue and yellow from heat.  I didn't know bike rotors could turn those colors.

I'm genuinely impressed by them.  My caliper remained cool, my brake force remained reasonable, and they gripped nicely, even as the rotor got hot enough to turn colors.

I wholeheartedly suggest them if you're rocking an ebike in hilly terrain!

Monday, May 25, 2015

Notes on the Sunkko 788+ Battery Spot Welder from China

Sunkko 788+ Battery Spot Welder

So you've got one of these, and know very little about it.  That's great!  None of us who speak English know very much about them, except perhaps the manufacturer, and they're not talking much about it.  The manual is an utter joke (if anyone will even send it to you). contains a slight overview of the welder, and some pictures.

It's a microcontroller-based, transformer-powered welder, and it's cheap.  Very, very cheap for a spot welder.

If you have any way to power the 220v version of it, go with that version.  The 110v version is unreliable and is likely to blow triacs.

Here are some of my notes from welding up a pack or two with it.

The electrode pressure, as shipped, seems to be a bit low.  The knob on top adjusts this.  Increase it if you're getting arcing.  I think I have another 5-6 turns on it from stock.

Clean the electrodes.  If they're sticking to your work or arcing, clean them.  If it's been a little while since you cleaned them, clean them.  They seem to benefit from being cleaned regularly.

Start low with the current, and ramp it up until the welds are good.  Too much current will burn welds and increase the risk of frying the welder.  A scrap battery or two here is useful.

The right-most digit selects the number of pulses - 1 or 2.  You want to be double pulse welding.

I have no idea what the "current set" knob does yet, but it seems to increase the weld power or duration.  If you have the 110v version, I'd suggest leaving it at 0, and using the digital display to up the power for now.

The inrush current (especially on the 220v version) is brutal, and it has a tendency of popping breakers when turned on.  If this is the case and you can swap breakers around, consider putting in a Type C circuit breaker instead of a Type B - they are designed for higher momentary peak (inrush) currents.

Once I finish my analysis of this thing, I'll have more information...

Saturday, May 23, 2015

"Cree 2000 Lumen Bike Light" Disassembly and Testing

If you've gone shopping for bike lights, you've probably run into the Cree 2000 Lumen Bike Light.

They look like this, more or less:

They cost about $20 with a battery (quad 18650s in 2S2P, usually), you can get them from an endless supply of vendors (eBay, Amazon, and plenty of others), and they have a surprisingly tight beam.

But what if you want to run them on ebike pack voltage?

I couldn't get anyone to give me an answer, so I set out to find out.

Click through to see what I found!  And, if you just care about the answer, it's "No."  They're 8v lights, and by 12-14v, components on the board are smoking.

Thursday, May 21, 2015

iZip Ultra Pack Rebuild 3/3

Rebuilding the Pack for the iZip Ultra

The actual pack rebuild process went smoothly at first, then took forever while I repaired the welder, then smoothly again after I got the welder repaired.

I started with 50 Samsung ICR18650-32A batteries and a lot of parts, and ended up with a new battery pack!

Continue for an awful lot of photos of rebuilding a battery pack.

If you're here because you have an iZip battery pack you want rebuilt, please go here for information on my pack rebuilds.

Tuesday, May 19, 2015

iZip Ultra 2011 Battery Pack Rebuild 2/3 - The Parts

After deciding to rebuild the battery pack for the 2011 iZip Ultra, I got the pack torn apart.  After I knew what was in it (50 Samsung 18650s), I had to figure out what I needed to rebuild it.  I'm starting from ground zero here - I've never rebuilt a battery pack before.  Usefully for you, I had to do all the research myself to figure it out, so I can share some of that to help people who may find themselves in the same position.

If you find yourself interested, read on!

Friday, May 15, 2015

Sunkko 788+ Welder failure and repair

I have a Sunkko 788+ Spot Welder.  It failed on me rather quickly, either from a faulty triac, or from overheating the triac due to an aggressive duty cycle (I'd say I exceeded the rated duty cycle, but that would imply there was enough documentation to determine this, which... not so much).

The quality customer support on eBay was at least nice enough to suggest I replace the triac.  They did imply that this was about the only support I was going to get, so... well, in I go.

This might be part of the problem...

Failure Behavior

I was welding away at a battery pack, happily popping nickel strip onto batteries.  I stepped away for a bit to get the next part of the pack assembled, and when I came back, the unit wouldn't power on.  Well, I'm smart enough to know that if a unit comes with spare fuses in the box, blowing a fuse is somewhat common.  Annoying, but common enough.  I removed the fuse holder, dumped out the shattered remains of a fuse (it apparently crumbled when the holder was turned), and replaced the fuse.  Excellent.

I plug it back in, hit the power switch, and... BANG.  Something inside the unit fails, hard.

The unit still powers on, but it won't weld anymore. shows it's behavior after the failure, if anyone is curious.

Well.  Time to dig in. Read on for the photos.

Overview of a Sunkko 788+ Welder

Power 788+ Battery Spot Welder

So, you find yourself needing to spot weld a battery pack (or something else) together.  And, spot welders are expensive, and most people end up building DIY devices, but there's this little gizmo (and it's siblings) all over the internet.  Alibaba, eBay, Amazon... it's a common item that claims to be a decent spot welder. It runs about $200 shipped to the US.  Be sure you get the 110v one - most of them run on 220v (unless you have 220v power, of course).

But what is it?  What makes it tick?  Why is it so much cheaper than every other spot welder out there except ones that are very obviously related to it?

Well, as it so happens, I've gotten very friendly with one (details in a separate post), and will happily share some of my insights with you.

Let's dive in.

Thursday, May 14, 2015

iZip Ultra 2011 Battery Pack Teardown 1/3

2011 iZip Ultra Battery Pack Rebuild

Someone at work was getting rid of an ebike they were sick of.  It didn't work.  One of my flaws is that I'm a sucker for free stuff I'm interested in, especially if it originally sold for a lot of money.  Please ignore the stack of phones and tablets on my desk that I need to fix or strip for parts...

A quick trip to pick it up, and I had the following sitting in my garage:

It's a 2011 Currie iZip Ultra.  This is a 500W geared rear hub motor, pedal assist ebike, with a 36v, 10AH pack.  Of note are the very small, high pressure tires - it's supposedly quite efficient as far as power use goes, even on a higher assist setting.

Unfortunately, this one wasn't going to do any assisting at all.  The battery pack was stone dead.  I got a back story involving the charger, a power outage, and the pack dying, so perhaps the charger drained it after the power outage, but whatever the case, it was dead.  Really, really dead.

The bike uses lithium cells - ICR (LiCoO2) cells to be specific.  Lithium cells are great in terms of power density and energy density, but they require some specialized care and feeding.  They must exist in a voltage range between about 2.7 and 4.3 volts per cell (and spend most of their life in the upper 3v region).

Discharging a lithium cell below 2.7 volts tends to do physical damage to the cell if it's left there (and, really, you shouldn't ever have them below 3v/cell for any length of time).  Skipping to the punch line, this is a 10S pack.  That means the pack should live between 30v and 43v.  Maybe down to 27v, briefly.

10 volts for the whole pack is right out.  That's "bad."  That voltage, combined with the time sitting, means the pack is physically damaged, recharging the batteries is not a good idea, and even if it will take a charge, it's very likely significantly short on capacity.  Individual cells were between about 0.6v and 1.2v.  Neither is 2.7v or greater...

A replacement OEM pack is $600.  A bit of research indicates that I can do a lot better.  So, of course, I tried to.

Continue for lots of interesting teardown pictures...

Tuesday, May 12, 2015

My Second Ebike: A properly good build!

After spending a year commuting on my first ebike, it finally failed on me - I overheated the motor too many times, and it quit for good.  There was a lot of other stuff starting to go wrong as well, and I'd learned a lot more about what I wanted and what worked, so I built myself a new one in October 2014!

This bike is built with everything I've learned from my previous ebike, and is built as a robust, rugged commuter designed for my 10 mile daily round trip commute.  I'm not a fan of fixing my daily driver, so it's built with this in mind.  As may be obvious from the pictures, I'm not a huge fan of washing it, either.

It's built on a used 2007 Specialized Hardrock frame with 26" wheels, uses my existing battery pack, is driven by an HPC Thunderbolt motor/controller combination, and is built to be rock solid reliable.  So far, so good!

Features I wanted when building this bike:
  • More power.  The 600-700W output of my previous build just wasn't enough for the hills I deal with and my desired level of "e-motorcycle" behavior.
  • Disc brakes.  The rim brakes on the previous build were better at grinding the wheels into dust than stopping the bike, especially when wet.  Paired with Seattle traffic, this was quite terrifying on multiple occasions.
  • Better fenders.  The mountain bike style fenders didn't keep me dry in the rain.

The frame and basic donor bike were purchased on Craigslist.  However, I'm not sure that purchasing a donor bike was the right option for this build.  I ended up replacing most of the hardware that came with it to get it to where I wanted it, and I'm thinking it might have been slightly cheaper to go with a frame-up build.

Read on for more details...

Saturday, May 9, 2015

My first ebike: Lessons Learned

Sometime around November 2013, I became tired of biking to work and being sweaty at both ends of the trip.  I'd been motorcycling, but traffic was terrible and getting worse - my record of "45 minutes to get 5 miles home" was not something I cared to continue with.

I've known about electric bikes for a while, but never knew anyone with one.  I knew of the BionX kit, but didn't want to spend the money on that for something I had no idea if I'd like (and it requires a bit of work on an existing bicycle, which I wasn't sure I wanted to do).

So, where does one go for something along these lines but Craigslist?  A few listings later, I'd found a $400 ebike that ran, test rode it briefly, and brought it home.

It looked something like this (though this is a slightly later version of it - note the adequate size wiring).

It was some year of MGX D50i, it had a 24v Heinzmann geared motor (brushed) in the rear wheel, a Chinese 36v brushed motor controller, and 3 12v/8AH lead acid batteries for 36v of overvolted fury.  A thumb throttle provided power on demand.

I had an ebike!  *whirrrr*

Wednesday, May 6, 2015

House fan for vertical windows: DIY Version with 120mm fans!

I had a problem.  I solved a problem.  In extreme overkill form, as is right and proper.

The problem was that my office ran too hot in the summer.  It's on the southwest corner of the house, and has both a good southern exposure and a good western exposure.  Also, it's on the second floor.  And, finally, the house is poorly insulated.

Prevailing winds get me a bit of ventilation, but the direction of the wind will force the hot air from the office into the rest of the upstairs, and generally make the rest of the upstairs hot and miserable to be in.  This is not a good solution.

The last few summers, this led to the office being more or less uninhabitable in the afternoons.  Several times a year, I have to shut down computers because they've tripped thermal alarm setpoints and are beeping loudly about the heat.  I've lived with this, but this year, the ferrets are in the office, and they don't deal with high heat.  So, I set about finding a new solution.

The solution was to find a way to exhaust hot air from the office, against the prevailing winds (yes, I know, this is terrible, but... it was either that or move the office, so, I'm just fighting nature).

So I fought nature.  And, so far, am winning.