Endless Sphere

My pack of Samsung 30q doesn't sag near this bad, even when it's really cold. My 12s12p 30Q pack only sags about 5 volts when drawing 60ish amps after being stored in similar temperature conditions. The 30q is a more advanced cell than these old dinosaurs, cold affects them a bit but not near as bad...

After heating the batteries with a box and a hair dryer set on low until the internal 10k thermistor I put in the pack read a steady 29°c, I did another test of the battery's internal resistance. Hooking up a load (subwoofer) that drew 27 amps, I measured a whole-pack voltage drop of only 0.5 volts ...

Looks like these cells don't like the cold at all. After storage in the garage overnight (overnight low about -8°c), the pack measures an abysmal 193 milliohms, even worse than my old recycled 18650 battery pack. Hopefully the internal resistance is a lot lower at 30°c.

You'd get a more accurate graph if you charged/discharged at a lower rate and measured more often. In your first charging graph where the voltage goes up from 3 to 3.5 in 400mah and one measurement, the "line" between those data points appears more like an exponential curve. Your discharge graph loo...

The pack is almost completely built, all that's left is to add balance wires and shrink wrap (after a few tests on the bike). To join the cells, I used a torch and solder to tin each tab and join them together, and a pair of 14AWG solid copper wires (about 3/4" between each cell) to join the cells t...

Would you actually use a silicon controlled rectifier or are you just hypothesizing that it would maybe be a good idea? They are designed to switch AC, not DC. If you are using them to switch DC you'd need a super low resistance MOSFET to turn them off, defeating the point. You could just heatsink t...

They're decent mosfets. Is there a particular reason you stopped using this setup? When I made the board, I accidentally left a small air pocket where the control switches for the on/off circuit was. Water managed to seep in through the XT60 after about 6 months and shorted out the control transist...

Before I had XT90 Anti-spark connectors on my bike, I used 3 IRFB3077s in parallel to switch off current from the battery. The whole circuit was in an aluminum enclosure filled with silicone for waterproofing, similar to the Luna Cycle product. I was a bit wary of using XT90s at first, but now that ...

I don't have a CAv3, I have a homemade Teensy 3.6-based system that can measure volts and amps, calibrated against my multimeter. Once I have time (next week is Spring break), I'll write a program that sets the current to a low value (~10A) for 10 seconds, measures the voltage, sets the current to a...

SpinningMagnets, I was considering adding compression plates on both ends and after a bit of research it sounds like a good idea. I plan on using some 1/4" high density fibreboard and fiberglass-reinforced strapping tape to apply pressure to the cells. To evenly distribute pressure across the face o...

Those GreenTec auto cells look like a great deal. At only 5" by 7" (out of the pack) they are a bit chunky but they should fit in my center triangle. I've charged my cells at 10 amps continuous and could not feel them getting noticeably warmer than the ones sitting on the bench. I haven't done any t...

In terms of internal resistance, you're getting such a big number because you're not paralleling the cells in your calculation. Sure, if I made a 14s 1p pack from 14 random cells I'd probably get around 60-80 mΩ, but my pack is going to have 2 or sometimes even 3 cells per parallel group (for the we...

If you've cooked it that much, everything needs to be inspected. I'd start by taking the hub motor apart to see if there are any burnt windings. If there are, you need to get a new motor, preferably a more powerful one. If the windings aren't burnt count yourself lucky and replace the wires going to...

I've been pretty busy with college for the past couple days and have finally finished categorizing my battery pack. I will be using 32 cells to make a (mostly) 2S14P pack, with 3 cells on 4 of the parallel groups because they have weaker cells. According to my measurements and calculations, the fini...

My rear motor's peak power / torque is only limited by how much current I can send in. If I send more than about 45 battery amps during hard acceleration, the wires going from the controller to the rear motor get too hot to touch. The fact that I rewound my motors motor for higher KV is also contrib...

About a week ago, I stumbled upon a really amazing deal for the SPIM08HP lipo batteries a lot of high-power bike builders have been talking about for the past few years. The seller (batteryclearinghouse) was offering 32 cells for a bit over 75 dollars, and it was simply too good a deal to pass up. T...

As part of my new SPIM08HP battery build, I decided to capacity-map one of the cells to get better range estimates. I don't have a computerized battery analyzer or fancy charger, so I charged the battery at 8 amps in 1 AH intervals and measured the voltage with a volt meter. Here are my raw results:...

About three weeks ago, one of my e-bike's controllers wasn't working. It wouldn't even attempt to power the motor and appeared completely dead. Opening it up, it was soaked with water. After washing it down and drying it thoroughly, it powered the motor again, but there was a weird vibration when ac...

June 2019 Update The "Cycle Analyst" device is largely finished and I have uploaded the code to my Github repo at https://github.com/thorlancaster/electric-bike-controller . The documentation is not quite there yet, but all the code and a few sparse schematics are in the repository. The three contr...

I was expecting to finish the bike sooner, but with college and finals and whatnot, it got pushed to the back burner and I have just now finished it. The wiring clutter of last year's setup is long-gone, with only a serial cable and battery power running the length of the bike. I've also nearly doub...

That's quite the build!
Have you considered putting a chain guard over the mid-drive chainsaw mechanism?

It was definitely a good idea to put zeners on the power rails. During testing the regen brake, I was spinning the wheel with the pedals and heard a faint pop. It's likely that the few-volt spikes generated by regen, plus a nearly fully charged 12s battery, pushed the Chinesium LM2596hvs over the ed...

I've got a power zener across the output and a low-value low-watt resistor on the input, so if it fails it shouldn't take out more than the resistor and possibly the diodes. If that happens, I'll just buy a genuine one from Arrow or Mouser and replace the dud one. The one in my (currently front) con...

I had finally got it working. The motors were spinning up at the same time, the sensors were calibrated, the PID loops were tuned, and the regen brake was smooth and the FETs for the regen were barely getting warm. After making a few last-minute tweaks in the code, I spun the wheel to test the regen...

This thing is starting to look more and more like an electric car build. Definitely one of the most street-legal fast setups out there.
How many KWh of battery do you have for the main pack? With that vehicle, I'd personally go for at least 2 KWh of battery.