Ecky considering another Insight

[Ecky]

I took a chance on some $12usd shipped AliExpress 20Ah cylindrical cells, and assembled a pack out of them. So far, they appear to exceed their rated specifications.

[Ecky]

Chevy Aveo rear springs fit the Insight front struts, and up the spring rate around 40% (?). The car feels a lot better - it's adequately sprung now.

I also took the time to do a measuring tape alignment while I was at it. Front toe is now within 0.2 degrees (1mm) of neutral.

[Ecky]

Belly pan assembled. Needed to bend the exhaust hangars and pull the exhaust up a bit closer to the body.

[Ecky]

I've been prepping to install the Fit lithium packs in my car, but came across something else - someone selling a Plug-in Prius battery pack for $160 US. The battery is 13 years old and has seen around 75,000 city miles. I decided to give it a chance.

Specs:
Working voltage range 3.0-4.15v
56 cells in series
21.5Ah per cell
0.73kg (1.6lbs) per cell
5c continuous discharge (110 amps)
10c pulse discharge (220 amps for 10 seconds)
7c pulse charge (150 amps for 10 seconds)

Based on this, the pack will support 2.5x the electrical needs of a stock Insight IMA system. The Fit cells would have as well.

The complete pack weighs 80kg or 180lbs. This suggests the cells make up only half the weight of the pack. I expect I'll reconfigure it to 48 cells, which will result in 35kg of cells (77lbs), and I'll remove what I deem unnecessary to make it a bit lighter and more compact. For comparison, the stock Insight battery pack weighs 33kg or 73lbs. You could probably run over this pack with a truck and it wouldn't dent it. Typical Toyota over-engineering.

Pack loaded into the car.




Disassembled for easier removal.






Each module weighs 12.95kg, suggesting the cells make up 80% of the weight of the assembled modules. There is stuff I can pull off these to make them lighter. It'll end up a touch heavier than the original NiMH pack.




The Fit lithium batteries for comparison:




Very promising! My bench power supply measured 20.4Ah into the pack, from 3.0v to 4.2v, suggesting 96% of the original capacity is still available.

[Piotrsko]

Unfortunately AFAIK the only way to gauge actual capacity of lithium is to cycle them a dozen times to specific voltages/currents/ tempratures and average those results and that will only get you close. Hopefully your electronics are better than Harbor freight

[Ecky]

Originally Posted by Piotrsko

Unfortunately AFAIK the only way to gauge actual capacity of lithium is to cycle them a dozen times to specific voltages/currents/ tempratures and average those results and that will only get you close. Hopefully your electronics are better than Harbor freight

I have everything needed. The batteries are being cycled as I type this. I have an Android tablet connected to a UniT meter measuring volts and amps, while it's connected to a constant current discharger. I'll plot the discharge curve as I'll need that for programming the BMS.

[Ecky]

20.41Ah in, 20.41Ah out. Looks like a good cutoff voltage is 3.5v per cell. I appreciate that these cells have most of their capacity at high voltage. The Fit cells were pretty linear down to 2.7v, whereas these are basically empty below 3.5v. The Insight's IMA logic is based (mostly) on watts, so this will keep currents down.