I frequently charge 12S LiFePO4 to 42V because I have a bazillion 42V chargers everywhere. That’s the same per cell voltage as charging a 24S LiFePO4 to 84V.
The problem is, I do make sure that they get the full 43.8V charge at least sometimes to keep the pack balanced. You’d need to do the same unless you could find a BMS that balances at 3.5V or use a smart BMS.
The other thing, is that if you have board lighting, even if it’s just like a watt, a 24S LiFePO4 pack is going to fall from full charge (87.6V) to under 84V in probably 20 seconds per Ah (for my board) or so, just idling the ESC and running the lights, and the moment you touch the throttle it’s going to fall below 84V instantly.
The LiFePO4 discharge curve is super steep on the top end.
Personally I like the properties of the LiFePO4 chemistry. Higher durability, larger operating temp range, and a flat discharge curve once it gets down to about 3.2V per cell.
Yep the elimination of premature voltage sag for a balancing vehicle seems ideal even over immensely decreased range, at least for testing and not a final product.
and @b264 partially charging 24S lifepo4 would be sweet with some kind of alarm to make sure the battery is within safe limits before the motor turns on.
But yeah I owe the community a decent manual and stuff. Such things are under way. I also have ideas for other useful documentation to help cover the gaps in not only my own products but the VESC project in general.
Also, just got the controllers. Dem heat sinks aren’t fucking around. They have some heft to them. Looking forward to going 35mph on my kids razor mx500 .
Yeah having a lot of thermal mass goes a long way. And you can bolt that block down onto whatever else in your rig. Ideally a plate or part of the chassis that’s exposed to air.
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