12S6P 30Q pack, braking is set to -24 per vesc for -48 total (double fast charge rate). My METR logs show I’ve never braked harder than - 20A.
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This 12s9p pack is made of HG6s when they were super cheap at $2 a cell. The price was the biggest factor for me really. It’s a 20650 cell though and everyone is on to 21700s now.
Has been performing very well for me (as expected)
Battery work done by @BenjaminF
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Thanks.
I agree, no immediate destruction of the pack. But very high charge rates can plate out lithium and accelerate aging of the pack compared to staying near the fast charge rating. But going in the other direction, as you note, is potentially even worse.
For me personally, high braking current isn’t a big concern as long I am not launched off the board. It has been very interesting seeing what the community thinks about this! Thank you for contributing to the thread.
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I go with 2 times the total maximum fast charge rating. It is enough to make me feel safe if i need to stop fast, let’s say from 35mph i can keep up with the car in front of me braking, but if the same thing happened downhill i would suddenly have trouble.
That is on 12s4p vtc6. On the upcoming same config p42a pack i think i will eliminate any issue.
Sucks for the guys with 2P or less packs…
Video for the sake of an example. Ground is compressed sand
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Can handle a lot. We pulled the VTC6 far far beyond any safe limits for extended periods of time.
Since braking reduces speed and reduced speed reduces the amp flow towards the battery, there is no issue with 4P packs from such good cells.
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So -60A on 40T’s at 3p should be good?
Can confirm that vtc6, even though is theoretically head to head with 30q cells, is a lot cooler in most circumstances.
30q in 3p would get hot charging at 4A
Vtc6 in 4p is lukewarm charging at 8A
Heat while discharging is also nonexistent at 16A/cell. Solid performers!
The VTC 6 is really a good cell.
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That’s probably because of the low traction…
Yes exactly that it’s the limiting factor by a large margin
Not the motor-
Not the battery regen
Iv never been able to matin max duty cycle with max motor - as it will never have the traction to do that as @trampa said
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Does the incoming current to batteries while braking at these levels fucks up the batteries so eventually fucks up their ability to fully charge ? I’m have also a pack that won’t charge past 93-94% ?
Yes, cells lose their capacity over time, resulting in them only being able to charge to lets say 4.13V
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lol thread title is like asking who has the best traction and strongest ankles.
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What @Bavioze said. Just chemistry getting older. Like a phone or anything else with a li ion cell. More cycles, more wear. But happy with the performance still. Great little milk runner board. Gives me about 15k of range on a full charge.
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Agreed.
It’s really just a question to help with my pack design. Being an esk8 noob means I would go airborne at braking levels far below what you guys can handle.
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Ramp up/down times greatly help you handle both sudden and harder than usual braking. They also help smooth out signal cutouts at speed
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How does that work? Charger stays on forever?
Or you see the “aging sag” after you take it off the charger and let it settle for a while?
I had cell damage (result of water) one one of my p groups. It was like 1.2 volts?
I forced it back up with a “dumb” charger, but it would not go past 3.8 V, even after 1h (yes i had it in a safe space dw) and it did not even get hot or anything. After this they lost charge completely to 1 volts again so i disassembled the pack.
So i think ur right, they sag down again. This is (i think) what causes cell drift aswell right?
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Hmm… i had some new 30q cells in a 12s3p that would drop to ~49.5v in minutes off the charger, even fully balanced, all fancy. Now 12s4p vtc6 is rock solid at 50.4~.5v and they have taken more than 2000km abuse.
I think your cells were just done for, nothing to do with aging. They may need very slow charging to nominal, like, days of it, and even with that a lot won’t recover and the rest will be severely behind
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no i know, my cells were ded, but its the same behavior i meant yours have, Just a different cause (my cells had 500 km probably?), and thats why i feel the 30q is kinda a frail cell. My friends his pack has 200 km and they already show that they only charge till 41,8V, but that can also be the bms?
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