Battery cutoff settings

I have a 12s2p battery 6374 190kv motor focbox nano remote This is my first time setting up a vesc so bear with me, just wondering what my battery cutoff settings should be (start and end)?

Fully charged your batteries will be 4.2v per cell, so that’s your max voltage.

Fully discharged you shouldn’t let them go below 3.2, some would say 3.1 is ok but remember 3.7 is the nominal voltage.

So… 3.2v x however many cells you have is your absolute cut off voltage. Dependant on how much warning you want to have, raise that a fraction of a volt or two (per cell) for your cut off start.

I actually bought the diyelectricskateboard battery pack and I’m not sure how many cells there are?

You’ve already told us…

12s = 12 cells. ‘s’ = cells in series. ‘p’ = cells in parallel.

Also important is your Batt max setting because you have not much amp output from 12s2p. I just looked at their Homepage, no info which cells are used but the BMS is rated for 30A Continuous Amp Output and 80A Peak Amp Output. If the cells are 20A cont. you have 40A max from battery, but the cells will get hot when used at their limits. Would be good if they have used 25A or 30A cells, maybe someone knows. Batt regen would be about -8A, Motor regen (brake) should not be too far away from motor regen (maybe -30 to -40A).

3.2 V per cell is too low imho. You’ll feel that after 3.7V they start to get sluggish and sag a lot more. That’s because momentarily they’re reaching even lower voltages (when accelerating for example) - like 3.3 or 3.2V. When you stop and check the voltage they get back up in voltage. Running them too low often, they’ll degrade sooner.

Under 3.5V they are starting to loose charge, voltage drops abruptly. My opinion is that 3.6 V is absolute low if you want long term performance, reliability and safe operation. To reach 300-400 duty cycles, discharge them to 3.6V, rare to 3.5V.

My 8S setup gets me to over 12km when I discharge them to like 3.7V per cell. Which is more than enough.

I have an 8s pack too, I kind of agree with you, if you’re pulling they’ll drop significantly at anything around 3.6v, but if you wanted the most out of your pack and wasn’t too worried about pack longevity, you could go lower…

I have 10S zippy 8000mah which are rated 5C current charge. Does it mean I can have 40A batt regen? I’m currently on 25A or 30A.

Also - I think I should check if my Bestech BMS 10s 80A allows regen. I’ve heard it doesn’t but board breaks fine. If your bms doesn’t support regen I would only have motor min to play with ? That’s regen also … Or does bms just produce heat instead of feeding batteries with current?


So I have researched and there is no clear answer :wink: well as long as it works and breaks I’m happy :wink:

Exactly :wink:

Here is a clear answer for you:

I tested the Bestech HCX-D223V1 (Not Bypassed) braking continuously downhill while monitoring pack voltage. And I am pleased to inform you that this bms in this configuration does support regen charging. And not only that. I conducted the test with a full battery. My total pack voltage climbed to 42.8v but would not go any higher because the bms’s overcharge detection is set at 42.8 from the factory to allow some headroom while charging(they feel that this is a safe threshold so I went with it). So it stopped climbing at 42.8 and as soon as I stopped braking, the bms quickly trimmed the voltage back down to 42v while supposedly balancing the cells.

During this test I experienced NO issues with the Vesc shutting off or any brake failure.


@Namasaki That’s great news! Thanks ! If I was to put in batteries of 42.3V charged with seperate charger and connect them to bms would it immediately start trimming them down? How long did it take to trim them down from 42.8 to 42? Just out of curiosity.

Although overcharging less than 1v on the total pack voltage seems to be an acceptable amount, I would not recommend doing so intentionally. It would be nice if the Vesc allowed adjustment of the regen braking voltage.

Noted! How long was trimming of excess voltage?

It only took maybe 10 seconds.

Wow! That’s quick! I’m thinking of investing in bench power supply to get my balancing working, at the moment my charger shuts off at 42V ;( and I have to balance lipos individually with separate balance charger. Doesn’t take long but it’s a pain in the butt :wink:

Are you using a bms? The bms wil balance the cells but it will do so by trimming them down unlike a hobby charger which holds the full cells while bringing up the low cells. IMO, nothing charges better than a hobby charger.

Understand that under charging is said to increase battery life and this is why Bestech designed their bms to trim the cells down to a voltage under full charge when balancing.

So using a brick charger with a bms instead of a hobby charger or power supply could increase the life of your battery. So it’s up to the individual users idea of whats more important. Maximum battery life or Maximum power and range. There’s is always a trade off.

Let me clarify, charing to 41v instead of 42v is said to increase battery life substantially and honestly, the difference in range and power would be negligible.

Indeed I have bms 10s 80a. My brick charger ( 4 or 5A can’t remember) charges up to 42V and then noting happens, some cells are undercharged and some overcharged and total is 42V. After I reach this 42V nothing happens, I left it for 45 min and no difference to individual cell voltage. What I’m currently doing is charging with brick charger to 40.9 ( quick charge ) or so and then finishing and balancing with hobby charger separately each lipo. As you said I’m happy with 41V rather than 42V. Sometimes I would go to 41.5 on each cell.

I’m not over the moon with bms being set up for 42V balancing start. Shame this value wasn’t customisable.

Balancing 0.2 volt of each lipo with 2A hobby charger isint a pain, takes 10 minutes each or so, I just need to watch it so it doesn’t go over voltage I aim for.

Bit tedious but manageable. Also I balance only every second charge, can’t be bothered to do it every time. After non balanced charge I check each cell voltage. If they are more than 0.3 volt between highest and lowest I then balance manually with hobby charger to get it as close as I can.

I hope this makes sense, sorry for being so all over my post :wink: I’m on mobile and at work haha

Here is my current settings, see anything that needs addressed or corrected?.

Yeah, battery cut off ends I would put approx1-2v lower than the start. Otherwise you will damage cells with current settings.

Cut off start 35v Cut off end 34V

Or even better 36v and 35v for longevity of your batteries

Are you charging with the bms E-switch turned on? Are you leaving it on for 45min after charging?