How many battery amps do I really need?

Im planning on an 18s6p pack with p42a cells, and that gets me a lot more discharge amps than i think i would ever need. At 18s on gear drives what is the max current that a dual motor setup would likely draw on normal roads, with some hills? Ideally i would like to use a larger capacity cell with lower amps but i dont want to damage my cells with too high of a current draw.

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That very much depends on your weight and riding style. If you’re not super heavy and you will just cruise casually without crazy acceleration, at 18S you’ll be under 30A most of the time. If you went with Samsung 50E instead, you’ll get max continuous discharge of 60A. At 18S that’s ~4 kW and IMO that’s plenty unless you want to race.

Kaly XL50 uses 50E cells and the battery is only 12S8P.


18s6p = 108 cells. That’s a lot! More cells means less power draw per cell, so I agree –

I think unless you are racing up steep hills you will be better suited with a capacity cell like the 50E Jan mentioned or even better, the Molicel M50A, instead of a power cell like the P42A or Samsung 40T. That being said, if the power cells happen to be cheaper and/or you don’t care about squeezing every extra km of range since you already have such a big battery – no harm in going for the power cells either. :slight_smile:


I feel like we should have some W/kg benchmarks per riding style, for me 20W/kg covers medium street riding with pneumatics and hills


Yikes the 50E and m50A seem to be very hard to find in stock, not to mention quite a bit more expensive than a p42a. I am not too keen on spending 40% more on cells for range that I most likely wont use.

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These look to be a solid 10 amp cell.

Always go to the tables. :slightly_smiling_face:
No report to read (unless you want details), nothing technical to understand, just choose the cells with the higher score at the current level you will be operating at.

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So for the BAK N2100CG, it would be a good option for my use case looking at the table, especially considering the price. I have looked at your reports on cells and just want to know if theres anything else I should know about these cells before pulling the trigger on them?

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How can I answer that? There are a million things that can be said but I have no idea what you’re interested in hearing about. :slightly_smiling_face:

The report has everything I thought might be of broad interest but if you had a particular question I’d be happy to answer it.


Haha, you have a point. I was wondering if there are any special temperature concerns with these cells with regard to cell life. I know they should be ran a bit lower than rated for longevity. Or something that would affect their ability to be spot welded, like a vent. I have seen it on some of your other reports so I thought I might confirm before buying

For me the main benefit of having more battery amps at your disposal is less voltage sag. On my prototype board with 12S6P P42A, at 6kw the voltage sags by a significant amount, in fact even when at 4V per cell I was managing to reach the 3.4V/cell soft cutoff which was frustrating when you accelerate and the board suddenly hesitates from hitting soft cutoff. I have since reduced soft cutoff to a lower voltage which has helped, but I was hoping for a bit more performance from the Molicels. Aspirationally would like to reach 12kw peak and I think lipo is the only way without lugging around a huge battery.

On my old junk board I had some 30C 5Ah lipos in 12S config, and I remember that thing felt surprisingly powerful with only some 6355 motors. The less voltage drop you have when you accelerate, the more performance you’ll get from your motors. If say on 12S you sag to 42V under load, you have dropped down to 10S power.

Some things to consider. Of course less noticeable at lower power, but still noticeable


Not really, just the standard recommendation to keep them below 60°C at all times. The cells in the middle of a pack can get a lot warmer than the cells on the outside.

The photos in the test report show that there is no bottom vent. Just the standard venting disk under the top contact.

I think something other than the cells was a work here. Or certainly working with the expected P42A voltage sag.

At 6kW with a 12S6P pack you’re at about 20A-22A per cell. That brings a P42A down to about 3.7V at the start and doesn’t hit 3.4V until about 1.6Ah have been delivered. I think you were also seeing a lot of voltage drops in the spot welds, cell interconnects, wiring, connectors, solder joints, etc., that all added up.

Just curious…why such a high soft cutoff voltage setting? Using 3.4V under that 20A-22A load means you’re starting to cut off at about a 3.7V resting voltage, or even higher. There’s still a ton of charge still left in your cells at that cutoff.

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Yeah theres definitely some voltage drop going on in the leads and rest of the circuit. The battery itself is super overbuilt and should have very low resistance in the connections.

A lot of people seem to use 40.8V cutoff start and 37.2V cutoff end for 12S, which did always seem very conservative to me. I’ve now lowered it to 38/32V although have to be careful accelerating hard at the lower end of charge as the voltage drops so quick that vesc reduces power very suddenly and someone not ready for this can be thrown off


Damn, now you got me worrying about sag with only 6p 10a cells. Decisions, decisions…

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I usually have my cutoffs at 3.4 and 3.0

I’ve seen a few instances of people with a lower or narrower window who have sagged straight through soft and all the way to hard cutoff and that gives me the heeby jeebies.

At 3.4 the cell still has a bit of performance left in it and in my mind makes it difficult to sag through that whole window.

With lower cutoff/narrower window, i feel like you risk missing out on the advantage of even having the soft cutoff in the first place.


Yeah I do 3.2 soft 2.8 hard so not as big of a window but enough for me. And the few instances I need that last bit of range I prefer to walk as little as possible