Yep, and I’m knowingly contradicting this entire comment:
I have a feeling you didn’t read mine though. Battery safety is no joke.
I’m doing it like this right now, no problems.
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Oh mosfets…
Alrighty, I hope you are knowingly assuming the associated risks of overvolting a battery system.
That’s such a funny idea, I love it. You’re thinking of running it as a brushed DC motor controller to charge? We already have retroactive current limiting. All you need is some extra brains to update the max “ERPM” setting to vary the max output voltage. Although I’m not sure if ERPM works differently for brushed DC in the vesc firmware.
Ah, might be because I’m doing it on LiFePO4, charger set to 36.5V for 10S (36V is full charge, absolute max is 42V but no reason to go there as only adds 1% capacity). I’ll go back and rectify my post.
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LiFePO4 are much more tolerant to overvoltage than li-ion. 3.65V/cell is perfect
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Ooh, saucy. I love me some lifepo4 tech, IMO there’s not enough of it in ESK8 aside from boosted. I totally get your charger setup now, quite unique haha
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Yeah my apologies mate, just came back from a few beers with mates and didn’t take chemistry into account. Went back and rectified my post.
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I also like LiFePO4 and think there isn’t enough. On shorter range boards, it’s very good. If you want range, it’s not your friend. If you want high current, fast charge, strong brakes, tolerance to cold, long lifetime, robustness, and not worry much about your battery, then it’s a fair tradeoff.
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Compared to my previous LiPo’s, four times the weight for three times the range, seems like a fair trade-off (6Ah LiPo vs 15Ah LiFePO4).
Main reason I went LiFePO4 was the ability to charge unsupervised without worrying about a 1,500 degree Celcius chemical fire.
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As I said it Im.not telling people what to do but I was able to charge the battery. Im sure I coyld have gone to a 42v full charge but why take the risk? This is for a situation whrn you don’t have the ability to charge a with the correct charger.
Ya charging my 10s board from 20% to 90ish% is definitely charging. I said what bms I used and said I wouldn’t advise anyone to do it and just letting people know my experience. I am literally able to.ride the board so I can say it worked.
Oh gawd sorry it got long, tldr at bottom…
The answer to the question in title is yes. The real question seems to be, would it be bad to do so and why?
CC/CV is a 2 stage charge, holding current constant and varying voltage in the first stage, then holding voltage constant while letting current diminish in the second stage, until you hit termination conditions, typically when current is C/10.
CC/CV is an approximation of perfect charging conditions that works pretty well and is safe for just about all lithium ion chemistries.
The way I look at the charge strategy is, when the battery is empty, you pour in power hot and fast. When the battery is almost full, we make sure not to go over Vmax for the cell, and if energy keeps going in, let it keep going in.
I think a more ideal charge curve could be fashioned for each particular cell model. For example, instead of holding current constant, when SOC is low we can use a lot more current, and taper off as SOC increases.
Given all that, if you charge a 42v max pack (10s) with a 50.4v cc/cv supply and cut charge at 42v, it should be pretty close to identical to using a 10s charger and cutting off at 42v. You probably get 70% or so of the charge into the pack. You won’t trigger balancing in the bms. Voltages might be drifty, but if the pack was previously balanced, might even out if you were to keep going to 100% soc.
Oh and doing this will not give the BMS balancers any time to work.
If you leave the 50.4v charger connected after pack reaches 42v, this will hurt the pack. How much depends on how far you go and the cell model. If you have a bms, I really really don’t know what would happen, I think it depends on the bms model. In theory it’ll cut off charge but in practice will it let it overcharge for 30sec? 2min? Will it blow a mosfet?
In theory, the BMS’s job is a line of defense for anomalous conditions in the pack. I don’t think it’s particularly a good idea to trip the safety conditions on the bms routinely. It will probably be okay, but maybe it’ll put some wear on some components and things will degrade, kind of like a circuit breaker in a house. And a firmware/hardware glitch could of course burn your house down.
TLDR Do this only ocassionally and with very close supervision, and a running path to outdoors where I could toss the pack. 
@janpom I really like your thinking with cutting off charge at 4.15v/cell and disabling balancing. If we have good metrics, no need to balance on every charge unless you really really need that last 5-10%.
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Yes I believe that is how the electric car do.