72v Lithium Battery Maximum Charge = 88.2v?

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anonyxuser
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72v Lithium Battery Maximum Charge = 88.2v?

Post by anonyxuser » Jan 09, 2018 9:13 pm

I got the Cycle Satiator battery charger, freaking awesome I might add!! I can charge any kind of battery from car batteries to freakin ebike batteries to whatever the heck I desire pretty much! Also gives me the option of charging my battery to literally whatever I want pretty much... Another cool thing is that the other day I totally depleted my battery and it wouldnt charge because of it. It wouldnt detect it or something at that point... But the Cycle Satiator suddenly asked me if I wanted to force charge, pretty badass.

Anyway I was wondering... Is 86v bad to charge my 72v 20s lithium battery? It seems to hold at 86.1v when I unplug the charger too. I heard its not really good for it and it lessens the life of the battery when fully charging it all the time but I am not certain if this is fact or not. Anyone have any experience they can share on the subject?

Thanks guys! :)

Tags: cycle satiator, cycle satiator review, buy cycle satiator, grin technologies, maximum ebike battery charge, 72v, 48v, 36v, 12v
Last edited by anonyxuser on Jan 11, 2018 5:44 pm, edited 1 time in total.

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Re: 72v Lithium Battery Maximum Charge = 86.1v?

Post by e-beach » Jan 09, 2018 10:58 pm

At 4.3v per cell you will kill your cells fast. You might also set the on fire. They might hold the charge for a short period of time, say a few weeks at most, but it won't last and you are potentially setting yourself up for a fire. Top end charge and heat are the two main killers of lithium batteries. Finding your house on fire because it overcharging, well that is another story.

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Re: 72v Lithium Battery Maximum Charge = 86.1v?

Post by wturber » Jan 10, 2018 1:18 pm

Yep. 86 volts is a bad idea if you want your batteries to last a long time. Many people charge to 4.1 or 4.0 per cell series (80-82v in you case) to help extend the battery life. It is also generally considered not so good to discharge to the lower limits of the cells.

OTOH, if you'd rather squeeze out the last bit of performance then charge to 84v and run it until the bike won't go no more. It's your battery pack after all. But for me, I'm perfectly happy to give up a little bit of performance and capacity to have my battery pack last perhaps twice as long is it otherwise would.
Last edited by wturber on Jan 10, 2018 1:47 pm, edited 1 time in total.
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Re: 72v Lithium Battery Maximum Charge = 86.1v?

Post by fechter » Jan 10, 2018 1:27 pm

Maximum for 20s should be 84v. I wouldn't go above that. 82v should give you about 90% capacity and make the pack last about twice as long.
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Re: 72v Lithium Battery Maximum Charge = 86.1v?

Post by anonyxuser » Jan 11, 2018 5:41 pm

UPDATE: Just charged it to 88.2v and I unplugged the charger and turned on/off the ignition multiple times and its still reading 88.2v! How is this possible? How is it holding its charge when its over the freaking maximum maximum? Most likely over the maximum of the BMS I presume as well, which for those of you who don't know is the little circuit board inside the battery pack that tells how many volts each of the battery cells are worth, and in my case they are 18650 cells most likely worth around 4v each. Maybe this is possible because my BMS uses a range for each cell?? Note that older ebike batteries may not use 18650 cells, this is more of a newer and more safe way of building and manufacturing ebike batteries. Thanks! :D

(note: this was before I checked back on your replies)

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Re: 72v Lithium Battery Maximum Charge = 88.2v?

Post by wturber » Jan 11, 2018 6:13 pm

I can't answer your question, but I wouldn't leave the cells at that charge level for long. I'd run that battery down to 60% capacity and give it a rest from being tortured.

If you can open the case and examine the cells and/or BMS, that might give you a clue as to what's going on.
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Re: 72v Lithium Battery Maximum Charge = 88.2v?

Post by fechter » Jan 11, 2018 10:30 pm

The BMS should slowly bring the voltage down, but it's real slow. Might take days.
It's really bad (and dangerous) for the pack to sit at that voltage. Best to find a way to drain it part way. Of course ebikes are the best load, but if that's not an option, a large incandescent light bulb made for 120vac will work. I've used hair dryers before too but don't try to turn it off with the switch, just unplug it.
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Re: 72v Lithium Battery Maximum Charge = 88.2v?

Post by wesnewell » Jan 12, 2018 1:16 am

Only you know what cells you have. some are rated for a max charge of 4.35V, while most are rated for lower max voltages, with 4.2V being the max rated for many 18650 cells. Some cells for the military are rated as high as 4.5V. But you can overcharge any of them. Overcharge them too much and bad things can happen. The other thing may be your voltmeter is not accurate. In any case, it's not good to give them a max charge and not use them immediately. And it's not good to overcharge them any time. Any commercial pack with a bms should not allow any of the cells to overcharge. If it does, it's defective.
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