72v battery low voltage cut off

[Tkseward]

Hi all, I am having trouble finding what is the lowest I should drain my 72v battery to? Right now I have no idea what voltage is too low for a 72v battery.. it charges up to about 82.3v and i hav only taken it down to 71v so far. I want to set the battery cut off on my CA v3 to a safe voltage so I prolong my battery life.. any help much appreciated

 

[wesnewell]

Depends on the kind of 72V battery you have, For lead acid 72V battery, typical LVC is between 61-63V. For a 20S lipo pack, 70V would be my minimum.

 

[Tkseward]

its a lithium ion 20s 72v

 

[wesnewell]

Then it would depend on the cells used in your pack, but as long as they're well balanced, 60V should be safe with any of them. That's a 3V per cell average. Most or rated for 2.5-2.8V cutoff, but I wouldn't go that low.

 

[Tkseward]

How does one find out this knowledge? Is there a diagram or something that will help me understand these figures for different battery types or is this just given knowledge for batteries in general?

 

[amberwolf]

Check with the manufacturer for the cells you used in your pack, if you built it yourself.

If you bought the battery complete as-is, check with the seller, or the manufacturer of the pack if that is different from the seller.

BTW, if the pack has a BMS, it should protect you against overdischarge on it's own.

 

[wesnewell]

The lower you run a battery below its nominal voltage the more stress you put on it. That holds true for all battery types that I know of. That's why your computer ups shuts off before the battery gets too low. That's why your ebike controller has a low voltage cutoff. Most battery manufacturer LVC specs are way too low imo. They do this so they can squeeze every little bit of capacity from them for ad purposes. But in reality if you run them as low as they state, you just end up shortening the batteries life. As an example. most rc lipo is rated down to 3.0V. In reality, its reached 0% soc at about 3.28V. And there very little actual capacity at the lower end of the charge. look at discharge charts for batteries and you'll see it. here's test I ran on rc lipo.
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