Battery charge versus run down question

[SloNEZ]

I have an EM3EV triangle battery (50v 25 amp hour) with his Mac 8t 40 amp kit.
Now that it's cold, I find I can run the motor harder without it getting too hot.
I'm using quite a bit of the battery (about 17 amp hours on my 26 mile each-way commute, up to 20 if I run errands).
Is it better to keep charging it to 90% and run it down lower, or is it better to charge to 100% and not run it down so low?

 

[wesnewell]

It's better to do a full charge and not run them low.

 

[silviasol]

Running lower then the nominal voltage will make it loose cycles, however the graphs for the actual cycle times for the cells are based on a full charge to full drain each time. A quality battery will last 500 full drain cycles before it looses more then 30% charge. If you are home and it is still 3.3-3.6v a cell(with li-ion voltage) I assume it would last 1.5 times that or more. Myself I don't worry about it because that is a long time and would probably upgrade before then anyways.

 

[dogman dan]

I wouldn't worry about 20 ah being too low. But if you start running completely out, then of course charge to the higher voltage. Insulating your battery container will help when it gets really cold, as will bringing a warm pack out from inside.

The bms will protect you from a catastrophic over discharge, but do allow more time for the pack to balance any time you ride till bms cutoff.

One thing to realize, if you charge to full voltage and then ride immediately, the pack spends very little time at 4.2v. This will be better than storing the pack overnight at 4.2v.

One strategy I use for a longer ride, is to charge to 4.1v, then at dawn before I leave, finish charging to 4.2v.

 

[dnmun]

that's what i do too. all my packs charge up on the Elcon charger for the SLA pack and it goes into standby current and leaves my lipo at around 3.8V so i leave them there and when i gotta go somewhere i turn on two more chargers (18A) for the lifepo4 and lipo and push it up to full charge (4.1-4.2V avg) and then jump in and go.

that way it doesn't spend long at full charge.

charging in the cold is hard on them too. if you have to charge outside and leave the pack out in the cold then get a battery warmer to warm it up before charging and discharging.