Chalo said:Yes, it's normal. The term is "self discharge", and batteries vary widely in their tendency to do it. In your case, the voltage between 77.0V and 76.75V probably doesn't represent very much energy in the pack.
Back when some of us used NiCd batteries in e-bikes,self discharge were about 10% of the remaining capacity per day.
you say "controller connected" - do you mean connected and turned-on? or just connected? i don't know how much the big input caps draw over time. i always disconnect the controller.Joey11 said:Thanks for you reply.
My bad, battery is sitting for 5 days (since Friday noon). As I said, 5 days ago, voltage was about 77v, now (5days later) voltage is about 76.7v(losing 0.015v per cell) with controller and BMS connected..
Cells voltage different are 0.01v.
I know my bms "Static power" consumption is less than 200uA.
jimw1960 said:Dumb question, but is your controller turned off with a key switch? One time, I accidentally left my controller turned on while the bike sat idle for several months and the battery drained slowly like that. I caught it before it hit the LVC but it had drained several volts over a three or four month period.
dogman dan said:Holy cow! That's all they lost after taking them off the charger? That's doing great!
But yeah, a bms or anything else connected to your battery will gradually draw them down some in a week. But your "problem" is no problem. Just don't put your battery into winter storage connected to stuff.
72v is empty... I set the BMS to cut off at 72v..dogman dan said:YES Thought I did say that. I'm assuming 72v is empty?
Good idea to park it a week half full, but not if it's too close to empty.
dogman dan said:Yes, especially since voltage will drop faster at the tail end of a charge. If above 50% charged, you might lose those watt hours with almost no change in voltage.
But if its easy, is there a reason you don't unplug the controller? I'd just unplug. I just set up all my bikes like that. the off switch is unplug it completely.
This is because I never charge on the bike. I don't like to set my bike, garage, or house on fire.
Ykick said:Most BMS have tiny idle current 20-50uA but over several months that can significantly deplete 5-10Ah cell groups. That’s why any commercial eBike battery pack should always be partially charged once per month.
IIRC my controllers when switched OFF using the ignition switch wire continue to draw around 10mA? Can anybody confirm or refute that for the basic Infineon controller?
But for estimating purposes let’s use that 10mA. In 1 hour we would burn 10mAh, over 10 hours we’ve burned 100mAh. 4 days (100 hours) sitting with that seemingly small drain would be about 1Ah burned up in the ignition OFF position.
Even if my estimate’s off and it’s only 20-50uA give it enough time you can see how controller/BMS circuits will eventually discharge packs.
This is different from what I was describing earlier about “Leaker” cells. They drop voltage merely sitting not connected to anything. Definitely something you want to avoid in your life.