Charging issue (flashing green light)

Phifty

1 mW
Joined
Jun 28, 2022
Messages
12
Hi, I just recently upgraded my bikes motor and battery to a 72v 20ah 3000w battery. The battery and motor works great and I’m getting the output I was looking from it, on the other hand I’m having an issue with charging it. When the charger is plugged into the wall without the bike connected I get a solid green light, when plugged into the bike I get a flashing green light and the battery hasn’t increased in charge as well. Is there something I’m doing wrong or missing here?
 
Phifty said:
72v 2ah 3000w battery

What? 3kW at 72V from a 2Ah battery is more than 10C discharge rate. Are you sure?
 
It would be interesting to see what the voltage on the charging leads is doing when that happens.
 
Chalo said:
It would be interesting to see what the voltage on the charging leads is doing when that happens.

I have a multi meter coming in the mail soon.
May I ask; what are the possible reasons this would happen?
 
Sometimes chargers have a low voltage cutout to prevent them from attempting to put current into a over discharged battery.
Or the reverse... The battery is already at a higher charge than a charger thinks is safe.
I've also had one or two weird BMSs on the battery make the charger do that while it's trying to balance, but it was so slow it was shutting down the process basically.
All of it's a big guessing game until you have a meter.
 
Voltron said:
Sometimes chargers have a low voltage cutout to prevent them from attempting to put current into a over discharged battery.
Or the reverse... The battery is already at a higher charge than a charger thinks is safe.
I've also had one or two weird BMSs on the battery make the charger do that while it's trying to balance, but it was so slow it was shutting down the process basically.
All of it's a big guessing game until you have a meter.

Thanks for Info. Every so often it will charge for a good 20-30 minutes or so, then itll just resume flashing green. It’s quite frustrating.
 
Voltron said:
That does sound like really slow balancing

With that said, should I leave it plugged in for a while as it flashes green to “balance” itself out?
 
Yes, probably. It can take days.
But also don't leave it unattended.
I had a new charger fail and start overcooking the whole battery.
I heard little pattering noises and thought it was starting to rain. But it was the vents popping all across the pack....

Plus, sometimes you can have one group in there self discharging the whole time so the charger never stops, but it's getting hot in one spot on the pack.
 
Voltron said:
Yes, probably. It can take days.
But also don't leave it unattended.
I had a new charger fail and start overcooking the whole battery.
I heard little pattering noises and thought it was starting to rain. But it was the vents popping all across the pack....

Plus, sometimes you can have one group in there self discharging the whole time so the charger never stops, but it's getting hot in one spot on the pack.

Days??? I can do it in spurts yeah? I definitely do not trust the battery unattended whilst it charges.
 
Voltron said:
Yes, spurts is fine probably.

Maybe go digging into the battery when you get your meter, and see how out of balance it still is?

Just an update; after having it left plugged in for a few hours, I’m finally getting a consistent charge. No more flashing green light and the battery percentage is increasing. Thank you for the bit information
 
I believed that I spoke too soon; the blinking green light has returned.
Is there a possibility that the bms balances the battery cells or multiple times?
 
Voltron said:
It could be there's a group of cells that keeps discharging faster than the others.
It doesn't sound good though.

What are my fixes? My multimeter came in, but I wouldn’t know what numbers to look for or even how to read it
 
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