I got a new 12v battery that's completely discharged, 4.6V at clamps. I'm afraid to charge it. Should I return it to the store, or are LiFePo so good with deep discharge that I should be OK?
Posted Dec 22, 2021, 11:14 AM UTC
That's an awfully low voltage for a new battery. So low I'd be surprised if it's not permanently damaged. Assuming it has a BMS and it lets you charge it then you could try.
I don't know how many cells there are in the battery but the absolute minimum you should let any single cell drop to is 2.0V.
The manual says charge voltage is 14.6 and it shouldn't drop below 9.6, so I guess it's 3S. It does have a BMS and even a small LCD.
So that would be 1.5V per cell, way below 2.0V you're saying is safe.
Each manufacturer might have their own specific variations but I've never seen a specification that allows for below 2.0v.
https://en.wikipedia.org/wiki/Lithium_iron_phosphate_battery#Specifications
Lithium iron phosphate battery
Cell voltage Minimum discharge voltage = 2. 5 V Working voltage = 3. 0 ~ 3. 2 V Maximum charge voltage = 3.
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I've seen this 2.0V value as an absolute minimum quite a lot around the internet, after doing a quick search.
It's 4s, LifePo4 is a lower voltage cell than more common li-ion chemistries.
Most of the links in the search results refer to "100% discharging" a battery pack, like the one I have. "100% discharge" meaning ~9V in that context (BMS cutoff voltage)
Yea, sorry - I edited the post when I realised.
Are you saying that is how you got it out of the box brand new???
Yes.
I'll be taking it back to the seller today., maybe the for 3rd time they'll replace it with a working one finally...
Test it before walking out.
See if you can see the production date.
Calling it New is fraud if it's been on the shelf in extreme heat for years or attached to vampire-loads like BMS
The BMS cut off the battery because the voltage is below 10v. The actual voltage of the battery is not 4.5v, because that is the voltage across the bms. It is probably 9.5-10v
Do not accept anything below 12V
Even if not dangerously low, indicates substandard goods.
Just chargeback with your CC if they won't refund.
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If this was lead-acid it would be dangerous
This is such incorrect information, I'm not sure where to start. Lead acid is one of the safest batteries out there as far as charging goes. But a lead acid battery left at 4.6v is junk and probably could never be revived.
u/FolieAJew are you having a stroke?
Thanks!
Does it have a BMS with low voltage cutout? It might of just cut off and needs to be jump started to reactivate it
Regardless, if you paid money for it, I would send it back, who knows what's happened to the thing or the quality of the supplier if they fail to do even that basic of a quality check
Yeah that's a shit supplier, it's a replacement actually. I bought one that had a broken LCD, returned it, they said they replaced it with a new one, and the replacement has 4.6V on clamps. Green Cell.
It's supposed to have a BMS with under voltage protection.
Dang, this is already battery #2 from that supplier? I'd return that shit, ask for a refund, and start shopping somewhere else.