New 52v battery sat unused for two years...

I see on Craigslist a Luna triangle battery 52v, 28ah, GA. It is unused, bought in 2017, still with wrappings on the plugs. How much capacity will it have lost? They are asking $600 for it ($1000 new). Thanks.

if they haven't kept it charged the bms probably drained it dead and destroyed it.

There are lots of GOOD battery options out there, I wouldn't touch that.

If it sat in the heat of a garage, it might have been baked to death. Lithium degrades in the heat.
I would avoid. Batteries have a limited shelf life anyway.

The only way that battery could possibly be ok would be if the BMS was disconnected at the factory and had to be connected by the purchaser. Ping Packs came that way.

Might be worth testing, if V over 2.5V offer $100

Thanks everyone! Very clear.

Could be perfectly Okay... A 28Ah battery is massive and can take a decade to drain from BMS if the pack was stored full...
But if it was stored near 0%, then some of the cells could be toast.

Assuming the cells were NMC, never used, and stored at 50% and a in a garage at ambient temperature of 25°C, the cell should have a remaining usable capacity of above 95% and a DCIR no more than 110% that of brand new. But that's before considering BMS parasitic current draw.... Wich is typically in the uA (microamps) range...

If overall the battery still sits at a voltage anything higher than 50V, i would buy it for a best offer of 400$. 300$ would be more reasonable. Then I would manually balance each cell string as the BMS drain is normally uneven, ofter targeting the first 3 parralleled cell groups...

But if I assume the BMS has a 50uA drain and the guy did not lie about the 2 years duration, then

50 uA = 0.05 mA = 0.00005 A (of BMS draw)
So in 1 hour, thats 0.00005 Ah drained out of 28Ah
So in 1 day, thats 0.0012 Ah
So in 1 year, thats 0.436 Ah
So in Two years, thats about 0.9Ah ...

So in 2 years, such BMS would drain 0.9Ah out of 28Ah. Meaning in two years it would drain about 3.5% of the capacity of that huge battery.....

So unless it was stored empty from the start, I'm quite confident the battery cells are still good.... But look up the specs of the BMS in that pack to be sure about the current it draws... Also, make sure the pack is made of good, brand name 18650 cells... Finally check to see how many cycles (from story, i would assume zero cycles) the pack has.... Also was it stored at 25 or 40 degree celcius ????

Matador

Another name for this BMs spec figure is "BMS Quiescent current draw"... This figure should be on any respectable BMS datasheet.

Matador

Me - I would not risk it. It might be ok but no way would I pay $600 for it.

But if I assume the BMS has a 50uA drain and the guy did not lie about the 2 years duration, then

50 uA = 0.05 mA = 0.00005 A (of BMS draw)
So in 1 hour, thats 0.00005 Ah drained out of 28Ah
So in 1 day, thats 0.0012 Ah
So in 1 year, thats 0.436 Ah
So in Two years, thats about 0.9Ah ...

So in 2 years, such BMS would drain 0.9Ah out of 28Ah. Meaning in two years it would drain about 3.5% of the capacity of that huge battery.....

Click to expand...

Nice BMS if you can get it! They do have a habit of drawing more than that, though - a lot more. I have two 20AH Ping packs. The earlier, hand-built by Ping himself, pack does have a very low vampire drain. The later one, though, draws about 10X that much, by my estimate. It's better to assume the worst but hope for the best than the other way around...

This is why I would only buy packs where the BMS can easily be disconnected, bypassed or replaced.

Thanks everyone for you cautions. I let it go!