Hello. 

I received 3 packs of 48v 50ah batteries today, from China, almost 4 months after my order. The problem is that they have around 13V per pack, and dropping fast. They are 15s packs. 

 

Is it safe to connect them to the inverter if i set something like 10A max charging current? Or do I need to find another Kind of charger or power source that can bring them back to life? 

 

Thanks! 

1 hour ago, Nickso said:

Hello. 

I received 3 packs of 48v 50ah batteries today, from China, almost 4 months after my order. The problem is that they have around 13V per pack, and dropping fast. They are 15s packs. 

 

Is it safe to connect them to the inverter if i set something like 10A max charging current? Or do I need to find another Kind of charger or power source that can bring them back to life? 

 

Thanks! 

That is pretty bad to have them at below 1V each. If you have time I might use 'n boer maak 'n plan. If you don't have a power supply where you can use say 5A I would connect 4 in series and connect say to a car 12V battery while the car is idling. Do it on each set for 10min. After 11 sets done I would use about 4mm wire and connect all 45 in parallel to balance them. This can be left for 6-8 hours. Once this is done I would connect 15S on the Axpert and charge. Once each set reaches 45V I would switch off and connect the next set. Only then would I connect 15S 3P. Then hopefully during full charges the BMS would help to balance them. This might take as long as a week or more. Then one can repeat the parallel connection of all 45 to balance them again before putting them in normal use. If the BMS does not provide per cell voltage then measure each one when not under load or charge and record the voltage for each one. Number the cells to compare during testing and use.

I would pay a lot of attention to see if all the cells in fact do reach their normal level in use. These cells should not have discharged so low even in the 4 months it took to get them.

Please tell me I am dreaming with my boer maak 'n plan.

Sadly, I think you have to get them replaced. The cells will have severely curtailed life, even if you can revive them somehow. LFP cells should never be allowed to fall under 2.5V.

I would suggest a 50v lab psu with current limiting, start slow on current say 1A on one just to see how they react. 

If the charge is absorbed, without excess heat, then keep turning up the current until either they get hot or 10A is reached

Just connecting to 48v and to much current may result in something blowing up/melting

as coulomb says they're possible faulty, see if there's a way to ensure they're actually 48v units before attempting to charge them

If you've got a friend with electronics experience, maybe ask them to pop around, check the units out. 

This isn't great news, was planning to bring in a 200ah 48v unit 

Edited December 23, 20213 yr by Nitrious

7 minutes ago, Nitrious said:

ensure they're actually 48v units

Duh, yes. 13 V makes much more sense for a nominally 12 V module (3.25 V per cell average). Is it possible that the order was screwed up?

Edit: if the cells really are below 2.5 V, definitely charge at no more than 1.0 A to start with, and do this outside, there is real chance of fire.

Edit 2: is it possible that the battery modules are "turned off" and needs a special sequence to "start" them? It could be that the 13 V is just due to leakage of the BMS pass MOSFETs, coupled with the very high input resistance of a modern multimeter.

Edited December 23, 20213 yr by Coulomb

perhaps pics of the units, along with models numbers, then connect the bms one by one to a laptop and check them while following the startup procedure, these units are apparently (they say) normally shipped between 40%-60% soc which makes sense for li ion, as its where they are most comfortable, as a storage charge. 

Thank you all for your replies. 

 

I took the chance to connect one of them to the inverter, with a 10A limit current and a 51.2 charging voltage.

It seems, for the moment, that Coulomb might be right with the leaked current from the bms. When i connected it, it started with a 50.8V voltage measured at the battery, 10A charging current and 2 out of 4 SOC lights turned on solid. 

 

 

This is the inverter state at the moment, with the inverter "turned off" and actually no load on it. 

Seems like they should be working as expected. Do you mind me asking, how much did you end up paying for the batteries (including shipping)?

I paid around 2000 USD, including a 50 ish PayPal fee (for an extra level of safety) and i received 200usd back from alibaba when i asked for a refund because the order appeared as received when it was not. So, at 600 usd per piece, it is lower than half the price for a local bought pylontech US2000. 

 

The shipping was ddp, shipped to my door with all taxes included. 

Wow, that's very good. Do you know what brand/make cells are inside? Are they first or second life cells?

 

No ideea about the brand, but i probably will check later on. There should be new cells inside, but i guess you never know. As far as I know, i bought them straight from the factory....

9 minutes ago, PowerUser said:

Wow, that's very good. Do you know what brand/make cells are inside? Are they first or second life cells?

 

To me they appear to be second life cell, Checked on they site and they only guaranty 2000 Cicles @ 100% DOD.

 

LiFePO4 Battery

 

• Volt: 12V / 24V / 48V
• Capacity: 0.8Ah ~ 300Ah
• Cycles: 2000 @100% DOD and remaining 80% capacity

Edited December 23, 20213 yr by Antonio de Sa

16 minutes ago, Antonio de Sa said:

To me they appear to be second life cell, Checked on they site and they only guaranty 2000 Cicles @ 100% DOD.

 

LiFePO4 Battery

 

• Volt: 12V / 24V / 48V
• Capacity: 0.8Ah ~ 300Ah
• Cycles: 2000 @100% DOD and remaining 80% capacity

On the Alibaba site, it says 6000 cycles but the batteries look different:

 

Can't argue, one way or another. I asked and the answer was this. 

2 minutes ago, PowerUser said:

On the Alibaba site, it says 6000 cycles but the batteries look different:

 

They sell the pylontech style batteries as well, a little more expensive and with CAN. 

27 minutes ago, Nickso said:

So, at 600 usd per piece, it is lower than half the price for a local bought pylontech US2000

Using todays prices:

You purchase: USD1968 / 3 * 15.74 (R/USD) = R10 324.

Local Pylontech 2000B (Powerforum Store): R12 822

Not exactly half. 80% in fact.

Calvin, I said local bought. I am from Romania and the price here is over 1200 usd for an US2000. Sometimes you can find it around 1100 usd, but it is usually ot of stock. 

10 minutes ago, Nickso said:

Calvin, I said local bought. I am from Romania and the price here is over 1200 usd for an US2000. Sometimes you can find it around 1100 usd, but it is usually ot of stock. 

Ha ha, and we are complaining about the prices in South Africa 😀

48 minutes ago, Nickso said:

I am from Romania

Apologies - I did not know that.

1 hour ago, PowerUser said:

Ha ha, and we are complaining about the prices in South Africa 😀

Yeah, the market here isn't very developed on this segment. It was a good deal, all things considered, if they are what they're supposed to be. 

 

28 minutes ago, Calvin said:

Apologies - I did not know that.

No worries, it doesn't really say anywhere. Glad to know we're getting ripped off around here 🤦‍♂️