LiFePO4 280Ah Batteries - Odd Capacity Issues/Expectation Setting?

MaryMark

New Member
Hi,

I bought 4x 280Ah cells from Nikkie @ Dongguan Lightning New Energy Technology.

(https://www.alibaba.com/product-det...a2756.order-detail-ta-ta-b.0.0.a87e2fc2XZgpd7)

They finally turned up the other day. I've top balanced them and they wouldn't get above 3.3v (The PSU is plenty powerful enough). Indeed the video she sent showed the same voltage per cell.

So since I've now hooked up the BMS - and App is showing only half full. Are the capacity of these batteries actually 3.3v (and not 3.5-3.6 volts as I've read else where?)

Thoughts...Are these cells duff? (Physically they look okay) or is this going to take ages? The PSU is set to 10Amps - but batteries are only pulling around 7 amps (Please see attached photos)

Many Thanks

Mark
 

Attachments

  • Screenshot_20210517-105604_xiaoxiang.jpg
    Screenshot_20210517-105604_xiaoxiang.jpg
    139.5 KB · Views: 15
  • 20210517_111428.jpg
    20210517_111428.jpg
    1.3 MB · Views: 14
Last edited:

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
It takes me 12 hours to charge a single cell from 3.30V to 3.65V using a 40A Bench charger. At 10A you'll be waiting the long game, especially if you are doing a full 4 cell pack. Appreciate that a 280AH cell can take a Max 140A for charging.
 

MaryMark

New Member
It takes me 12 hours to charge a single cell from 3.30V to 3.65V using a 40A Bench charger. At 10A you'll be waiting the long game, especially if you are doing a full 4 cell pack. Appreciate that a 280AH cell can take a Max 140A for charging.
Cheers Steve - probably what i didn't make clear is that the cells are only wanting to draw 7ish Amps. I can crank the PSU up to 40Amps but as it stands at the moment that wouldn't make a difference as they wouldn't pull that.
 

upnorthandpersonal

Administrator
the cells are only wanting to draw 7ish Amps. I can crank the PSU up to 40Amps but as it stands at the moment that wouldn't make a difference as they wouldn't pull that.

Your connections are bad - use ring terminals and proper wire size, those alligator clips and included leads don't cut it.
Also, don't change the voltage on your supply to 'crank up the amps' - you put it to 3.5V or so before connection to the cell, then connect and don't touch it.
 

MaryMark

New Member
Your connections are bad - use ring terminals and proper wire size, those alligator clips and included leads don't cut it.
Also, don't change the voltage on your supply to 'crank up the amps' - you put it to 3.5V or so before connection to the cell, then connect and don't touch it.
Don't worry I know my elec' eng :) Not going to change the voltage. the connections are fine, amps are too low to cause the clips any issues. This is all through BMS now
 

OnTheRoadAgain

Solar Addict
Healthy cells will charge above 3.3v

I just had a similar situation. Thought I knew something but it turned out the brand new PSU simply was not delivering the VOLTAGE or some other electrical anomaly. The current was there, and my clamp meter confirmed full current was flowing ....but the battery would not charge. Bad power supply was the outcome.

In your case, a simple battery resistance check should reveal any real issues that would cause this.
Also other visual clues like very puffy cells indicating prior use.

Get a different charger and charge directly to the battery to confirm.
 

upnorthandpersonal

Administrator
. the connections are fine, amps are too low to cause the clips any issues.

It's not the clips that would have issues with the amps, it's the amps aren't flowing because the horrible connection you get with the clips in the first place and that's why the current isn't flowing. Try a decent cable with proper connections.
 

GSXR1000

Solar Addict
Don't worry I know my elec' eng :) Not going to change the voltage. the connections are fine, amps are too low to cause the clips any issues. This is all through BMS now
if you know EE then you know small wire and teeth will cause resistance which in turn will cause voltage drop which will lower amp at a given voltage.

Put in parallel. set PS to 3.6 and let sit for a week.... the voltage won't move for day or more

 
Top