Lifepo4 40AH stops charging

perra

perra

10 mW
Joined
Aug 31, 2015
Messages
27
My Lifepo4 40Ah/48V/Bms has worked fine for 2.5 years. But now all of sudden it stops charging after only 3 minutes, even when the battery is empty. Is battery already old and finished, or is it fixable somehow? Any ideas are welcomed. I have tested two chargers, same result :(
 
You will need a Multimeter.

You start by measuring the battery connector voltage, charger output voltage, and if necessary individual cell voltages.
 
Could be just the bms, but at 2.5 years old it could be a cell group has given it up. That's a bit early for lifepo4, but not unheard of.

You can measure each cell groups voltage at the bms plug.

One hopeful possibility, your wire is broken at the plug, on the charger or the battery, causing the charger to turn off when the contact breaks.
 
Thanks guys. I will first check all wires from Bms to the battery.
 
Have you checked the stuff that was wrong before?
https://endless-sphere.com/forums/viewtopic.php?f=14&t=72341&p=1093322#p1093322
just to see if it's gone wrong again?
 
Yes amberwolf, this is something completly different.
I got a multimeter and checked all cells, they look all ok with about 3.5v.
I cannot find any loose cables. I tested with two chargers also.
Is it really possible that a lifepo4 battery can fail after 2.5 years?
Im a bit depressed now...
 
Where did you get the battery ? Link ? How have you been using the battery. Controller and motor info ? 3.5v 16 cells sounds fine. list cell voltage and write on paper. Voltage of battery pack ?
1. 3.50v
2. 2.89v
3. 3.51v


16. xxx volt
 
OK, so I need to replace the BMS. Please help me connect the cables. This picture are the cables A,B, C.
Bms 0.jpg

The cables from BMS are:
Bms1. Charge minus
Bms2. Power minus
Bms3. Battery minus
Bms4. Battery plus (red signal wire)

Please help me make correct connection, e.g. Connect A to Bms3 etc.
Thanks!
 
The signal wires are also tricky. Picture below is the signal wires from the battery.
Signalbattery.jpg

This picture is the ports for the signal wires.
Signalbms.jpg

So they are not the same connectors, which wire from battery is battery plus?
 
Where did they connect on the old one? That's where they connect on the new one.

perra said:
OK, so I need to replace the BMS. Please help me connect the cables. This picture are the cables A,B, C.


The cables from BMS are:
Bms1. Charge minus
Bms2. Power minus
Bms3. Battery minus
Bms4. Battery plus (red signal wire)

Please help me make correct connection, e.g. Connect A to Bms3 etc.
Thanks!
Click to expand...
 
Not really any way for us to know from the pics you've got there.

You'd have to either measure connections on the BMS board itself to it's main + and - connections, or you'd need to check the documentation for the BMS from the manufacturer or seller. If none is provided, you're stuck with measuring things with a multimeter set to continuity or ohms, or visually tracing them out.



perra said:
The signal wires are also tricky. Picture below is the signal wires from the battery.
View attachment 1

This picture is the ports for the signal wires.


So they are not the same connectors, which wire from battery is battery plus?
Click to expand...
 
OK, wires to connect :
Wire A to P- (load)
Wire B to C- (charger 48v)
Wire C to P- (power control)
Red signal wire is Battery+
Signal wires to battery cells

So what can go wrong :)
 
One fault there, wires to connect :
Wire A to P- (load)
Wire B to C- (charger 48v)
Wire C to B- (power control)
 
Well, there is nothing wrong with the BMS. The voltage on each cell is also fine.
The battery has been completly discharged. This is maybe the fourth time the battery has been completly discharged.
So my focus now is the issue of charging a completly discharged battery, this seems to be an issue. I read about slow charging etc.
Any practical help on this is welcomed.
 
perra said:
So my focus now is the issue of charging a completly discharged battery, this seems to be an issue. I read about slow charging etc.
Any practical help on this is welcomed.
Click to expand...
Charge it slowly, 1-2A should be fine. If you're not in a rush, charge slowly all the way up to full and then let the BMS balance it for a good 24 hours or more. Otherwise once it's up to 3V/cell or above you can go at a more normal rate. Personally I use a lab power supply to limit charge current on the first charge or when charging near empty. What are the cell voltages right now? Might help to give more specific recommendations.
 
Each cell seems ok with about 3.1 to 3.2 volts.
So I need a special slow charger? Is there a charger that use 1.2A, or is it a charger that you can set ampere level?
 
With a pen and piece of paper write down the voltages of each cell starting from the negative end.
1. 3.54
2. 2.98
3. 3.25 volts


16. Xxx volts
Report back. This is Step one and where to start.
This will give you the state of charge of each cell plus report back with the charge of the battery. You can test the with a light bulb.
 
Here are voltage for each battery cell:
1 3.33v
2 3.33v
3 0.02v
4 3.36v
5 3.33v
6 3.28v
7 3.37v
8 3.33v
9 3.33v
10 3.32v
11 3.33v
12 3.29v
13 3.4v
14 3.00v
15 3.6v
16 3.4v
 
Well, end of the line for this battery. Lessons learned; avoid complete discharge and measure each cell first, before starting fixing anything.

My new battery got installed today. Its custom size enabled a larger 60Ah battery. My range should increase to over 100 kilometers. Thanks all you guys for your support.
 
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