Rebel 48v LifePo4 cell failure Help Repair?

[yachtdr22]

I think the problem is solved... Thanks to you all for your input

Greetings All.
I have a Rebel Waterproof 48v LiFePo4 battery. 16 cells, BMS.
1 of the cells has failed and I hope to repair. I have been searching and have found no advice.
How do I replace the one bad cell (Marked with a small X in marker) voltage confirmed. not a lose connection

Help?

Thanks
Drew

 

[yachtdr22]

Am I in the right place to be asking this question? is there another thread I should look at?

 

[kommando]

US based board, they are asleep so wait until they get up.

 

[42OhmsPA]

How did you determine the cell is bad?
Since you have it open I would manually charge cell 13 and see if it stays in balance with the rest before doing anything else.

Since they are welded busbars you're going to be pretty much SOL for an easy replacement. A laser welder or cutting, drilling, extending, etc.

 

[Q-Dog]

How did you determine the cell is bad?

I am also curious. The BMS screen shot doesn't look bad at all.

 

[yachtdr22]

I am also curious. The BMS screen shot doesn't look bad at all.

Cell# 13 will not take a charge

 

[yachtdr22]

How did you determine the cell is bad?
Since you have it open I would manually charge cell 13 and see if it stays in balance with the rest before doing anything else.

Since they are welded busbars you're going to be pretty much SOL for an easy replacement. A laser welder or cutting, drilling, extending, etc.

Best way to do that?

 

[perpetual]

do you have an adjustable power supply to charge the individual cell to 3.6V ?

 

[yachtdr22]

I would think that the cell would equalize on it's own?
I figure I could drill out the weld ?
I would like to use this battery to learn.

 

[perpetual]

depending on the bms settings, cell balancing may not start until after 3.4V

 

[42OhmsPA]

I would think that the cell would equalize on it's own?

Not if the other cells are hitting HVD and it's a passive balancer.
What voltage do you charge your pack to?

 

[yachtdr22]

Does this info help?

 

[42OhmsPA]

Does this info help?

Enough to show multiple BMS settings should be changed.
Low temperature charging should be 0C or higher, high cell disconnect should be 3.65V. There are others but those two stand out the most.

What voltage do you charge your pack to?

 

[yachtdr22]

Enough to show multiple BMS settings should be changed.
Low temperature charging should be 0C or higher, high cell disconnect should be 3.65V. There are others but those two stand out the most.

56.0v
there are a couple of settings that i see could be "High Cell Disconnect", which one?

 

[HRTKD]

In the picture of the cell voltages in the first post, none of the cells have hit 3.4 volts. Balancing doesn't start until then. As suggested above, charge the one low cell with a benchtop power supply. Or, charge the entire battery pack with a lower amperage which will give the BMS more time to balance and hopefully bring the cells into alignment.

The "Hardware Overvoltage Protection" in the second picture is set to 3.9 volts, which is too high. It should be 3.65 volts, which is a universal absolute for LiFePO4. The setting for "Hardware Undervoltage Protection" of 2.3 volts is too low. This one is a bit of user preference. I set mine to around 2.8 volts. The "Pack Overvoltage" and "Pack Undervoltage" should similarly be adjusted.

Setting these parameters should be done after consulting the datasheet provided by the cell manufacturer, if you can figure out who made the cells.

All of the BMS settings should be considered your last line of defense. The charge and load devices should be your first line of defense with proper charge and load profiles.

 

[42OhmsPA]

56.0v
there are a couple of settings that i see could be "High Cell Disconnect", which one?

See the post above this one, solid advice.

I would charge to and hold at 55.2V for a few days / weeks if you don't want to manually charge the low cell.

 

[yachtdr22]

In the picture of the cell voltages in the first post, none of the cells have hit 3.4 volts. Balancing doesn't start until then. As suggested above, charge the one low cell with a benchtop power supply. Or, charge the entire battery pack with a lower amperage which will give the BMS more time to balance and hopefully bring the cells into alignment.

The "Hardware Overvoltage Protection" in the second picture is set to 3.9 volts, which is too high. It should be 3.65 volts, which is a universal absolute for LiFePO4. The setting for "Hardware Undervoltage Protection" of 2.3 volts is too low. This one is a bit of user preference. I set mine to around 2.8 volts. The "Pack Overvoltage" and "Pack Undervoltage" should similarly be adjusted.

Setting these parameters should be done after consulting the datasheet provided by the cell manufacturer, if you can figure out who made the cells.

All of the BMS settings should be considered your last line of defense. The charge and load devices should be your first line of defense with proper charge and load profiles.

I will change those parameters as recommended...Unfortunately Rebel Battery is out of business. there are a few other companies that have a similar design but not sure about the cells and BMS

 

[Alkaline]

Greetings All.
I have a Rebel Waterproof 48v LiFePo4 battery. 16 cells, BMS.
1 of the cells has failed and I hope to repair. I have been searching and have found no advice.
How do I replace the one bad cell (Marked with a small X in marker) voltage confirmed. not a lose connection

Help?

Thanks
Drew

Sorry but from what I see you should have asked on the board before opening up the battery. Nothing looks out of the ordinary in your pic.

 

[HRTKD]

I'm not convinced that you have a bad cell. I don't see smoking gun evidence of that, but maybe I just missed it.

 

[Brett V]

Even if all the cells were the same as your lowest “dead” cell, 3.364 x 16 =53.824. That’s around 95% SOC. Your pack is out of balance somewhat but not bad.

 

[GXMnow]

I agree, it just looks like a balance problem. Charging the low cell up should get it back in line. Then charging the battery to 56 volts should kick in the balancer each time the battery tops up. The main problem is that most BMS passive balancers are less than 0.1 amps. If the cell is just 1% out of balance, that is a full amp hour difference for a 100 AH cell. It will take a 0.1 amp balancer 10 full hours to take off that 1 AH from all of the higher charged cells. And since it ONLY balances while charging AND above 3.4 volts, this can take several days. And that is just for a 1% balancer error.

If you don't have an adjustable power supply, there are a few other options. My E-Bike batteries get out of balance and were causing some issues. So I purchased a 100bapance Smart Active Balancer. The cheap one can move energy at a full 1.0 amp from the highest cell to the lowest cell. And you can set it to work any time the battery is above say 3.35 volts per cell and let it crank all day and night. It pulls my 12 AH E-Bike battery into balance in just an hour. It may still take a couple days on 100 AHs, but it will work much faster than the built in BMS balancer. There are betetr and more powerful balancers, but at just $40 on Amazon, this is a great deal.

https://www.amazon.com/100Balance-Equalizer-Balancer-Lifepo4-Transfer/dp/B0CMTL1RFW/ref=sr_1_8?crid=3U5PFSGXVDJYE&dib=eyJ2IjoiMSJ9.ya60Uo0INmi4rgGvyD7MAReIpaOKNUU2x3mID4Mqs9yrkZJR-7FPbw0oTCdIUfoeGpkSCyMvkZSqt2ww9HoiGZhbejFVWhVpRV_9qNl4Y51TRV6imSqUdS_QKls9WkfqEwvdM3fwlwBMVHpdmvqKUIkasAuyl0TpCy_ZRorjbAOvs-6lvzK543Lh-CzkT8JkbgVF0n_PeXM1E1fqyAHTMlFwCDfTBmrfGyP9NNwu7R4.qjtnRLWTdjgxjlyLGc1sjVFHqykswnNB-i0dZZb2lQ0&dib_tag=se&keywords=16S%2Bbalancer&qid=1734917532&sprefix=16s%2Bbalancer%2Caps%2C199&sr=8-8&th=1

It also allows me to monitor my dumb E-Bike batteries from my cell phone.

They can be set to a lower cell count, but it's not easy or straight forward. Buy the one for the cell count you need it for and it is plug and play easy. I got the 16S and now have it set to do my 14S batteries. I expected it to be as easy as my JK BMS, it's not.

If you have other uses for it, then it may be worth getting a programmable bench power supply. For about the same $40 USD on Amazon, they have a 30 volt max 10 amp max adjustable supply. That would make fairly quick work of charging up the low cell. If it was fully discahrged, it is still 10 hours to top it up to full, but by the BMS pic you sent, it is well over 50% charged already.

https://www.amazon.com/NICE-POWER-Adjustable-Switching-Regulated-Adjustments/dp/B0CDW12H3X/ref=sr_1_3?crid=KAPU0TY5P3B1&dib=eyJ2IjoiMSJ9.QJsNuiB8esaDp70hqZNatQFPKmaWRlNEIeZeGaghpQVFRvMBWN-QA-om_MqfN6N6018SwrKle8b427XhDA_YZXbFMpS-4fy1HrkLKRCG7DIqRrYjWT-5-FDk-VBN2Wuq8dkOGKTziVESOtmTIjUhurkZYgI_dkaZTCvCMia3Xzc17cxs3psIcxrjpR4gzVSzCFAd-uOnW3cDlBMQcja4OqlwW42Rv6ohW4vI0dgIQcw.uIVt_1NCh3mZeIWqciAyRcDseL5b_B8T0qlFDO6n9nY&dib_tag=se&keywords=Bench%2Bpower%2Bsupply&qid=1734917889&sprefix=bench%2Bpower%2Bsupply%2Caps%2C191&sr=8-3&th=1

 

[yachtdr22]

I am going to put a load on the battery tomorrow. it seems that there is no activity on that cell

 

[Skypower]

I am going to put a load on the battery tomorrow. it seems that there is no activity on that cell

That cell(s) are probably way behind the others. Put the lowest charge rate on the battery, like 5 amps from your main charger and use a bench top power supply to give an assist to the low cell. I like to mark a red + on all the positive terminals to avoid any confusion at a glance. DO NOT clip the bench top on and walk away. This is a touch and hold down, manual operation only because once it begins to move it happens fast. If things are moving well you could move the main charge current up from 5 but watch for runners. I have also used 250 foot spool of #10 as resistor to bring down a stubborn running cell, again this is a manual operation.
I like to bring the problem cell into the average before releasing and will most likely have to repeat it numerous times before it wants to behave. It’s like bop a mole. I would suggest that you set the bulk voltage to 55.2 volts instead of 56 to give the bms more room to work on a runner.

 

[Skypower]

I am going to put a load on the battery tomorrow. it seems that there is no activity on that cell

Loading isn’t going tell you much except the low cell is going to drop. Doesn’t necessarily mean bad.

 

[yachtdr22]

I want to thank you all for the help and support. There is nothing wrong with the battery except a lagging cell. I would assume this cell has a little more internal resistance then the rest.
I think this whole thing was an exercise to get me to finally replace the mix-matched batteries in my bank. I have sold these and ordered a 6 pack of EG4's