WHOA! That was weird, Need some help plz

[Sunnytheskoolie]

Hello,

I have been running a LiFePo4 48v 2p16s battery for the last two years and two days ago it dropped off a cliff. Now when I try to charge it back up it keeps on hitting the max voltage for my settings and stops charging. I have attached screenshots of everything I have, I lost my logs from my BMS so I can't show you before the drop happened but I installed a new SD card and now am recoding the logs again.

I was thinking of taking the battery apart and doing a top balance and then possibly doing a capacity test. But I have a couple of concerns.

1. What capacity tester would you use for such a large system? Can I just hook it up with my BMS to my system and read the capacity from the BMS?
2. Can I run my system without a battery just plugged into shore power? It's completely off-grid. I have a Victron Quattro, Victro Lynx distributor, Victron Cerbo, and 12v step-down converters Rec Q1 BMS with wifi module and precharge. Most of my system is run off the 120v. So can the Quattro run the system without the battery until I get the battery sorted out? I don't see why not since the whole system goes through the Lynx and if I have the Quattro plugged in it should feed the system's needs.
3. Can I break the battery down to a 16s and charge it most of the way to the top with the solar/shore power and then use one of these( https://www.amazon.com/Kungber-Adjustable-Switching-Regulated-Adjustments/dp/B08DJ1FDXV?th=1) with the cells in parallel to hit the top limit, do I need the BMS connected when it is in parallel(probably not)


In the images, you can see the BMS settings, and the Battery cell voltage log, you can see the battery was at 47% and then 3% 40 min later, and the cell voltage min max.


Thank you for your help and time

Edit, I did check all the battery connections and the cells don't look damaged. What about taking the cells out and changing the 2p cells around?

 

[Tomthumb62]

Have you checked all your connections?

 

[DIYrich]

Any reason Balance End Voltage is not the same as Max Allowed Cell Voltage? Active or Resistive balance?
Top balance would be good. Maybe you need to keep it at 57.0-57.6v for a day or two to give more time for the BMS to bring up the lower cells.

 

[Sunnytheskoolie]

Have you checked all your connections?

yes

 

[Sunnytheskoolie]

Any reason Balance End Voltage is not the same as Max Allowed Cell Voltage? Active or Resistive balance?
Top balance would be good. Maybe you need to keep it at 57.0-57.6v for a day or two to give more time for the BMS to bring up the lower cells.

No, I have never had them the exact same. The battery doesn't go that high. Should they be the same?

 

[rodrick]

You might consider making 2 16s batteries with a new bms and compare results

 

[LydMekk]

Sounds like your BMS has gone to the long sleep in the heavens ^^
Get another?

 

[DIYrich]

No, I have never had them the exact same. The battery doesn't go that high. Should they be the same?

The top cells are getting close to 5.58v (Balance End Voltage). If it means it stops balancing a cell above 5.58v, then cells above that won't be balanced. Don't know why there is that option.

 

[Sunnytheskoolie]

The top cells are getting close to 5.58v (Balance End Voltage). If it means it stops balancing a cell above 5.58v, then cells above that won't be balanced. Don't know why there is that option.

But they don't get up above that voltage. They stop there. I think the max is set so that it shuts down the system if it hits that level so that it doesn't overcharge.

 

[Sunnytheskoolie]

Sounds like your BMS has gone to the long sleep in the heavens ^^
Get another?

But why would the BMS be the issue when the batteries are what lost voltage and then won't charge up properly?

 

[DIYrich]

But they don't get up above that voltage. They stop there. I think the max is set so that it shuts down the system if it hits that level so that it doesn't overcharge.

Graph shows some cells getting to 3.588, which I belive is higher than 3.580.

 

[WindWizard]

Your cells are out of balance. Looking at your data one cell is 3.3 volts and one is 3.5 volts. They need top balancing. I have achieved this without breaking the pack apart and connecting them in parallel.

If this is a DIY lifepo4 16s pack, then I can offer a solution for you. If this is two purchased battery packs then you will need to get to the individual cells to balance them.

 

[Sunnytheskoolie]

Your cells are out of balance. Looking at your data one cell is 3.3 volts and one is 3.5 volts. They need top balancing. I have achieved this without breaking the pack apart and connecting them in parallel.

If this is a DIY lifepo4 16s pack, then I can offer a solution for you. If this is two purchased battery packs then you will need to get to the individual cells to balance them.

it's a DIY Lifepo4 pack. 2p16s, 32 cells. Tomorrow I am taking the battery apart, if I can't get another solution tonight. It's going to be hell to top balance them as I am off-grid and running on solar. haha good times are ahead. Please let me know your solution.

 

[Sunnytheskoolie]

Graph shows some cells getting to 3.588, which I belive is higher than 3.580.

Yes, that is true but then it gets balanced back down with the pack. If I set my max at the same as the end of the balance then I would have the issue as well but it would be above the max that the cell is rated for.

 

[WindWizard]

it's a DIY Lifepo4 pack. 2p16s, 32 cells. Tomorrow I am taking the battery apart, if I can't get another solution tonight. It's going to be hell to top balance them as I am off-grid and running on solar. haha good times are ahead. Please let me know your solution.

It is a rather simple easy solution. Purchase an Active Cell balancer and hook it up to your cells. Allow it to do the job of balancing your cells. The Active Cell balancer can be hooked up permanently if you turn it on around 54.2 volts. You only want the Cells to balance on the top end.

Amazon has a number of them.

https://www.amazon.com/Equalizer-Balancer-Transfer-Equalization-Capacitor/dp/B09W4H2VWD/ref=sr_1_13?crid=GTBP6AY1YG31&keywords=heltec%2B16s%2Bactive%2Bbalancer&qid=1693274710&sprefix=heltec%2B16s%2Bactive%2Bbalancer%2Caps%2C216&sr=8-13&ufe=app_do%3Aamzn1.fos.18ed3cb5-28d5-4975-8bc7-93deae8f9840&th=1

Make sure it is a 5 Amp Capacitive balance board. Basically it transfers the charge from the highest Cell to the lowest Cell.

Procedure:
Hook up the active cell balancer to the cells. Monitor the Cells with the BMS or a meter. Wait until the Cells are balanced within 10mv of each other. Disconnect the active cell balancer and then enjoy using your batteries again.

I use this approach on mine however I have my Victron Controllers programmed to turn on the Active Cell balancers automatically at 54.2 volts and then off again at 51 volts permanently hooked up so I dont have to diddle with the Cells.

 

[DIYrich]

Yes, that is true but then it gets balanced back down with the pack. If I set my max at the same as the end of the balance then I would have the issue as well but it would be above the max that the cell is rated for.

This is a pretty good description of how your system is supposed to work:
Post in thread 'Rec-BMS & Victron' https://diysolarforum.com/threads/rec-bms-victron.12758/post-142414

For some reason, your bottom cells do not charge. My guess is that you have a passive balance. Either the cells are bad, or the balancer is draining the cells and keeping them from charging.