DIY battery bank help please!

[dwhoover]

I am building battery bank consisting of 16 eve 3.2v cells in series 16S, back to back in 1 row in series configuration. No BMS. INITIAL VOLTAGE WAS 51.7V. I hooked it up to my 5000w eco-worthy solar inverter and 5 400w solar panels.

Next thing I know, the inverter stopped charging, saying the battery is full. I knew that was not possible because the initial voltage was 3.2 V on each battery And it had only been hooked up to the inverter for about 20 minutes... The battery was now reporting that it was 57.6v...

I then checked each cell and 11 were only 3.3 volts average...the other 6 were 4.4v. Ouch. I immediately disconnected the battery from the charger.

I then separated the batteries and put 2 cells in parallel with one of the cells being the overcharged cell. I successfully revived the other 6 cells back down to 3.3 volts. Yay!

For the life of me I can't figure out why just 6 of the cells got overcharged and the others did not!! Does anyone have an idea why that happened? I thought hooking it up directly to the cells with no BMS would be fine.... Famous last words

 

[MisterSandals]

No BMS.

You are the BMS. Hopefully you are attentive.

he other 6 were 4.4v. Ouch.

You're fired as a BMS. (and as a battery builder)

Does anyone have an idea why that happened?

How many Ah are the cells/battery?

Can you post a pic of your wiring?

2000W solar / 58V charging = 35A charging

What charge do you have and what are your charge settings?

I thought hooking it up directly to the cells with no BMS would be fine.... Famous last words

You are far from the first to try this. You did well to keep from destroying a bunch of cells.

 

[Nobodybusiness]

I am building battery bank consisting of 16 eve 3.2v cells in series 16S, back to back in 1 row in series configuration. No BMS. INITIAL VOLTAGE WAS 51.7V. I hooked it up to my 5000w eco-worthy solar inverter and 5 400w solar panels.

Next thing I know, the inverter stopped charging, saying the battery is full. I knew that was not possible because the initial voltage was 3.2 V on each battery And it had only been hooked up to the inverter for about 20 minutes... The battery was now reporting that it was 57.6v...

I then checked each cell and 11 were only 3.3 volts average...the other 6 were 4.4v. Ouch. I immediately disconnected the battery from the charger.

I then separated the batteries and put 2 cells in parallel with one of the cells being the overcharged cell. I successfully revived the other 6 cells back down to 3.3 volts. Yay!

For the life of me I can't figure out why just 6 of the cells got overcharged and the others did not!! Does anyone have an idea why that happened? I thought hooking it up directly to the cells with no BMS would be fine.... Famous last words

You need a BMS with balancing if you have them in a series configuration IE 48 volts.
Almost always going to have runners.

Make sure you connections are tight at busbars and sense leads.

What we normally do with new cells is put them in parallel charge them with a DC power supply to 3.60-3.65 VDC if LIFEPO4.
Called Top balancing.

Not sure if you damaged them or not but probably something I wouldn’t repeat.

 

[hwy17]

You must've had 6 cells significantly out of balance with the other 6.

If you really want to run no BMS I would use Will's bottom balance methods.

 

[Nobodybusiness]

You must've had 6 cells significantly out of balance with the other 6.

If you really want to run no BMS I would use Will's bottom balance methods.

I have seen Jehu do that but I’m just not that lucky.

 

[dwhoover]

You need a BMS with balancing if you have them in a series configuration IE 48 volts.
Almost always going to have runners.

Make sure you connections are tight at busbars and sense leads.

What we normally do with new cells is put them in parallel charge them with a DC power supply to 3.60-3.65 VDC if LIFEPO4.
Called Top balancing.

Not sure if you damaged them or not but probably something I wouldn’t repeat.

I had the charging set to a maximum of 20 amps... I had no idea that I could have "runners". I do plan to use JK BMS It will be here today and I will try this again... At least now I'll be able to monitor it easily in real-time. And I will keep it in front of me until they're done charging. Then I will let that new JK BMS do the top balancing. It has the 2a active balancing system.

 

[SparkyJJO]

Now you know why you need a BMS.

 

[time2roll]

If you insist on no BMS there is a bare minimum requirement to do a parallel top balance to 3.65 volts.
Good luck.

BTW, outcome was very predictable.

At least some time and money was saved by avoiding the BMS

 

[rhino]

Why were you thinking without a BMS would be fine? Did you read something somewhere saying that would be okay?

 

[Nobodybusiness]

I had the charging set to a maximum of 20 amps... I had no idea that I could have "runners". I do plan to use JK BMS It will be here today and I will try this again... At least now I'll be able to monitor it easily in real-time. And I will keep it in front of me until they're done charging. Then I will let that new JK BMS do the top balancing. It has the 2a active balancing system.

Each cell has a slightly different capacity and internal resistance.

How you place the charger cables also plays a role.

That is how one can charge or discharge faster than the other.

I just called him runners

 

[Suijkerbuijk]

Set them now in parallel in 3.3 volt and let them self balance them .
Make a big 3.3volt battery and leave it for a day.
And than see what all battery gone do