Battery imbalance problems

[pda1]

My system is;

Panels- 2kW (2S-5P)
SCC- Victron 150/60
24v-100Ah (two Battleborn batteries in series)
Battery Balancer- Victron
Inverter- Multiplus 24/2000

Today, at around 12:30 PM,, various alarms went off indicating low voltage and battery imbalance.

Here's the battery imbalance screen shot;



Here's the "mid-point voltage alarm;



The Victron battery balancer activated and made an effort to bring the "Bottom battery" back into balance with the "Top battery". I called Battleborn, talked with their tech, and, as it was supposed to happened, the imbalance voltage difference was reduced to where the Battery balancer shut off. Notice the huge (to my thinking) voltage difference between the two batteries. At one point the Bottom battery was over 15v.

I have no idea what the "Mid-point voltage alarm" is about. I assume that reflects the BMV figuring there's a difference between the two batteries.

This is a screen shot of the batteries about two hours later;


Is what happened (a large imbalance at the batteries) a cause for concern....more than usual?

Thanks.

 

[sunshine_eggo]

Sounds like it's time to put them in parallel and charge/hold at 14.2V for a day or so.

 

[timselectric]

Or buy a correct 24v battery, for the 24v system.

 

[sunshine_eggo]

The Victron battery balancer activated and made an effort to bring the "Bottom battery" back into balance with the "Top battery".

Balancers are good for maintaining balance. Not so much for restoring it.

Batteries must be regularly fully charged to maintain internal cell balance.

I called Battleborn, talked with their tech, and, as it was supposed to happened, the imbalance voltage difference was reduced to where the Battery balancer shut off.

Notice the huge (to my thinking) voltage difference between the two batteries. At one point the Bottom battery was over 15v.

No it didn't. What you were measuring was the charger voltage minus the other battery's voltage. The battery you thought was at 15V was actually in charge protection mode and out of the circuit.

I have no idea what the "Mid-point voltage alarm" is about. I assume that reflects the BMV figuring there's a difference between the two batteries.

It's an alarm for when the voltage deviation between the two batteries is too large.

This is a screen shot of the batteries about two hours later;
View attachment 228993

Is what happened (a large imbalance at the batteries) a cause for concern....more than usual?

Yes.

 

[pda1]

Sounds like it's time to put them in parallel and charge/hold at 14.2V for a day or so.

Battleborn was suggesting that idea but they say to just charge each battery, using the Victron IP65 charger (which I used to use to balance the batteries once per month) according to the charging profile on the IP65.

Maybe it'll be necessary but here's a screenshot of the batteries voltage;



That's pretty close. We've got another 2 hours of sunlight so we'll see how things go tomorrow.

Thanks for the ideas.

 

[pda1]

Or buy a correct 24v battery, for the 24v system.

I paid $1,500 for those two batteries! They darn well better be the right ones! Now that I look back on it, a single 24v BB would've been better but I like being about to, if need be, tap 12v off one of the batteries.

 

[sunshine_eggo]

I paid $1,500 for those two batteries! They darn well better be the right ones! Now that I look back on it, a single 24v BB would've been better

This is what Tim was saying. Better to get a 24V than two 12s. Far more likely to experience issues with 2S 12V.

but I like being about to, if need be, tap 12v off one of the batteries.

for the love of all that is holy NEVER DO THIS UNLESS IT'S A MATTER OF LIFE AND DEATH AND NOT DOING SO WOULD RESULT IN YOUR DEATH. If you're not going to die, don't do this.

If you're doing this, then that's what's wrong. Stop doing this. You can't do it. Get a 24V-12V converter and do it right.

 

[pda1]

This is what Tim was saying. Better to get a 24V than two 12s. Far more likely to experience issues with 2S 12V.




for the love of all that is holy NEVER DO THIS UNLESS IT'S A MATTER OF LIFE AND DEATH AND NOT DOING SO WOULD RESULT IN YOUR DEATH. If you're not going to die, don't do this.

If you're doing this, then that's what's wrong. Stop doing this. You can't do it. Get a 24V-12V converter and do it right.

Uh oh

Now the truth comes out. Today, this morning, I put a 12v computer fan (3 watts) connected to one of the 12v batteries to cool the SCC.

Perhaps that caused the problem?

Ok....won't do it again....ever.

 

[timselectric]

Absolutely yes.

 

[pda1]

Absolutely yes.

Man, I'll never do that again.

Thanks fellas for the help.

 

[sunshine_eggo]

When you charge @ 24V, exactly the same amount of current flows through both 12V batteries. Period. Always. No exceptions.

When you draw off a single 12V, current only comes from that battery. The other 12V knows absolutely nothing about it.

The ONLY ways to bring them into balance is by 1) charging the 12V with exactly what you took out of it, OR 2) the balancers transferring charge from one to the other.

As I mentioned above, balancers are good for maintaining balance... not restoring it when you hose it...

 

[pda1]

When you charge @ 24V, exactly the same amount of current flows through both 12V batteries. Period. Always. No exceptions.

When you draw off a single 12V, current only comes from that battery. The other 12V knows absolutely nothing about it.

The ONLY ways to bring them into balance is by 1) charging the 12V with exactly what you took out of it, OR 2) the balancers transferring charge from one to the other.

As I mentioned above, balancers are good for maintaining balance... not restoring it when you hose it...

Thanks for the explanation.

' Hope I didn't wreck them.

 

[sunshine_eggo]

Thanks for the explanation.

' Hope I didn't wreck them.

Nope. You just unbalanced them. They still have their BMS protecting them.

I would put them in parallel and charge them to restore balance.

 

[Brett V]

Uh oh

Now the truth comes out. Today, this morning, I put a 12v computer fan (3 watts) connected to one of the 12v batteries to cool the SCC.

Perhaps that caused the problem?

Ok....won't do it again....ever.

 

[sunshine_eggo]

View attachment 229081

You'd award that to me the instant you saw the front of my house and my 6 Prii... then you look to the right and see a 2500HD with the 454 in it. It would give you serious second thoughts.

 

[pda1]

Nope. You just unbalanced them. They still have their BMS protecting them.

I would put them in parallel and charge them to restore balance.

View attachment 229081

Man card? Show me your legion!

 

[Brett V]

You'd award that to me the instant you saw the front of my house and my 6 Prii... then you look to the right and see a 2500HD with the 454 in it. It would give you serious second thoughts.

 

[Brett V]

All in good fun.

 

[pda1]

All in good fun.

Pity me- I used to own a Ford Excursion. I got really good at replacing the injectors. Man, I hated the car. It was the last Ford I'll ever own.