Difference in displayed battery Voltage between 2 x Growatt SPF5000ES in parallel

[Pink]

On my 2 x Growatt SPF5000ES in parallel i see 0.6-0.8 Voltage difference for battery voltage. The 2 parallel batteries actual voltage is more or less equal to each other. Will this affect anything? Should i try calibrate this?


Pink

 

[sunshine_eggo]

That feels pretty significant, but it's about 1%.

How do the values compare to a separate meter with measurements taken at the battery connections on the inverter?

Does the discrepancy change when charging/discharging/no current?

 

[Pink]

That feels pretty significant, but it's about 1%.

How do the values compare to a separate meter with measurements taken at the battery connections on the inverter?

Does the discrepancy change when charging/discharging/no current?

Voltage on JK bms and with voltmeter is more or less identical between the two batteries. This example i just give was when charge. I will give a update in a few hours when charge completed.

Pink

 

[sunshine_eggo]

Voltage on JK bms and with voltmeter is more or less identical between the two batteries.

On battery terminals or inverter terminals where battery attaches?

This example i just give was when charge. I will give a update in a few hours when charge completed.

Pink

A change in the deviation when charging vs. discharging may indicate a loose/poor connection. If the voltage difference stays pretty static between charge and discharge, it's probably an error in measurement.

If that's the case, than the higher reading means the charger will hit the absorption voltage prematurely and reduce charge current prematurely thus adding some time to the charge.

 

[Pink]

On battery terminals or inverter terminals where battery attaches?



A change in the deviation when charging vs. discharging may indicate a loose/poor connection. If the voltage difference stays pretty static between charge and discharge, it's probably an error in measurement.

If that's the case, than the higher reading means the charger will hit the absorption voltage prematurely and reduce charge current prematurely thus adding some time to the charge.

I just had a temporary drop on the solar production and drop on the charge then i see battery voltage on the inverters was identical at that point when no or low charge current. Then when charge back on higher current I also measured the voltage on inverters connectors for battery and i was surprised to see a 0.5 v difference in the voltage. I thought it was just a difference in the display but its a actual difference.

Pink

 

[Pink]

I tested to restart the inverters in a way so i switched master and slave to see if anything change but look to be same difference and same issue.

Updated after more charge time.

Pink

 

[JWLV]

Is that a cracked screen on the second inverter? Was it used and you bought it like that? Maybe there’s something wrong with that unit besides just a cracked screen.

 

[timselectric]

It's not a problem.
If you look at the load % on each unit, you'll notice that it isn't equal.
Which means that they are not providing the same amount of charge current to the batteries. This will affect the measured voltage on the individual units.
My guess is that there are some differences in cable lengths, on either the DC or AC side. Affecting the balance of loads and charging.
This will only be a problem if you need the full output of the system. As it can be limited by the unit doing the most work.

 

[Pink]

Is that a cracked screen on the second inverter? Was it used and you bought it like that? Maybe there’s something wrong with that unit besides just a cracked screen.

There is no cracked screen..but i did noticed I had accidentally get some black line on the image. I did not notice when I posted it.

Pink

 

[Mattb4]

Voltage on JK bms and with voltmeter is more or less identical between the two batteries. This example i just give was when charge. I will give a update in a few hours when charge completed.

Pink

With 2 units your charging current may be slightly different (especially since there are separate solar arrays) leading to a difference in displayed battery voltage. I see this all the time on my 2 AIO's that feed different AC circuits but have a common battery.

 

[sunshine_eggo]

I just had a temporary drop on the solar production and drop on the charge then i see battery voltage on the inverters was identical at that point when no or low charge current. Then when charge back on higher current I also measured the voltage on inverters connectors for battery and i was surprised to see a 0.5 v difference in the voltage. I thought it was just a difference in the display but its a actual difference.

When current is 0, and they are both reporting the same, then there is no error between them.

Since you see a difference in operation, it's because of a difference in loads, charging and/or wiring resistance. It would be a good idea to double check torque of all connections between inverters and battery.

 

[Pink]

When current is 0, and they are both reporting the same, then there is no error between them.

Since you see a difference in operation, it's because of a difference in loads, charging and/or wiring resistance. It would be a good idea to double check torque of all connections between inverters and battery.

Thanks for very usefully info and help. I have some issues on loose connections and hot breaker/wires that I'm improving on now. I will update tread when done with more details.


Pink

 

[Pink]

When current is 0, and they are both reporting the same, then there is no error between them.

Since you see a difference in operation, it's because of a difference in loads, charging and/or wiring resistance. It would be a good idea to double check torque of all connections between inverters and battery.

Update:

Just completed first charge after correcting some connectors/wires/breakers etc who was loose hot etc. Heat is gone and difference on battery voltage now 95% of the time was within 0.1v and a few times tipped over to 0.2v. So that was a successfully fix.

Pink