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Parallel connected inverters communication to battery bank


divanvanderwatt
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Hi everyone

I am very new to this forum as well as solar installations.

I just had an installation done at home with two inverters in parallel (KODAK Solar Off-Grid Inverter MAX 7.2kW 48V) with four 2.4KW PlyonTech Batteries.

I have a question regarding the communication to the batteries, only one inverter has a comms cable (RJ45) that goes to the batteries.   The result is that one inverter knows the exact capacity of the batteries at a certain time, say 97% fully charged while the other inverter thinks the batteries are only 23% charged for example.

Can both inverters be connected to communicate to the batteries and if so, how?

Attached are some pictures showing the batteries fully charged, with one inverter showing almost full and the other only has one bar.

 

PHOTO-2021-01-21-09-07-54.jpg

PHOTO-2021-01-21-09-07-53.jpg

PHOTO-2021-01-21-09-07-38.jpg

PHOTO-2021-01-21-09-07-30.jpg

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This was a firmware issue on the Kings and VM IIIs. It's disappointing to see this being delivered in a relatively new model.

What firmware versions are you running? Main DSP and removable display.

You can't connect the BMS to the other inverter, and there should be no need, as they communicate with each other over a CAN bus (the grey paralleling cables).

Edited by Coulomb
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  • 3 weeks later...

Thanks!  Sorry for the late reply, where can I see the firmware for the removable display?

The installer came and connected 2x Plyontech batteries to the one inverter and the other 2x Plyontech batteries to the other inverter, so both have communications now while still functioning as one battery bank.  Not sure how it works but batteries work fine now 🙂

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8 hours ago, divanvanderwatt said:

The installer came and connected 2x Plyontech batteries to the one inverter and the other 2x Plyontech batteries to the other inverter, so both have communications now while still functioning as one battery bank. 

Not all installers know their craft. Voltronic explicitly warns against using separate batteries for paralleled inverters. I don't know the reason, possibly to make the firmware easier to manage, but I think it's a bad idea. Sorry.

Maybe they're actually still paralleled, since you say "while still functioning as one battery bank". 

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41 minutes ago, Coulomb said:

Not all installers know their craft. Voltronic explicitly warns against using separate batteries for paralleled inverters. I don't know the reason, possibly to make the firmware easier to manage, but I think it's a bad idea. Sorry.

Maybe they're actually still paralleled, since you say "while still functioning as one battery bank". 

I believe they are paralleled still, however not being an expert at all, I can’t be a 100% sure. 

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1 hour ago, divanvanderwatt said:

I believe they are paralleled still, however not being an expert at all, I can’t be a 100% sure. 

Yep! Still parallel but two separate pairs of parallel batteries. i.e two parallel battery banks with one bank connected to Inverter #1 and the second bank connected to inverter #2. Shouldn't you have one battery bank, four batteries connected in parallel making one bank, instead of two banks of two parallel batteries? the two inverters should be able to see that you have four batteries and in your case it looks like each inverter sees only two batteries. And looking at the dip switches of your batteries, looks like they are all in the similar positions. The master battery needs to have different settings of the dip switches from the slave batteries. One battery should be a master while the other three should be slaves. same applies if you are going to have multiple banks.  I might be wrong, Not sure how it works with KODAK. Looks like the installer just hid the problem by taking the short cut, problem is still there 🙈

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7 hours ago, hoohloc said:

Still parallel but two separate pairs of parallel batteries. i.e two parallel battery banks with one bank connected to Inverter #1 and the second bank connected to inverter #2.

IF that's the case (i.e. there is no connection between the batteries of the two inverters) then that's not right.

6 hours ago, divanvanderwatt said:

Eish, any advice/suggestions how to fix it?

There should be a spare positive and a spare negative terminal on each battery pair. Connect the spare positive to the other spare positive with another set of cables; same with the negative obviously. If you're not confident, try and get someone to do this for you. Maybe even your present installer will do it, even if "just to humour the customer".

It's not ideal, but it should work and prevent problems in the future. I believe that the master will look for battery voltage differences with the slave, and stop with a fault code if it detects a problem. Also, without the battery pairs being paralleled, the charging algorithm will be confused, and one of the battery pairs will likely not get fully charged, or at minimum, at times there will be spare PV capacity that goes wasted.

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