Connecting different batteries to inverters configured in parallel

mnakkach

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I am planning to configure 3 inverters in parallel, can I connect different batteries to every inverter separately or all DC should be on 1 line and 1 battery system?

I am asking this because i have different sets of batteries, all lithium but different brands and amps.

Thanks
 

timselectric

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Check manufacturers instructions.
Generally, all parallel inverters must be connected to a single battery bank. And the battery cables need to be the same length to each.
 

OffGridInTheCity

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If you have different sets of batteries - it may not be advised to parallel them! I agree with @timselectric that 'normally' most of us have 1 larger battery bank and do multiple loads of the one battery bank. Obviously, having 1 bank means you only have to charge 1 battery.

Can you re-arrange, match capacities, add proper BMS etc and create 1 battery bank?

You could have 3 separate smaller battery banks and charge each one separately - but sound complicated.
 

timselectric

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If the inverters are using parallel communication cabling. They usually have to be connected to the same battery bank. Or, the system will error.
 

mnakkach

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Thanks for the information, this is clear. I understand in parallel inverters AC output will be merged, Batteries out (supply) and in (charging) will be merged, but PV will be independent by inverter? can't be merged i guess?
 

OffGridInTheCity

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Thanks for the information, this is clear. I understand in parallel inverters AC output will be merged, Batteries out (supply) and in (charging) will be merged, but PV will be independent by inverter? can't be merged i guess?
I don't understand these comments - and for the sake of getting you useful info....

Could you share details?
What hardware do you have - is it all-in-one MPP or GroWatt units? Or do you have individual components?
What is your battery situation?
 

mnakkach

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I don't understand these comments - and for the sake of getting you useful info....

Could you share details?
What hardware do you have - is it all-in-one MPP or GroWatt units? Or do you have individual components?
What is your battery situation?
Planning to get Voltronic Infinisolar V IV inverter, it is a hybrid on grid off grid inverter. will configure 3 in parallel.

I was checking if i can have different sets of batteries connected to every inverter separately but i got the answers from the above gentlemen it won't be possible. It sounds like expanding the batteries in the future won't be practical since i will be having different battery brands and the age of batteries won't be the same. Best will be to configure and buy the maximum batteries requirements from the start.

Thanks
 

SolarMaxIt

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Planning to get Voltronic Infinisolar V IV inverter, it is a hybrid on grid off grid inverter. will configure 3 in parallel.

I was checking if i can have different sets of batteries connected to every inverter separately but i got the answers from the above gentlemen it won't be possible. It sounds like expanding the batteries in the future won't be practical since i will be having different battery brands and the age of batteries won't be the same. Best will be to configure and buy the maximum batteries requirements from the start.

Thanks
I understand if your using LIFEPO4 then its easier to add additional battery banks in parrallel in the future, because the charge curve is so flat(not much voltage change over the charging) that when you connect of disconnect different banks in parrellel they don't create a big draw (balancing from higher charged batter to less charged) i.e re-balancing like LEAD acid of similar create.
 

OffGridInTheCity

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I understand if your using LIFEPO4 then its easier to add additional battery banks in parrallel in the future, because the charge curve is so flat(not much voltage change over the charging) that when you connect of disconnect different banks in parrellel they don't create a big draw (balancing from higher charged batter to less charged) i.e re-balancing like LEAD acid of similar create.
I'm lithium-ion rather than LifePo4 - but in general I wouldn't do what you suggest because even if the voltage is similar the SoC is not, and you want parallel batteries to act together. For LifePo4, with cells of similar specs - one technique (I read often) is to charge each battery up to 100% SoC and then parallel them. At that point they'll be top balanced and the overall battery bank will have a better chance of operating well.
 

vguroma

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quite a strange requirement of 15 kW of power on a single phase. there must be a sufficient wiring in the house. 66A for 230VAC requires AWG 7 or 10mm2 - quite thick and expensive wire. Maybe it is better to group users according to the consumption and allocate each group with appropriate battery capacity?
 

SolarMaxIt

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I'm lithium-ion rather than LifePo4 - but in general I wouldn't do what you suggest because even if the voltage is similar the SoC is not, and you want parallel batteries to act together. For LifePo4, with cells of similar specs - one technique (I read often) is to charge each battery up to 100% SoC and then parallel them. At that point they'll be top balanced and the overall battery bank will have a better chance of operating well.
Yep I assumed that all cells 16 for my 48V system which comprise a bank of batteries would be top balanced in parallel before being put into service, and of course a bms used. I didn't mean that different cells in a bank would be added or removed, but only a whole bank. And I didn't mean that this is the norm to do, but just a valid upgrade to add more capacity to a larger battery bank. I think this is what people do when buy rack mounted pylon etc batteries ?
 

chess-equality

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What are the benefits of paralleling inverters? I've known it will produce 220v from 110v, but what are the other benefits?
 

burgerking

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If I have multiple Inverters in parallel, this implies I need a lot of DC/battery amperage. And if I have multiple batteries in parallel, this implies each battery BMS will be handling fraction of that amperage which is nice.

Assume BMS are configured to limit 150A each.
Assume at night all inverters combined were drawing 300A from the battery bank.
One by one the batteries fell below undervoltage thresholds and starts disconnecting. Last battery will experience full 300A load will disconnect overcurrent threshold.

I have seen Andy torture tested a JK bms with 200A load and after a preset duration it cuts off but one of the transistors popped. I guess the transistors did not shut off perfectly at the same time so much so one of them took the full blunt of the 200A alone and died.

Having said that, is it more dangerous for the BMS to have parallel batteries to parallel inverters?
 
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timselectric

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If I have multiple Inverters in parallel, this implies I need a lot of DC/battery amperage. And if I have multiple batteries in parallel, this implies each battery BMS will be handling fraction of that amperage which is nice.

Assume BMS are configured to limit 150A each.
Assume at night all inverters combined were drawing 300A from the battery bank.
One by one the batteries fell below undervoltage thresholds and starts disconnecting. Last battery will experience full 300A load will disconnect overcurrent threshold.

I have seen Andy torture tested a JK bms with 200A load and after a preset duration it cuts off but one of the transistors popped. I guess the transistors did not shut off perfectly at the same time so much so one of them took the full blunt of the 200A alone and died.

Having said that, is it more dangerous for the BMS to have parallel batteries to parallel inverters?
Andy's mishap was believed to be a fluke. Haven't heard of anyone else having that happen. And even that BMS continues to work, without the one FET.
Parallel batteries with Parallel inverters is a standard installation. It's has proven to be reliable.
 
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