Storage for 2 grid tied inverters

Plan is to have two Sunsync inverters both grid tied, and battery storage. My question is can I have two different batteries, one on each of the inverters.

One of the inverters already has a 15.5 kWh battery and whilst I know I could add another battery to that to parallel them up, I have the opportunity to buy a large but different battery and so I’m wondering whether I can attach that to the second inverter. Sunsync say that the inverters have to be set up in a primary/secondary configuration so that one knows what the other one is doing, which makes sense, but will the addition of a second battery pack on the other inverter confuse the issue? It seems to me that it could be the one battery gets discharged in order to charge up the other one for example, which is not ideal . I’ve reached out to Sunsynk’s technical department in the UK but not had a reply yet so was hoping experts here might have some insight.

(I’ve asked this question in a slightly different way earlier but I’m not yet sure of the replies I’ve had there as the whether it will actually work or not so I’m focusing my question in the battery forum!)

Again, you question has already been answered multiple time on the forum.

If you parallel 2 sunsynk's ( or deye's or sol-ark's as the are the same thing), they need to be connected to the same common battery bank, using the same length of cables

This common busbar, common chemistry, size of indivial batteries may be different, but that is highly unrecommend

sorry, but I can't find the exact answer - maybe I;m looking in the wrong place. I get that the standard way is to connect them to the same common battery bank. But is it possible to connect each to their own battery instead? There must be people who've started with a lead-acid battery and then expanded their solar and batteries and so face the same question.

The info I've found on here is that the idea was is a larger common battery bank, but that's not my question.....

xcentric said:

sorry, but I can't find the exact answer - maybe I;m looking in the wrong place. I get that the standard way is to connect them to the same common battery bank. But is it possible to connect each to their own battery instead?

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No it is not, will cause damage

xcentric said:

There must be people who've started with a lead-acid battery and then expanded their solar and batteries and so face the same question.

The info I've found on here is that the idea was is a larger common battery bank, but that's not my question.....

Click to expand...

But the exact answer..
Common battery, or don't parallel

houseofancients said:

No it is not, will cause damage

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Ok - and not trying to be awkward, but are you able to explain why? Not doubting you, but would like to understand. Each inverter is synced to the grid, each can provide power to house or export to grid based on settings and available solar. If one inverter wants to charge the battery and there's available power (either timed from the grid or excess solar) then it can do. The only scenario I can see that be a problem is that one inverter wants to charge the battery and so there's a demand for power, and the other uses battery to provide it - but then that will balance out over time anyway. I'd just like to understand why it won't work ok.

xcentric said:

Ok - and not trying to be awkward, but are you able to explain why? Not doubting you, but would like to understand. Each inverter is synced to the grid, each can provide power to house or export to grid based on settings and available solar. If one inverter wants to charge the battery and there's available power (either timed from the grid or excess solar) then it can do. The only scenario I can see that be a problem is that one inverter wants to charge the battery and so there's a demand for power, and the other uses battery to provide it - but then that will balance out over time anyway. I'd just like to understand why it won't work ok.

Click to expand...

When paralleling the inverters do not sync to the grid, only the master does and passes that information on to the slave..
The do however both sync to eachother using the common battery.
Guess what happens if that fails

This video is about single phase inverters, but using 3 phase inverters don't make a difference

thanks, v useful!

Maybe this treat will get you the answers on not letting your LA go to waste :

thanks- it's not a LA one I have, but an eBay bargain I decided to bid on. New LiFePO4 10kWh for £800..... however it looks like I'll have to return it.....

Also found that I can't parallel a 5.5kW and an 8kW inverter, which is annoying. So have to decide whether it's 2x5.5 or 2x8 I need to get, and am possibly at the limit of their 20m comms range. Though on a wired connection, am not sure that's not just a number plucked from thin air.....

Ah, the joys of learning stuff