Connecting several hybrid inverters to one battery - Manufacturers position

[RealNail]

I'm planning to install several hybrid inverters and connect them to one battery. Each inverter has its own solar array and own AC load. The purpose of the battery is to store excess energy and therefore to share the solar power between inverters (consumers). I've read all discussions here and they all generally support connecting two inverters to one battery. However, the solar systems installers here in the UK refuse to install in such way. They refer to the manufacturers (Sunsynk and Growatt) that do not allow such installation. I need you help to find answers to the following questions:
- Is there any inverters/battery manufacturer that supports connecting several inverters to one battery?
- How can I properly connect the communication cable to BMS? Connecting to one of the inverters? Or through a bus bar?

 

[zanydroid]

Won't you easily exceed just the max discharge current of one battery, with multiple inverters of average modern kW-AC rating?

5kWh server rack - 100A discharge - 5kW-AC best case. 5kW-AC inverter is pretty modest by today's standards. So you have a fundamental physics/electrical engineering problem here.

Internationally - there are plenty of inverters with native stacking (just search for this keyword), in that case they will load share on AC side and all communicate BMS if that's needed locally. I'd start with one of the ones known to work, and then find the local name of that identical inverter.

The instructions should be covered in the wiring guide.

All that said, at least here in the US advanced installations for residential require some better installers. If you go for the bottom rate installer they might not know, or be willing to learn.

 

[kommando]

You will release lots of smoke if you connect a comms cable to a busbar.

 

[zanydroid]

You will release lots of smoke if you connect a comms cable to a busbar.

I assumed they meant comms hub. A Data bus.

 

[SeaGal]

I'm planning to install several hybrid inverters and connect them to one battery. Each inverter has its own solar array and own AC load. The purpose of the battery is to store excess energy and therefore to share the solar power between inverters (consumers). I've read all discussions here and they all generally support connecting two inverters to one battery. However, the solar systems installers here in the UK refuse to install in such way. They refer to the manufacturers (Sunsynk and Growatt) that do not allow such installation. I need you help to find answers to the following questions:
- Is there any inverters/battery manufacturer that supports connecting several inverters to one battery?
- How can I properly connect the communication cable to BMS? Connecting to one of the inverters? Or through a bus bar?

I have Solis that doesn't support such parallel operation. The issues will be whether the battery side is isolated or not (the Solis isn't) and whether the inverter supports daisy-chaining of comms between inverters.

In the UK, it would appear that Sunsynk / Deye (=SolArk in USA) do support multiple inverters with one battery, with the caveats that Keith in his tidy office explains in this video...

 

[zanydroid]

In the UK, it would appear that Sunsynk / Deye (=SolArk in USA) do support multiple inverters with one battery, with the caveats that Keith in his tidy office explains in this video...

Thanks for sharing.

TBH none of that is counterintuitive with enough baseline experience with household electrical ( I guess except for the part that the inverter can't handle suddenly getting too much load because the breakers weren't ganged together, I would expect that to need to be handled if a inverter in a stack fails, because effectively the remaining N-1 inverters have to not die in that case).

 

[timselectric]

Connecting multiple loads (inverters) to a source (battery) is not a problem. As long as the source can handle the loads.
Since your inverters are completely separate from each other. All that they are, is a load on your battery.

 

[zanydroid]

Connecting multiple loads (inverters) to a source (battery) is not a problem. As long as the source can handle the loads.
Since your inverters are completely separate from each other. All that they are, is a load on your battery.

I believe this assumes open loop. If they all are closed loop (for whatever reason, maybe the inverters work better that way or there's a local regulation requiring it ?) then I don't think it's this easy.

 

[SeaGal]

Connecting multiple loads (inverters) to a source (battery) is not a problem. As long as the source can handle the loads.
Since your inverters are completely separate from each other. All that they are, is a load on your battery.

Does that not depend on the isolation of the inverter? My Solis is not isolated and the battery negative runs at half the internal DC bus which, with around 380V PV input, put it at -190V to ground - don't ask me how I know

 

[timselectric]

I believe this assumes open loop. If they all are closed loop (for whatever reason, maybe the inverters work better that way or there's a local regulation requiring it ?) then I don't think it's this easy.

Yes, open loop. Or closed loop with only one of them.

 

[timselectric]

Does that not depend on the isolation of the inverter?

It shouldn't matter. As far as the battery is concerned, they are just loads.

My Solis is not isolated and the battery negative runs at half the internal DC bus which, with around 380V PV input, put it at -190V to ground - don't ask me how I know

That's definitely odd. but I would expect that to only be measured potential. And not able to carry any current. (Unless a fault occurs)
Even then, I don't see any problem with it. As long as everything is connected to one grounding system. (As it always should be)

 

[zanydroid]

That's definitely odd. but I would expect that to only be measured potential. And not able to carry any current. (Unless a fault occurs)
Even then, I don't see any problem with it. As long as everything is connected to one grounding system. (As it always should be)

That does sound kind of weird to allow that level of voltage on the 48V side, because that would exceed the allowed voltage limit for the safety class (IIRC 100VDC in the U.S., above which everything hot needs to be a lot more shielded, which is definitely not how most people on the forum build their 48V setup)

There is the one HV AIO schematic that’s floating around the forum, wonder if that will happen in that design.

 

[timselectric]

High voltage battery systems are definitely a different animal.
Nothing said here applies to them.

 

[houseofancients]

Connecting multiple loads (inverters) to a source (battery) is not a problem. As long as the source can handle the loads.
Since your inverters are completely separate from each other. All that they are, is a load on your battery.

Connecting them to the same battery shouldn't matter I agree, but better not connect them to the same ac panel..

Magic smoke !

 

[Zwy]

I'm planning to install several hybrid inverters and connect them to one battery. Each inverter has its own solar array and own AC load. The purpose of the battery is to store excess energy and therefore to share the solar power between inverters (consumers). I've read all discussions here and they all generally support connecting two inverters to one battery. However, the solar systems installers here in the UK refuse to install in such way. They refer to the manufacturers (Sunsynk and Growatt) that do not allow such installation. I need you help to find answers to the following questions:
- Is there any inverters/battery manufacturer that supports connecting several inverters to one battery?

Doesn't make sense to me, you want a central busbar connected to the batteries to make it a bank and all inverters powered off that busbar. This allows all batteries to be balanced. If instead one inverter is on one leg and another inverter on another leg with each inverter having it's own battery without a common connection, the one leg will draw down it's battery more than the other simply due to loads will be different on each leg. The other problem is the unbalanced batteries will lead to not getting full capacity from all the batteries. The unbalance condition could cause a shutdown of one leg and thus the other inverters shut down while those batteries might still be at 50% or more SOC. There are other problems I could occurring, this just seems like uneducated installers to me.

I'd find different solar installers or do it yourself armed with a good education before starting.

- How can I properly connect the communication cable to BMS? Connecting to one of the inverters? Or through a bus bar?

I run without any communication between the BMS and inverters. I see it as an unnecessary "feature" that creates another failure point. I like to minimize failure points, keep it simple, keep it stupid, use the matter between your ears and when troubleshooting you have less complexity to wade thru to find a cause.

 

[Zwy]

Connecting them to the same battery shouldn't matter I agree, but better not connect them to the same ac panel..

Magic smoke !

I know OP is in the UK and thus EU wiring voltages. But as far as batteries, it should be a bank comprised of a central busbar where the batteries are connected with equal cable lengths on positive side and equal cable lengths on negative side to keep batteries balanced and loads powered equally off all batteries.

 

[SeaGal]

see my posting here about the isolation issue

isolation of battery to inverter comms

Pretty wild having a 48V battery biased to some -150 or -200V with respect to earth. Is it floating, just charged up? Would a high impedance pull it back to relatively safe voltages? Yes, it surprised me to see that voltage on the battery, as I often touch my battery bus bars when it's all...

diysolarforum.com

 

[timselectric]

Connecting them to the same battery shouldn't matter I agree, but better not connect them to the same ac panel..

Magic smoke !

Right
The OP stated that they are for completely separate systems.

 

[Zwy]

see my posting here about the isolation issue

isolation of battery to inverter comms

Pretty wild having a 48V battery biased to some -150 or -200V with respect to earth. Is it floating, just charged up? Would a high impedance pull it back to relatively safe voltages? Yes, it surprised me to see that voltage on the battery, as I often touch my battery bus bars when it's all...

diysolarforum.com

But it needs a path back to source in order for anything to occur. It's part of the reason the can bus adapter fired, you created a path where a path would not normally exist.

 

[Zwy]

Right
The OP stated that they are for completely separate systems.

I missed that part. Yes, then a separate battery for each system.