Parallel Deyes (=Sol-Ark) backfeeding each other through critical load connection?

[shadowmaker]

If I had only one inverter AC coupled and batt is 100%, where would it send the power then? I mean how is it different?

 

[timselectric]

If I had only one inverter AC coupled and batt is 100%, where would it send the power then? I mean how is it different?

If it can't put it in the batteries, or into the grid.
It must be able to control/ throttle it.
Frequency shifting is not always fast enough. Which is why it's recommended to have a relay that can disconnect it.
The generator port can do this. The loads output can't, without shutting down the loads. And that's probably not fast enough, either.

 

[shadowmaker]

If it can't put it in the batteries, or into the grid.
It must be able to control/ throttle it.
Frequency shifting is not always fast enough. Which is why it's recommended to have a relay that can disconnect it.
The generator port can do this. The loads output can't, without shutting down the loads. And that's probably not fast enough, either.

I know I'm little bit thick when it comes to electricity (and unfortunately so many other things too), but I don't see how my "parallel" setup is different from having only one Deye with AC coupling? I mean when grid goes down, my ATS should open (UPS)LOAD connection to my main panel 75m away within 20ms and simultaneously close GRID-port connection. My base consumption is ~2kW in summer and ~3kw in winter. If PV production is bigger at that moment, Deyes can shut down their own production immediately, only throttling down AC coupling is going to take some time (so I have been told before). If at that time Deye senses there's more power than consumption AND the batts are 100% (power has nowhere to go) it will open GEN-port relay and kill AC coupling no matter how many Deyes there are. After that Deyes will immediately start fulfilling consumption through (UPS)LOAD-ports with PV+Batts, like they do normally through GRID-ports (also my grid ports are connected parallel to feed my main panel 75m away). After few minutes AC coupled inverters will power on again and try to provide additional power if needed. If not Deyes will kill them again.

I mean if AC coupling is OK with one Deye and 100% batt, why would it be bad with two or more Deyes "parallel"? At least Litium batteries should be banned with AC coupling by Deye as lead batteries can always take more than 100% for a short period of time.

I can see the problem if GEN-port relay opening is not fast enough, but then it shouldn't matter how many Deyes there are. Even one could make the same damage.

 

[timselectric]

I know I'm little bit thick when it comes to electricity (and unfortunately so many other things too), but I don't see how my "parallel" setup is different from having only one Deye with AC coupling? I mean when grid goes down, my ATS should open (UPS)LOAD connection to my main panel 75m away within 20ms and simultaneously close utility connection. My base consumption is ~2kW in summer and ~3kw in winter. If PV production is bigger at that moment, Deyes can shut down their own production immediately, only throttling down AC coupling is going to take some time (so I have been told before). If at that time Deye senses there's more power than consumption AND the batts are 100% (power has nowhere to go) it will open GEN-port relay and kill AC coupling no matter how many Deyes there are. After that Deyes will immediately start fulfilling consumption through (UPS)LOAD-ports with PV+Batts, like they do normally through GRID-ports (also my grid ports are connected parallel to feed my main panel 75m away). After few minutes AC coupled inverters will power on again and try to provide additional power if needed. If not Deyes will kill them again.

I mean if AC coupling is OK with one Deye and 100% batt, why would it be bad with two or more Deyes "parallel"? At least Litium batteries should be banned with AC coupling by Deye as lead batteries can always take more than 100% for a short period of time.

I can see the problem if GEN-port relay opening is not fast enough, but then it shouldn't matter how many Deyes there are. Even one could make the same damage.

The problem is that your Deyes are not in full parallel (no communication).
They are just AC coupled together. So one can overpower the other. If it can't take control of it fast enough. And since the connection is through the loads port, they can't disconnect from each other. Without shutting down completely.

 

[shadowmaker]

The problem is that your Deyes are not in full parallel (no communication).
They are just AC coupled together. So one can overpower the other. If it can't take control of it fast enough. And since the connection is through the loads port, they can't disconnect from each other. Without shutting down completely.

Only time I see power backfeed through LOAD-port is when other Deye has 100% batt and the other hasn't. Now if utility goes down with my setup there's a way that both Deyes can use that "common" available battery capacity if needed to throttle down their AC coupling. Even the one with full battery can this way use the other ones battery to put excess power somewhere at least in theory. If both batteries are full or both batteries aren't full I haven't seen any power exchange so far between Deyes through LOAD-port. It doesn't mean it couldn't happen though in an event when both batteries are full and AC coupling need to be throttled. I see your concern, but even with "actual" paralleling the same problem remains: More power than can be consumed or put to battery, those LOAD-ports are connected to each other exactly like mine (if it's a whole house backup system like mine). And if there's no safety features on those LOAD-ports the same can/will happen. This is why I expect there to be some safety features.

Also there has to be some sort of relay in LOAD-port too as I'm somewhat sure I can de-energize LOAD-port completely by adjusting UPS reaction time. With 0s reaction LOAD-port is always energized, but if adjusted higher, LOAD-port gets de-energized when in normal mode. I just don't remember where this UPS reaction time could be adjusted, but I think I've had a conversation about it with my friend long time ago. Or I just can remember it wrong...

 

[timselectric]

Hopefully you never get into the situation where both batteries are full, and the grid drops out.
That's when everything can go bad.

 

[shadowmaker]

Hopefully you never get into the situation where both batteries are full, and the grid drops out.
That's when everything can go bad.

That will most certainly happen at some point soon as after getting "weather proof electricity" from my PoCo number of blackouts in a year has at least tripled (5 ->15). Only improvement is that they only last for 10sec to15min usually instead of 2-4 hours previously.

 

[timselectric]

A good safety option is to set charging to only 90%.
That way, there's always a cushion.
Keeping in mind, this is not the best thing for the batteries.
There's always a trade off, it seems.

 

[shadowmaker]

A good safety option is to set charging to only 90%.
That way, there's always a cushion.
Keeping in mind, this is not the best thing for the batteries.
There's always a trade off, it seems.

Thanks Tim for the heads up. I will get Deye engineers to have a look at my setup. ATM i'm just going to charge up to 100%, but disable UPS mode for now.

 

[BALCOSOLAR VN]

you should accept that Deye Cloud has not finished yet. I just move to Solarman Bussiness App. All of problem is gone

 

[shadowmaker]

They aren't designed to be connected this way. (Output to output) if battery is full,there is nowhere to send excess power. (Before frequency shifting can get control)
It would be safer to only parallel the inputs.
Or connect the second input to the first output. (In succession)

I have also ATSs between both Deyes and GT inverters (I can choose if GT inverters are AC coupled or if they just work parallel with Deyes and feed my loads/grid). Would you think it would be safe if I let ATS disconnect AC coupling when batteries are >95%, so it's impossible to have blackout when batteries are full with AC coupling enabled? I mean even AC coupling disabled by ATS, LOAD-ports are still connected to each other and batts can be still be 100% when blackout happens.

 

[timselectric]

Would you think it would be safe if I let ATS disconnect AC coupling when batteries are >95%, so it's impossible to have blackout when batteries are full with AC coupling enabled?

Safer, yes.
Completely safe, can't be sure.
Possibly, if the function never fails.