Connecting different batteries to inverters configured in parallel

[chess-equality]

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?

I will let the inverter or the breakers disconnect early rather than giving this decision to any of the BMSes, given that even at ideal conditions, BMSes can be quite finicky. I would rather deal with one or few (inverters / breakers) than many (battery BMSes) that you can't access quite easily.

And I would never max out what the specs say. I'm running two inverter systems (3kw and 3.5kw, respectively) as UPS, each for a 30A (220v) AC outlet, but I appropriate my load to use only half (1.5kw) max of each. Each also has a PDU-style power strip with a breaker and watt meter for monitoring.

Using only half may be quite a waste, but it's just me.

 

[DrZ123]

Can you have two identical systems, with different batteries and solar setup, different types of batteries, but hook up the inverters in split phase? Have the Victron Quattro 5000w

 

[timselectric]

Can you have two identical systems, with different batteries and solar setup, different types of batteries, but hook up the inverters in split phase? Have the Victron Quattro 5000w

No
If they are providing power together. They have to be connected to the same battery bank.

 

[Solar Guppy]

No
If they are providing power together. They have to be connected to the same battery bank.

This isn't correct, any non-isolated inverter / hybrid design requires that the battery connections are NOT connected in parallel as potential voltage differences are expected ( changes due to loads and typology used for battery voltage boost ).

Inverters that have galvanic isolation on the battery input might be ok, but refer to the manufactures manual for what is or is not allowed.

As an example the Solis HV hybrids ( S6 series ) require complete isolation between inverters, or plainly stated, independent batteries for each inverter.

 

[timselectric]

This isn't correct, any non-isolated inverter / hybrid design requires that the battery connections are NOT connected in parallel as potential voltage differences are expected ( changes due to loads and typology used for battery voltage boost ).

Inverters that have galvanic isolation on the battery input might be ok, but refer to the manufactures manual for what is or is not allowed.

As an example the Solis HV hybrids ( S6 series ) require complete isolation between inverters, or plainly stated, independent batteries for each inverter.

My response was to the question about two Victron Quattro's configured for split-phase.
And they definitely have to be connected to the same battery bank. In fact, I don't know of any brands that can stack two to create split-phase, and not be connected to the same battery bank.

 

[Solar Guppy]

There is no one size fits all. Many of the new generation of Hybrid inverters to improve efficiency make use of non-isolated buck/boost converters for the battery to HV rail internal to the inverters. This means the battery potential between inverters is not the same and magic smoke will happen if the battery is parallel. Most inverters already do this for the PV inputs, some do for battery as well, it is a more power efficient typology.

Here from the Solis S6 manual for example:

It is not an ideal requirement as the batteries and system state of charge would be difficult to determine as the loads or even the capacities could be different. WIth non-isolated inverters on the batteries, it is not possible to use a common battery.

 

[timselectric]

There is no one size fits all. Many of the new generation of Hybrid inverters to improve efficiency make use of non-isolated buck/boost converters for the battery to HV rail internal to the inverters. This means the battery potential between inverters is not the same and magic smoke will happen if the battery is parallel. Most inverters already do this for the PV inputs, some do for battery as well, it is a more power efficient typology.

Here from the Solis S6 manual for example:View attachment 162908

It is not an ideal requirement as the batteries and system state of charge would be difficult to determine as the loads or even the capacities could be different. WIth non-isolated inverters on the batteries, it is not possible to use a common battery.

Thanks, for the information.
But, that has nothing to do with stackable inverters.
You are referring to AC coupled inverters.

 

[Solar Guppy]

Thanks, for the information.
But, that has nothing to do with stackable inverters.
You are referring to AC coupled inverters.

I believe there is a misunderstanding of terminology here.

This is directly paralleled on the backup loads ( stacked ), there is no frequency shifting being used for throttling the second energy source to the backup loads. This is identical to isolated DC battery paralleled inverters, just separate battery banks with Canbus communications for sharing of the loads.

This typology is common for High Voltage Storage inverters is an overall higher energy conversion rate than stacked isolated architecture

 

[timselectric]

Ok, thanks.
But still has nothing to do with stacking two inverters to create split-phase.