Two different inverters fed from same battery bank?

I currently have a single 6000xp running off of four lifepower batteries. I was thinking of adding a second inverter to help with running my two 2.5 ton AC's this summer, as I don't like pushing a HF inverter too hard with inductive loads. The obvious and simple solution is to add a second 6000xp but I was actually considering adding a LF inverter. SS has the Growatt 12kw LF inverter on sale and am considering to use that for the motor loads in my house. Is there any way they can share the four lifepower batteries? Since the Growatt can only accept 145 volts PV, and my current array is way over that I was thinking having the XP running all PV input to the batteries and the Growatt running the heavy loads, with only battery input going to the Growatt and PV only to the XP.

Currently, All the batteries are in a server rack connected to the bus bars and all communications are connected to the 6000xp. Maybe all the batteries can stay connected to the same bus, with both inverters connected to the same bus, but two batteries communicating with the XP and the other two batteries connected to the Growatt? Is that possible?

I would not do that.

Is this a grid tied system? If so, does can this new inverter "communicate" with the current to set phases and voltage? I don't think two different brands or even models of inverters from the same company can communicate.

If this is not grid tied, then the loads would need to be separated.

If the 6000XP is communicating with the battery bank and the XP is handling all charging functions then should work ok to connect the LF to the whole bank with no comms.

The bank will still see the loss of SOC and still report it to the XP. The XP and bank afaik do not do any kind of comparison of consumption that would lead them to get upset about the "missing" power.

As @chrisski says loads will need to be separated and you will need to be able to competently handle the neutral considerations. It's not complicated, but it might be some high effort wiring.

I would get a second 6000xp for simplicity.

If adding the Grow watt I would leave coms hooked to the 6000xp and not the grow watt. I was going to do this with a 3000ehv-48 and just tack on a Victron Phoenix.

Won't be a problem, as long as the AC is completely separate.
Leave everything as is, and just add the Growatt as a load to the batteries.

But, it would be better to just add a second 6kxp, for simplicity and redundancy.

Yes you can add more inverters to the same battery bank. The question of if you want to parallel them for a common AC output would require them to be capable of running this way. If only powering separate circuits than all that matters is your battery and your connections will be able to handle the power needs of the two devices.

You do not want battery communications with the inverter/AIO that is not handling charging tasks. Since you are not hooking it up to its own array it is simply a dumb device for taking DC and inverting it to AC.

chrisski said:

I would not do that.

Is this a grid tied system? If so, does can this new inverter "communicate" with the current to set phases and voltage? I don't think two different brands or even models of inverters from the same company can communicate.

If this is not grid tied, then the loads would need to be separated.

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The loads would be separated between the two different inverters. I have two reliance 10 circuit transfer switches. If I went the Growatt route instead of adding a second XP, I would run another set of AC output wires to the other transfer switch to keep the AC output separated between the XP and growatt

timselectric said:

But, it would be better to just add a second 6kxp, for simplicity and redundancy.

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I'm kind of leaning that way. Alot of guys have that set up and it seems bulletproof.

Do you think adding a second Xp in parallel would help solve the problem of light bulbs flickering during motor/compressor inrush?

Kent86 said:

I'm kind of leaning that way. Alot of guys have that set up and it seems bulletproof.

Do you think adding a second Xp in parallel would help solve the problem of light bulbs flickering during motor/compressor inrush?

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I assume it would help. Because the loads will be split across two.
But, it depends on what is causing the flickering.
If the flickering happens at low loading, it could actually make it worse.

So I still haven't pulled the trigger on anything but I'm considering adding a Schneider XW pro 6.8 to my system. I currently have an EG4 6000xp connected to four lifepower batteries. My plan is to add the XW pro as a load to the battery bank and the XW Pro to power all AC loads. All the solar will go into the 6000xp to charge the battery bank and the battery bank will only have comms with the 6000xp. So essentially the 6000xp will charge the batteries and have communication with the batteries while the XW Pro is connected to the same battery bank and powering the AC loads. The 6000xp will not be powering any AC loads, just being used as a solar charge controller and battery charger, as it will have utility power wired into it as well.

The reason I'm not considering using the Schneider MPPT 100/600 is first the price, and second the start up MPPT voltage is 195 and my west array is only about 160 volts, with no room for more panels (Canadian Solar 390's)

I ran this plan by Signature Solar tech support and they said that having a second inverter connected and pulling a load on the battery bank while another inverter is charging the same battery bank via solar or utility will cause an alarm status on the batteries. I'm not sure that's true because I've used another dedicated battery charger to charge the same bank while the 6000xp is charging/ discharging and no alarm occurred. Does this make sense?

Kent86 said:

I ran this plan by Signature Solar tech support and they said that having a second inverter connected and pulling a load on the battery bank while another inverter is charging the same battery bank via solar or utility will cause an alarm status on the batteries.

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I wouldn't think so. But maybe some weird things happen between them in comms.

timselectric said:

I wouldn't think so. But maybe some weird things happen between them in comms.

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Only the 6000xp is connected to the bank comms. The XW pro would only be connected to the battery bus bars, no comms to the XW pro

Kent86 said:

Only the 6000xp is connected to the bank comms. The XW pro would only be connected to the battery bus bars, no comms to the XW pro

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Yes, that was my understanding.
I don't know what information is passed between the 6kxp and the BMS.
Generally, it's just the BMS controlling the charging.
But, it's possible that more information is being added as time passes.
I haven't kept up with it, so I don't know how "advanced" it's getting.

Hypothetically
If the BMS commands a certain amount of charging current, and doesn't receive it, maybe it could throw an error.

You would not be able to connect two different inverters (RS485 Master) to the "Master Battery BMS" (RS485 Slave) as that would cause two master devices trying to talk to the Master BMS Slave which is not allowed.

If you split the battery to battery communication such that the top two batteries are connected via the short cat5 and the two bottom batteries are also connected to each other via the short cat5 thus creating two pairs of batteries with one battery in each pair set as "Master" (address 0) . The two pairs are not connected via a cat5 cable. The top pair talks to the 6000XP and the bottom pair talks to the new inverter. You would however need an EG4 Communications Hub if the new inverter is not an EG4 inverter as the LifePower4 BMS can only talk to an EG4 inverter. Just verify that you can set the correct protocol in the EG4 Communications Hub that is required by the new inverter (i.e. Pylontech for Hub and Inverter).

Each inverter is connected to all four batteries. Each inverter for charging purposes would act as separate SCC's. Each would also act as a load on all four batteries.

You would need to consider the situation where one inverter is charging the batteries and the other is drawing power from the batteries.

I don't know what would result if for example the 6000XP for whatever reason (lots of PV and little output load) is providing a large charge current/power charging the batteries whereas the new inverter needs to pull from the batteries due to low PV and large load, in essence the 6000XP is providing input power to the new inverter.

There are settings in the Master 6000XP when two 6000XP share the same battery bank. Only the Master 6000XP is connected to the Battery BMS and communicates battery status to the second 6000XP over the inverter to inverter parallel communications cable. You would not have this with a second inverter that is not an 6000XP.

The batteries are either idle (no charge or discharge) or they are charging or they are discharging. Can't be in two states. I don't know whether the inverters would fight each other (i.e. oscillations or hunting) as unlike multiple SCC (which only charge) the inverters are also loads on the battery.

marionw said:

You would not be able to connect two different inverters (RS485 Master) to the "Master Battery BMS" (RS485 Slave) as that would cause two master devices trying to talk to the Master BMS Slave which is not allowed.

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Comms is only going to be connected to the 6kxps.

marionw said:

You would need to consider the situation where one inverter is charging the batteries and the other is drawing power from the batteries.

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This is the plan.