Multi Unit Xantex XW, sperate battery banks

Les Nagy
Les Nagy Solar Expert Posts: 121 ✭✭
in Off Grid Solar & Battery Systems #1
I am trying to set up two XW inverters in multi-unit configuration but with separate battery banks for each inverter. Where I am in Chile we are running some semi-critical systems from solar only with generator backup. So the idea is to have two different XWs supplying our internal grid with the redundancy and so we are able to do maintenance on one system without dropping power.

Simply paralleling the inverters in 1 phase multiconfig only has the extra (slave) inverter kicking in when the power draw exceeds the capacity of the master. Also, one cannot shut down the master system without killing the slave system too.

I have a few ideas.
One is to cross connect the inverters (with breakers of course) so that each feeds the others AC1 input and each of their outputs to the internal grid. Then set each to load shave and only have one online with the other feeding the AC1 input. This way I could set a comfortable discharge rate on the load shave for one bank and the inverter online would then supplement the power to make up the other half of the usage. Then every two weeks (for example) I could switch them so they would trade places and balance the usage of the battery banks. This way too, if one system failed, the other would be still supplying power. I am sure I am missing a detail or two here.

The second idea is to have both inverters online at the same time in AC sync mode. I have no idea what would happen but could only hope that they would share the load and not get into some kind of weird oscillation with one trying to feed the other and killing the batteries. I am sure this would be a most unstable and unworkable solution.

The third idea is to configure it with the special configuration software as described in the XW inverter documentation:
"Although the XW Power System does support multiple XW Inverter/Chargers connected to multiple battery banks, such configurations cannot be set using the System Control Panel. A special configuration application provided by Xantrex is required."
Does anybody here have experience with this?

Any other ideas?
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Comments

  • Les Nagy
    Les Nagy Solar Expert Posts: 121 ✭✭
    #2
    Re: Multi Unit Xantex XW, sperate battery banks

    I received a reply from Schneider(Xantrex).

    There is no need for special software to combine two inverters with two separate battery banks, contrary to the instruction document supplied with the inverter. Just set each to use its own named battery bank and it is done. (Edit: Actually that should be the same battery bank name even if they are connected to separate banks)

    If the slave is set to search, then the master will carry all the load up to 60% of the total capacity of the inverter's capacity and then switch on the slave unit. If the slave is not set for SEARCH, then they will share the load equally.
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  • Les Nagy
    Les Nagy Solar Expert Posts: 121 ✭✭
    #3
    Re: Multi Unit Xantex XW, sperate battery banks

    Well I finally got the system connected and configured, and it does not work as the tech at Schneider said it would. If I set the second inverter to use anything other than the same battery bank name (or any other connection name), I get a F.66 which means configuration error. If I set both of the inverters to all the same connections, they sync up and start inverting, except....

    With the 6048 as a 1 Phase Master and the 4548 as the 1 Phase Slave AND the other way around too, the 4548 starts dumping power through the 6048 into its batteries. So there is definitely something not working the way the tech said it should.

    I am hoping someone here (Solar Guppy?) can shed some light on how to make this work.
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  • Les Nagy
    Les Nagy Solar Expert Posts: 121 ✭✭
    #4
    Re: Multi Unit Xantex XW, sperate battery banks

    It now works, thanks to some missing details from the techs at Schneider.

    When hooking two inverters in parallel but with separate battery banks, the output voltages of the two inverters must be finely tuned so that they "see" the same voltage. It is not merely a matter of setting the voltages in XW Config to the same value as the XW inverters do not have very accurate outputs according to the setting. I had to set one inverter to 218V and the other to 224 volts for them to be in balance. Otherwise, the one that is in reality higher in output voltage will push its power into the other's battery bank through AC coupling.

    The best way to set this IMHO at this point is with XW Caltool which allows much finer control over the output values and a better balance.

    I hope this experience can help someone else set things up more quickly.
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