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multiple battery banks / one hub

Posted: Mon Mar 01, 2021 5:50 pm
by Fritz
Old system, ancient but workable bank0, misc. panels & micro hydro,
New system, new bank1, misc. panels on 4 mx + hub10 + mate2 (+fx)

At times bank0 is struggling and I am wanting to divert the output of one of the mx controllers from bank1.
Will the COMM system object?
one mx being powered from different battery bank?
will it blow the hub?
(disconnect the COMM before switching?)
I don't care if the summary data for bank1 is wrong for the duration but are there electrical gotchas?
Thanks
Fritz

Re: multiple battery banks / one hub

Posted: Mon Mar 01, 2021 8:20 pm
by raysun
In general it would be ill-advised to swap battery banks in a system of sufficient complexity to require a communications hub.

The solar charge controllers are MX series? The charge controllers operate autonomously, so its possible the controller could be safely disconnected from the PV array, then disconnected from the main battery at its Bat +/- terminals, then connected to the old battery and PV reconnected . If the two batteries are of the same chemistry, structure and voltage, then the charger might not need reprogramming. The controller being used to charge the old battery can also be unplugged from the hub to eliminate any possible interaction.

NEVER make any connections that combine the battery banks in any way.

Re: multiple battery banks / one hub

Posted: Tue Mar 02, 2021 10:00 am
by Fritz
complexity?!
(digression:) I bought a new battery cause the old ones' capacity wouldn't pull my lifestyle anymore. It edall the AC loads.
But there is enough capacity in the old battery to pull the dedicated DC wired loads, SunFrost and some emergency lights. (/digression)
Yes the controller in question is an MX. I have disconnected it from battery A and then connected to battery B with impunity (without PV disconnecting) but that was without any COM at all. Now that the MX is on the COM network i just want to make sure the two battery banks won't try to send hundreds of Amps through the hub ;-)

Re: multiple battery banks / one hub

Posted: Tue Mar 02, 2021 10:21 am
by raysun
Fritz wrote: Tue Mar 02, 2021 10:00 am complexity?!
(digression:) I bought a new battery cause the old ones' capacity wouldn't pull my lifestyle anymore. It edall the AC loads.
But there is enough capacity in the old battery to pull the dedicated DC wired loads, SunFrost and some emergency lights. (/digression)
Yes the controller in question is an MX. I have disconnected it from battery A and then connected to battery B with impunity (without PV disconnecting) but that was without any COM at all. Now that the MX is on the COM network i just want to make sure the two battery banks won't try to send hundreds of Amps through the hub ;-)
The Hub is a communications device. It doesn't carry primary battery current.

Disconnecting the MX from the battery without disconnecting from PV first can cause damage to the unit. Obviously not in all circumstances, but the risk is definitely there.

Re: multiple battery banks / one hub

Posted: Tue Mar 02, 2021 11:49 am
by Fritz
actually I was worried more about COMM pileup or worse because of ground level mismatch.
Thank you kindly

Re: multiple battery banks / one hub

Posted: Tue Mar 02, 2021 2:50 pm
by raysun
Fritz wrote: Tue Mar 02, 2021 11:49 am actually I was worried more about COMM pileup or worse because of ground level mismatch.
Thank you kindly
The easiest way to avoid that is simply unplug the MX from the hub when connected to the old battery.

Re: multiple battery banks / one hub

Posted: Tue Mar 02, 2021 4:54 pm
by Fritz
Indeed. Thank you. I apologize for being a smartass.

Re: multiple battery banks / one hub

Posted: Tue Mar 02, 2021 5:47 pm
by raysun
It takes one to know one.

YW.