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Old 20-07-2019, 13:17   #1
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Can multiple MPPT controllers all go to one bank?

Installing two 100W panels, each will have its own MPPT controller. Is it OK to connect them both to the same battery bank? Will they get confused and read the other's output as the battery voltage?

Right now I just have two house batteries set up "old school" as separate banks, with an additional start battery kind of on the sidelines. Going to add a 3rd house battery and make all 3 as a single bank with start as #2 bank. Would prefer to dump all the solar into the house and let the start be charged by alternator when needed.
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Old 20-07-2019, 13:38   #2
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Re: Can multiple MPPT controllers all go to one bank?

How else could you do it, of course they will read it as the banks voltage, cause it is, but it won’t matter cause they are looking for absorption voltage and won’t back off until that is reached.
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Old 20-07-2019, 14:46   #3
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Re: Can multiple MPPT controllers all go to one bank?

Yes. I have 6 of them going into my bank, one per solar panel
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Old 20-07-2019, 14:49   #4
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Re: Can multiple MPPT controllers all go to one bank?

There are solar controllers that can be wired up such that only one controls the charging and the others slave to it.
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Old 20-07-2019, 15:42   #5
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Re: Can multiple MPPT controllers all go to one bank?

But the increase in total Ah put into the bank per day is quite marginal.

To be honest even if all the currents paralleled into the bank come from wildly different charge sources, amps, voltage setpoints, in the end it really does. not. matter.

It is ideal if their charge profiles are similar, and of course none should be outside the bank mfg spec'd ranges. . .
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Old 20-07-2019, 19:19   #6
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Re: Can multiple MPPT controllers all go to one bank?

As long as the panels are in parallel, I‘m not seeing much advantage beyond redundancy to multiple controllers, although I do like in the event of a failure, you lose only the one panel.
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Old 20-07-2019, 19:38   #7
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Re: Can multiple MPPT controllers all go to one bank?

Each panel getting its own MPPT optimization is the key advantage to going to a 1:1 ratio. Going to parallel does not completely eliminate the disproportionate impact of partial shading of one panel on the system's total power output.

Victron's pricing often means there is little extra cost going that way, other than wiring and the mounting space consideration.

It isn't a huge improvement, and for many solar is a small input compared to others, but worth considering.

Certainly if panels are on one side or the other, splitting to two SCs altogether is a decent compromise.

And of course making do with what you have, mismatched panels etc, could be plenty of other reasons.

Question wasn't, should you, more like, if you want to, is it OK?
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Old 21-07-2019, 08:52   #8
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Re: Can multiple MPPT controllers all go to one bank?

It's OK, but the best solution is to have one be configured to float and the other not to float. CC-A would have a float voltage of 13.5, and CC-B have a float voltage of 12.6V (for example. That way when absorb stage ends, CC-A continues to float the battery and CC-B turns off, so they are not confusing each other. I have my Outback Flexmax setup that way.
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Old 21-07-2019, 09:36   #9
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Re: Can multiple MPPT controllers all go to one bank?

Short answer: yes. For details please see attached.
Attached Files
File Type: pdf Marine-Solar-Systems---Planning-and-Installation-V4.pdf (718.0 KB, 153 views)
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