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Old 08-29-2017, 02:16 AM   #1
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Multi Bank Solar Controllers

Conventional battery chargers can serve up to 3 banks, catering for the requirements of each, though they probably have to be the same battery type.
As far as I can tell,solar controllers in general serve one bank. That`s how I wired my modest set up, using 2 controllers. You could wire one controller to 2 banks, but how would the controller distinguish, I expect both banks would receive the needs of the inferior one.
I found, by online searching, 20A controllers that can serve 2 banks, but nothing larger. 10A per bank is not even the rule of thumb 10% of capacity for many batteries, and it limits the controller to 240watts of panel. While searching I found a number of mono 200watt panels for around $200AUD, they have certainly become cheaper, which encourages upsizing the panel array.
I also found some online discussion, incl at CF, but it was quite limited.
You could use a Blue Seas type switch between banks, but something which does what a mains charger does, 2+ banks simultaneously, is better.
Has anyone found higher amp multi bank controllers? Any other ideas for getting around it? At this stage I`m working in theory, no identified boat that I`m trying to fit out with solar.

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Old 08-29-2017, 02:40 AM   #2
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The way my set-up 'gets around it' is to connect the solar controller to the house bank, and then use ACR's for the start batteries. House is 1284 Ah, port and starboard start batteries are the same type/model and 214 Ah each.

But, these days I tend to run with the 3 banks in parallel, and when anchored isolate the two start batteries so that all solar is to house bank. After all, the start batteries will be fully charged by the time I'm ready to anchor, so no need to have them in a charging circuit.

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Old 08-29-2017, 06:25 PM   #3
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Brian, I know from your posts your system works, but unlike a mains charger, it does require human intervention.
A number of members viewed the thread, no one is pointing to a multi channel solar controller of > 20A size. My searches did not find one so I`m thinking they don`t exist, and wondering why that is. Maybe it is just not feasible.
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Old 08-29-2017, 07:05 PM   #4
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I believe very few if any of those shore chargers actually treat each bank independently, they keep every one on Absorb until the last one is ready to drop to float.

The few that do would in effect have three separate chargers wired together in a box.

The fact is that the SoC of the target bank completely changes how the controller is dealing with the panel, MPPT only applies to the Bulk stage PWM for Absorb and float.

So that's the why.

Now let's turn things around. Best for partial shading and redundancy is a 1:1 ratio between SC and panels.

Victron MPPT 75/15 is a fine product, under $100. Put one per panel, ideally rated 36-50 Voc and 200-250W output.

Now send your power portioned out to wherever you like.

Personally I think **all** charge inputs should go directly to the Main consolidated/house bank, and only from there to a Reserve (starter).

At the other end of KISS, there are gadgets like these,

also from Promariner

Finally, B2B DC-DC chargers.
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Old 08-29-2017, 07:57 PM   #5
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I agree with john61, send the power to the house bank and apportion it with an ACR. I would also recommend at least 600 watts, I have 2 - 300 watt mono panels in series and an Outback 60 Amp controller. My batteries are in float by noonish each day, I have not started my genset since I installed it. Also, easy install, I used the racking that was sold for my panels, easy peasy. I have not found a dual controller either.
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