Where to Locate MPPT Solar Charge Controller

MikeM said:

I have read conflicting guidance on where the controller should be located, and the installation guide for the controller itself doesn't directly address it. I've seen a guide that says to locate it in the same compartment as the batteries so they are at the same temp. But my batteries are in my engine room, and I have read that the controller should not be in the engine room.

What do folks think?

Thanks, Mike


Mike Metts
KK 42-165
Virginia Beach, VA

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Panacea123 said:

Located mine under the lower helm next to the main elec panel "morning star TS-MPPT-60 amp"
Wired direct to the panel as I have robust wires from there to batt bank 780 watts of solar. 900 amp/hr bank.
Plenty of space and ventilation, also have batt temp sensor, a must IMHO
Just avoid heat(no small enclosed spaces) and voltage drop due to long or undersized runs.

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djmarchand said:

Here is my advice and the reasons why:


An MPPT controller drops the higher voltage that the solar panels produce to the lower voltage that charging the batteries require. So if you keep the voltage drop in the wire from the solar panel to the controller to 3% then there will be plenty of voltage at the controller terminals to work. Use the Isc spec to base wire sizing on.


For the run from the controller to the batteries you need to minimize voltage drop, otherwise the batteries won't be getting the correct charging voltage. This usually means locating the controller near the batteries, but if you can't do that, then size the wire accordingly. I would shoot for no more than 2% voltage drop in that circuit. Use the total wattage of the solar panels divided by 12 for the amperage in that circuit to base the size on.


Everything electronic is affected negatively by heat. Engine rooms are hot. QED- don't install your controller in the engine room. If that is unavoidable, then I would downrate the controller's amperage capacity by 25%.


David

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MikeM said:

I have read conflicting guidance on where the controller should be located, and the installation guide for the controller itself doesn't directly address it.

Click to expand...

MikeM said:

I've seen a guide that says to locate it in the same compartment as the batteries so they are at the same temp.

Click to expand...

MikeM said:

But my batteries are in my engine room, and I have read that the controller should not be in the engine room.

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MikeM said:

What do folks think?

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CMS said:

This is because it "depends"..

If your controller does internal ambient temp sensing, for temp compensation, then it needs to be as close to the bank as is possible, and safe. In other words if the controller is not sensing the same or similar temp to the batteries, without an on-battery sensor it will never be entirely correct, then your batteries will be seeing too high or too low a voltage.





Unless it uses a remote on-battery temp sensor lead then yes this would be the most optimal location in regards to properly charging your batteries..

For example I had a customer install an local ambient sensed MPPT on his vessel. The controller was outside the engine room in the locker backing up to cold Maine ocean water. The controller was regularly at a much cooler temp than the batteries, often a 30F spread or more. The batteries were in the engine bay, a horrible location for batteries.. The controller was actually compensating charge voltage up, based on controller location, instead of down based on battery location. A battery that charges at 14.8V at 77F can not charge at 14.8V at 95F or 110F or 120F...



It's not just the controller. The bigger issue is that your batteries should not be in the engine room either so your problem really started out with "stupid builder tricks". Builders don't care about the longevity or health of your batteries but they do care about saving nickles. As a result far too many batteries are installed in engine spaces that regularly exceed 100F. I have measured engine rooms 8+ hours after running still exceeding 110F. This is just bad news for batteries.



Purchase a controller with remote temp sensing and ideally remote voltage sensing such as the Morningstar TriStar MPPT series. Place it outside the engine room and run the temp and voltage sense leads to the battery bank..

As a bonus get the batteries out of the engine room into a more hospitable environment. With batteries in the engine room all charge sources should have on-battery temp sensing not just the solar..

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djmarchand said:

CMS:


Do the controllers with remote battery temperature sensing capability revert to internal sensing when the probe is not attached, or do they disable that feature?


David

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MikeM said:

The controller I have (Morningstar Prostar) does revert to internal sensing if there is no RTS.

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JDCAVE said:

Mike: I put my controller in the AC bus-bar compartment, simply because 1) there was room and 2) it's close to the batteries.
View attachment 56160



Jim kk42 owner.
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MikeM said:

Jim,

My AC bus bar compartment is in the world engine room....

Mike

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JDCAVE said:

World engine room?


Jim
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JDCAVE said:

Mike: I put my controller in the AC bus-bar compartment, simply because 1) there was room and 2) it's close to the batteries.
View attachment 56160



Jim kk42 owner.
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JDCAVE said:

It's in the engine room on the bulkhead between the engine room and the guest stateroom. This is an earlier photo of the space. I've since use some of the space in the ACD compartment.mthe DC compartment is starboard of the ACD compartment.
View attachment 56209
DC compartment
View attachment 56210



Jim
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