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burp asked

Charge LifePo and Starting battery from solar

Hi all, thanks for reading my question.

I know that similar questions have already been asked, but not specifically what I want to use in my situation. I can imagine that many camper owners have the same question.

My setup is simple but effective. Solar panel with a Smart Solar 100/20 MPPT on a LifePo battery. From the car a Smart Orion 12/12 30 to charge the LiPo while driving. I can disconnect the LifePo from the system using a switch. Victron Multiplus 12/1600/70 with VE.Bus to control the inverter remotely.

Now the next thing, when the camper is in the garage, which has a glass roof, I want to charge the starter battery. I was thinking of putting a second MPPT (simple 75/10) in parallel with the 100/20 with a profile for the starter battery. The LifoPo will then be disconnected from the system. Does this cause problems? Even if there is less power available, it is not a problem, what matters is that the starter battery is charged when there is sun, surviving the winter. I don't care about maximum efficiency for those few months. Maybe even let the LifePo connected. I know from other answers that the both MPPT's will try to get the maximum power but the LifePo will be full all the time and doesn't require much power. Uploaded a scheme how things are connected. Goal is to charge starter battery in the left corner.

If this is really not possible, are there other solutions that can be found without throwing everything in the heap? Maybe another orion on the load from the 100/20 but that is a much more expensive solution.

camper-schema.jpg

MPPT SmartSolarorion-tr smart
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3 Answers
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pwfarnell answered ·

You can not have 2 MPPT controllers on one set of panels running at the same time and get reliable operation as they will interact with each other. The cheapest Orion appears to be the Orion-Tr 12/12V 9A which is marginally more expensive than the 75/10 MPPT and will keep the system simple. There are third party trickle chargers that are more expensive than this. The other option is to swap the MPPT to the starter battery when the camper is laid up with a well charged lithium battery left isolated.

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burp answered ·

Thanks. What about a second mppt where I can switch the solar input lead to that one when going into storage?

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pwfarnell avatar image pwfarnell commented ·
Yes that would work but you would need isolation switches on the solar side.
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burp avatar image burp pwfarnell commented ·

A simple scheme attached. The switch is going to switch the solar between "normal operation" (MPPT1) and for storage to MPPT2 this is the Starter charger. When I put the Camper in storage the Litium will be fully charged, I can switch that completly off without any issues. Starter battery is still connected to the Orion DC-Dc to charge the Lithium during driving. I think I can attach the leads to the input of the Orion because that is attached to the starter battery right?

In the scheme it's a dual pole switch but I think I can get away with attaching the black from the solar to both MPPT's and only switch the red one to keep the switch more simple?20240710-125620.jpg

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burp answered ·

Or do you mean the Orion on the load from the mppt? Also a possibility I guess.

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pwfarnell avatar image pwfarnell commented ·
The lithium battery would need to remain in circuit when the camper is laid up, so the extra Orion would just connect to the positive and negative bus bars with an isolator so it does not run when using the camper.
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