Charging with MPPT and DC-DC charger simultaneously

DavidD

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Apr 4, 2022
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Greetings,
I'm building a solar system with 40 amp MPPT, a Renogy 20 amp DC-DC charger and 200 aH LifePo4 battery. How do I wire these up to be able to charge my battery using DC-DC charger and MPPT solar charge controller at the same time?
Thanks,
David
 

MisterSandals

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Nov 5, 2019
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Wire them up the same as if you only had one or the other. If you have bus bars, it will be much easier than connecting everything to the battery terminals.
They will notice the charging voltage of each other, and may alter their charging, but its very common for this scenario of multiple chargers.
 

DavidD

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Apr 4, 2022
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Thanks. Another question: For the D+ wire on the DC to DC charger, can it be to any source that supplies voltage when the ignition is on, or should it be a source that supplies voltage when the car's engine has started? I know that may sound like a dumb question, but I have little experience with electric circuits.
 

MisterSandals

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For the D+ wire on the DC to DC charger, can it be to any source that supplies voltage when the ignition is on, or should it be a source that supplies voltage when the car's engine has started?
Sorry i am not familiar with the wiring or that unit. I do know that whatever you tap into needs to be able to supply the amps that the DC to DC will pull. Is there a wiring diagram in your install guide or online?
 

Theo74

Solar Enthusiast
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Feb 14, 2021
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33
Normaly your alternator should have a D+ contact. You need to connect a wire on to this contact, and connect it on to the D+ of the DC-DC.
 
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