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cc5084 asked

Will MPPT Solar Charger or Alternator Take Priority

I am going to be hooking up a victron mppt 100/30 to an already existing auxiliary (lithium) battery bank. The alternator is a "smart" alternator so it is safe to charge the lithium batteries. I understand that the mppt charge controller has its built in bulk, absorption, and float charging sequence. How will this be effected when the alternator is also charging the battery system? Will one take precedence over the other or is there a way I can program them to work properly if they do not coexist?

MPPT Controllersbattery chargingMPPT SmartSolarLithium Batteryalternator
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kevgermany avatar image
kevgermany answered ·

Assuming sufficient solar input the MPPT is controlled by the voltage of the battery. So you'll need to measure the charging voltage of the alternator output and set this in the MPPT.

Generally alternators, smart or not, are not suitable for charging lithium. But I guess you've checked this already.

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cc5084 avatar image cc5084 commented ·
So if I am understanding what you are saying correctly, as long as all of my charging sources are all the same voltage they should all coexist with one another to an extent? If I were to set something to a higher output voltage, is that how I would have it take priority?
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skippeer answered ·

Possible issue is when solar MPPT is in bulk phase, 14.4 volt, and alternator/regulator has reached say float phase, 13.5 volt, the alternator stop to charge and on my Penta engine panel the buzzer sounds.

Considering using MPPT rx cable to disable solar charging when running engine.

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