diy solar

diy solar

Single Solar Array Multiple MPPT Chargers, and Dual Batteries (12V & 24V)

mmmnnn

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Oct 16, 2019
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I'm looking to setup a solar array as follows

Single solar array that will be expanded over time

I'm looking to charger two separate batteries Battery A 24V and and Battery B 12V from the single solar array

Since it's hard to estimate which battery will be more drained in the morning, i don't want to separate the PV power from MPPT A => battery A or from MPPT B => Battery B. I'm looking to split the PV output among both batteries

Battery A has much higher capacity, so i'm looking to have two mppt charge controllers dedicated to battery A and charging from the single PV Array

After a quick google/you tube search, i'm getting mixed answers about this setup, however if it's possbile, any future solar expansions can be accomodated by adding additional smaller MPPT chargers.

Thanks in advance
 
I do this with a 12v charger running off the inverter of the 24v system which only runs when there is sufficient solar power available (using a 10w solar panel and relays).
 
For optimal output, each MPPT needs it's own PV string.

Alternatively, you could put all MPPT into the 24 volt battery, then add a 24-12 DC-DC charger to keep the 12 volt battery charged. Some DC-DC chargers have the ability to sense when the 24 volt side has plenty of capacity to allow charging of the 12 volt side.
 
Problem with putting two MPPT controllers on a single string is the MPPT algorithms used in each controller will not be synchronized, and may interfere with one another.

MPPT searches for max power point by loading the PV down to determine at what point does it produce the most. We'll two controllers will be doing this, and the results they find will be affected by the other in a totally unpredictable way.

I have not tried it, but know how this works, I never attempted. I might just try it for science ;)
 
For optimal output, each MPPT needs it's own PV string.

Alternatively, you could put all MPPT into the 24 volt battery, then add a 24-12 DC-DC charger to keep the 12 volt battery charged. Some DC-DC chargers have the ability to sense when the 24 volt side has plenty of capacity to allow charging of the 12 volt side.
I like the DC-DC charger idea, will try that. the issue is the extra loss from double conversion MPPT - > Battery -> Charger -> Battery
 
Problem with putting two MPPT controllers on a single string is the MPPT algorithms used in each controller will not be synchronized, and may interfere with one another.

MPPT searches for max power point by loading the PV down to determine at what point does it produce the most. We'll two controllers will be doing this, and the results they find will be affected by the other in a totally unpredictable way.

I have not tried it, but know how this works, I never attempted. I might just try it for science ;)
yeah, tempted to try that, but wish somebody already did with real data
 
is it an issue if the the solar array have double the amp capacity of each MPPT?
 
is it an issue if the the solar array have double the amp capacity of each MPPT?
Unusual and requires a awg upgrade. The PVs’ VOC*T°coef is the critical factor. MPPT’s amp rating is primarily the amps used in charging the battery bank and also for determining the watt total of one’s array.
 
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