Adding 2nd MPPT controller

[vortac55]

Hey Guys
First Post Like some feedback and information and thoughts I was watching a lot of Will videos which guided me

Wondering if anyone has installed 2 MPPT controllers off the solar panels

I have 2 -175 watt solar panels
I parallel the panels and ran #8 wire to the MPPT controller
This is powering my 4-4D flood house batteries

I have 1- AGM battery I would also like to charge off of this solar array
I wanted to parallel 2 MPPT controllers and charge both
My understanding is not to charge different batteries. So the thought was to parallel
I would install fuses before powering each controller and I was thinking of a bypass encase the panels were not outputting enough so i can direct the charge to either battery bank


Thanks in advance

Chris

 

[timselectric]

One charge controller per array circuit. Two will fight over control of the MPP. Resulting in less output.
Each MPPT should have their own panels. Either get more panels, or divide what you have between the two.

 

[vortac55]

One charge controller per array circuit. Two will fight over control of the MPP. Resulting in less output.
Each MPPT should have their own panels. Either get more panels, or divide what you have between the two.

Thanks Unfortunately Limited on the boat
I guess the only option is an AB switch to isolate and charge one at a time Not the best scenario but an option

 

[DThames]

First off, if you have an MPPT charger, why put panels in parallel? That is not a good plan, as the MPPT needs at least X voltage to work and that will come easier if the panels are in series.

You can connect two chargers to one array but it is less than ideal. If the array is large compared to the loads created by the chargers, they can work fairly well together as neither if them will try to bring the load toward the MPPT load point, because they will have plenty of current without doing that step. For example, say your array could deliver 40 amps at the battery. You have two small batteries and two 10Amp MPPT chargers. Regardless of the battery state of charge, both controllers would be in current limit before loading the array to the MPPT point in good sun.

Two 40amp chargers and 2 larger batteries (in this same example) would be a situation where the chargers would likely take "turns" trying to find the best load point. At some point in time both batteries would get charged if there was plenty of solar power for the load.

One thing that might work for you is to put breaker/switches on the array so you can feed the PV to the charger that you want to work right now. If manually switching one off and the other on would work for you, that will work. I have a 24v and a 36v connected to the same array. If real charging is needed, I turn on the one that I want to charge. If both are charged and I want to float both, I might turn both on. While some say the chargers will "fight", it is not so much as a fight as a struggle for control. One will try to control by increasing the load, but if the other does that too, one or both will back off the load and then later increase the load and try again. The charging watts on both chargers will go up and down but as I said, they will charge the batteries after some time. I posted some graphs where you can see the two chargers output side by side.

 

[DThames]

Note, I just noticed your comment about A-B switch. I brought my PV to a terminal block, then from that block to two different breakers. I can turn both off, both on, or either on. One is for the golf cart which is often not plugged in. So it is handy to kill the PV to that charger before unplugging the cart battery.

 

[timselectric]

The easiest solution is to let the array charge the larger battery bank. And use a DC to DC charger for the other.

 

[vortac55]

panels are in parallel my system is 12-volt system

feed 12 v dc to 12 v dc charger to charge the engine battery that is not a bad idea

 

[vortac55]

panels are in parallel my system is 12-volt system

feed 12 v dc to 12 v dc charger to charge the engine battery that is not a bad idea

What is the charge rate

IE how long does it take for full charge

 

[RCinFLA]

Thanks Unfortunately Limited on the boat
I guess the only option is an AB switch to isolate and charge one at a time Not the best scenario but an option

Typically, on a boat there is a lot of problems with partial shading. The more independent MPPT controllers/PV panels the better.