Connecting two different charge controllers to the same battery bank..

[garyb1st]

I have two Renogy charge controllers. One is a 20A PWM controller which I removed from a solar suitcase. The other is a 20A MPPT controller. Is there any way I can use both to charge my house battery bank without additional devices?

 

[Mark_K5LXP]

Generally you can parallel multiple sources. One would have to review the panel setup to see if there's optimization to be done there.

Mark B.
Albuquerque, NM

 

[DonTom]

Is there any way I can use both to charge my house battery bank without additional devices?

I am not clear on what you're asking. Same solar panels on two controllers to the same house battery pack? For what purpose?

If the outputs are for two different things, sure.

Also okay is each controller is for a different set of solar panels to the same battery pack. You can then parallel the outputs of the controllers.

-Don- Auburn, CA

 

[Lou Schneider]

If they're on different solar panels, yes. But not both from the same panels - they'll fight one another.

 

[Domo]

It sounds like OP is trying to use two 20 Amp controllers on one solar bank/panel to achieve a 40 amp charging current to the batteries.

I'd put diodes on the outputs going to the batteries to protect the controllers from each other while still allowing the batteries to charge. The input side of the controllers shouldn't matter since the panel output is varied already and those inputs are basically passive as far as the controllers are concerned.

OP - Don't forget to increase the wire size or use two sets of wires, one from each controller, to the battery bank.

 

[Lou Schneider]

I'd put diodes on the outputs going to the batteries to protect the controllers from each other while still allowing the batteries to charge.

Would you also put a diode on the output of a solar controller to protect it from the output of a vehicle alternator or DC to DC converter that's also charging the battery? It's not necessary there and likewise isn't necessary on multiple solar controllers feeding the same battery pack.

 

[Tulecreeper]

It sounds like OP is trying to use two 20 Amp controllers on one solar bank/panel to achieve a 40 amp charging current to the batteries.

I'd put diodes on the outputs going to the batteries to protect the controllers from each other while still allowing the batteries to charge. The input side of the controllers shouldn't matter since the panel output is varied already and those inputs are basically passive as far as the controllers are concerned.

OP - Don't forget to increase the wire size or use two sets of wires, one from each controller, to the battery bank.

Would you also put a diode on the output of a solar controller to protect it from the output of a vehicle alternator or DC to DC converter that's also charging the battery? It's not necessary there and likewise isn't necessary on multiple solar controllers feeding the same battery pack.

I'm thinking they already have internal protection for just that.

 

[Lou Schneider]

I'm thinking they already have internal protection for just that.

Yup, the same circuitry that protects against current feeding back into the controller when the solar output and controller voltage drops below the battery voltage.

 

[Domo]

Would you also put a diode on the output of a solar controller to protect it from the output of a vehicle alternator or DC to DC converter that's also charging the battery? It's not necessary there and likewise isn't necessary on multiple solar controllers feeding the same battery pack.

Good question - I don't know solar controllers other than the single one I had installed years ago... my curiosity made me google a little - seems they can be in parallel with the same battery bank - however the two controllers are supposed to be connected to completely separate solar arrays. So that means the outputs can be connected but the inputs should not be common - backwards from what I was thinking.

Thanks for hopping on the thread and pointing out the needless diode!

 

[Lou Schneider]

Good question - I don't know solar controllers other than the single one I had installed years ago... my curiosity made me google a little - seems they can be in parallel with the same battery bank - however the two controllers are supposed to be connected to completely separate solar arrays. So that means the outputs can be connected but the inputs should not be common - backwards from what I was thinking.

Thanks for hopping on the thread and pointing out the needless diode!

View attachment 169720

Right. A MPPT controller actively regulates the load on the panels so the voltage and current stay at the point where maximum power is produced (thus the acronym for Maximum Power Point Tracking). A PWM controller simply switches the panels rapidly on and off to get the correct voltage going to the battery and this changing load on the panels will confuse the MPPT controller.

 

[garyb1st]

My solar system is two 100 watt panels and a 20 amp PWWM controller. Previously I had a 100 watt solar suitcase with a PWM controller. My question was whether I could use both systems at the same time. I didn't want to have to purchase additional equipment to do this.

I've watched one video where this was done without any special equipment. However the video didn't specify whether or not the controllers were both MPPT or as in my case, an MPPT and PWM controller.

The other option I've been working in a separate thread was to parallel my two 100 watt panels with my 100 watt solar suitcase and run them through my 20 amp MPPT controller.

The 20 amp controller has a max solar input of260 watts so I'll lose a bit of power. However, I think it's a cleaner option.

 

[Merlin TC]

This might help you, this was my set up at my old shop in Florida.

the main thing I have learned is, the more batterys the better. I have 5 batterys wired in my system now.
This video shows our system powering my bigger shop here in Greensboro n.c.

I am no expert, but this is what's working for me. also an update, 6 panels was about to over load my charge controller, I am now only using the 4 100 watt harbor freight panels and still getting 72 volts into the charger controller, even in the winter now where the sun is not even facing the panels.