Two solar charge controllers

swordfish_designs

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I'm new to the solar systems, so any and all help will be appreciated.

I'm presently using a 100w panel with a 20a solar charger, and the battery in my system is my John Deere lawn tractor (set up is to maintain charge on my battery). I want to set up my LED lights in my shed, but want to be able.to use them even if my tractor is not in the shed. So I will get a deep cycle battery for my lights, but I want to maintain the trickle charge on my tractor.

Can I use a second PWM charge controller, and have the solar + and - on my tractor's charge controller be fed by my load circuit on my main charge controller?

Thanks for the help.

Been looking for a 12v-12v DC charge controller but can't find anything.
 

acdoctor

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I don’t believe that will work. PWMs chop the DC voltage at high frequency. When the sun is out there’s no telling what it would look like after the second one. With out sun the input voltage into the second would be to low to start up.
You could just have some cables from the deep cycle to the tractor in parallel. Just don’t discharge while interconnected. That should work fine so long as you don’t cycle the bigger one very far.
 

Rednecktek

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Can I use a second PWM charge controller, and have the solar + and - on my tractor's charge controller be fed by my load circuit on my main charge controller?
That's exactly what I do for my motorcycle and riding lawnmower. Even the cheapie 10a PowMr PWM controllers can be set to shut off the LOAD ports at a set voltage, so I just set that to 12.6 and when I get too much cloud cover it stops charging the bike/lawnmower until the main battery has recharged enough, then starts topping up the bike/lawnmower again.
 

acdoctor

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That's exactly what I do for my motorcycle and riding lawnmower. Even the cheapie 10a PowMr PWM controllers can be set to shut off the LOAD ports at a set voltage, so I just set that to 12.6 and when I get too much cloud cover it stops charging the bike/lawnmower until the main battery has recharged enough, then starts topping up the bike/lawnmower again.
So you have ?
Panel > PWM >BATTERY
………..Load
…………..|
………. PWM >BATTERY
 

Rednecktek

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Close, I have 2 systems:
Panel > MPPT > Battery
Battery -> PWM -> Load -> Bike

The other is Panel -> PWM -> Load -> Lawnmower
. . . . . . . . . . . . . . . . . . . . |->Battery

I don't have a panel connected to the Bike's PWM controller, I just use it as a low voltage cutoff.
 

swordfish_designs

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So I advanced on my solar setup, here is what I have so far.

100W panel --> 15A PWM charge controller // group 24 65aH marine deep cycle battery.
PWM --> load : distribution block with fuses, 4 circuits of 36w LED with 5A fuse each.

My question now is, how do I set up a second charge controller for my lawn tractor's battery?
I have three options that I can see working, with more or less success each.
1- run a circuit from my PWM load to my tractor's battery, but I'm afraid of over-charging the tractor's battery
2- PWM load --> 120v inverter --> NOCO charge maintainer installed in my tractor, but I'm afraid of parasitic drain from the inverter
3- DC-DC battery charger, but the only ones I can find are 200$ +, and I already sank more into this project than I had originally anticipated.

Of the three options, which is best? And do you have any other suggestions?
 
Last edited:

Rednecktek

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1- run a circuit from my PWM load to my tractor's battery, but I'm afraid of over-charging the tractor's battery
If the controller won't overcharge your Group 24's then it won't overcharge the tractor. The load ports can't put more power to the Load than it can to the main battery. The advantage is that you can set the Low Voltage Cutoff so if the main batteries get too low (I set mine to 12.4) so if the batteries get too dead it doesn't risk draining the tractor.
 
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