Using 2nd SAE port for additional power

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FoxenTec

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Is there any reason why this might not work?

Camper has two solar panels on the roof and an Overland MPPT controller for two AGM 12v batteries. Is it possible to cable an additional AGM 12v battery to the outside SAE Solar port on the rear of the camper to provide additional power to the controller?

In other words, the two existing AGM batteries are running down and there is not enough sun to bring them back up. Would a 3rd battery plugged in before the MPPT controller provide charging power. (it would already be fully charged) Could this be incorrect due to 12v being fed also towards the two roof solar panels.

The battery would be inside a battery box mounted on a rear cargo rack in the event that the two house batteries run low.

Thank you,
 
hmmm creative thought. i think not, since the power being applied there would “look “ like some solar power coming in, same as the roof panels
 
Thank you Vic. On one hand that is what I thought it would look like to the controller and it would use the energy to charge the existing batteries. The more I thought about it though, I think the solar panels might draw the current to. I found that out when playing with a small 5w solar panel, no controller and a battery. The sun charged up the battery to full voltage but after the sun went down, the panel drew energy away from the panel. I am still learning and have a long way to go.
 
Guess I'm confused, but certainly not an expert in electricity. You would keep that auxiliary battery hooked up to the side SAE port all the time? I think that would work, but it would pull juice from that battery when a load was on just like the others. If you hooked it up when things got desperate that might work, but how to recharge that battery? At home w/a separate charger?

If you have the ability to carry that battery w/you on your travels, why not just wire it into your battery bank? If it's wired in series you might have an issue, but if it's in parallel, then ....?
 
radarcontact said:
Guess I'm confused, but certainly not an expert in electricity. You would keep that auxiliary battery hooked up to the side SAE port all the time? I think that would work, but it would pull juice from that battery when a load was on just like the others. If you hooked it up when things got desperate that might work, but how to recharge that battery? At home w/a separate charger?

If you have the ability to carry that battery w/you on your travels, why not just wire it into your battery bank? If it's wired in series you might have an issue, but if it's in parallel, then ....?
Click to expand...
I would only connect to the SAE port when needed which would be on a rare occasion. It would make more sense to just wire more batteries in parallel. I was just trying to get a bit more juice for the fridge on those extended trips without hookups. Yes, the battery would be charged at home and carried on the hitch cargo rack. I have been looking at carrying a small generator or a using something like a Goal Zero Yeti but I have a list of pros and cons with each of those.

I like these but their largest is only 35ah. I would also have to either connect my fridge to it directly as I am not sure how I would supplement my existing battery setup with one of these.
gallery_8354_1238_3258.jpg
 
Connecting a spare battery up when necessary sounds like a good backup plan, and you have a place to carry it. I see now why you wouldn't necessarily hook up to your battery bank...the spare is outside, and you'd have to run wires inside, and shut the door.

Sounds like connecting to the SAE plug with something like this might work...is that what you're thinking?

https://www.amazon.com/Terminal-Wiring-Harness-Disconnect-Extension/dp/B07BKZ89TS/ref=sr_1_14_sspa?s=automotive&ie=UTF8&qid=1533615174&sr=1-14-spons&keywords=sae+to+battery+cable&psc=1

Not the right gauge, but you might find something heavier or solder your own with thicker gauge wire. Maybe someone else has done this before....
 
I was thinking the same thing, but aren't most generators at least a little noisy? Don't have any experience w/any except for those big ones people have when their home power goes out. They have those power-pole devices, which I think are basically just a rechargeable battery, but I might be wrong.
 
+1 for the generator which may actually weigh less than the 3rd battery.

Without a boost regulator, you would not likely be able to charge thru the charge controller as the 3rd battery voltage never rises even to float voltage. You could wire a 3rd into the system thru an switched ACR as a backup power source.

Paul
 
Love your Yet'ee setup.

After much thought, for now, I will add a 3rd flexible panel to the camper for when we are in one spot for an extended period of time and with limited sun. It will plug into the rear SAE port on the back of the camper on occasion. Our top panels use the SAE on the roof. I wanted to have my cake and eat it to, but with limited space for a generator and adding a IOTA DLS-30 which I just cannot find a spot for, I decided to add the solar. Adding an extra 100 watt solar was also the least expensive route to go. I still may build a box like "thisoldcamper" has above to run a few things should we really need extra 12volts when the batteries are to low.

My thinking (or lack of it) is that with 300 watts of solar instead of 200, I might be able to eek by with our ARB fridge and limited sun when camped in one spot for multiple days. I might be dreaming too. Thank you for all your assistance. I will update and let everyone know how it went.
 
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