Trailer charge system

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Professor Fate

Professor Fate

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First I'll explain my situation and thought process.
I've got a camper, and a utility trailer; both with 12v deep cycle batteries and electrics. Solar charging is not always viable for various reasons, SO-
I'm thinking along the lines of adding a secondary charging circuit to my tow vehicles (a wagon and a pickup) that is run in parallel to the vehicle's charging system; ie a second VR connected to, say, 10g wires with an appropriately sized breaker run to the rear bumper near the trailer light plug, with a plug similar to an electric winch plug that would allow me to plug the trailer's battery in and recharge while in transit (or on cloudy days or parked in shaded areas). Plugs like these:
1689695209357.png

Both vehicles use the Denso 90/120a alternators (early 90s Dodge pickup variety), so the additional current load should not be an issue...
Does anybody see any glaringly obvious issues with a setup like this? I'd like to keep the two circuits independent of each other without adding a second alternator. 10g sound about right? 30 ish amp breaker? Or am I having '60s LSD flashbacks?
 
I'm thinking a voltage regulator like for a dual battery setup?
 
Suggest you look on internet for dual battery schematic. Dual batteries require an isolator of sorts. Does not look that difficult based on what I've found. They have been using dual batteries in trucks and marine applications for many years. This way you can use only one charging system.
 
jawbone said:
Suggest you look on internet for dual battery schematic. Dual batteries require an isolator of sorts. Does not look that difficult based on what I've found. They have been using dual batteries in trucks and marine applications for many years. This way you can use only one charging system.
Click to expand...
I've done that, of course... My line of thought was that I could eliminate the isolators and solenoids or priority switches (and in some cases the $$ controllers) by simply running a second voltage regulator in parallel to the vehicle charging circuit. Much simpler to my way of thinking, and can do it with common parts, most of which I already have.
Think of it as if you were plugging 2 separate loads into one portable generator. Each load functions independently as needed, with no need to switch between the two.
 
I'm told that isolators are different now, or can be. You used to have two maybe three choice

1...(My opinion, the worst) a 3 terminal isolator
2...So called continuous duty solenoid, activated by the key
3....A manual A-B-Both battery switch

A....3 terminal isolator THEY CAN CAUSE ISSUES and I'm aware of at least two of them in boats. A 3 terminal isolator is nothing more that two big diodes. You BREAK the alternator output wire, and connect it to the common of the diodes. You connect the original cut charge wire to one of the two outside posts. This now runs the alternator output IN SERIES through one of the diodes to the main battery. You then connect a wire to the remaining post and run that to the aux battery. IF THE HEAVILY USED main diode pops, there is no SENSING to the alternator and it will charge the aux. battery WIDE OPEN along with NOT charging the main. THIS DOES HAPPEN

B...Continuous duty solenoid. This in my opinion is the best option. This is a solenoid which is DESIGNED to be powered for long periods, UNLIKE a starter solenoid such as Ford. You activate the coil with the switched igntiion "run" power, and run a new wire from the alternator (fused) back to the aux battery. Anytime the key is "on" the aux battery is connected in parallel. These are VERY popular and work well

C....A-B-Both manual switch. These are used in fire and other trucks, boats, etc and are perfectly fine IF YOU remember to switch them EVERY time, otherwise, you will discharge the main as well. In your case you would want to use only A and Both
 
You can not run two regulators on one alternator unless you have a high power regulator that deals with the main output. Plus it would not work well as because if the alternator output fell for some reason, the second regulator would not be able to jack it up

I WOULD SIMPLY run a continuous solenoid. THEY WORK. If you are worried about the connection with no trailer, you could add a series switch to the coil so the key cannot activate the solenoid.
 
So far as independent regulation, I found this: It's simply a DC--DC inverter that takes the vehicles main power and generates output independently to charge the aux. Sounds expensive

gnomadhome.com

Best DC-DC Chargers And Battery Isolators For Vanlife (How To Charge Your Van While Driving) | Gnomad Home

Adding a smart battery isolator will let you charge your batteries from your van's engine. Read on to see why you need an isolator and how to install one.
gnomadhome.com gnomadhome.com

A 40A one is 130 bux. How reliable? No idea
 
Agreed with the switched continuous duty solenoid as being simplest. I don't know if this applies, but if you have any 120 volt loads that you need to use while out, you could use a 12 Volt to 120 Volt inverter and plug up a battery tender charger with a plugged pigtail to your trailer batteries when on the road.
 
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Well, I can always just go with the wife's suggestion- just get an extra battery and carry it with us...
Probably cheaper, all in.
 
You could get a battery tender like this.

Instead of feeding it with solar, feed it from the 12 to 14 volt tow vehicle electrical system.

That way it will not over charge the trailer batteries.

Feed it from a switched source as it could drain the tow vehicle's batteries. And be sure you have enough amp capacity on your wires.

Screenshot_20230718-134147.png
 
How about a belt driven off the driveshaft. I've seen kits for that. But a lot more expensive and there can be vibration issues.
 
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Dana67Dart said:
You could get a battery tender like this.

Instead of feeding it with solar, feed it from the 12 to 14 volt tow vehicle electrical system.

That way it will not over charge the trailer batteries.

Feed it from a switched source as it could drain the tow vehicle's batteries. And be sure you have enough amp capacity on your wires.

View attachment 1716116410
Click to expand...
Hmmm... I'll have to recheck my solar controller- I think it is hardwired, but if it has the screw terminals like the one you showed, that might be the ticket. Didn't even think about wiring it that way!
 
Professor Fate said:
Hmmm... I'll have to recheck my solar controller- I think it is hardwired, but if it has the screw terminals like the one you showed, that might be the ticket. Didn't even think about wiring it that way!
Click to expand...
You already have solar and a controller? If you just add the solenoid to the mix, you have the best of worlds. You have a booster, higher amp charger when the tow engine is running, and solar for slower, top off charge. If the solar controller is properly regulated, you are set
 
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