Making a DC-DC battery charger for less than $25

I do a lot of camping, and I am starting to work on building my own trailer. I was looking for a way to use the ACC power from the 7way plug and I think I found it. Granted, this idea won't quick charge a battery, but it will maintain it while driving.

First you need a charge controller, I found this little gem on Amazon for $10.99:
https://www.amazon.com/Docooler-Con...4&sr=8-5&keywords=12v+solar+charge+controller

Next you need 14-16VDC. Most solar panels output 14-16V and the solar charge controller is looking for that power range. I originally thought of using a small inverter and a laptop power supply, but I figured there had to be a simpler solution.

Then I found this for $12.99:
https://www.amazon.com/Pawtec-Unive...1473865235&sr=8-5&keywords=laptop+car+charger

So for $23.98 (plus shipping) you can have a battery that is isolated from the rest of the truck completely and still keep it charged while driving. The "laptop adapter" is actually 90w (draws ~9.5amps from the trailer plug), so it could be compared to a 90w solar system. If you don't normally have your solar panels out while driving, or if you are driving in bad weather, this could help a lot.

Anyway, just thought I would share my idea. Have a great day!

 

Neato, good stuff!

 

Thanks! I suppose this could also be used for those who put an AUX battery in the bed and would save them from running uber heavy gauge wire.

 

Any pictures of your set up?

 

Haven't actually tried it yet, just a working idea at the moment

 

After some tests, not installed yet, this works well. Sort of. If you are pulling a lot from the battery then ~90 amps isn't enough to keep up with the drain for very long. However a small inverter or a fridge would be fine. I think the best use of this would be to use it as a supplement to a solar panel for when bad weather hits or you are driving at night. I think it would be fine to keep the battery charged while doing highway miles and not running beyond a fridge or some other accessory so long as ten draw is less than the 90amps this puts out. But you are running a fridge, a lot of lights, charging a lot of accessories, all at the same time then output of the charger becomes an issue. It does work well for what it is and the wire from the front to the back is a lot smaller than a battery cable. I suppose I could add a second charger to the input of the charge controller for around ~180 amps which would be more than enough for most uses.

 

Watts not amps. Oops.

 

Getting closer