Definitve answer

[Justin & Katy]

Is there such a thing as a defintive answer when it comes to charging an auxillary battery. I have read the sticky in the section about running a 10 gauge wire from the hot side of the battery with in line fuses. I have also read this ( http://www.surepower.com/pdf/ebr_int.pdf ) which brings up several concerns that I had before reading it. Help!

and...if some one out there has found a product that they like for these applications, could you share it with me?

[eamarquardt]

Not sure what your question is. I’m guessing you want to have a battery in your trailer and charge it from your tow vehicle (TV). Pretty simple once you understand what’s required.

What you want is to connect both batteries together positive to positive and negative to negative with some wire. You need to protect this wire from overheating if too much current tries to flow through it. So you need to install a circuit breaker that is matched in amps to the current capacity of the wire you use. They have all sorts of charts to tell you what size wire to run etc, etc, etc. In your house, 12 gauge wire will use a 20 amp circuit breaker. If it works in your house and your house doesn’t burn down, I think a 12 gauge wire and a 20 amp circuit breaker will work for connecting the TV to the trailer. Plus, you’ll have a hard time fitting wire larger than 12 gauge into the connectors that connect the TV to the trailer. Another factor is that you shouldn’t charge a battery with more than about 10 %of its Amp/Hour rating so 20 amps will charge up to 200 amp hours worth of battery(ies). You can get circuit breakers or fuses at an auto parts store and there are some circuit breakers that will automatically reset should they trip.

Finally you shouldn’t leave the batteries connected together when the TV is not running and charging the batteries. If you do the electricity can flow back and forth and discharge both batteries. This can be a pain in the posterior but it does take a while. Some people use a relay that only connects the two when the ignition is turned on. If you don’t know what you’re doing a battery isolator is an inexpensive and foolproof (as long as it doesn’t fail) way to connect the two batteries together. Here’s a link to a site that sells a bunch of them. As long as the isolator has a capacity bigger than the wire you’re using you should be ok. But why not call these guys and see what they suggest and verify what I’ve suggested. Bear in mind the only current that should flow between TV and the trailer battery is the current required to charge the trailer battery (and this should not be more than 10% of the batteries capacity). Should you kill your TV battery and connect the trailer(with a fully charged battery) too much current will probably try and flow and the fuse will blow or circuit breaker should trip.

http://www.ase-supply.com/Battery_Isola ... _s/153.htm

I’ve never actually done it but the above is what I plan to do and I have a pretty fair amount of experience with electricity. On my boat I just connected the batteries (I had three) with a switch when the engine was running and then disconnected them all when I stopped the engine and then switched on only one at a time. Worked for 10 years without a hitch.

If this isn’t a good plan I’d like to know from someone with more experience.

Hope this helps.

Cheers,

Gus

[Justin & Katy]

Thanks for the information. It has been very helpful.