Originally Posted by gtbzz85
Folks.. the 1976 Airstream Sovereign
remodel is coming along well, but I have an electrical question!
I have 2 AGM Lifeline 210amp-hour batteries run in parallel, producing 12v
for the trailers electronics.
I would like have the option of adding charge to this battery bank using the tow vehicle alternator, BUT I'm afraid to just hookup the charge line from the tow vehicle directly to the battery bank (wrong voltage, wouldn't know when to stop charging) so I assume I need a charge controller for the battery bank?
If so, what size charge controller do I need.. 10 amp.. 30 amp? How does the tow vehicle know how much of the alternator's current it can 'spare' and send to the Airstream for charging purposes?
Thanks for everyone's help!
I am not sure what you are planning.
Are you going to have the Vehicle be the only method of charging the batteries?
The tow Vehicle does not to need to "know" anything, The design of the alternator, the condition and state of charge of the TV battery and the TT batteries, the size and length of the wiring in both the TT and TV will determine how much of the alternator's output goes to what purpose.
The loads will be: (in no particular order)
Running the vehicle and whatever accessories are turned on
Running whatever things are turned on in the trailer
charging the TV batteries
charging the TT batteries
You cannot control the priority of these functions without changing the design or construction of the system in some way or another.
In any case a controller in the TT would not help in any way. If you tried to use one, it would only be able to lessen the ability to charge, It could not improve it.
If you are talking about charging the trailer while driving, then just hook it up and go. The same factors above will determine how much charge you are getting to the TV batteries.