|
Location: Green Bay, WI | In the case of the ACR, the alternator does charge both batteries...but not simultaneously, as I understand it. I haven't installed mine yet, but I believe I read in a book on boat electrical systems, that the ACR units switch to first charge the battery with the lowest voltage--and then charge the other battery. But I am not 100% sure of this. The point is that they do not charge both batteries at once.
That being said, my RV has a Caterpillar engine and I just installed two new starting batteries. We bought it used, and it only had one chassis battery--but the tray holds two. When we picked it up in Florida a month ago, a mechanic I hired told me to simply buy two new start batteries (you never want to put a new battery next to an old one, by the way), and then just wire them in parallel. In other words, the alternator just charges both units. So that's what I did when I got it back home, and man what a difference it makes in turning that Diesel engine over! It's pretty remarkable.
So if I were you, I would probably just buy another battery and set it in a tray next to your current start battery--and only use it when/if needed. This would be the easiest way to go, and then you could simply charge it with your 3-bank charger, alternating a cycle with the main start battery. In this case, the ages of the batteries would not matter, as you're not going to be using them simultaneously anyway. Your other option(s) would be to replace both batteries and either install an ACR to isolate them each, or simply take your chances and wire them directly in parallel. It shouldn't hurt the alternator, as far as I know. Look at your battery charger when you first start charging the start battery--I don't think you'll see that many amps being drawn, although don't forget that the charger is 110v so the current may not be the same as that from your 12v DC output engine alternator (depending upon your particular battery charger). Still, your alternator should have plenty of output to charge both batteries. Don't forget...neither start battery will be discharged nearly as much, as they are in parallel and share the load from the starter. Thus you really shouldn't need all that much more current from the alternator.
Another thing you could do is to do a search on the forums at:
http://www.thehulltruth.com/
Copy & paste "parallel battery starting" into the search engine. I found several threads there that look helpful for you.
Good luck!
TB
Edited by tcbetka 4/22/2009 3:16 PM
| |
|
