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Old 01-17-2009, 05:46 PM
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Rzeppa Rzeppa is offline
Cruise Moab Chairman
Join Date: Aug 2005
Location: Kittredge CO, USA
Posts: 6,725

Originally Posted by MtnTrucker View Post
I'm thinking I need to go to a two battery setup in the 40 to ensure enough juice if I ever have to do some heavy winching. A few questions:

1-What is the most economical way to do the HW for dual batteries? Get an extra stock battery tray and fab something up? I already have 2 new HD 1000 CCA batteries so I don't want to go red or yellow tops if possible.

Currently I am running the stock 1974 alternator with a new, electronic voltage regulator. How much bigger should I go with the alternator and how much bigger can I go with the VR I currently have?

Last question-I just got a 2F out of the 1980 FJ40 that Timmbuck is parting out including the alternator. That unit looks like it has the VR built onto it. Is this unit any bigger that it would be worth my while to swap it with the current unit?
I ran a dual battery setup for many years in my 76 FJ40. The RV isolator is the way to go and worked extremely well for me. Basically, your main battery starts your truck up and runs your automotive related things like wipers, heater blower and lights. Your aux battery system runs your big stereo (what I put mine in for), winch or whatever doesn't relate to getting you down the road. I have a schematic on my web site, in sig line below.

The stock 40 series 40 Amp alternator works fine for these applications in my personal experience. You are basically recharging two batteries, and the isolator makes sure that one doesn't get overcharged when the other one doesn't need it.

An interesting side note, when you have an isolated dual-battery system, you only need one jumper cable to get you going again in case you left your lights on and drained your regular battery. You jump yourself + to + and bada boom bada bing, off you go.
Jeff Zepp
Kittredge CO USA
1971 & 1976 FJ40s, 1978 FJ45, 1987 FJ60
Rising Sun 4WD Club, TLCA #4063
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