What battery isolator comes in which model camper? The relay under the drivers seat in a Westy Vanagon is wored to disconnect the refrigerator circuit when the alternator is not charging. The blue wire is connected to the alternator warning light circuit. When the alternator is charging, it actually powers the relay. For some reason, they wired the ground to the starter solenoid circuit. I guess this is to disable the relay during engine starting. Of course, it would be unlikey that you would have alternator output while cranking the engine. Anyway, the ble wire is an ideal source topower a larger relay to chrge the auxiliary battery. Since it will power the relay only when the alternator is operating, there is no need to worry about one battery discharging into the other. You also don'y need wiring heavy enough to support the starter as would be needed if energizing the relay off the ignition switch.

Dennis

-----Original Message----- From: developtrust [mailto:developtrust@home.com] Sent: Tuesday, December 11, 2001 7:40 PM To: Dennis Haynes Subject: Re: Re: Battery isolator

Are you suggesting to replace the one that comes in the camper with relays to isolate-charge the "house" battery? I have not hooked up my Optima yet but soon will and I see my auxiliary battery box has a relay of sorts in it now. Will this suffice or should I consider replacing it?

William Polowniak

----- Original Message ----- From: "Dennis Haynes" <dhaynes@OPTONLINE.NET> To: <vanagon@GERRY.VANAGON.COM> Sent: Tuesday, December 11, 2001 3:54 PM Subject: Re: Battery isolator

> Normal battery isolators are a poor choice in a VW due to the forward > voltage drop. All power diodes drop over 1.0 volt when cool. As they > heat up, the drop increases. The vw senses and control the alternator > output internally so this drop is not compensated. Only 11.5 to 12 volts > actually charges the battery. Many American cars sense and control the > charging voltage remotely so the alternator output will increase to > overcome the resistance. The alternator can be modified to overcome > this. I feel it is not worth the effort. Virtually every RV manufacturer > uses relays to isolate-charge the "house" battery(ies). It is simple, > reliable, and low cost. It is also more efficient as you do not have the > heating effect with a relay. > > Dennis > > > -----Original Message----- > From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf > Of Julian Burden > Sent: Tuesday, December 11, 2001 2:11 PM > To: vanagon@GERRY.VANAGON.COM > Subject: Battery isolator > > I was told that a regular battery isolator will not work in a Vanagon by > someone who was told by someone who . . . > > I did not believe this as my understanding is that a battery isolator is > just a pair of diodes on a big heatsink. > > But, then I looked at the JC Whitney website catalog - they list several > isolators, many of which are described as not suitable for all VW vans! > > Why is this so, and what do I need? >