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Flash Alert! Dual Battery Relay

Flash Alert! Dual Battery Relay
From: Harold Rust

To all westfalia camper owners, and especially those using a dual battery. If you bought a used camper with a "dual" batt. setup, it would be a good idea to check this out. I did some research at my VW dealer today about the different relays used in VW vanagons and campers. We came up with the following. 1.) The vanagon westy camper with the 3 way refrigerator (propane, 110 and the 12 volt while driving only) does not have a factory installed auxiliary batt. system. It is equipped with a small shutoff relay located under the driver's seat in the empty batt. box. It is a small 1" by 1" cube. This relay is called a : Refrigerator 12-volt heater relay. Part Nr. 231 069 555 price: 32.72 This relay is not designed to be used to charge a second battery. To do so could damage your camper. In addition the wire to the relay is only a 2.5 mm wire routed through the fuse panel. This factory setup was not designed to handle the load to repeatedly charge an empty battery. Reference, Bentley 80-91 page 97.32b, 97.33b 2.) Some vanagons did come equipped from the factory with a dual battery system. Some of these are also called campers in the Bentley, but appear to be weekenders. (no 3 way fridge) VW does list a relay called: Relay for 2 batteries. Part Nr. 411 915 511 B Price a hefty 60.39 ( maybe someone with a weekender camper with a factory dual batt. setup can verify this part number.) If the vanagon was factory equipped with a dual batt system, the second battery is shown in the Bentley diagram for that vehicle. The second battery is always conected via a 6.0 mm2 cross section wire, to prevent overheating and insure efficient charging. Reference, Bentley 80-91 page 97.34a, 97.222, 97.225

In summary: If one wants an efficient dual batt. system in a full westy camper with the 3 way refrig., it is necessary to install a new system. You have your choice, one of the following: 1.) install a manual switch, or 2.) install a 30 or 40 amp relay or 3.) install a batt. isolator.

Also note: Bentley sometime shows wire sizes in standard (awg) gauge, and in the later Bentleys mostly as mm cross-section.

Harald 90 westy with a dual batt system.

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