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Thread: Second battery

  1. #1
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    Default Second battery

    This topic had become too large & cumbersome (7 pages). Much of the topic was covering individual errors in wiring or attempts to modify the wiring for unique circumstances. We have cut the forum down to deal with installation and wiring of the 2nd battery per VW's option.

    Sorry, but we can't devote the amount of resources we were asked to totally unique topics . . . "I wanna wire my hot tub to the auxillary battery." The most common are trying to wire the interior lights or radio to the auxiliary (neither practical) and I'll try to leave those posts. The other unique wiring additions don't apply to sufficient members to continue them.

    Occasionally, you will find a post that isn't clear because the answer refers to a post that has now been cut. Sorry for the confusion and you can email me direct for any requests to edit -- I'll do my best.
    Last edited by Capt. Mike; 04-20-2008 at 06:06 AM.

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  3. #2
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    Dual batteries are common on Vanagons and were standard on some models. The Bentley shop manual Section 97.9a shows the layout for Canadian Westies where dual batteries were standard.

    The well under the driver's seat will hold a 2nd size 42 battery. It is not sealed and outside vented like the main, but few have reported problems. VW sells the standard parts necessary -- a special camper dual lead positive cable, a ground strap, and the hold-down clamp. Most Vanagons were pre-drilled & tapped for the hold-down & ground bolts. Since the seat doesn't swivel 180, you may remove it per Bentley 72.2 for working room.

    In the US version the relay is wired "backwards" to allow the sink to operate without the engine running. The relay cut off the fridge when the engine stopped. You will have to rewire it so the relay now places both batteries in parallel when the engine is running to recharge it. When the engine stops, it will remove the main battery from the fridge circuit to prevent draining it. You may have to move the relay slightly to clear the battery box -- it's a tight fit. You MUST have a positive post guard (comes with new batteries) as the metal box lid is very close to the post.

    There is a copy of dual battery wiring on my pic post site linked from the home page. Look in the technical diagrams folder. Note that I chose to add the heavier cable in picture 97.9a to cross-connect the two batteries rather than rely on the smaller gauge wire through the power panel that is stock.

    Most put the sink pump on the new auxiliary battery. Replacing the 3x10W incandescents with an 8W flourescent is adviseable, but other than that, it is not practical to change the normal cabin lights.

    Also on my pics post site are pictures of a 2nd battery monitor gauge, some additional interior lights and the use of DIN standard electrical accessory jacks instead of the inferior cigar lighter style sockets.

    See the post under TIPS forum on Battery Care -- dual batteries add another set of considerations.
    Attached Images Attached Images
    Last edited by Capt. Mike; 02-09-2009 at 07:31 AM.

  4. #3
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    Sort of an add-on note: The purpose of the 2nd battery is to allow you to run the fridge on DC when stopped for a short while without changing over to LP. Shopping, lunch, a quick attraction sort of thing. It can also allow taking the sink pump off the main. But it is not some magic power source so you don't have to run the engine/recharge the main every so often. For example a 72Ah battery is just that -- 72 amps for one hour or 7.2 for 10. So don't count on a big load like a heater over several days. I always advise people on electrical items to "DO THE MATH!" V x A=W; A x Hrs=Ah.

    I suppose you could wire a DIN accessory plug to it as well for some in-cabin accessories. I have a DIN plug mounted in my cabin (rear seat wall), though I didn't try to wire it back to the auxiliary battery. It's for things like a car vacuum or air compressor.

    I've seen some put a cigar lighter or the DIN plug on the face of the sink cabinet near the indicator panel, which might be a solution with a shorter wire run along an existing path.
    Last edited by Capt. Mike; 11-08-2010 at 07:33 AM.

  5. #4
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    Transferred from another forum to keep similar topics together.

    rickcrooks

    Junior Member posted 09-25-2000 10:29 AM

    My girlfriend and I are on the road for two months in my '86 syncro and I wired in a second battery as directed after reading through the archives. But my cabin light still seems wired to my regular battery. That is, it doesn't come on until I reconnect my main battery. The two wires from the fuse box behind the drivers seat seem to connect to the fridge and the indicator lights on the fridge/stove console--not the cabin light as said. Am I correct in assuming this? Do I need to find the wires to the cabin light and wire into my second battery directly? Confused and without the book. Trying to find one on the road.

    thanx for any info

  6. #5
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    Yes, your cabin lights still run off the main. Since a 2nd battery was not standard, all the electrics are set to run off the main.

    The cabin lights run through the fuse box and would therefore be difficult to switch over. The 2nd battery is just for the fridge & water pump unless you re-wire other things. Probably not worth it. See the post under accessories -- some switch the main cabin light from the 3x10W bulb style to an 8W flourescent to save power yet better light.

    You can get the Bentley shop manual at any dealer -- most still stock them.
    Last edited by Capt. Mike; 04-20-2008 at 05:56 AM.

  7. #6
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    There is an addition to the TIPS forum, "Care & feeding of batteries" thread concerning deep-cycle batteries that might be of interest to owners considering the auxiliary battery retrofit in Type II's & Vanagons.

  8. #7
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    I am adding and aux. battery and I am not sure were the normal ground location is. There is a hole for the hold down and another hole located behind the relay. Is this the correct hole? Also, I saw mention of a dual lead postive strap in this post. Does anyone have any idea of a part number. The parts guy at my dealer was tring to sell me parts for the battery in my engine compartment. Clueless.

    Thanks

  9. #8
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    What year & model? Read the Message Board Guidelines, especially #3.

    I'm assuming, because of your comment about the battery not being in the engine compartment, you have a Vanagon. Tell your dealer to look at the fiche, plate #153-40, key #1. It should say Harness for 2nd battery, P/N 255 971-228A. This is from an '88> fiche, but probably the same for others.

    My Vanagon has a threaded ground strap hole in the rear edge of the swivel seat platform. It doesn't really matter as long as it grounds to solid metal and doesn't short the relay. I moved my relay further to the right putting it behind the battery box frame instead of on it out into the box area.

  10. #9
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    Indeed, I have an 85 westy. I just slipped

    The part 255 971-228A has two pigtails that are mounted to the terminal clamp. I have looked at the tech diagrams on your web page and I am not sure to which the lead are supposed to connect. It looks like one of the leads connects to #30 on the relay (alternator) and the other to the fridge. If this is the case do I leave the wire to the sink pump connected to the relay?
    Last edited by Capt. Mike; 04-20-2008 at 05:58 AM.

  11. #10
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    There's a wiring diagram on my pics site linked from the home page that should clear up the what-wire-goes-where. The harness is color coded and I've noted the numbers on the relay connections.

    Understand how a relay works; 2 terminals, #85 & #86, trigger the relay. In this case activated by current from the alternator so that the relay closes only when the engine is running. #30 & #87 then connect the battery power (hot lead from main) to the appliance (in this case, 2nd battery).
    Last edited by Capt. Mike; 04-20-2008 at 05:59 AM.

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