Aux. Battery connection to fuse panel

Probably like a lot of you Vanagon Westy owners, I have been powering my interior lights, radio, and cig. lighter from my auxiliary battery by running a (fused) wire up and into the bottom contact of the #3 fuse spot (fuse removed) on panel. This works ok, but its sort of a kludge. I looked at the wiring diagram and noticed that there is a spare connection on “E” multiprong connector, “E3”, that goes directly to the circuit that fuse #3 powers. I have a bunch of scavenged wire pigtails that have the molex-type connecter on one end. Connect one of those pigtails to the aux. battery wire, and pop the other end into “E3”. Fuse spot #3 is left without fuse as before. Diagrams below might help, I should make an annotated one… crudely annotated diagram added.

  1. #1 by Simon on January 19, 2011 - 8:52 pm

    Looks like a nice clean solution… and no more loose kludgy wire – yippee!

  2. #2 by joe on February 4, 2011 - 9:31 am

    I’m interested in adding a powered sub under the rear seat and running it to my aux battery. I think that switching the stereo and lights over to the aux would be great to do too, but I have such little knowledge of the wiring that I don’t understand your description. Is popping the fuse#3 out all that is required to pull the circuit off the main battery? Should I remove the red wire running to that fuse and move it to the E3 connector? Any help would be very appreciated for this noob.

    • #3 by albell on February 4, 2011 - 3:57 pm


      I’ll email you with details if you like, but really its pretty straightforward. The stock wiring has the interior lights (except overhead sink light in westy), the cig lighter, the lcd clock, the radio (if wired properly) all on the circuit protected by fuse #3. If you want to power that circuit from aux battery then you would lead a fused wire up to fuse box and connect it to the lower tab of the #3 fuse slot (fuse removed). Terminating the wire with a male spade terminal allows you to connect there. My modification moves that wire that comes from the aux battery, to the back of the fuse panel and connects to the pin labelled E3. This pin is part of a group of pins that mates with the plastic multiconnector “E”. So to do my mod, you need a terminal on the aux wire that will go into that plastic multiconnector, its a molex type connector (see here
      If you can live with the aux battery wire just connecting to the front of the panel via a male spade (0.25″ wide I think) into the lower slot of fuse#3 spot, then that would be the simplest and easiest thing to do.


  3. #4 by joe on February 6, 2011 - 10:58 am

    Thanks ab,
    I’ve got an 8 gauge, fused wire running to the fuse box now. I’ll probably step this size down to a higher gauge wire before connecting. Do you think radioshack has the proper terminal for attaching to the wire to plug E3 of multiconnector E?

    • #5 by albell on February 6, 2011 - 11:35 am

      I think 8 gauge is big enough. To make sure, add up all that you think will be powered by the circuit, in wattage, then divide by 12.5 (or so) to get amp draw, and look up tables for recommended wire size.

      Radioshack should have the right terminals, and crimpers if you need them. Get some heat shrink too and make a nice job of it 🙂


  4. #6 by albell on May 9, 2011 - 10:27 am

    I want to correct last comment about 8 gauge wire to the E3 connection. That gauge wire is a bit too thick and stiff to route nicely into block. You don’t need that much current carrying capacity and perhaps, if you draw a lot of power on that circuit (inverter in cig. lighter for instance), the E3 terminal and internal trace may not be large enough to cope.


  5. #7 by kevin p gilleran on October 5, 2013 - 12:31 pm

    Auxiliary Battery wiring: It looks like the existing wiring from the starter battery to the auxiliary battery is too small on existing 86+ Westys. Did you have to pull a new #6 or #8 with inline fuse from one to the other as part of adding the ACR kit?
    I am looking at adding a 30+ amp amplifier for a new stereo that will likely drain the auxiliary battery and I concerned that when the aux battery is charging, while driving, it will draw too high of an amperage across the existing wiring to the starter battery.
    If you did pull a new wire how did you locate it ie run it under the car or through the car under the carpet?
    Thanks for your insight.

  6. #8 by dandurston on November 5, 2015 - 9:36 pm

    Thanks for the info. Much appreciated. I’m going to try this soon.

    One semi-related question: Is there a simple way to manually connect an auxiliary battery into the van’s charging system to charge up an auxiliary battery on road trips? I’ve got a 300w solar array that does a nice job keeping my 310aH battery bank charged up, but on a road trip it seems like a shame to not also charge it off the alternator so I can really use power. If there is a simple spot I can just plug a positive wire from the aux battery into whenever I’ve got a road trip going on that would be sweet. Thanks!

    • #9 by albell on November 22, 2015 - 9:07 pm


      Forgive the delay, my fault.

      You don’t want to use an ACR? If not you can use one of those marine switches, the rotary type. I understand leaning towards a manual switch but my ACR works well.
      Give me an idea of yours set up, ie circuit from panel, collar charge controller, battery.


      • #10 by dandurston on November 22, 2015 - 9:30 pm

        Looks like I do want to use an ACR. I hadn’t seen those before. My solar is working pretty great right now though (8 amps at mid-day, likely a lot more in the summer) so I might not get around to it for a while.

        I’ve got three 100w monocrystalline flexible solar panels from Renogy, 40A MPPT charge controller, 2 x 155aH 12V VMAX Tanks batteries and then a 2000w Samlex pure sine inverter. I’ve also got a positive wire from the batteries going to a fuse panel (like the one GoWesty sells) and then wires from there split off to run the propex heater, van lighting etc.

      • #11 by albell on November 22, 2015 - 10:00 pm

        Hi dan,

        Loads of power, lucky dog 🙂

        If or when you do decide on an ACR, I can recommend the blue seas one. My older model has worked without fail for, jeez, now must be 13-14 years?

        Do you charge up your aux batteries at home once in a while? I would, well I do with my 200 Ahr. agm. Just to make sure it’s getting a good hard charge once in a while. I could go on boringly about charging regimes etc but you probably know all that.

        I’m guessing you live in a stunner place than southern BC?




      • #12 by dandurston on November 23, 2015 - 8:02 am

        Actually I seem to live near you. I’m in Victoria, BC and got those 8 amps at Tofino this past weekend (5-8 amps from 9am to 2:30pm). We just moved into the van a few weeks ago so the solar is new, and my wife always takes the van to go to work so it was the first time I got to see how it did in full sun. The worst I ever do is ~1.5amps on a dark rainy day (unless I’m parked in the shade), which is still enough juice to run the Propex HS2211 at night. My issue is that my wife’s parking spot at work is shaded after 11am and she doesn’t have anywhere else to park.

        I met another van guy (not a Vanagon) with the same solar panels and he says in southern BC he gets up to 15 amps in the summer (i.e. 200w out of 300w theoretical) but I should do a little better because I can tilt my panels using the pop top.

        The WestMarine store in Victoria has a going out of business sale so I’ll see if they have any ACRs in stock. I have a Canadian Tire plug in charger that we may use but it maxes out at 4 amps. I don’t know too much about charging regimes – I’ve been researching all this one piece at a time. I know a lot about panels, batteries, inverters and charge controllers now, but pretty much nothing about anything else. It would be great to get a good “shore charger”.

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