Saturday, May 25, 2013

115ah aux. battery upgrade 2000 EV

I recently upgraded the aux battery system on my 2000 Weekender and am very pleased with the outcome.  For starters I got kinda lucky and happen to find this huge sealed AGM battery at the local battery shop while I was looking for a replacement deep cycle that would fit under my driver's seat.

The only new option they had size-wise was an Optima yellow or blue, but these are a measly 55-60ah and cost close to $200.  I got the 115ah battery for $75.  It was a used unit from an electric car that they had pulled when it reached 80% capacity.  Some quick napkin math informed me that that still puts me ahead of the game (theoretically 92ah) and at a fraction of the cost of an Optima.

 It took a little figuring to get that 13x9x7 battery to fit under the driver's seat.  In terms of fitment, I had to delete the rear plastic shroud at the rear of the seat box, cut off the batt hold down stud and space the front of the seat up 2mm on each side.  With any custom endeavor there are always tradeoffs and these seemed minor to get nearly double the batt capacity using the same space only more efficiently.
 Battery installed under driver's seat.
 Sits pretty much flush with the seat box.
Pic with seat removed to show placement/orientation.  Stock aux. battery relay still in place (L top corner of seat box), but soon to be replaced with a Sure Power 1315A smart solenoid (below).

picture courtesy of
 Ok, top L of the batt box is where the SurePower 1315 is installed.  I installed this with two rivets so the finish on the outside of the box is pleasantly stock looking and flush.  To connect to the main battery I left the stock 10ga wire in place and also ran a 4ga wire in parallel from the sure power solenoid to the main batt so that if/when I need to do an emergency boost to the main battery to perform an ad hoc jump start, it will be just a switch throw away.  This 4ga wire exists the int through the same grommet as the stock 10ga wire and it follows the same path under the vehicle up to the battery fuses where it is protected with a 125a strip fuse.

 Out with the stock 10ga ground wire (bottom brown wire), in with a VW customized 2ga ground wire.

For kicks I installed this little volt gauge which is on-demand (still need to wire in a switch for that, just connect the trigger wire for the pic).  And to the L is my aux. batt jump start switch, which manually connects the aux batt to the main batt for emergency start situations as described above.
 A few days earlier I had epoxied an LED indicator light to the sure power unit which lights up when the emergency start switch is activated.  This way I will know when it's on, if it got bumped accidentally or if my kids discovered it.  Also in view in this pic is the Anderson connector sitting on top of the batt.  This is my preferred method for hooking up my small 20w solar panel when camping for longer periods.  It's a safe and positive connection and way smarter IMO than a cigarette lighter.  I like having a small moveable panel like this as it is easy to move around and keep in the sun at the best angle all day to maximize charging potential.
 The stock EV weekender fuses are visible to the L, and the two new ones I added are installed right next to it (two red 10a fuses) using spare VW fuse holders that clipped right into the extra slot--factory fit n finish.  One is for the 1315 isolator and one is for the solar panel connection wire.
 Another view of the fuses and some of the wiring.

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