Battery behind the passenger seat? Beware...

[Paul Workman]

A couple unique issues unique to those that have relocated the battery to behind the passenger's seat tossed me a curve or two I thought I'd pass on to those having done this particular modification:

For starters, if the battery is "stone dead", i.e., zero volts or very nearly so, you can't access the battery by opening the electrically activated hatch release. *

Once you manage to recharge the battery, or install a new one, you would be wise to measure the current draw to determine perhaps the cause of the dead battery condition in the first place! But, that likely means having the hatch open to access the battery for the static (current draw) load test; & there in lies the problem unique to those with this (behind the seat) mod: The light switch for the lights in the hatch area comes ON while the hatch is open - spoiling the static load test (by introducing approx 4.5A draw for the lights).

To measure static (keep-alive) battery current, you need to have ALL of the lights (courtesy, etc) turned OFF. (pls continue on...)

Ordinarily, a person performing the "keep alive" current test wouldn't have to think about the hatch area light switch. But, most procedures you'll find DO NOT consider the hatch light switch b/c the hatch is usually shut. Not so with the battery moved to behind the seat (mod). You'll have to rig up something to keep that hatch light switch depressed while testing current draw! (I use a bolt with a nut on it screwed out so when the bolt head is against the switch plunger, the nut can be wedged against the underside of the (hatch plunger) hole in the plastic fascia - thus keeping the switch depressed in the OFF position.)

Once the hatch light switch is addressed (turned OFF), the hatch can be open to easily facilitate access to the battery to do measure the typically <25 mA (21-23mA) parasitic current "keep alive" drain.

Now, if the current drain is excessive, I find the "fusible links" (behind the normal battery compartment space) is the quickest place to start isolating the circuit(s) with excessive draw before proceeding to the fuse panels.

Oh! In case you were wondering, in my recent experience it was the dash light dimmer switch that was accidentally left in the full ON position. Apparently, over a 3 day period (even with the headlights turned OFF) that was enough to kill the AGM battery to the point where it could not be revived.

NOTE: As a suggestion, the battery relocation mod is enhanced by running a separate pair of battery cables to inner fender - ahead of the original battery location - and attached to the plastic inner fender. This facilitates attaching jumper cables in the event the battery has become discharged for some reason, w/o having to access the battery compartment behind the passenger seat! Justa thought!!

[Erik]

Great post. Thanks, Paul.

[WARP TEN]

Sounds very much like the voice of experience. Hope you got it sorted out. How's life in the country? --Bob

[XfireZ51]

Perhaps some of u may recall that the battery was licated behind the driver in the C3 and obviously moved to engine compartment for C4.