battery reroute

[bmwrp8]

Originally the battery in my e34 is in the engine compartment, I decided to put the battery in the back seat. I've bought the original wiring harness from a donor e34 with the battery in the rear. My question is where does the obc gets its info on voltage in test 09? bec since i rerouted the battery it says 13.48volts no load. and with a/c , lights it says 10.90-11.48!WTF! but when I hooked up a digital volt tester directly in the rear battery it says 14.10-14.24 no load and 12.98-13.55-13.98 with A/c and lights. the obc is waaayy off. It does not do this when i still had my batt. in front. Any info guys will be appreciated. tnx:)

[shogun]

I have in my E32 the battery under the rear seat. Last year I tested with 3 different DMM on battery direct, at plus pole under hood and the indication on the OBC, the OBC was always lower, probably because of various connection points up to the OBC , I assume.