Thread: Battery in the trunk low volt reading

Hi All,

I have U13 DET with a few electronics on board (EVC, SAFC, Turbo Timer, DEFI Guages, HID Bixenon Lamps and a regular CD player.) currently using sp800 stinger which is located at the trunk of my B14.

I have a gauge 4 wire for ground which trail directly to the head and the other one on the body. My Positive power cable is gauge 0 (RYAN AUDIO).

The problem I have now is that my volt reading says 11.6 v erratic +/- 0.3v. when I have everything turned on including the AC it goes down to 9.9v +/- 0.3v. Please help on where to look?

Check your battery ground wires. I have 3 wires going to different places in the trunk haha. But make sure theyre got going to a painted surface or somewhere that doesnt really make sense. The rear seatbelt box is a good place ( where the bolt is)

Your ground should be just as big if not bigger then your positive cable.

Also, if you're going to ground at the chassis in the rear it is HIGHLY recommended you run as big a cable as you are willing to from battery ground to the engine.

Thanks I'll try to ground it on the seatbelt box, the car was newly painted which I was thinking could interrupt a bit but not this big.

the ground in the body goes directly to the (-) negative terminal as well as the ground to the engine. There are two ground wires connected directly to the (-) negative terminal of the bat.

Where are you reading this voltage? at the battery? Alt? Dash? And with what? Gauge, meter, other? 0 AWG is overkill, having too big of wire is just as bad as not enough, 4 AWG is plenty. Make sure you have a good ground from the alternator to chassis and use a nut and bolt to ground the battery in the rear. Make sure to remove any paint before grounding then use some clear or other paint to protect the connection, or the red anti battery corrosion spray. With the battery in the rear your voltages will vary from front to rear.

Squirlz,

I'm reading the volt with an Apexi turbo timer, Stinger voltmeter and the NEO SAFC they have +/-0.3V variance. Before I switched to the 0AWG wires I have less than 1 volt to what I'm reading now, I gained 1 volt by having it replaced by a bigger gauge wire.

Yesterday got me to 12v with AC on from my erratic 11.5v when I ground the battery to the seat belt box at the rear.

The ground from alternator to chassis I'll have to re-check and probably sand some ground points, thanks

To be clear: ground everything to everything. Engine bay, make sure youve got grounds from all parts of the engine to the body. In the trunk, make sure there are plenty of grounds to the body as well.

i seem to be having a simular issue, mine is that when i start my car i see 13.2 13.3 max then it trickles down to around 12.9 and as i drive my car a little more it goes up and down +.1 to -.2 . this is a brand new alternator, probably around 600 miles on it. i also have my battery in the trunk, i have yet to be able to figure out what it is. im also reading my voltages on my apexi turbo timer. seems like we both have somewhat of the same issue

i had a 4 gauge in my car battery never stayed fully charged went 1 gauge and im in 13.3 with everything on with 2 2000watt amps

it might just be the cables.im running a 0 gauge power wire and a factory size ground, maybe i need a larger ground?