Battery in trunk ... Lights Surge ... What gives?

[eng0270 10]

I bought a trunk mount kit for my battery from Summit Racing. Everything went in fine and the car starts but when running at night, all my lights seam to surge. Is the gauge of the battery cable too small or do i need to change my stock alternator out? Any help would be appreciated!

 

Thanks,

Kevin

[foothilltom 33]

Did your surging problems begin with the migration of the battery to the trunk? Was that the only change you made prior to you noticing the problem?

 

Voltage drop is relevant depending on the length and gauge of the wire, but given the distances involved here, I can't imagine that's an issue. Even if it were, it wouldn't produce a surging effect, just reduced voltage consistently.

 

I would suspect your voltage regulator. Its job is to "smooth out" the voltage generated by your charging system. Its a pretty cheap part, but I normally like to diagnose more thoroughly before I buy stuff. If you can reproduce the surging behavior in the driveway, get a meter on there and see what you're producing at idle, then rev it up to cruising RPMs and see what gives.

 

Good luck.

Tom

Edited June 2, 2010 by foothilltom

[Angel 24]

I bought that same kit and I've never had that problem.

[danno 128]

My guess is that the alternator is turning on, and when it does the lights get brighter. This could happen if you have a high output alternator with the long connection to the trunk. I am not sure where the minus of the battery connects to the body of the car, but if it is in the trunk make sure it is a super clean connection. The second thing to try is to attach a large seperate wire, like 10 gauge, from the minus of your battery to the point where the headlights wiring harness connects to the chassis ground. A third thing to try is to take a different seperate heavy wire from the plus terminal of the battery to the accessory feed to the car. With this method, you have one wire from the plus side to the starter, alternator, and regulator. A seperate 10 gauge wire connects to everything else. I hope something helps.

[danno 128]

You should also check the ground connections of the voltage regulator and the ground (minus) wire that connects between the engine and the body. With the battery in the trunk and the ground wired to the chassis in the trunk, all ground connections become more important. So check all these first.