Possible bad battery cell

STREETTERRORIST

MEMBER
2006 SUBARU IMPREZA
2.5L
4 CYL
4WD
MANUAL
150,000 MILES

Okay, I am going try and keep this short, so if you want more details just ask.

Recently installed a new stereo system (loud subwoofers) after install normal idle voltage has been 14-14.3 (quality aftermarket voltmeter). With stereo at full tilt and engine idling I'd get voltage drop to 13.4 at worst and recover to 14+ immediately.
Few days later now my idle/driving volts read 13.1 with stereo off.

(Edit: had bad voltage drop (down to eleven volts at times) for a couple weeks with stereo full tilt until I had amp set professionally, added second battery day before that was done. Then few days later the above started)

Upgrades I have done:
One year old stock lead acid battery up front.

200 amp alternator.

Big three in 1/0 wire

Secondary larger AGM battery in trunk, 1/0 wire from front battery. 1/0 ground in back also.
(About one year old out of my truck)

SMD VM-1 volt meter. (Reads very accuratly)

What I am assuming is happening now is that the lead acid battery has a bad cell even though it is only one year old. Yes, it is a cheapo wally world battery. But should not happen that quick. But I guess with the abuse this stereo does to them okay.

Question is, can someone confirm my thoughts or is there possibly another issue going on as well?

2 Replies

STREETTERRORIST

MEMBER
2 POSTS

Well was not expecting this.

First to add to OP I have been idling my car for most of the day with stereo full tilt, turned subs off for over two hours and idled for forty five minutes/drove car around on beach for a good twenty five minutes at twenty five mph, 2,000 to 3,000 rpm's. Still had the lower voltage.

So hours later I get on highway and up to sixty mph and volts read 14. Idle still 14

So apparently over and hour of driving around on beach/stopped and idling was not enough to top off batteries after being abused for several hours at idle.
Do not know when voltage dropped off to begin with initially, only noticed after turned off subs and shut car off. But after the charging back up on highway I am going to assume my reserve voltage slowly fades at idle with stereo full tilt.

So I think that solves my issue for now. If I notice low volts later I might be back for information, but think I got it figured out.