Weak battery and engine performance

meteg · Post by **meteg** » 03 Jan 2011, 11:29

Hello dear friends,

I have noticed that my 95 850 Glt's battery is weak. its showing 12.00 volts when I measure it.. the alternator works properly but the battery is weak. and the car performs also weak.. I believe this is due to low battery affecting the ignition performance.. is this possible? if so I will replace the battery.. the funny thing is even the car sits for a while for example for a few days or for a week the car starts..

any comments?

Post by **phils94850** » 03 Jan 2011, 15:00

It should show12 or a little more than 12 or so when engine not running, and high 13s or low 14s with engine running ( thats your alternator taking over. )

If it sits for awhile and it starts up fine then id say the battery is fine. You need to have it load tested to see how much of a voltage/amperage drop your getting when cranking the engine over.

Post by **Pauloil** » 03 Jan 2011, 19:11

need 12.4V or more to load test batt.
search voltage drop on the this site
you need to be sure your cables are good and transmit the voltage to the batt from your good alt.
an easy way to test ground wires is, under load, measure voltage at batt. Put jumper cable bet neg post on batt and metal on motor. if voltage goes up by more than 0.2v, then bad grounds

meteg · Post by **meteg** » 04 Jan 2011, 08:37

thanks for replies Pauloil,

however I need an insight about something.does the battery power affect ignition? in other words when my battery was good the car sounded better and pulled better.. its seems that since the battery is wear the engine sounds weak and the car pulls slower.. mabye this is a psychological issue maybe not..

any comments..

I will do the test as you describe..

Post by **vjaneczko** » 04 Jan 2011, 09:40

The battery is only used to start the car. Once it's running, the alternator provides the electrical juice for the car and charges the battery.

Have you checked spark plugs, wires & distributor, air filter, vacuume hoses, etc? That would alter the car much more than the battery - unless your alternator is not performing properly. If that's the case, it may be as simple as your serpentine belt is slipping a bit, or the alternator is on its way out.