Car batteries affecting power output (kw) and performance

[Dyldo]

howdy all

A friend of mine in a SS Commondore ute had starting problems on Sunday after noticing his battery was slowly dying over the past few weeks. But since he was a busy man he didn't need to change it as it was still kicking his engine over so he would do it later.

Anyway, yesterday morning she was just dead. the battery could only click the solenoid on and wouldn't even turn the bendix on the starter motor. so he zipped off and bought a new battery and voila!! not only does the engine tick over of course but he defintiely says the car is much more eager and has a noticeable power "gain". Of course, it hasn't gained any new power over stock, it has just regained the power it was slowly losing over time.

I'd just like to know if this is a) True and b) a common occurence felt when changing batteries.

If it is, is there a good way to tell i need a new one?

[blutopless2]

it is possible that it is the alternator that is at fault here and not the battery.
if the alternator is not outputting enough to recharge the battery then this will cause the drain over time, either slowly or very quickly depending upon alternator performance.
Not sure in new cars if a poorly charged battery coupled with a dodgy alternator will effect the ignition system enough to make the car feel like it has lost power.
i have never experienced this "feel" of power gain when replacing batteries.
guess if the ignition system can be effected by the alternator then it is possible a new battery will temporarily give you the impression of increased power as it will be taking the power from the battery to top up what the alternator is not providing.

[Dyldo]

yeah i hear you, and in fact it was the first thing i said about the alternator possibly failing or dropping charge but the battery was 4 years old as well. apparently was definitely the battery.

[Peter Jones]

My '02 Bora definately picked up some HP with a new battery. Also gave it more torque, particularly at low rpm. I really noticed that I didn't have to get as many RPm on board before bringing the clutch up to take off a the lights.

The very next day it blew a coil

Pete

[sci_fianime]

Saw improved fuel consumption when I replaced my battery under warranty...

[VOLKSMAN]

i say its more got to do with the ecu resetting itself- as ecu's now cater to how heavy or feather footed the driver is. back to normal settings now-

or he's just gotta be suprised the difference it is from a parked car. lol

[DVR68U]

could it be that there is less drain on the alt when a good battery is in the system.
which equals less drag on the pulley side of the motor increasing the felt willingness of the engine

[Golf Loon]

Lots of electrical bits on a Mk4 that will give you pain with a crappy battery.

[Mr.B]

i say its more got to do with the ecu resetting itself- as ecu's now cater to how heavy or feather footed the driver is. back to normal settings now-

or he's just gotta be suprised the difference it is from a parked car. lol

I'm more inclined to believe this.

It could also be that he's under the assumption that a newer battery performs better and he just thinks it feels faster when it actually isn't.

[Ben_GTI]

From experience in a 318iS..... if the alternator is dying, the battery is providing the power for the coils and the plugs don't work as well as they should. Hence you get less power because the fuel isn't being ignited as well as it could be.

Well thats my $0.02 of experience with power (both electrical and mechanical) issues.

[Spyda]

A flat battery shouldnt have much effect on the ignition coil as the car runs off the alternator when it is on. The battery is only used after the current drawn is greater than the current avaliable from the alternator.

[Ben_GTI]

A flat battery shouldnt have much effect on the ignition coil as the car runs off the alternator when it is on. The battery is only used after the current drawn is greater than the current avaliable from the alternator.

Depends on how good your alternator is.

[Spyda]

Depends on how good your alternator is.

what?

By having a good alternator i asume you mean the alternator is in good working order and is capable of producing the correct amount of current.

If you alternator is not working than its just what i said, the current drawn will be more than your alternators output and then your battery will be in used.

[Ben_GTI]

Yea dude, hence I'm just pointing out that buy getting a new battery you could be fixing the symptoms, not the cause of slightly less power.

[Lomo]

I've been trying to diagnose faded power and increased fuel consumption on my Subaru Impreza for the past 2 years. Over that period I've changed the oxygen sensor, cleaned the MAF, replaced the temp sensor and changed the timing gear, always expecting the car to get the power back I remember it had when I bought it from my mate. I was just about to remove the injectors for a clean when the batt started to die and so I replaced it. The car has finally gotten it spirited feel back, sooo much more power, 10% better fuel efficiency and the auto gearbox changes so much more quickly. It's like a new car again

The car has had its ECU reset numerous times and it didn't change a thing. After talking to two mechanics about this amazing recovery they both said that modern cars are very sensitive to voltage drops which messes with sensor outout. The voltage drop occurs as the battery ages and thus increases it's internal resistence meaning that the alternator can't deliver its full potential.

If youre worried about voltage drops you could always do a grounding mod which is very popular in Subarus. Pretty much running a grouding wire form the Neg batt terminal to every place on teh engine where sensors are located thus reducing voltage drop introduced by corroding engine pathways etc.

BTW If you're after a batt, find a Bosch distributor and get yourself one of these, cheaper than other batts and they're maintenance free