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E36General discussion and technical help for (E36) 1992-1999 3 series cars. 318, 323, 325, 328.
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Your Ride: 1995 325i
New battery, better running?
I'm almost embarrassed to ask this question, but would a brand new replacement battery make any difference in the way a car runs, aside from starting up more quickly (and reliably)? I just put one in yesterday after my original (!) was put to rest, its length of service and the cold weather were just doing it in; sometimes cranking over the engine lately was getting to be a bit too dicey a propostion. With the new one in the engine turns over strongly right off the bat, but it also seems that the car just runs more smoothly and powerfully now even in normal driving. Is this just my imagination or might there be something to it (that passes the laugh test)?
When I put my new battery in, I thought the same thing. But when you think about it, the alternator runs pretty much everything after the car is started, so a new battery wouldn't really have much affect at all.
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Your Ride: 1995 325i
Yeah, exactly, once the battery got the engine going and then that in turn the alternator, I figured that was it. But my perception was so strong that I thought I'd ask the question anyway. At least I've got some company with the same experience...
Well, not exactly; it's a valid question- a new battery does make a big difference. It's true that the alternator pretty much runs everything once the engine is running. But you have to remember that the battery is also seen as an electrical load by the alternator. As long as the charging voltage (typically 14.4v) is greater than the battery voltage (12v), that greater difference of potential keeps the current flowing to the battery. This is because the higher voltage is able to overcome the internal resistance of the battery. Thus, if the battery is old and doesn't charge as fast or as well anymore, the voltage difference is even greater and it becomes even more of a burden for the charging system, leaving less current to power everything else. That's the difference in performance that you're experiencing
03-01-2007, 04:25 PM
. Well, that may still be debatable...
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