Car battery matching with alternator

On Wed, 29 Oct 2014 09:03:02 -0700, Jim Thompson Gave us:

Funny how now, they wouldn't hesitate to, and would even give a watertight line and term caps for it.

On Wed, 29 Oct 2014 09:03:02 -0700, Jim Thompson Gave us:

This is why, as you say, it is a voltage driven current source.

It will drive into the load only up to the max driving voltage of 14.8 VDC, OR the alternator's max design driving amperage at that voltage or below, whichever comes first.

The added voltage actually places the battery under a charging state, and makes up for small cable drops as well. When all one has is 14.8 at the alternator terminals, minus cable drop, every half volt of that drop matters a bit.

Long starter cables pose problems at times for that task too.

That is why good, solid terminal connection cinching is one of the most important elements in power circuits and their connection and feed elements.

Thanks for that detailed explanation, as well as the less detailed ones from other respondents. My car's battery uses 24F terminals on the top. The old battery was an Interstate MT-24F model that had 600 CCA and 5 yr warranty. Because the same model was not in stock, I had it replaced with Interstate MTP-24F model, which has 800 CCA and has a 6 yr warranty. But is also 5 lbs heavier. BTW, the car is a 20-year old Honda Accord that still runs very well, despite the 320 K miles in it.

There is also the rule, "If it ain't broke, don't fix it!" The current method seems to work pretty well. What would the consumer get from a more accurate battery temperature measurement?

Because of temperature mis-match most charging systems over- or under-charge the battery.

Over-charging shortens battery life by overheating and water/electrolyte loss.

"The current method" is still what I designed almost 50 years ago ;-) ...Jim Thompson

I think that is the point. It works plenty well enough so that I can't remember the last time I bought a battery. I just know my 17 year old truck is on its third battery.. well, fourth if you count the one that was replaced under warranty after just 3.5 years. There is no problem to solve, so don't try to fix it.

You clearly don't live in Arizona. ...Jim Thompson

What's wrong with incremental improvements over time? That's what the whole car industry has been doing ever since Henry Ford.

Nothing is wrong with incremental improvements. But what improvement is needed? Will this make the batter last longer? I've yet to read anything saying that.

You missed my post ?>:-} ...Jim Thompson

No, I read it. Didn't see anything to reply to.

On Thu, 30 Oct 2014 14:18:37 -0400, rickman Gave us:

What about the alternator? They fry too.

Decades ago, lead acid batteries were dirt cheap, and slapping in another of those was cheaper and easier than a new alternator. Now, both the task complexity, and the price are closer together, so longevity needs to be engineered in to both in a more focussed manner.

One does not see '73 Cadillac batteries in a '15 Chevy Monte Carlo. The charging gear differ too, and the watchdog charge manager on that alternator did not previously exist.

Damn! And I thought the horse was dead.

Cretin. ...Jim Thompson

That is your way of explaining why you are asking where I live?

Your assumption is incorrect. The manufacturer considers the CCA (Cold Cranking Amps) and AH (Amp-Hour rating) of the battery. The AH rating is of lesser importance since the alternator keeps the battery fully charged unless you're operating electrical equipment with the vehicle off.

The batteries in my truck, from Costco, rarely last more than three years, probably because I don't drive the truck very often. So I always get a warranty replacement. It's not really free, you get a refund of the price you paid then you buy a new one at a slightly higher price.

Usually a battery replacement is free for the first year. The battery I bought at Costco extended that free replacement to three years and prorated after that. All in all it is a pretty good warranty and the second battery is working fine after more than three year... I think. I really can't recall just how long it has been.