What battery do I need?

August 2, 2008 1:34 PM

Googlefu = fail. Answer not in owners manual. What is the cold cranking amps rating for the battery which is recommended for the 2002 Nissan Sentra SER Spec V, 2.5 L. Or alternatively, what battery do I need to buy.

I have received conflicting answers. Sears tells me its 490, yet the reading on my currently installed (yet failing/dying) battery is 550. I would love it I could find an official source (ie from Nissan) which specifies which battery I need. Any ideas?

posted by yoyoceramic to travel & transportation (10 comments total)

If in doubt, measure the battery tray's physical size and get the biggest battery you can fit in there. That is what I'd do in every instance where money wasn't an object.

If money is an issue, then get the Sears rated level one. 490 is plenty, but with batteries, a good stonking powerful one is a nice peace of mind product to have. Good quality batteries tend to last longer, too.

An alternative money saving idea is get one that is as big a rating as possible for the same physical size as the one you have now. It's all about how much you want to spend, to be honest.
posted by Brockles at 1:58 PM on August 2, 2008

It has been 6 years since I took physics, but I want to make sure I cannot hurt my car by having a battery which outputs "higher" amps than what the engine is "supposed" to take. Quotations qualify my ignorance.
posted by yoyoceramic at 2:05 PM on August 2, 2008

Nope, you can't hurt anything by getting a battery that's got a higher current sourcing capacity than the minimum for your car. I could prove it using some math, but I don't think it's necessary. I think all you'll notice is that your car's starter will turn snappily and your car will come to life pleasingly quickly, if you notice anything at all.
posted by TheNewWazoo at 2:30 PM on August 2, 2008

I want to make sure I cannot hurt my car by having a battery which outputs "higher" amps than what the engine is "supposed" to take.

You can't. Extra voltage would be an issue, but amps will not be.
posted by Brockles at 2:37 PM on August 2, 2008

They way "electronics" work in general is that the source, battery in this case, will provide as current as is asked for up to its limit. Specifically, the battery won't force the car to choke down extra current it doesn't want.
posted by humanawho at 2:38 PM on August 2, 2008

Batteries are sold by size, and if you live where it gets cold in the winter you should get the highest rated battery that fits you can find, as suggested by Click and Clack; as the linked article points out manufacturers can fudge these numbers considerably so you might want to verify them from a source like Consumer reports if you want to get the most CCAs for your buck.
posted by TedW at 2:43 PM on August 2, 2008

Well, we're talking about an aluminum four-cylinder engine here, just about any battery will do. A higher rating will give you the snappier starts mentioned above, but I'd bet any car battery will be sufficient.
posted by knave at 4:41 PM on August 2, 2008

Go with the Sears battery. I've put DieHards in all of my cars over the years and never been disappointed.

Where are you located? Sears online has several DieHards for your car. The DieHard Gold North specs at 640CCA. The "Gold South" version has 550CCA. They must be showing you the "Weather Handler" version.

If you live in a warm area (i.e. you don't have to worry about starting the car on sub-zero mornings) the 490CCA battery will be fine.
posted by Thorzdad at 6:53 PM on August 2, 2008

The number of amps that flows through your starter motor depends on:

(1) voltage at the battery terminals

(2) resistance of wiring, connectors, solenoid contacts etc. between battery and starter

(3) starter motor resistance

The higher the voltage, the more current; the lower the resistances, the more current.

You can take (2) as being pretty much constant. (3) depends on the speed that the starter is turning over; the slower, the lower. On cold starts, the engine is stiffer and harder to crank, the starter will turn slower, its resistance will be lower, and it will draw more current than on warm starts.

That leaves (1). A battery with a high CCA rating will have a lower internal resistance than one with a low CCA rating, and this would in fact yield a somewhat higher voltage across the battery terminals during a start (you'd see no difference under normal, non-starting loads like headlights etc). So your naive assumption that a high CCA battery might stress your starter is not completely unfounded. In fact, such a battery might well pump a little more current through there.

However, if a starter motor is going to burn out, it will do that because its windings get too hot. Winding temperature rise depends on how much total energy the motor is fed during a starting cycle, and that in turn depends on two things: the amount of power (voltage x current) dissipated by the motor, and the time that this happens for.

With the slightly higher voltage available from a high-CCA battery, you'd find that the starter can turn the engine over faster. This reduces the current drawn by the motor somewhat, making the power dissipation in the starter a little lower than you might at first expect, but the main thing is that it makes the engine more likely to catch, which reduces the starter motor's running time. The net effect may well be to reduce the total starting energy required, and make the starter motor less hot.

All of which boils down to TheNewWazoo being exactly right.
posted by flabdablet at 3:12 AM on August 3, 2008

This is news?

I keed, I keed!
posted by TheNewWazoo at 7:45 AM on August 3, 2008