Dead Battery Diagnosis
by Pat Goss
Sooner or later, most of us will be faced with a dead battery. Now if that dead battery happens to be the result of a car that sits for long periods of time, well there’s an easy solution. It’s a battery maintainer, such as we have here. Now maintainers charge the battery, and then shut off when it’s fully charged. This is not like a trickle charger, which you don’t want to use, because it never shuts off. So you’re looking for a maintainer. But, suppose that’s not the cause. You’ve got a dead battery. And the technician comes out with a tool like this, and hooks it up to your battery and pushes the button and says, “Oops. You need a new battery!”
Well your response to that is, “Oops. I need to get out of here!” Reason is, this is a good tester to determine what the next step in testing the car might be, but it is not a good tester to determine if you need a new battery. No matter what they have printed on that dial.
Alright, so what are you looking for, when you have a battery problem? You look for a modern tester. Now modern testers use electronics to test the battery. They measure the internal workings of the battery, using sophisticated circuits and so on. They may be hand-held like this, or we have another one that is more typical these days. This one uses a unit that connects to the battery, and then this handheld wireless unit receives signals from that, and it gives you the ability to test the battery, the battery and the alternator, the battery and the starter, or the entire system. This is the sort of thing that you’re looking for. Because this will tell you whether or not your battery is simply discharged, or whether it needs to be replaced.
But suppose it does need to be replaced? What then? How do you wisely shop for a battery? Well, in the past, you always looked for the most in cold cranking amps that would physically fit in the car. Well that’s still true, but we have to add something else to it: we have to add reserve capacity, or RC. Reserve Capacity is the amount of time it takes for a specific load to drop the battery where it won’t start the car. So, because modern cars have all kinds of computers that draw power out of the battery all the time, you want high cold cranking amps, and you want the biggest reserve capacity that you can buy. And you do that, and chances are the battery will last longer; the alternator, the starter, all sorts of things will last longer on the car, and you won’t be stranded.
And if you have a question or a comment, drop me a line right here at MotorWeek.