What method do YOU use to determine a bad battery?

[Joseph C]

Posted here, since it isn’t a repair. Do you do the “Headlights on and crank the car” load test? (Heard that doesn’t work on all cars.) Do you use a voltmeter? How? Do you pop the caps off the battery and see what you see? Do you volt-check every cell? ..

And, a related question: have you ever had to break a “surface charge” on a battery? Do you ever charge a battery with current from the house? Automatic charger, like a CTEK (I have an MUS 4.3?) A manual one? Do you shake it 48 times to “mix” any added distilled water? Do you believe in desulfators? Does a CTEK really have a Desulfate mode? ….

Asking, because my new car’s battery read 8.5 volts and had me freaked out i triggered the immobilizer.. 2 and a half hours later, actually three, put a jump pack on it and let it sit about 2minutes, had 12.6V approximately at the terminals (I have and use a multimeter) and it started right up, not just a “click.”

I am concerned the formerly 8V battery is draining quickly, and will drain down again. I may have had electricals in the car on.. I just know I got stuck. And I’m broke right now, so.

I’m presently enjoying this fine night guarding my wonderful shiny car against jerk kids that would love to scratch it up, as they have my vehicle at least once before, and therefore likely will again. I’m also slow charging said battery at 2A rate, though I’m not sure what I’m looking for on my multimeter, or when. I also read that. It is of no harm to charge a battery while its IN the vehicle… This Volvo’s antitheft is a place I don’t want to go…

Let’s discuss!

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Topic

[Jason White]

For warranty I have to use the Midtronics but for others, if they are having a problem but the midtronics can’t find it, I go to other methods. One is to load the battery with a constant load and watch the volts with a DVOM. It should drop, then slow, then hold steady, with a very slow drop. Constant drop you have a problem. Also, see how the voltage comes back up. Then load again. Try to start it and watch the volts. Another way is to watch the amps while charging right after a start. A bad battery will take too long to charge. Also, check the state an hour or so after the initial test. The test shouldn’t vary that much. I think it takes experience on this but lots of ways to check a battery and with modern cars, a slightly bad battery can cause all kinds of issues.

Honestly, it kind of blows my mine that it’s 2016 and we are still using wet cell batteries.

[zero]

If you can remove the caps and “service” the battery, Remove them and take a peak to see if the tops of the plates are exposed. If they are, top off the water. If you’re on a municipal water system with clean water (not a well), it should be sufficient. If not just toss some bottled water in there.

Charge the battery on it’s lowest setting for a few hours until the battery has reached 12.6 volts. You seem to have a battery maintainer and since it’s digital, just plug it in and let it charge overnight as it will shot off when it sees adequate voltage.

Hook your DVOM up to the battery terminals and (you’ll probably need help for this part) crank the engine while watching the voltage. It will ideally stay above 10 volts, but if it drops below 9 you run the possibility of setting low voltage codes and that is when you will start to have issues during hard starting conditions. Watching the cranking voltage on a fully charged battery is the easiest way to determine the health.

A mechanical load applied with a carbon pile is still the best way to test a battery. Electronic testers can be hit or miss. I have a cheap one I use for quick diags, I’ve used a couple of different expensive hand held units and even a wheel unit worth several thousand dollars. I would still rather have a $100 carbon pile.

Over time a car battery will die from the static loads the car puts on it. Most modern cars draw about .05 of an amp at rest which will completely kill a good battery in a month.

[Joseph C]

^^ Cool.

On the battery I just now am testing:

1. Took off charger..Battery immediately dropped from 14.25V area of charging to 12.86V fairly fast.

2. Let it sit about 6-8 minutes, charger off of course.. Battery voltage was 12.11V. Car started pretty well. (I did have the key to the “1” position on this Volvo, charging a phone from the power. cigarette lighter port when that happened.)

I now have the car running, and voltage while its running: 14.01-14.04V (this car is 1998 Volvo V70 XC)

Just turned it off and came in and typed this. Immediate voltage at battery after doing so, key back to “1” and charging this phone: 12.94-12.95V.

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[Author]

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