1. Home
  2. Car Maintenance
  3. testing a battery: voltage results

testing a battery: voltage results

Hi,

I've bought a max/min multimeter as recommended by you all.

The voltage before I started the car was 12.2V

When I started the car the voltage dropped to 9.1V minimum during staring.

Once the engine was running, the voltage was 14.5V maximum.

Am I right to be worried about the 9 volts? It seems low to me but OTOH I am not having any problems starting the car at the moment, so isn't that the biggest test of the battery?

I compared it to my other half's car and the voltages for that were:

12.4V before, 10.1V during, and 14.6V after starting.

By the way, the multimeter claims to have two settings to test 1.5V and 9V batteries. The manual claims it puts a small load across the battery and displays the voltage. Anything about 1.2V is ok for a 1.5V battery, and anything over 7.2V is ok for a 9v battery, or so it says. I had some flat 1.5V batteries that measured 1.25v, so they passed the meter test but were useless in practical terms. Are these [non-car] battery test settings a waste of time? I seem to remember that when I was at school we were told you should test a battery by its current, not its voltage?

TIA

Reply to
Fred
Loading thread data ...

That's the critical bit, the 9V just tells you that it's borderline, the

14.5V tells you the alternators working properly

Generally they'll just tell you when it's dead flat.

Reply to
Duncan Wood

If meter is accurate, and battery fully charged and healthy you should be seeing 12.5 - 6v at rest.

dropping to 9v under cranking is somewhat low. I would say you have a dead cell.

Tim..

Reply to
Tim..

Battery not fully charged - but not uncommon in practice. Or it could be on the way out. Only way to be sure is a proper test with an electronic tester. Your local battery specialist will have one as do Halfords. But of course you have to trust the operator. ;-)

That is distinctly borderline. Could indicate the battery is past its best or the starter motor taking too much current. The first is far more likely.

Again suggesting a low battery. It should be approx 13.8 when fully charged. Either charge the battery externally or check again after a daylight run of about 20 miles.

Reply to
Dave Plowman (News)

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.