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Recommend me a battery tester

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Looking to get a car battery tester, does anyone have any recommendations, just want to be able to check its charging and at full charge and so on or if it needs replacing.



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A cheap multimeter will sort the basics out as to whether it's charging ok and the best and cheapest test to see if it's any good is to listen to the car starting up. You can tell whether the battery has enough umpy or not just by feel and sound.

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Unless you're spending $$ on a proper load tester, then a dedicated battery tester is a waste of money when you can just get a multimeter that can do so much more.

Or do you mean a permanent one you can monitor in the car? That's just more hassle than it's worth. It won't really give you any pre-warning somethings about to fail. I guarantee you'll be back asking the question "my voltage has dipped from 14.5 to 14.2, is my alternator/battery dying?" after a while.

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Just a decent Multimeter/DVM.

You can measure :

  • No load volts
  • On load volts (eg put your headlights on)
  • Discharge current indication

All with engine off.

  • Charging volts - engine running.

By knowing the difference between "No Load", and "On Load" and having a vague idea of the load current you can calculate an indication of the internal resistance of the battery, record it for future reference.

If you measure between the -ve terminal of the battery, and chassis earth, you will measure a low voltage, probably in the millivolt range, this will again give you an indication of discharge current.  On a car with incandescent sidelights, switch them on, and the voltage will increase. With say 6x5W = 30W@12V=2.5A, so this increase, say 25mV is equivalent to 2.5A, so you have now calibrated an ammeter to measure discharge current, ie 10mV=1A.



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