14.4v batteries

[David Lang]

Hi

Is there a way to test 14.4v batteries from a drill driver to see what condition they are in?

I only have a volt/ohm meter.

Dave

[brugnospamsia]

IMHO the most realistic test for drill batteries is going to be to time how long the drill or an equivalent load is adequately powered - when they're knackered, they're knackered

Why can't you just charge em all up then use the drill and chuck out the ones that don't cut it ?

I imagine measuring the voltage drop under a standard load of apparently fully-charged batteries would give you an idea ...

You'll need to use a lamp or something as a dummy load ....

[mrcheerful]

if you can open the pack, then check each one with a voltmeter after you have used the pack , and have left it over night. you will soon spot any dodgy cells. each should be around 1.2 volts, usually you will find the worst ones are almost nothing, change those and the pack will be much better. best solution is just to have it rebuilt by re-cell though !

mrcheerful

[Dave Plowman (News)]

You'll get a rough idea by discharging them into a known load - something like a car 21 watt stop light bulb would be ideal.

If they are Ni-Cads, they're likely to have a capacity of about 1.5 amp/hr, so I'd expect them to run the light at full brightness for about

45 minutes. However, one or more cells always fail first, so if there's a problem, I'd expect it to be very much less.

High quality cells in good condition should do longer than 45 minutes.

[Ian Stirling]

Whatever you do, never discharge below 12V. If you do, one or more cells will be reverse charged, and damaged. This is also the reason why you shouldn't use a failing battery till the tool stops. Swap batteries, and recharge.