Best way to load test a motorcycle battery?

[mrsilv04]

What is the best way to load test a motorcycle battery, without taking it out and taking it to someplace like Advance... who may or may not even be able to test it?

I do have a digital multimeter on hand.

 

[JHZR2]

Put a known load on it... A few headlight bulbs or something. Then you can use a multimeter and look at open circuit (unloaded) voltage and loaded.

Vt=Voc-IR

If you know the resistance of the loads (bulbs), then you can calculate out the battery impedance.

That helps to know battery health.

 

[Quest]

12V?

Get either a carbon pile tester or something portable like this:

http://www.harborfreight.com/100-amp-6-volt-12-volt-battery-load-tester-90636.html

Q.

 

[Rand]

motorcycle battery is nothing special
its just a small car battery.

the easist way is

a carbon pile load tester
http://www.harborfreight.com/500-amp-carbon-pile-load-tester-91129.html

or the newer style battery analyzer
http://www.harborfreight.com/digital-automotive-battery-analyzer-66892.html

 

[Rand]

just a note if you are interested in purchasing at harborfreight make sure to use the 20% off coupon (available online)

 

[HerrStig]

A volt meter is of little use without a load. They put them in cars because it is CHEAP, unlike an AMP meter.

 

[JHZR2]

Originally Posted By: HerrStig
A volt meter is of little use without a load. They put them in cars because it is CHEAP, unlike an AMP meter.


A 55w light pulls about 4.5A at 12V, which on a 20Ah motorcycle battery is like c/4, which is enough load to see a voltage drop on a weak battery that has higher impedance especially.

 

[HerrStig]

Source impedance, right?

 

[JHZR2]

Originally Posted By: HerrStig
Source impedance, right?


Right. Loaded voltage for a known current load (which is related to the load impedance for a known resistive load like a bulb), gives you the source impedance for the battery.

Surely not the most accurate way but it is a good approximation.

 

[Eddie]

Check cranking voltage which should remain above 9.0 volts? Remove spark plug wires while load testing.

 

[Rickey]

Originally Posted By: Eddie
Check cranking voltage which should remain above 9.0 volts? Remove spark plug wires while load testing.


Agreed.
--------------------------------------------------

My

You could leave the bike's headlight on for a calculated length of time to check reserve capacity.
Battery should run the headlight for 1/2 hour minimum if it's a good one?
Of course running a starting type battery dead is considered abuse.

By all means be thoroughly sure it has a FULL charge prior to testing.
If the battery has been inactive for awhile; a trickle charge for a day or two should be done prior to testing.

Rickey.

 

[meep]

I like the check V while cranking test. must stay above 9. pull plug wire. you may need to select "range" to keep the meter from trying to autorange during cranking.

 

[mechanicx]

Don't forget to check the battery electrolyte level. Most motorcycle batteries need frequent water additions especially in hot weather. The battery made need to be removed to accurately check the level. This might be your entire problem if the battery seems to lack charge.