Wednesday, September 26, 2007

Testing Automotive & Heavy Duty Batteries

Here's a great video on testing a battery using the proper battery tester . There are many different battery testing models and they all work, all you want to accomplish is to put a load on the battery and read the voltage level. You need to know the CCA [cold cranking amp] rating labeled on top of the battery, then draw 50% of that off the battery with your tester for 10 - 15 seconds [the tester has a carbon pile that absorbs the heat from the heavy draw].

A general rule of thumb I use is a battery voltage drop of no less than 9.6 Volts after a 10 second load of 50% of the Cold Cranking Amp Rating. One important factor is the battery must be fully charged before testing, preferably around 12.6 Volts.

A battery tester is affordable but if you don't own one & you're not sure of the condition of your battery then a quick load test at a repair shop is worth it. A reputable shop won't charge you for the test if you buy a battery from them [since the test only takes less than a minute from start to finish].


Anonymous said...

I need to replace the batteries on my 1986 Carpenter school bus (GMC 8.2L diesel) and I don't know what kind to get. The labels are gone and there's nothing marked on there. There's two of them on a slide-out shelf, each 12 v attached in parallel.

Also, is there a CHEAP place to buy batteries? I think I need a VRLA type with a pretty high cca like 950? Or do I? I probably don't know what I'm talking about.


austin said...

When buying a new battery I suggest you purchase a battery with the greatest reserve capacity or amp hour rating possible. Of course the physical size, cable hook up, and terminal type must be a consideration. Be sure to purchase the correct type of battery for the job it must do. Freshness of a new battery is very important. The longer a battery sits and is not re-charged the more damaging sulfation build up there may be on the plates. Most VRLA batteries have a date of manufacture code on them.