Battery Load Tester Discrepancy

[Frbl]

I tried two different load testers on my battery. Both show the voltage drop to about 10.3 volts under load. However, the ranges on the meter display for "good" and weak differ from each other. One shows a good range for 600 CCA to be 10.8v to 12.8v while the other show 10.2 to 12.8.

In other words, one says my 10.4v (under load) battery to be fine, the other does not. Which range is more accurate?

Anything I find online just gives a general statement that anything above 9.6v under load to be fine.

BTW, load tests were done at 70F with a fully charged battery. All other tests seem fine. Battery is five year old Toyota battery from which I have had NO problems at all - car starts right up every time. I am just testing to see if there are any potential problems.

 

[The_Jeff]

You are good to go. I doubt your starter motor draws 600 amps; the spec gives some extra capacity. Did you do the test for the whole thirty seconds?

I guess the best course of action for you and you new toys would be to load test your batteries every six months, keep a log, and dump them when your readings start getting worse quickly.

My own experience with nearly dead batteries is the computer, spark, and fuel pump have all worked well enough with whatever voltage gets the starter to turn over. Could be one of your voltage specs was intended for something with a direct drive starter, points ignition, or other older technology.

 

[George7941]

The discrepancy in the two ranges is probably because of different load currents applied by the two load testers. The higher load tester will pass the battery at a lower voltage.

Load Testers are GO/NO GO types of testers and do not tell you how close the battery is to failing. I use a Conductance Tester and it enables me to track the slowly deteriorating batteries in the dozen or so vehicles(personal, friends, at work)I maintain.

http://www.midtronics.com/shop/products-...-battery-tester

That is the one I use but there are cheaper ones available.

 

[Frbl]

Wow! Quick and good answers!

Thank you very much. I feel better. Keeping a log is a great idea, though that might be moot if a regular load tester is not all that capable of showing deterioration. Still, it can't hurt.

 

[The_Jeff]

... and the time to dump a battery (IMO) is not when it cranks slowly, though it does. It's when something changes in its internal resistance... which messes with your alternator, making it overwork, and makes your headlights flicker when you hit the brakes. You can have a mostly shot cell with some surface charge that appears to work properly.

In the old days when we used to have to crank an engine over several times in the winter with it stalling and us fiddling with the choke, lousy batteries gave more warning.

That Midtronics tester sounds like the bee's knees for this.

 

[George7941]

Conductance Testers work really well if you want to keep track of the health of the battery. I test all vehicle batteries once a year, just before winter and replace ones that are weak before you end up with a no-start because of a weak battery. I record all the CCA readings.

My Motorcycle battery starts out at 240CCA and loses about 40CCA a year. I change it when it gets to 110CCA. I would keep it longer but BMW had done away with kickstarters by 1987.

My truck battery started at 620 CCA and lost about 40CCA a year. Last year, my battery was at 480CCA and a friend of mine needed a size 78 battery, so I gave him mine and installed a two year old Costco Kirkland 78 and it tested at 800CCA!

MD truck batteries at work start out at 1050 CCA and lose about 100CCA a year.

The Midtronics does not catch failure of batteries in one of the trucks which heavily cycles the batteries because of a hydraulic lift gate. The tester will show 900CCA on each of the heavily sulfated batteries but the batteries would barely crank the engine.

 

[Bob Woods]

The most accurate way is with a hydrometer, its the old fashion way but still the most reliable.

http://autorepair.about.com/library/a/1h/bl403h.htm

 

[George7941]

You are right, the hydrometer is a good way to test the battery.
Two problems, though. For real accuracy, you need a refractometer

http://www.usatoolwarehouse.com/usatoolwarehouse/ROB-75240-p-ROB06.html

Some battery caps, if removed, will not seal properly when reinstalled and then you are dealing with acid spillage. Who needs that!