Battery load test

ldj

Well-known Member
Is a battery load test conclusive? I have a 6 year old battery that went dead. I charged it so they could test it. Started to not even have a 6 year battery tested, but I did. The test said battery is good. Brought it back and next day after about 3 starts it wouldn't start car. I jumped and checked volts while running, 14v. With a cheap multimeter I checked amp draw. Set on 50 MA it pegged meter but on 500MA meter didn't move the needle even a little. All indications tell me the battery is bad but load test says good. Any ones thought?
 
(quoted from post at 14:40:47 08/28/16) Is a battery load test conclusive? I have a 6 year old battery that went dead. I charged it so they could test it. Started to not even have a 6 year battery tested, but I did. The test said battery is good. Brought it back and next day after about 3 starts it wouldn't start car. I jumped and checked volts while running, 14v. With a cheap multimeter I checked amp draw. Set on 50 MA it pegged meter but on 500MA meter didn't move the needle even a little. All indications tell me the battery is bad but load test says good. Any ones thought?
f you mean that the everything in vehicle turned off battery drain is between 50 and 500ma, that is excessive.
 
(quoted from post at 14:00:19 08/28/16)
(quoted from post at 14:40:47 08/28/16) Is a battery load test conclusive? I have a 6 year old battery that went dead. I charged it so they could test it. Started to not even have a 6 year battery tested, but I did. The test said battery is good. Brought it back and next day after about 3 starts it wouldn't start car. I jumped and checked volts while running, 14v. With a cheap multimeter I checked amp draw. Set on 50 MA it pegged meter but on 500MA meter didn't move the needle even a little. All indications tell me the battery is bad but load test says good. Any ones thought?
f you mean that the everything in vehicle turned off battery drain is between 50 and 500ma, that is excessive.

Would that kill the battery in 18 hr?
 
if test is good, batt. should be holding its amps or close to it for 10 sec's on the load test. if its a 700 amp batt and it shows say 200 amps on the test the batt. is pretty well done for. as it will start your car a couple times , but will not crank for long. so depends who checked it also. charge it let it sit for a day or two and recheck. load testing is about the only accurate way i know how to check a batt.
 
The way we checked in the shop was battery on a big charger for an hour or more, 20-40 amps rate, then disable the ignition and crank the starter with a VOM on the battery posts. Needed to read above 9.6v to pass for the 7-10 seconds the engine cranked. The starter puts a 150 to 300 amp load on the battery, so it's a pretty good test.

Then pry off the caps if possible and check the specific gravity in the acid. We found a lot of batteries that would pass the load test and then find a half dead cell with the hydrometer. Those were the ones that would work for a couple of days and then mysteriously die.

A lot of the time I would check the acid before we did the load test and then do it after the load test and see how much it changed. There's something called a surface charge that will show a charged battery with the hydrometer, and then the load test would deplete that and show the actual state of charge.



Of course if you have a $2000 VAT-40 or whatever Sun calls it today, you didn't need a car to test the battery. But you could do my way with just the free VOM from Harbor Freight.
 
(quoted from post at 15:07:17 08/28/16)
(quoted from post at 14:00:19 08/28/16)
(quoted from post at 14:40:47 08/28/16) Is a battery load test conclusive? I have a 6 year old battery that went dead. I charged it so they could test it. Started to not even have a 6 year battery tested, but I did. The test said battery is good. Brought it back and next day after about 3 starts it wouldn't start car. I jumped and checked volts while running, 14v. With a cheap multimeter I checked amp draw. Set on 50 MA it pegged meter but on 500MA meter didn't move the needle even a little. All indications tell me the battery is bad but load test says good. Any ones thought?
f you mean that the everything in vehicle turned off battery drain is between 50 and 500ma, that is excessive.

Would that kill the battery in 18 hr?
o. might knock off 10-15% of capacity
 
Had one in a car that wouldn't start after sitting a couple days. Two different places checked the battery and told me it was good. (They also said charging system was good too.) Finally just replaced it and end of problems.
 
The battery manufacturers never tell you that discharged batteries have a short life. Constantly fully-charged wet cell batteries will last 4-8, maybe ten years. It's easy to test voltage. Any voltage under 12.5 for a 12 volt battery is in a low-charge state and should be charged or trickle charged. Low state of charge is common with tractors and equipment used seasonally and not used in winter. It's wise to trickle charge these batteries regularly in the off-season.
 
(quoted from post at 02:05:58 08/29/16) The way we checked in the shop was battery on a big charger for an hour or more, 20-40 amps rate, then disable the ignition and crank the starter with a VOM on the battery posts. Needed to read above 9.6v to pass for the 7-10 seconds the engine cranked. The starter puts a 150 to 300 amp load on the battery, so it's a pretty good test.

Then pry off the caps if possible and check the specific gravity in the acid. We found a lot of batteries that would pass the load test and then find a half dead cell with the hydrometer. Those were the ones that would work for a couple of days and then mysteriously die.

A lot of the time I would check the acid before we did the load test and then do it after the load test and see how much it changed. There's something called a surface charge that will show a charged battery with the hydrometer, and then the load test would deplete that and show the actual state of charge.



Of course if you have a $2000 VAT-40 or whatever Sun calls it today, you didn't need a car to test the battery. But you could do my way with just the free VOM from Harbor Freight.

If not REAL load tester is available " so it's a pretty good test" Yes it is.
 
I have a carbon pile load cell on my battery tester, so I can lay a heavy starting load on it , so an actual load test works well.

One set rule, fully charge the battery then let it sit 24 hours before load testing. A partly shorted cell may test good within a few hours of charging, yet be near dead in 24 hours. I don't consider a load test valid unless it's atleast 24 hours since the last charge.
 
It's probably a battery issue. What was the voltage after the third time around of normal cranking? After it cranks slow take it back in and have it retested. If you get 6 years out of a lead acid battery you've done well. If it were mine I'd get a new one.
 
There are tests and then there are tests, the battery is probably shot, most batteries don't last over 6 years. Charge it up, leave it sit a couple of
days with one cable disconnected and then try to start it multiple times, if it won't do it it's shot. It depends how much time you want to waste! If
you need it for something you use regularly I would just replace it.
 
Thanks all, I'm getting a new battery. As I said in first post I wasn't gona even have it tested, but I did, I don't know why, after all it is 6 years old.
 
Just run down to the local Harbor Freight store and buy a load tester. They don't cost that much and are one handy tool to have around. measure 6-12 volts. measure amp out put from your systems. Measure the amps that your battery can supply. Can also help you find electrical problems. Just go buy one! You will soon think :how did I live without one:???? I have two of them. One for home and the other for the farm. You can use it like a multimeter if you care to.
a235929.jpg
 
If you had it tested at most parts stores, they didn't load test. Instead the new fangled testers are 'conductance' testers.

I've had 3 in the last 5 or 6 years that tested good using one of those at the parts store. But, they wouldn't reliably start the car/pickup.

After a new battery was installed, all was good.

I now own a load tester!
 
(quoted from post at 07:34:29 08/30/16) Just run down to the local Harbor Freight store and buy a load tester. They don't cost that much and are one handy tool to have around. measure 6-12 volts. measure amp out put from your systems. Measure the amps that your battery can supply. Can also help you find electrical problems. Just go buy one! You will soon think :how did I live without one:???? I have two of them. One for home and the other for the farm. You can use it like a multimeter if you care to.
a235929.jpg

Get 5 of'em and wire them together then it may bring a automotive battery to its knees so you can get a true load test. Sorry but they are no good on a automotive battery unless the bat is got to the point its useless...

They are more suited for a lawn mower bat are a small Scotter bat...

To do a good load test you will need a load tester that is rated at least 400 amps and the Moe the butter... If I were gonna buy another I would not look at anything under a 500 amp load tester.
 
Hello jeffcat,

Nice toy,@100 amps you can't properly load test a lawn mower battery. Othef functions may be ok. Check it for accuracy with a good digital meter....


Guido.
 
that one is likely a 150a load tester as Hobo says.. a high amp carbon pile is more better ;) for higher CCA batteries.

On the other hand.. if it fails the 150a load test.. you know for sure it's a junk battery. :)
 
I have one that looks like an antique & it is 0.025 Ohms..
12.5v/0.025=500amps.

9.6v/0.025=384amps
 
The originals were 50 amp and they worked just dandy. The newer 100 amp is over kill but will tell you very quickly if your battery is craped out. If the needle drops to almost zero that is your tip off. It should stay near the top of the red zone for several seconds at least. Even small mower batterys are in the 200 amp range.
 
Hello jeffcat,

Lawn mower batteries are at least 235 amps. I don't know if you can buy a smaller CCA ONE? A proper load test with a carbon pile tester, like the vat40, and a battery to be loaded at 1/2 rated CCA. So your100 amp tester is not enough of a load.
Here is the procedure to load test a battery: First fully charge it, and then remove the surface charge. Load test at 1/2 the battery's CCA Rating. Hold the load for 15 seconds. At the end of the fifteen seconds a good battery will have at least 9.6V reading at 80* F. for a 12V battery.1/2 the voltage for a 6V of course. Done it hundreds of times.....


Guido.
 

Sorry my friend but that thang is just a toy.

http://www.tooldesk.com/blog/?p=315

Now that you have tested your battery you are ready to do a battery load test. This is a simple and easy way to test your battery and really understand what kind of shape it is in. You will however need to purchase a battery load tester such as this ATD 5488. This tester will allow you to properly test batteries up to 1000 cold cranking amps. Ok before you start your load test you will need to locate the cold cranking amp rating on your battery. Once you have located the cold cranking amp rating you are going to want to divide this in half and use this to apply half the amperage with your load tester.

The biggie most folks miss and your toy can not test is the initial surge it takes to push the starter. Its not uncommon for the starter to to pull 5/600 amps for the initial push to get the starter moving.

That's my take on why you need a tester that will load the bat to haft its rated CCA for at least 15 sec.

I am open explain how your toy can do'dat... This is what I do it comes EZ now but took years to master. Now someone comes along with a toy and declares he's the master. I do have a challenge for your toy I bet I will have a kill rate of 99% and would wadger your toy to have a kill rate of less than 10%. That means 99 out of 100 the bat is good are bad look are elsewhere for the problem. Using Your toy 89% of the time you are guessing were the problem is at. How many starters and alt's will it take to put you out of business from guessing with your toy.
 
(quoted from post at 07:54:07 08/31/16) Hello jeffcat,

Lawn mower batteries are at least 235 amps. I don't know if you can buy a smaller CCA ONE? A proper load test with a carbon pile tester, like the vat40, and a battery to be loaded at 1/2 rated CCA. So your100 amp tester is not enough of a load.
Here is the procedure to load test a battery: First fully charge it, and then remove the surface charge. Load test at 1/2 the battery's CCA Rating. Hold the load for 15 seconds. At the end of the fifteen seconds a good battery will have at least 9.6V reading at 80* F. for a 12V battery.1/2 the voltage for a 6V of course. Done it hundreds of times.....


Guido.

And why is this so fudgen hard for folks to understand :shock:
 
Hello Hobo,NC,

I read the test procedures on the link, pretty good but why is there no mention of ambient temp? Is is
seldom if ever mentioned. Temperature sure playes a role on the test results! That is one of my pet peives!

Guido.
 

Another google hit with more info.

http://www.autometer.com/media/manual/2650-791X.pdf

I have a few customers that replace there bats every 5 years sometimes sooner they do not care for the inconvenience of a weak bat. I have a gal that does dog show's we replace the bats (3) in her conversion van every 2/3 years you got to keep those dogs cool :wink:

Then we have the tight wads that run'em till they die.

We have a low end number of 9.6 That's a healthy bat that still up to leaving the head lights on while you grocery shop and will still crank when you come back out and discover your mistake.

Bats that test in the low 9's will still give service but are not as long winded.
 

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