The Stovebolt Site Forums The Shop Area Engine Shop load test on the battery

If I have my battery load tested should I charge it up first or not?

I was run down again and I charged it...Will that throw off the load test?

Rich

Hy rust bucket 53, you can't perform a load test on a discharged battery, if you're going to test it immediately after charging, then you should put a moderate load on it for ten seconds to disipate the "surface" charge. Then after a minute perform your load test. Is the battery marked as to how many amps to use to do the test?

Take the battery to a shop that uses a digital tester. It will be much more accurate than a load tester. The cheap load testers now a days only will only pull an average of 200 amps max. If the battery is rated at 750 cranking amps, and only puts out 350 it may pass the load test, but still won't do it's job.

I will take it in to have it tested ...I just didn't know if the fressh charge would skew the test. I guess not.

I hate electrical problems since I am not well versed in solving them.

Rich,

One reason a battery will discharge by itself is because of a shorted cell. If you pull the caps on the cells when you load test a battery and during the test one of the cells bubbles and boils, it's an indication that cell is shorted and could be the cause of a self discharge or the reason the battery won't accept a charge.

Stuart

I hope you practice extreme caution if you attempt this. It could be very dangerous

Battery explosions aren't any fun. Been there, done that, had to clean up the mess afterwards...

If You have a shorted cell most of the time it will show less voltage 1 bad cell will be 10 volts . If You put a volt meter on the battery and turn the lights on the meter should read 12 volts if the voltage takes a dive to say 10 volts right away it means one of the cells is shorted or if You charge the battery and right after You charge it the voltage drops to 11 or 10 volts, bad cell.A volt meter even a cheap one is a great tool for the garage .


Pete

I guess I don't understand the comment. Load testing batteries is done all the time...it's a common pratrice. If you have a bad cell, it bubbles, that's just how it is. How is this more dangerous than charging a battery or walking across the street?

Stuart

You shouldn't have any concern with load-testing your battery, just take the cell caps off, and don't make any sparks around the battery. I have heard reports of load tests causing an explosion, but I have never seen it happen. Connecting a charger with it being turned on, or getting a spark while connecting booster cables often will cause a battery to blow.

The usual current load on older batteries is three times the ampere-hour rating. The ampere-hour rating is different between 6-volt and 12-volt batteries, so there is a difference in current load. A typical 6-volt battery is about 100 AH, a typical 12-volt is 60 or 70 AH, 70 being at the higher end of the rating for passenger vehicles. If you don't have the proper load tester for that purpose, find a shop or auto supply that has a proper load tester to do the test for you. The typical load testers you find for sale in auto supplies are not very good for that purpose.

Batteries presently are rated in cold cranking amperage, CCA, but there is conversion from AH to cranking power for a load test; I don't remember the conversion at the moment.

Any time you are making connections to the battery, especially one that is discharged or believed to be faulty, you should take off the cell caps and make sure the electrolyte/liquid level is at the full level. That way if you strike a spark and set off the hydrogen gas, the result will be less devastating. If there is such a thing with a battery explosion.

Harvester

The load tester where I had this testyed had a cover with instructions that the cover must be closed for the duration of thetest. I am sure to prevent injury.

I have never seen a battery explode (and hope I never do) however I have accidentally created sparks while hooking a battery up to jump. I have always hooked up the dead battery first then the positive of the live one then the ground to prevent minimize sparks.

Does this procedure minimize risk of injury? I am concerned now as I have taught my kids this procedure as well.

RB53

Don't attach the ground cable at the battery on either vehicle. Use the engine block, cylinder head, alternator mount, etc. That way, if a spark happens, it's away from the battery. Connect positive to positive at the battery, then do the ground cable last, on a chassis ground somewhere. I have blown up batteries, and it's not a fun thing to do!
Jerry

Hy Guys, someone said to remove the cell covers to check electrolyte level before charging, that is a good idea, however replace the caps and keep them in place while doing any charging or testing, afterall they are in place as the vehicle is driving down the road aren't they!

The cover on the load tester is indeed to contain an explosion if it happens. Depending on the battery, there is a lot of force and often many fragments flying around when one blows up. The cover is a standard feature on most bench-top battery load testers.

As for cell caps being on or off for testing and charging, it is not only long-standing advice and practice, but it is necessary so as to see what is going on with the battery during both operations. Specifically, if one cell bubbles or foams during a load test, the cell is shorted- the test should be stopped. During charging, there should be mild bubbling in all the cells, somewhat equally; if one cell is bubbling harder or not bubbling at all when compared with the others, the cell is suspect, but not necessarily defective. More testing is in order in that case.

Keeping the cell caps off during charging reduces the possibility of hydrogen gas collecting inside the cells (reducing the possibility of explosion), and also permits easy access to the electrolyte with an hydrometer. The hydrometer not only will show specific gravity of the electrolyte, but during fast charging (40-60 amps or so), it will reveal plate shedding (indicated by a muddy, brown color) and severe sulfation (indicated by a milky color, like aerated water- gas bubbles). The plate shedding is a terminal situation, but the sulfation often can be remedied with slow charging for several hours. Anyone who tests or charges a battery without removing the cell caps is not doing the test completely, and is tempting fate and an explosion.

You can get by without removing cell caps if you are using a constant-voltage charger, which most are, set at a low charge rate, 5-6 amps steady-state current, but you are still tempting fate. Removing the cell caps is less trouble, and cheaper, than a trip to a hospital.

Harvester

Hy Harvester and guys, well I guess that means we can't load test a sealed battery then can we? I can't disagree with you more about the caps, I've seen battery explosions, and everyone I've seen took place with a battery with the caps off! The caps are not off in the vehicle with an alternator with a potential to charge the battery at 100 amps plus. Removing the caps only allows the explosive hydrogen gas to escape quicker, and hence more around the battery making the potential for an accident greater, say what you will, and do as you like, but I will err on the side of everyones safety everytime

My dad taught me about exploding batteries when I was just a little kid. I was standing behind him watching as he was charging a battery.

He disconnected the charger cables from the battery after charging then touched a crescent wrench across the posts to see if it would spark.

It did......the top blew off of the battery blowing acid all over the place, he spun around and ran slap over me as he made a hasty retreat.

It was a great lesson. I have treated batteries with respect ever since. My dad was always a good teacher.