I am on my second Sears Die-Hard battery charger that is demonstrating this same problem. Basically, when I have the charger hooked up and plugged in, it will charge for a second and indicate an amp draw on the scale and then drop off to zero amps. It then does this cycle over and over again. See the link below for a video of my charger doing this. I've put an amp clamp on the wire and verified it is pulling 10 amps then 0, then 10, then 0.



The guys at Sears are trying to tell me this is normal operation because it's an automatic battery charger. I don't believe that for a minute. I think there's a bad lot of chargers and the second charger I got was from the same lot. Does anyone have any clue what's going on here? Surely this can't be normal. Can it hurt a battery to charge in pulses like this?


http://www.youtube.com/watch?v=kG9c78sp108


Thanks!

 

This COULD be normal, depending on the state of your battery. If it is almost fully charged, the 10 Amp pulse will make it react like it IS charged and the needle will drop into the "safe zone". You'll probably get the "quick repeat" pattern you're getting.

What happens if you try charging it on the 2 Amp setting? I'm betting it will show near full scale at first, but then will fairly rapidly drift down toward the "safe" area (but it won't "drop" like it's doing at 10 Amps), and, it will probably move toward "safe" slower and slower as the amperage drops.

- Jack

 

What condition is the battery you are hooking it up to in ?

Have you had it tested, or has that battery sat a while ?

 

I had two batteries that were dead in two different vehicles that caused the charger to exhibit this behavior. There were also two other batteries of an unknown discharge level that were on the bench and did the same thing. This prompted me to exchange the charger. I've tried the new charger on only one battery and witnessed the same phenomenon.

 

"What does it mean when the green LED blinks ON/OFF and the needle bounces?

All automatic battery chargers in the automotive market today have some sort of voltage regulation to prevent overcharging the battery. The rate of the flashing is dependent on the battery type, its rated capacity, the degree of discharge, its age, the temperature, as well as the amperage rating of the battery charger.

If the charger’s green LED begins blinking when you connect the charger clips to the battery, the amperage in-rush current to the battery is reaching the pre-set shut-off voltage and the charger is shutting down. The voltage will drop as soon as the charger shuts down, turning the charger back on. This may also mean the charger has detected a battery problem - for instance, its ability to take or hold a charge. Sometimes a battery may be sulfated (accumulation of lead sulfate on the battery plates), and the sulfation is creating a high resistance to the current flow (ability to accept a charge). Or, perhaps the battery is deeply discharged (below 8-volts)."

from the page:

http://www.schumacherproducts.com/faq


So I'd say your charger is just fine...the batteries on the other hand....

 

It sounds like all four batteries you tested are below 8 volts, and this charger will not charge a battery that is below 8 volts. Why don't you go ahead and test it on a battery you know is charged.

Either way, I would return it. What good is a charger that is designed not to charge a battery if it does not meet the min volt requirements?

 

When a battery drops that far below its nominal voltage, the cells are usually damaged. Lead acid batteries (i.e. normal car batteries) are some of the most resistant to cell damage, but at 4-5 volts below the nominal voltage, battery damage has most likely occured.

Just for reference a properly disharged 12v battery should not drop below about 11.2 volts

 

Take the battery to the parts store and see what their charger reads when they hook up.I have seen if I start with a high 10 amp charge it drops fast,but if I start 2amp it stays up and gos down slow.