Newer vehicle battery chargers

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Old 12-29-20, 02:31 PM
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Newer vehicle battery chargers

Wasn't sure if this should go in the Automotive Repair forums - but I wonder if it's common for modern battery chargers with more sophisticated electronics not to charge dead or very low 12v batteries. I encountered this last fall while attempting to charge a battery in a lawn tractor I lent to my son. My new (discount national parts store) charger would just go dead when attaching the leads, no LED, no indication on the meter. Thankfully I hang onto things - brought out my Craftsman 2/6 amp charger which may be 20 years old and was able to charge the battery. I can get the battery to a certain level and have the new charger take over.

On several occasions my neighbor had to borrow my old charger when the battery in his spare car was deeply discharged. He just got a new charger from the same store as my new one (but with an LCD screen) and it was useless, just kept flashing red. Borrowed my Craftsman, charged the battery for a few hours - then his new one was able to take over. My old charger is very basic, a switch for 6 & 12 volts, 2 & 6 amps and a meter.

I wonder are these basic units not made any more? My neighbor brought his charger back for a refund. A different neighbor gave me a spare battery he had for my truck. That was around 9.6 volts so I was able to charge it with my new charger. The truck has been starting since Saturday - so it seems some new chargers just won't charge below a certain voltage.
 
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Old 12-29-20, 02:55 PM
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I quite often have trouble with digital lead battery chargers and I've largely stopped using them. I usually go for an old fashioned transformer style charger which are still available. Just look for a charger with an old fashioned meter where a needle moves.
 
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Old 12-29-20, 02:57 PM
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I wonder if it's common for modern battery chargers with more sophisticated electronics not to charge dead or very low 12v batteries
Yes this is normal. Smart chargers measure battery voltage before charging. If it doesn't detect voltage or very low voltage, it won't even attempt to charge. In some cases, it will detect the battery as a short and powers down.

One trick you can use is connecting a good battery in parallel.
 
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Old 12-29-20, 03:15 PM
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I have had this problem as well. I wonder if the manufacturers could fix this problem by lowering the voltage detection threshold? Would this have side effects? At any rate it is annoying, I protect my old charger like it's a fine piece of art, but it's a matter of time before something happens to it and I'm stuck with the newer chargers.
 
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Old 12-29-20, 03:32 PM
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A battery in parallel is a good idea - as well as hanging onto these old chargers. I'll look online to see what options are out there. Good to know the old technology chargers are still available. The parallel battery somewhat goes along with what I was thinking earlier - get one of those charging packs or whatever they're called. Looked at a couple, was amazed how small they are.
 

Last edited by stevek66; 12-29-20 at 04:50 PM.
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Old 12-29-20, 04:30 PM
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Those are called smart chargers. A low voltage could indicate a defective/dead cell.
That would damage an electronic charger.

I have several of the old Craftsman/Schumacher chargers still kicking around.
They're similar to this..... basic charger.
 
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Old 12-29-20, 05:54 PM
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The link showed the exact same charger I have that won't charge low batteries. Maybe mine is defective, It does charge fine with at least 9v on the battery.
 
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Old 12-31-20, 08:10 AM
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This is a safety function to keep people from touching the clips together and creating an arc or connecting the clips backwards.
They don't state how much voltage it needs to see to start charging.
As already suggested connect an additional 12V battery in parallel. There used to be a video that showed how to override this function.

From Schumacherís website:

Why don't I get sparks when I touch the battery clips together, creating a short?

With electronic short-circuit protection, the battery charger must be able to measure a battery's voltage before it turns on. There is no output power in the clips until they are hooked up to a lead-acid battery.
 
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Old 12-31-20, 08:43 AM
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I am considering getting one of those battery charging packs to have on hand - for the reasons as mentioned with modern chargers, and the convenience.

I looked at a few online, I was surprised to see how small they can be with today's technology.
 
 

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