12V is dead, charger/tender thinks it's a 6V

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brenton

Active member
Joined
Sep 17, 2017
Messages
25
My 12V battery was dead this morning. No problem, I had purchased a Suaoki chrger / maintainer (this one) for just this purpose. However, it is auto-reading it as a 6V motorcycle battery! It is charging at about 1 amp and about 7 volts.

Whenever I open a door or try to turn the car on, I hear a lot of clicking that sounds like it's coming directly from the battery.

Two questions:

Will this 6V charging program ever get my battery up enough to start the car, or do I need to find a dedicated 12V charger?

Is it expected for a dead 12V battery to be detected as a 6V battery?
 
Normal for a way overly discharged 12v battery. Need to remove the charger and jump the battery from a charged 12v. Then start the charger. Then remove the jumper. Or connect an old style manual 12v charger. Possibly if you have an old power cord that supplies 12v you could put it on and wait for battery voltage to get above 10 volts. Or just get a new battery.
 
I would take the battery out and take it to the auto parts store to be load checked. If ok, I would also recommend leaving it disconnected until and if it gets to a normal charge level.
 
smkettner said:
Normal for a way overly discharged 12v battery. Need to remove the charger and jump the battery from a charged 12v. Then start the charger. Then remove the jumper. Or connect an old style manual 12v charger. Possibly if you have an old power cord that supplies 12v you could put it on and wait for battery voltage to get above 10 volts. Or just get a new battery.
Personally I'd do this.
If the battery is truly that discharged I can't see that it would pass the load test, load testing after the battery is charged might be a good idea. If you don't like monkeying around and the battery is 3-4 years old you might just want to replace it and be done with it :)
 
brenton said:
My 12V battery was dead this morning. No problem, I had purchased a Suaoki chrger / maintainer (this one) for just this purpose. However, it is auto-reading it as a 6V motorcycle battery! It is charging at about 1 amp and about 7 volts.

Whenever I open a door or try to turn the car on, I hear a lot of clicking that sounds like it's coming directly from the battery.

Two questions:

Will this 6V charging program ever get my battery up enough to start the car, or do I need to find a dedicated 12V charger?

Is it expected for a dead 12V battery to be detected as a 6V battery?

You could try leaving the charger run until it's no longer putting out much current (less than 1A). By the time it thinks it has "fully charged" the "6V" battery, the battery might have enough voltage to convince the charger that it's a 12V if you reconnect it.
 
Deeply discharged batteries often fool "automatic" chargers so I keep an old manual 6- and 12-volt charger (switches select voltage and maximum current). It gives me a chance to recover a deeply discharged battery when my other chargers refuse to supply current.

For what it is worth, the LEAF's DC-DC converter will put out over 100 amperes to charge a deeply discharged 12-volt battery if you can jump start the LEAF (bad LEAF battery) or hook it in parallel with LEAF battery (bad battery for other vehicle).
 
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