battery charger, minimum volatge for safety circut

[just a number]

here's the situation

I'm trying to charge a 12v nonspillable battery. currently it reads of 1.4V. I know there is a minimum voltage that the charger needs for the safety, but I can't remember what it is.

I know there is a way to charge a extra low battery with a good one hooked up parallel to it, but I admit to forgetting how that all works.

BTW I've got 4 of these to do. trying to avoid the $50 a pop to replace

 

[WarWagon]

For large batteries you can use the procedure below. If these are the small UPS and security system batteries they can explode or emit H2S gas during thermal runaway. That low of a voltage best to just replace the small VRLA battery.

From Optima's website:

If an OPTIMA battery is deeply discharged (below 10.5 volts), most basic chargers will not supply a charge. Also keep in mind that an OPTIMA battery will not recharge properly if treated as a regular flooded or gel battery. To charge the battery, you can wire a second fully charged automotive battery (12+volts) to the discharged AGM in parallel (+ to + and – to –). Then hook up the charger to the deeply discharged battery, setting the charger at 10 amps. Leave for two hours, monitoring frequently. During this process, if the discharged battery gets very hot or if it is venting (hissing sound from vents), then stop this process immediately. When the discharged battery reaches 10.5 volts or more, remove the standard battery and continue charging the AGM until fully charged.

For normal charging, a relatively low current, such as one or two amps, can work well, but when the battery has been deeply discharged, some sulfation of the battery plates may have occurred. If you charge at 10 amps, the higher current will help to break up this sulfation.

If you have an automatic charger, let it run until the charger indicates charging is complete. If you have a manual charger, you can get a rough estimate of the charging time in hours of a completely discharged battery (11.2 volts) by multiplying the capacity (amp hours or Ah) of the battery by 1.2. If your battery is not completely discharged, the time would be less.

In most cases these steps will recover an AGM battery. It’s OK for the AGM battery to get slightly warm during the charging process. If it’s hot to the touch, it means there’s a short and the process should be discontinued.

 

[just a number]

thanks Warwagon.:thumbsup: I couldn't remember where I had read it.:rolleyes5: gonna have to give that method a try.

 

[Ed HD]

:stupid:

That's the best way to do it, period. Even the chargers that say they're for AGM/Gel batteries don't always effect a charge...