Quote:
Originally Posted by Ether
Did you mean "series" ?
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Quote:
Originally Posted by DonRotolo
No, I think he meant parallel. The myth is that good battery fools the charger into supplying energy, applying charge to the bad battery.
The sad reality is that permanent damage has already occurred, and no snake oil is going to change the chemical facts. Yes, you can get some charge into it, but hardly worth it, as even fully charged they will be woefully inadequate.
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Sorry I wasn't clear last night, I was tired after getting up at 5am to judge a FTC event and then not getting home until late.
Yes I meant hook it up in parallel with a
charged battery. That will fool the charger into turning on and charging the battery. That is no myth, that is what is recommended by manufacturer of the best known automotive application AGM batteries, Optima.
From the FAQ on their
website.
Quote:
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.
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Note the 2hour/10 amp recommendation is for an automotive sized (44AH and larger) battery not a FRC sized battery. Do not exceed the 4A recommended rate for the FRC battery and I would not charge it for more than 30 minutes at a time, before trying to get it to charge by itself. Pay special attention to the parts I've italicized in red above, with everyone in the area wearing safety glasses.
Even if they do come back to life, I would not consider the batteries to be competition worthy.