Bringing DEAD AGM battery to life.

Old 07-14-2015, 08:22 AM
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Default Bringing DEAD AGM battery to life.

so left my switches 'on' and after 2 months all 3 batteries are dead.

The starting batteries are taking a charge but the AGM deep cycle is un-responsive.
Did a little google and stumbled on this thread from 'Wayne's Words- Lake Powell fishing' which i found interestin:

"For those folks that use spiral-wound AGM batteries like Optima or Orbital on your boats,, you may have already discovered that they don’t tolerate a real deep discharge very well.. When completely drained they won’t accept a charge and you might then assume, reasonably enough, that the battery is completely shot..

But that’s not always true, and in most cases it probably isn’t. Here’s what goes on…. When those battery types fall below 9 or 10 internal volts they go on strike and will not take a charge by any conventional method.. But there’s a trick, not unlike a CPR rescue effort for dead batteries..

If you have a conventional lead-acid battery handy, you can connect the AGM battery to it with hard-connection cables (not jumper cables) and then hook up a battery charger to the lead-acid battery and turn the charger on..

Charging current flowing through the lead-acid battery is then accepted by the AGM battery.. Don’t know why this works.. It just does.. And since these spiral-wound batteries cost around double what a conventional L-A battery does,, its certainly worth giving it a try before junking what appears to be a dead dog..

I'm going to give this a try but was wondering why i shouldn't use jumper cables? I'm gonn ause them anyway because i don't have any hard-connection cables. But was just wondering what the difference is anyway?
I'll keep yoll posted how this works out.
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Old 07-14-2015, 08:25 AM
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I actually had this happen, and while charging the other battery (a 24v trolling motor setup), that AGM flowed juice through to the dead AGM which brought voltage high enough to kick the charger back on.

I still feel like it's not providing full juice, but we'll see.
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Old 07-14-2015, 08:50 AM
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AGMs do not like to be dead-if it gets dead it will never be happy again-just get a new one.Keep that one charged-they hold a charge a long time.
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Old 07-14-2015, 08:57 AM
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I would guess the "hard connnection'' is recommended as opposed to jumper cables is the possible resistance associated with jumper cables, since your attempting to parallel and mimic the impedance of the LA battery.

When a circuit is driven with direct current (DC), there is no distinction between impedance and resistance; the latter can be thought of as impedance with zero phase angle.

So when you connect the cables you do not want to add and additional resistance.

Last edited by DavenFla; 07-14-2015 at 09:04 AM. Reason: added a link
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Old 07-14-2015, 12:51 PM
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I am not 100% familiar with this process ( I am the ChargerGuy, not the BatteryGuy), but generally speaking you would not want to use jumper cables for charging. Safety is #1 as they can fall off.
Use the correct marine wire and terminals that support the amps.
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Old 07-14-2015, 01:30 PM
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Old 07-21-2015, 07:23 AM
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it worked.
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