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Post by jeepfever on Apr 24, 2015 21:18:32 GMT -4
I've just bought a Optima Yellow Top battery. Now I understand it's an AGM battery but does that mean I can't use a standard lead acid battery charger on it? Do I need a special charger designed for AGM batteries?
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Post by C Monster on Apr 24, 2015 21:25:55 GMT -4
Yes that's what I was told, when I bought my yellow top, This winter If it needs charging to use one for a agm battery. Or the jeep to charge it.
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Creepy
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Post by Creepy on Apr 25, 2015 9:18:58 GMT -4
Using the Jeep won't fully recover a drained battery. Needs to go on a charger. Use the Optima site for info.
My digital charger has an AGM setting that works on my big Yellow Top.
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Post by jeepfever on Apr 25, 2015 10:07:03 GMT -4
Well I guess I'm buying another battery charger capable of AGM battery charging. Exactly what does AGM stand for?
I bought the battery new but it doesn't appear fully charged. Maybe I'll be okay just dropping it in the Jeep and charging it fully while driving.
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justajeep
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Post by justajeep on Apr 25, 2015 11:03:19 GMT -4
Alternators are not meant to charge dead batteries, especially Optima's. If you want the battery to last, charge it the way Optima says to! CT has a nice little digital charger(12 amp with fully auto setting. I have big charger, but use this most of the time), about $60 but often on sale.
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Post by jeepfever on Apr 25, 2015 11:56:06 GMT -4
Yes I have to agree jstasn. I suppose putting a dead battery in a vehicle will stress the alternator. I have an AC Delco battery charger and from its specs it seems okay to use with AGM batteries. www.shinnfu.com/sf_eu/index.php/product/productList_detail/1488The model number on my charger is 99-1282-8. Likely a Cdn Tire product number.
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Creepy
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Post by Creepy on Apr 25, 2015 13:12:33 GMT -4
I bought the battery new but it doesn't appear fully charged. Maybe I'll be okay just dropping it in the Jeep and charging it fully while driving. Don't do this. Measure the voltage, decide what charge procedure to use, charge the batt properly, then install. This vid has all your question answered. Note the voltage/amps specs given for different discharge states. Charge at 10A at 13.8-15V for a normally dischagred battery. (reading above 10.5V) And note the mention of not using the charger settings that share 'AGM/gell cell' as a charge mode. AGM setting is ok, the combo AGM/Gell is not. For battery discharged below 10.5V, the modern digital chargers may not even turn on, and won't fully charge. Watch more vids to see how to correct that state. The battery tech vids on Optima's youtube site are the first 10 or so posted, you have to go back pretty far the find them.
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Post by jeepfever on Apr 26, 2015 22:49:10 GMT -4
I happen to have a Bosh C7 battery charger that I've never used and it appears to have an AGM setting. So I guess I'm all set. Attachments:
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Creepy
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Post by Creepy on Apr 27, 2015 8:18:25 GMT -4
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badwithcomputer
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Post by badwithcomputer on Apr 27, 2015 11:10:16 GMT -4
I summon OptimaJim *poof*
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Post by jeepfever on Apr 30, 2015 7:48:22 GMT -4
Damn chopshop, I had no idea. I just assumed because the Boch charger had an AGM mode that it would be fine to charge an Optima.
Well right now my new Yellow Top measures over 12v and I believe my attempts to charge it have brought it to full charge. That was my plan, to fully charge it before putting it in my Jeep.
Now, should I severely discharge the battery below 12v I know I may have problems recovering it. Maybe I'll have to buy an Optima battery charger.
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Creepy
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Post by Creepy on Apr 30, 2015 14:00:36 GMT -4
A fully charged AGM battery checked with a digital meter should be seeing 12.8V-12.9V. Not just 12. Do not check immdeiatly after charging, wait 12H so surface charge is gone. (checking right after charging gives false high reading)
Your charger won't turn on if voltage is below 7.5V, which is actually pretty good. Deep discharge is generally considered below 10.5V A batt showing only 7.5V is probably toast anyway.
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Post by jeepfever on May 2, 2015 6:48:32 GMT -4
I understand that I need a specific battery charger to properly charge a severely discharged AGM battery but can I use a standard lead acid charger to trickle charge a fully charged AGM battery?
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Creepy
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Post by Creepy on May 6, 2015 9:12:30 GMT -4
watch the vid a few more times, and read the manual for your charger a few more times.
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BawgBoy
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Post by BawgBoy on May 8, 2015 7:33:12 GMT -4
Charging of any acid battery whether gel, AGM, standard is a function of voltage applied (from charger, alternator, etc.) minus voltage of the battery, divided by it's internal resistance. The problem is the resistance changes with temperature, age, discharge level, etc. so it's difficult to calculate what charge current the battery will draw for a given charge voltage. If you estimate a battery has an internal resistance of 0.1 Ohm and it's sitting at 10V, to get the battery to draw 10A you would have only have to apply 11V. (11-10)/0.1=10 Amps.
If you throw that same battery on a good alternator, you would be charging at 40 amps for a short period with the current reducing proportionally as the battery voltage rises. There's lots of other variables affecting these numbers such as heat as the battery charges which alters the resistance, but that's the simplest way to describe it.
I've never tested one but I'm guessing the only difference between a standard charger and an AGM is the AGM's ability to put out higher voltages to get the charge current up to 10A when the internal resistance is higher in a deep discharge state, and a lower float voltage once full charge is achieved.
The bigger problem with an AGM in a vehicle is the float voltage. AGM batteries should have a float voltage of 2.25V per cell or 13.5V, since most alternators have a fixed output at 14V or greater, long term floating with not many heavy discharge cycles is technically worse for the battery than worrying about how you charge it. That said I have run Optimas in many Jeeps and never had an issue.
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