Deep cycle batterie

[honda lee]

I have a question about my AGM deep cycle batterie , I charge it to 13 vdc and wait 60 min  and recheck voltage 12.6 vdc.  Then hook terminals and recheck voltage and get 10.5 vdc after a few min. Is my batterie bad? Is there a way to Check it without a batterie load tester?

[Combustor]

        Hello Honda Lee,
                               A battery which is self discharging quickly is usually assumed to be faulty. But before you discard it, check several things. Be sure that the meter in use is accurate, compare it with a known accurate one, and then try charging the battery to about 13.8 or 14 volts, this is normal for an AGM battery. When disconnected after full charge it should remain above 12 volts for many days if not in use. Others here may have further info on charging AGM deep cycle cells.  Regards,  Combustor.

[BruceM]

I'd suggest some reading  to better understand AGM charging procedure.  I was going to recommend batteryuniversity.com but their current articles are a bit lacking in technical detail. 

No AGM battery (or wet lead)  is fully charged by charging it to 13v.  The bulk charge voltage for AGMs is higher than wet lead batteries, so initial charge would be more like 14.6 depending on temperature.  It must then be held at 14.6 for the absorption phase of charging until the charge current falls off significantly.  Only then is it fully charged.  Your battery may be sulfated, and needs some slow overcharge; float at say 14.3v for a few days may recover it. A small solar panel with a simple on/off controller set to 14.5 for a week or two will often do it as well.

AGM batteries must be well managed to have a decent lifespan.  They can't be given an extended equalization charge (at say 15V) because they will vent and dry up.   So it's even more important to read up on their proper care and charging to get your money's worth out of them.  I've got to run now but will try and find some decent web published articles for you later.

Best Wishes,
Bruce

[LowGear]

You can do some testing on the accuracy of your meter(s) by sticking them on your car battery.  Some day I will actually make some recordings when everything is working beyond notice.

I'm pretty sure the AGM Optima Yellow Top in my Subaru is 12+ years old.  I had to have AAA stop by the other day and it tested pretty weak.  I'm always uncomfortable with a service agent that just happens to have a replacement (wet lead) in the truck for only $125.  I've now had it on a charger for the previous two nights and last night it made a 45 minute run with lights blazing and went to bed without a charger.  This morning will be "interesting".  Of course my question now is "To Optima or Not To Optima" as these puppies scare the pudding out of two hundreds dollars.  But then again 12 years is 12 years.  Any simple readings would be appreciated?

Casey

[BruceM]

I wouldn't waste my time on a 12 yr old yellow top.  It's served it's life well, let it rest in peace.

My experience is that the Dekka (sp?) deep cycle AGMs seem to hold up just as well as Optima, but are sometimes a better price.

[mike90045]

12 years on a 6 year battery, you got lucky.
 Try http://www.batteryfaq.org/  for info about charging AGM batteries.  you NEVER equalize them, and must be careful about charging voltage, or you create too much gas for the re-combiner cats to handle, and you pop the vents, and loose water. Lost water = lost capacity and lost life

[BruceM]

Mike's right that equalizing an AGM battery as you would a wet battery will certainly damage it.

You can do it safely if you float the fully charged battery at a somewhat higher than normal float voltage, say 14.3V for 2-3 days, as long as the current is determined to be low (.5 amp or so). 

I've revived a couple older yellow tops this way. 

[BruceM]

I found an interesting article on equalizing AGM batteries. 
http://www.rvforum.net/SMF_forum/index.php?topic=30606.0

Seems as though if you don't do it very often, it can help, even at wet battery voltages.

[honda lee]

Spending that much for a car batterie it's time to think about going back to horse and buggy.
I think it my end up going back to that anyway with the amount of dollars being printed these days,every thing is going up in price so fast.
A few years ago I paid about $35  for my motorcycle batteries now they are $70. I am concerned it's going to get much worse!

[Tom]

I drive a '74 IH Scout II with a real stiff 4" lift and live on bumpy dirt roads. A battery would only last about 2 years in that truck. Cheap, expensive or what ever it was 2 years max. Then I tried an Excide orbital battery and it really lasted 12 years! So the entire fleet has been gradually switched to the orbital technology. The last few Excides have only lasted 4-5 years, so it seems their quality has slipped. On the Optima's it's still unknown how long they'll last as none has failed yet!

The AGM tech in the orbital batts also seems to handle being discharged due to lights being left on than FLA batts. Instead of equalizing AGM batts a desulfator seems to do an excellent job of restoring them if they have not been fried dry.

[32 coupe]

I am around batterys most days. All types, wet, agm blah, blah.
I work on private yachats and  most have good or better chanrgers and one
thing I have learned the last few years is that they (batterys) are all junk.
Batterys used to last 10 years. Not any more. If you get 4 years that is good.
Most of the boats they get changed every 2 to 3 years.  Most are in the 50 to 90 ft.
class and ocean going so no risks are taken.
Point being that with a 30 year background in such maters I will state again, they are all junk
at this poimt in time. I keep hope that they will get better but I won't hold my breath.
My rant for the day,
Doc