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behengold's avatar
behengold
Explorer
Aug 17, 2015

How to choose new 8D house batteries.

Existing batteries are 5 yrs old 8D AGM's. after only running my ceiling fan for an hour or two they're discharged down to 12.5V from 13.5. I'm guessing they are nearing the end of their lifespan.How can I test to make sure the batteries are ready to replace? I've priced replacements between $450 for house brand batteries to $650 and beyond for lifelines which seem to be the premium battery choice.The $450 battery specs at 250 AH and weighs 170lbs.Lifelines are about the same. What should I look for? Don't mind spending the money if getting better quality in return.But if they're basically the same I can put the money somewhere else. Thanks
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  • dons2346's avatar
    dons2346
    Explorer
    Aug 17, 2015
    You didn't say what brand AGM you have but my Lifeline 8D's installed in Jan'04 are still fine. If they are Lifeline, you can do a conditioning charge on them which is basically the same as equalizing a wet cell. Don't know about other brands.

    I wouldn't give up on yours yet.
  • pianotuna's avatar
    pianotuna
    Nomad III
    Aug 17, 2015
    If you find out you need replacement batteries, consider trying to find used cell phone tower back up batteries. They spec at 139 amp-hours and have lots of life left in them for RV'ing. I got mine from Interstate.
  • Ductape's avatar
    Ductape
    Explorer
    Aug 17, 2015
    Suggest you read the Lifeline manual -it's available on line- and run through the testing and possibly conditioning charge process before you replace them.

    Don't know if that's your current brand, but all the AGM's pretty much operate the same.

    Mex can correct me if there are any errors or omissions.

    Suggest you ask the mods to move this to the tech forum where it will get a better audience.
  • Vulcan_Rider's avatar
    Vulcan_Rider
    Explorer
    Aug 17, 2015
    sh410 wrote:
    A fully charged battery at rest 12.6V. The 13.5V you are seeing is a surface charge.


    The full charge for a conventional battery at 80 F is 12.65 but for an AGM it typically is 12.8.

    YOu can't use that 13.5 "surface charge" number for anything, except maybe to assure yourself that something is charging the battery.

    An AGM at 12.5 is about 65-70% charged and might be "on the way out"
    if that happened over a short period with a light load.

    The other consideration, however, is that 13.5 is just a float voltage for an AGM. If the charging voltage never goes above that they might not be getting fully charged......ever.

    You need to check that out before sinking a **** load of money into new batteries.
  • harold1946's avatar
    harold1946
    Explorer
    Aug 17, 2015
    sh410 wrote:
    A fully charged battery at rest 12.6V. The 13.5V you are seeing is a surface charge.


    Great catch. :@
  • sh410's avatar
    sh410
    Explorer
    Aug 17, 2015
    A fully charged battery at rest 12.6V. The 13.5V you are seeing is a surface charge.
  • harold1946's avatar
    harold1946
    Explorer
    Aug 17, 2015
    Without the proper equipment it cannot be. There are battery dealers that have the equipment to do so, Interstate is one of many. Some auto parts stores have the equipment, with the gaining use of AGMs in the auto and motorcycle industries.
    Life expectancy varies greatly, with the majority being 5 to 8 years, but I have heard of and had a set that made, lasted 11+.
    Have the batteries ever been desulfated ? If not it may be possible to extend their service life by doing so.
  • Bill_Satellite's avatar
    Bill_Satellite
    Explorer II
    Aug 17, 2015
    Check out Universal Batteries. I replaced my 10 year old Lifelines (awesome but expensive) with the UB 8D batteries for half the price. Even if they only last 5 years I will break even. We are now in our 4th year and they are still going strong.

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