Old AGM Batteries

stmar
stmar Solar Expert Posts: 370 ✭✭✭
What would be a good way to test an old AGM battery bank? Mine is past life cycle expectations but seems to be functioning. Since they are AGM sealed batteries you cannot measure like in flooded units. Is it possible for them to be good after 7 years??? For about a year they were only powering a Sun Frost RF-16 and were only on the solar array, not the grid.

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Old AGM Batteries

    It is possible for them to be good after seven years. You just have to define "good".
    All batteries lose capacity over time. No way around that. The rate of decline can be kept to a minimum with proper charging/maintenance.

    Now how do you test an AGM to see if it's any good? You use a load tester. This does just what they do to get the capacity ratings in the first place: controlled discharge over time. Looking at the Voltage decline as a function of that can tell the actual capacity. Chances are you haven't got one though.

    You can charge them 'fully', measure resting Voltage, and let them sit for two or three days to see how much that declines. For example if it comes up to 12.75 Volts on charge and is at 12.25 the next day it's shot. Not a very precise test.

    Really if they're still doing the job and you're not running out of power then they could be classified as "good". But you know they are getting older (no way to escape that whether you're a battery or a person) and will need to be replaced. Perhaps it is time to look at your options in that line.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Old AGM Batteries

    if they are still functioning then use them until they don't function. that sounds curt, but it's not. the actual time they will give out depends on who made them and the care they had while being used. in other words, your guess is as good as mine, but i had a sunxtender that had a bit of abuse that lasted 8yrs. i would have some $ put aside for new ones though.
  • stmar
    stmar Solar Expert Posts: 370 ✭✭✭
    Re: Old AGM Batteries

    Concordes seem to be a quality brand and they really have not been abused, most of the time in Float and only one time I can remember that they were down in the 23 volt range from a 3 day grid outage and that was 3 years ago. I have the $$$ budgeted for new ones but wanted to get as much as I can out of these, but I am thinking they need replaced before next winter. When the weather gets better and their use is not so critical I may put some stress on them and see how they rebound/function.

    P.S. Have any of you sold your old batteries to a recycler? I was told they paid per pound, anybody know how much or range I should look for? These batteries are over 150# each.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Old AGM Batteries
    stmar wrote: »
    P.S. Have any of you sold your old batteries to a recycler? I was told they paid per pound, anybody know how much or range I should look for? These batteries are over 150# each.

    Well I have taken lots of batteries in for scrap of course. But the price changes from day to day and place to place. Basically you get something for them and don't worry about how much because you've had the value in use.
  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: Old AGM Batteries
    stmar wrote: »
    Concordes seem to be a quality brand and they really have not been abused, most of the time in Float and only one time I can remember that they were down in the 23 volt range from a 3 day grid outage and that was 3 years ago. I have the $$$ budgeted for new ones but wanted to get as much as I can out of these, but I am thinking they need replaced before next winter. When the weather gets better and their use is not so critical I may put some stress on them and see how they rebound/function.

    P.S. Have any of you sold your old batteries to a recycler? I was told they paid per pound, anybody know how much or range I should look for? These batteries are over 150# each.

    Scrap Batteries here this week are $0.20 a pound.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Old AGM Batteries

    Get your new batteries first before you scrap your old.

    In California (at least), the dealers must have a core charge--And it is not always clear if the scrap price is higher or lower than the core charges (mandated by state).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • stmar
    stmar Solar Expert Posts: 370 ✭✭✭
    Re: Old AGM Batteries

    Will do, they are worth about $30 each scrap so the .20 per # was in the ballpark and that is 120 miles from here so will not be in any hurry to take them down there. I probably will not have to worry about a core charge because the new batteries will have to be shipped in and it would not be worth it to ship the old ones out.
    BB. wrote: »
    Get your new batteries first before you scrap your old.

    In California (at least), the dealers must have a core charge--And it is not always clear if the scrap price is higher or lower than the core charges (mandated by state).

    -Bill
  • H2SO4_guy
    H2SO4_guy Solar Expert Posts: 213 ✭✭✭
    Re: Old AGM Batteries

    Basic batteries here are about $.25 per pound unless they are the Absolyt type, then they are about $.10 per pound IF you can get a battery place to buy them at all. I was offered Absolytes @ $.25 per pound and I could have had about 1000 AH @ 48 volts. I almost went for it, but elected to get the Panasonic AGM's instead. The part that I was concerned with was a few cells of the Absolytes were bulging and I didn't want any issues.

    Good luck and let us know how it works out.
    12K asst panels charging through Midnite Classic 150's, powering Exeltechs and Outback VFX-3648 inverter at 12 and 48 volts.  2080 AH @ 48 VDC of Panasonic Stationary batteries (2 strings of 1040 AH each) purchased for slightly over scrap, installed August 2013.  Outback PSX-240X for 220 volt duties.  No genny usage since 2014. 
  • stmar
    stmar Solar Expert Posts: 370 ✭✭✭
    Re: Old AGM Batteries

    By coincidence I reconnected with an acquaintance that is building a rudimentary system and experimenting. I am going to give him my old batteries to supplement and experiment. Sharing resources seems a better recycle method than scrapping, then when he gets all he can out of them they can go to the recycler.
  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Old AGM Batteries

    One thing you may want to do is pick up a Cen-Tech model 66892 Digital Battery Analyzer.

    Although not a lab instrument (read: cheap), and mostly designed for measuring CCA's, it has a very useful internal resistance measurement which is far more useful for RE batts. It is the only relatively affordable meter with internal resistance metering I have seen. Fortunately you don't have to know or even care about the CCA value, the metering for internal resistance doesn't seem to change.

    I use mine to occasionally monitor the internal resistance of my AGM's, and make sure they are somewhat near the manufacturers spec. I set a baseline reading on them when they were new, and take measurements every so often afterwards.

    At least this way, you have much more to go on than just terminal voltages, which tell you nothing about the overall health of an agm battery. Might be handy weeding out the total duds from something salvageable - maybe.
  • stmar
    stmar Solar Expert Posts: 370 ✭✭✭
    Re: Old AGM Batteries

    With that instrument do you have to isolate/disconnect the batteries to test or do you do it while they are on line?
  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Old AGM Batteries

    Sorry it took so long to get back on this.

    The manual states not to attach the clamps while the car is running, and do not start the car until you remove it. Also use only in single 12v batteries, don't try using it in the middle of a string for example.

    That said, I only use it to test stand-alone non-vehicular batteries. I don't care about any CCA measurements.
  • stmar
    stmar Solar Expert Posts: 370 ✭✭✭
    Re: Old AGM Batteries

    No problem, I went ahead and had them checked and 3 were still good one was weak. I went with 6 volt AGMs so don't know if that instrument would work for that, will have to check specs and see, but disconnecting the banks and individual batteries would not be something I would want to do very often.
    PNjunction wrote: »
    Sorry it took so long to get back on this.

    The manual states not to attach the clamps while the car is running, and do not start the car until you remove it. Also use only in single 12v batteries, don't try using it in the middle of a string for example.

    That said, I only use it to test stand-alone non-vehicular batteries. I don't care about any CCA measurements.
  • stmar
    stmar Solar Expert Posts: 370 ✭✭✭
    Re: Old AGM Batteries

    After a month of sitting in the barn with no loads and no charging three batteries are at 12.8 volts and one is at 13 volts. The one at 13 is the one that checked out as weak. Anyone have an explanation of this finding? Just curious. Also do you think the service guy that checked them understood that they are deep cycle and did not check them just for cranking amps, they are an Interstate distributor and he seemed like he knew what he was doing??
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Old AGM Batteries
    stmar wrote: »
    After a month of sitting in the barn with no loads and no charging three batteries are at 12.8 volts and one is at 13 volts. The one at 13 is the one that checked out as weak. Anyone have an explanation of this finding? Just curious. Also do you think the service guy that checked them understood that they are deep cycle and did not check them just for cranking amps, they are an Interstate distributor and he seemed like he knew what he was doing??
    Voltage is a poor indicator, a square inch of good plate can give you voltage, but you'll have no capacity. Drop a known load on them and see how long it takes to get to 12.0 V. I have 4 old 50 watt head lights ( 16 amps ) with a set of clips I use.
  • stmar
    stmar Solar Expert Posts: 370 ✭✭✭
    Re: Old AGM Batteries

    I am charging the old 12 volt AGM batteries with a regular charger, using the 10 amp setting, it has 2, 10 and 50 for starting. So far I have done the 3 "good" batteries and they all start at 5 amps and quickly go to the 2.5 mark. Is this telling me that they are fully charged? I am only leaving them on the charger for an hour or so. The cables are not too hot, just warm. Just want to make sure I am understanding, want to keep them charged in case a guy who wanted them shows up, no loads they are at rest.
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Old AGM Batteries
    stmar wrote: »
    they all start at 5 amps and quickly go to the 2.5 mark. Is this telling me that they are fully charged?

    Depends on a couple of things...

    Is the voltage appropriate for those AGMs? If the voltage is too low the drop in current may not indicate that they are fully charged.

    What is the capacity of the battery? If it has reduced capacity because of sulfation, the current will drop just like a normal battery that is fully charged, but of course there is no capacity. Blackcherry04 gave you the correct advice... check their ability to handle a load.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Old AGM Batteries

    my advice is to get a proper charger on them before you destroy them. most agms cannot tolerate excessive voltage and will vent when that happens. you can't replace what has vented out of the batteries so you are ruining their capacities.
  • stmar
    stmar Solar Expert Posts: 370 ✭✭✭
    Re: Old AGM Batteries

    The batteries found a new home, I think they had plenty of life still in them to benefit the recipient. I gave them to him for less than scrap price plus some barter and I think we will both profit from knowledge exchanges, our systems are way different so I am sure there are nuances that we will pick up from each other.