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Thread: High Amp Hour AGM battery charger

  1. #1
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    Default High Amp Hour AGM battery charger

    Does anybody have a recommendation on a good battery charger for maintaining high amp hour 12 volt AGM batteries?

    I have 4 x 153 AH 12v AGM batteries that I want to put a maintenance charge on the while I finish building my solar system.

    I just bought them, but they have been sitting idle for a few weeks and never put in service. The manual says they loose about 3% charge per month and should be charged with at least 20 amps.

    I looked at the Optima1200 charger but from what I saw in the specs they were only rated for up to 130 AH batteries.

    Ideally I would like to find a charger that the output voltage can be set manually so I can match it up to the manufactures specs rather than using a general all purpose setting. A digital readout would be nice too.

    Thoughts?

  2. #2
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    Quote Originally Posted by johngalt View Post
    Does anybody have a recommendation on a good battery charger for maintaining high amp hour 12 volt AGM batteries?
    I looked at the Optima1200 charger but from what I saw in the specs they were only rated for up to 130 AH batteries.
    Thoughts?
    I think that the Optima 1200 charger recommendation is limited because they would like to see a higher charge rate as a function of battery capacity than most AGM suppliers for optimal battery service. But that does not meant that the charger would be incapable of doing a restore and float service on near-fully-charged batteries.

    There are other AC chargers on the market which are expensive but flexible. I have seen some from Iota mentioned but have never used one.
    SunnyBoy 3000 US, 18 BP Solar 175B panels.

  3. #3
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    Quote Originally Posted by inetdog View Post
    I have seen some from Iota mentioned but have never used one.
    I'll check them out.

    Thanks!

  4. #4
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    My needs are like yours - I only use a charger in cases where I have a few days of rain or bad weather, and need to charge up my AGM batteries every once in a blue moon since solar takes care of me 99% of the time.

    I went the automotive smart-charger route knowing full well that they are not ideal - but I have a combo that I really like and satisfies my immediate-gratification needs without going overkill on budget. I don't use any of the alternator-check, battery-boost start features etc - just the basic charging. It consists of:

    Stanley BC4009. 40amp smart charger. Detects my Odysseys and Sears Diehard Platinum properly as an AGM, and only takes it up to 14.8 volts during charge. Simple metering for both voltage AND current. Voltage is about .01 to .02 in accord with my Fluke meter. Haven't tested the accuracy of the current metering. (must be in current mode to start charge, afterwards you can lock in either display). Stops charging when current reaches about 1 amp and goes into the typical automotive "float-monitoring" mode, rather than a true constant float. Does an initial charge for a few minutes, stops for a minute to evaluate things, and then continues on until done. Switching type so it is very light. Seems well built, and has some monster clamps and cabling. Someone put some thought into cable management, and it wraps / stores very nicely. This is enough for the 2 or 3 days of bad weather scenario. Keep the garage doors open the first few times you use it as the new plastic smell is everywhere. Doesn't get hot, and fan doesn't scream, although it is audible. Not ideal for bedroom.

    To get a true continuous float, I can switch to the 6amp Stanley BC6809 which only goes up to 14.4v for my agm's, and will continuously float at 13.5 volts if I want to go that route and really get it charged 100%.

    I have about 6 or 7 other brands of chargers that I've tested, but I like this combo a lot for an inexpensive automotive type setup which gets used rarely.

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