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OT: Charging a deep cycle battery.

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  • OT: Charging a deep cycle battery.

    I charge my deep cycle battery with a 1.5 amp "maintainer" charger. I sometimes leave it on the charger for a week or more since it shuts off (or at least pauses until it needs to charge again) when the battery is charged.

    We had an electrical storm while the charger was on the battery. No direct hits but I suspect we had a power surge when we had a close lightning strike. (The family computer popped and was fried. We also had damage to the geothermal heating/AC unit.)

    Later, the charger wouldn't show "charged" so in the event I had a damaged charger I bought another and hooked it up to the battery. It doesn't show "charged" either.

    I've had the chargers off the battery for at least a week now and the battery is showing 13.01 volts.

    What's happening here?

    Thanks,
    Dan

  • #2
    That's pretty close to normal. A true deep cycle battery has a slightly lower terminal voltage than a starting battery when it has had a chance to "relax". After that it has a much lower self discharge rate than a starter battery does. When charging on a trickle charge the cutoff voltage is 13.7 volts. This will not produce a full charge, only about 90%. When fast charging the battery should be charged to 14.4 volts and then held to no more than 13.7 volts maintenance charging. That gives a full charge.
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    • #3
      So it sounds like the battery really is charged but the chargers aren't confirming that. I especially thought the new one, a Schumacher, would tell me it's "charged".

      Do you have any ideas on why neither of my 2 chargers are saying the battery is "charged"?

      Maybe the older one is bad from the surge and I got a bad new one. This is the first use for the new one. Could be a bad coincidence. I've seen stranger things happen.

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      • #4
        It's probably because of aging of the battery, again, perfectly normal. As it ages the fully charged terminal voltage drops slightly as does the actual charge capacity. All lead acid batteries gradually build up sulphates in the plates from normal use. That is the ultimate limiting factor on battery life.

        BTW, the old charger may well be fried and the new charger is telling the truth, a much more likely scenario.
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        • #5
          Thanks Evan! I understand now.

          I hope that both chargers are still good. On my place I can always use another maintainer type charger.

          I put a new battery in my bigger tractor a few days ago. I'll try each charger on that battery to see if they seem to be working right.

          I seldom use the deep cycle battery for deep discharging applications. I mainly use it as a bench power supply. But early last year is when I bought it and an inverter. Lucky move on my part. About a month later our power went out for 3 1/2 days due to an ice storm. I was able to use it and the inverter with my laptop to access email, to charge our cell phones, and to watch a little 13" TV. Definitely worth the cost. I'd like to make sure it's in good enough shape for this Winter. If not, I need to replace it.

          Thanks again,
          Dan

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          • #6
            I have heard that some top quality battery chargers have a desulphate cycle but I have yet to see one. Any one know of a brand name. We run 4 of the biggest yellow top Optima’s in our bay boat and had a problem with one and the desulphate was what we wear told to do to get it working.

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            • #7
              Every time you discharge a battery it sulphates, that is simply part of the normal chemistry. If you leave a battery discharged for very long then it can 'hard' sulphate. What happens is that the sulpfate crystals are constantly disolving and re-crystalysing, which tends to make the larger ones grow and grow into each other, making it very hard to get them to redisolve under charge. With an AGM like the Optima which has very thin plates with a large surface area it's possible to almost completely coat the active material so you can't recharge (Lead Sulphate is an insulator). In these circumstances you use a current limited bench supply (100mA or so) and wind the voltage up until the battery starts drawing current. I've had to go to 60 volt or more. As the battery recovers it will try and draw more and more current, but because you are using a current limited supply the voltage will drop instead. When it is down to about 15 volt you can use a conventional charger.

              The de-sulphator circuits do work if the battery is actually 'sulphated', but all the talk about hitting the resonance of the suphate bond is complete nonsense. They simply use a fast rise time, high voltage pulse (unregulated flyback converter). The fast rise time may help by creating pizoelectric stress in the crystals.

              Very few batteries die from sulphation. Mostly they die becuase the active material is no longer making good contact with the collection grid. This can be because they have been chronically undercharged, so that the discharge cycles are deeper, or they've been chronically overcharged which also causes corrosion of the positive grid.
              Paul Compton
              www.morini-mania.co.uk
              http://www.youtube.com/user/EVguru

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              • #8
                Originally posted by pgmrdan
                ...About a month later our power went out for 3 1/2 days due to an ice storm. I was able to use it and the inverter with my laptop to access email, to charge our cell phones, and to watch a little 13" TV...
                I also keep a deep-cycle battery and inverter at the ready. When power goes out, and if there isn't any other pressing need for power until morning, I use the battery and inverter to power my CPAP and get a good night's sleep.
                Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
                ~Practitioner of the Electromechanical Arts~

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                • #9
                  Yeah I got one

                  "Power on Board" from Sam's and I have used it 3 times on batteries that would not take a charge and after the cycle it took a full charge. The cycle is 24 hours and if after 5 of these cycles it doesn't take a charge head for the battery store. The neighbor even borrowed it and got two of his batteries working again.

                  http://reviews.samsclub.com/1337/190126/reviews.htm

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                  • #10
                    I have one of the "battery charger/maintainers" (Cdn Tire) that works very well on a car battery. However, when I charge a 12v gel cell it often doesn't work if the battery is close to fully charged. When slightly discharged it works fine and maintains correctly.

                    I have put it down to the relatively low ampere-hour rating of the battery.

                    Geoff

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                    • #11
                      The Schumacher charger is just "calibrated" for automotive batteries.

                      If you have "one" battery, it probably is not a deep cycle battery. It may be a "marine deep cycle" which is almost a gussied-up starting battery.

                      I use deep-cycle traction batteries in the solar system, Trojan T-105. They are 6V, and each one is double the size of a car battery, and at least double the weight. They are 220 ampere hour, vs the 50-60 A-H that many car batteries have.

                      Even the marine ones typically have more capacity, possibly somewhere around 100 AH, +-.

                      A small charger probably cannot provide enough current to get the voltage up, even with a marine deep cycle. That would be one issue.

                      it's also possible that the battery is indeed "sulphated". It takes a while to recharge with a small charger, and meanwhile, normal, natural sulphate is becoming the "hard" type, or simply falling off the plates.

                      Any material that falls off the plates is lost, representing a permanent loss of specific gravity and capacity. After that the voltage may never come up high, and if the charger can't drive enough current to "gas" the battery, the charger may not pick up the actual fully charged status.

                      The small charge current won't do a fast charge if the battery is drained down. Your charge rate is around "C/60", maybe, and if so it would take about 72 hours to completely re-charge the battery from "flat". Allowing a car battery, or a battery derived from a car battery, to ever discharge over 20% to 40% down, will usually lose capacity.
                      1601

                      Keep eye on ball.
                      Hashim Khan

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                      • #12
                        "A small charger probably cannot provide enough current to get the voltage up, even with a marine deep cycle. That would be one issue."

                        I use the maintainer as a maintainer. It has worked fine until now. Evan's explanation seems to be the reason.

                        When I significantly discharge (not nearly down by the 20% to 40% you mentioned) the battery I use a regular charger. It's used as a bench power supply and has been used once 1 1/2 years ago when the power was out.
                        Last edited by pgmrdan; 09-16-2009, 11:54 AM.

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                        • #13
                          Originally posted by Weston Bye
                          I also keep a deep-cycle battery and inverter at the ready. When power goes out, and if there isn't any other pressing need for power until morning, I use the battery and inverter to power my CPAP and get a good night's sleep.
                          Roger that! I store the deep cycle marine battery in the bedroom in a decorative basket. The wire and 12V coaxial plug are already hooked up and ready to plug into my cpap. So far I've used it 5 nights in a row without charging just to see how it would hold up.

                          I have 3 of the $32.00 NAPA Battery Tenders and love them. One on the cpap battery, atv and lawn tractor.
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