Battery drain question

Discussion in 'Homeowner Assistance Forum' started by dh500, Aug 21, 2006.

  1. dh500

    dh500 LawnSite Member
    Messages: 58

    Dixon MAG 44 Ram with 20.0 Honda

    After a couple of months on non-use, I found the battery to be almost completely flat.

    After recharging, I reconnected the battery and with everything switched off, measured the current drain with a digital multimeter.

    Reading was 12mA.

    Is this normal?

  2. Jason Rose

    Jason Rose LawnSite Fanatic
    Messages: 5,858

    A couple months? How cold has it been? If by chance it was a little down when you parked it, maybe not fully charged to begin with, a couple months sitting would drain a battery. I guess if I leave one sit for a couple months my expecations as to whether it's gonna start are not that great...

    I didn't even know dixon made it all the way down to you guys! That's pretty cool, lol

    Sorry I'm a dummy... I have no idea how to check the current drain on a system like that... However I'd assume with everything OFF it should have ZERO current going out of the battery. Not like there's clocks and whatnot to keep running on a mower.
  3. steve45

    steve45 LawnSite Bronze Member
    Messages: 1,325

    Sounds like leakage through the alternator diodes, normal. However, I don't know if this is still in the circuit with the switch off. A battery will have internal leakage, too. It's normal for it to lose it's charge after several months of inactivity.
  4. Daner

    Daner LawnSite Bronze Member
    Messages: 1,307

    This Is What I would do In your case...Do A load test on that battery...Its a devise that loads up the battery and tells you If you need to replace the ole gurl...I have seen many tractors drawing a tad of power...But I think you might have a battery problem there. Best of luck:weightlifter:
  5. dfischer

    dfischer LawnSite Member
    from Il
    Messages: 114

    IF the battery is good, that's not normal. You should be able to let it set for more then a few months. Not that that's good for a battery.

    12 mah, while small, seems like too much for a diode to be leaking. While 12 Mah is roughly 6 months to loose 12 amp hours, you don't normally see such a drain.

    Check the battery, and see if the local service shop can tell you what the alternator leakage spec is. I'm guessing lots lower.
  6. dh500

    dh500 LawnSite Member
    Messages: 58

    Thanks to those who replied.

    The reason for my machine sitting idle for so long was due to a shoulder injury. I will try to investigate where the current is going as I was surprised at such a large figure.

    I am also puzzled by dfishcer's calculation. Maybe I am misunderstanding something, but I worked out that 0.012 amps would correspond to 80 hours to lose 1 amp-hour.

    This is roughly 3 days so I would estimate 10 amp hours per month.

    I am not sure what the rated capacity of the battery is, but on this basis, it is not surprising that the battery did not have much charge left after 2 months - or have I miscalculated somewhere?

  7. dfischer

    dfischer LawnSite Member
    from Il
    Messages: 114

    If 1 amp hour is 80 hours, then 12 would be 960, yes?

    I simply acknowldeged a Milli =1/1000, took your number of 12 mah and did the math:

    12 mah= .012amp/hr = 12amp/1000 hr.

    At least we agree it's leaking too much....

    Btw, My math on 6 months is wrong. In a fit of idiocy I too 1000/40/4.3.

    Of course the 1000 hours is correct, and there ARE 4.3 weeks per month, but why I used 40 hours in a week I'll never know. sigh. It's more like 6 weeks to loose 12 amps...
  8. jkingrph

    jkingrph LawnSite Senior Member
    Messages: 812

    Had that problem on an old cub cadet lawn tractor about 15 years ago, a battery would not last over a year. Replaced it with a jd lawn tractor and found a small trickle charger device called a battery maintainer. Hard wired to battery, plugged in when not using mower and am still using original battery. Unit was placed in service spring of 2000. Had one on honda generator and moved it to new scag ztr because of mounting bracket and replaced one on generator with low amperage 0.5-1 amp trickle charger on gen. Seems to me that this approach works well on units in storage or off season.
  9. dh500

    dh500 LawnSite Member
    Messages: 58

    Just in case anybody else has a similar problem and finds this thread through a search, here is the end of the story....

    For a while I avoided the flat battery problem by disconnecting the battery when the machine was to be out of use for anything more than a week or two.

    Eventually I got fed up with this and investigated further.

    (1) I confirmed that the drain of 0.012A was still occuring.
    (2) I disconnected the 6 pin plug connected to the rectifier/regulator assembly ( a finned aluminium thing mounted between the engine and the battery)
    (3) With this disconnected, the current drain was zero.
    (4) I cleaned the plug and socket with a spray can of contact cleaner and when reconnected, the current drain was still zero.
    (5) As a precaution, I wrapped electrical tape around the plug and socket assembly to discourage entry of dust in future.

    As far as I can tell, everything is fine now.

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