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6v battery charger conflict

Discussion in 'Electronic Design' started by Dave, I can't do that, Sep 8, 2012.

  1. Hi All,

    Recently bought a weather station that wireless transits data to an inside console. It has four AA Alkaline cells and a small (about 1" square) solar panel to help trickle charge the batteries.

    All good, but the batteries are lasting only about four weeks. It is a major thing to get the station down from the pole on top of the garage to replace the batteries.

    Because it is outside and I don't care what it looks like, I want to use a sealed 6v 1.2AH lead acid battery and a 6v solar charging panel.

    I will remove the Alkaline batteries, run wires to the lead acid, but the question is, do I need to do something about that small solar panel charge? I was thinking just put a diode in series with the battery positive going to the station so nothing can come back to the lead acid battery.

    Would that all work or do I need something fancier?

    Thanks

    Dave
     
  2. Jamie

    Jamie Guest

    Unless you have the rechargeable alkaline cells, the standard types are
    not rechargeable.

    Have you tried rechargeable types? you may get a lot more time out of
    them. I have replaceable types in my solar lighting for my drive way and
    they have lasted for 3 years now. The panel charges them during the day.

    Jamie
     
  3. Guest

    From Wiki

    Ordinary alkaline batteries can be charged with a current pulsed at a
    rate of 40 to 200 pulses per second, with an 80% duty cycle. Pulsed
    charging appears to reduce the risk of electrolyte — usually potassium
    hydroxide (KOH) — leakage. The charging current is usually very low
    to avoid rapid production of gasses that can rupture the cell. Cells
    that have leaked electrolyte are a safety hazard and unsuitable for
    reuse.

    My experience is that ordinary alkaline batteries can be charged if
    they have been discharged to about 1.3 volts.


    Dan
     
  4. Jasen Betts

    Jasen Betts Guest

    A one inch solar panel cannot produce enough power to damage a
    lead-acid battery of the size you propose so you don't need to
    worry.
     
  5. hamilton

    hamilton Guest

    Please share the device in question.

    Where did you purchase it ?

    hamilton
     
  6. Guest

    First of all, please ensure that the batteries are
    rechargeable.
    Secondly, the 1" size for a solar panel seems unusually
    small. Given that the power conversion efficiency of
    solar panels is so low (maximum 25$ for very high
    quality ones) - this tiny thing does anything useful.
    Thirdly, because of the low power conversion efficiency
    it takes a long time (5 - 7 hours) for say 4 1000 mAH
    rechargeable NiCd cells to charge up/
     
  7. Syd Rumpo

    Syd Rumpo Guest

    Are you sure the 'solar panel' is supposed to be for charging batteries
    rather than measuring sunlight? It will give bugger all power, less at
    night.

    Cheers
     
  8. Thanks for replies.

    The manual states (yes, I do read manuals) "use standard alkaline batteries.." It also suggests Li-Ion for operating in temps below 15F (I think, too lazy to get the manual to check for the actual low temp range)

    Manual states the solar panel is there to trickle charge the batteries.

    Surplus 6v 1.2mH LA battery is 4-bucks.
    Surplus 6v solar panel is 7-bucks.

    For 11-bucks, that is not many D-Cells.

    Grid power would cost a bunch more by the time I get a 6v transformer and build a regulated 6v PS. It makes no sense to me to use grid power if I can do it with solar. Can't see the logic behind using grid when 11-bucks will provide free power for a long long time.

    I am more concerned about damaging the weather station electronics by allowing the solar panel and charger circuitry pushing volts/milli-amps to the LA battery. I am sure it would not harm the LA battery, but I do not want todestroy a 200-dollar station for the cost of a $0.06 diode or something.

    So, back to the original question, will a diode suffice?

    It would be so nice, if for once, this forum returned a direct answer to a direct question, rather than a long debate on peripheral nonsense. I am certain there is a wealth of technical know-how here but it rarely gets to seethe light of day.

    Dave
     
  9. hamilton

    hamilton Guest

    Please share the device in question.

    Where did you purchase it ?

    hamilton
     
  10. Guest

    Use your common sense. Since the manufacturer requires standard alkaline cells, there is no charging current going into the batteries. It is not necessary to use a diode.
     
  11. josephkk

    josephkk Guest

    With that small of solar cell against that LA battery it should suffice.
    The battery will regulate sufficiently to protect the instrument as long
    as it lasts. I would be more worried that tiny solar cell won't be enough
    the overcome the LA self-discharge. Perhaps using rechargeable lithium
    1.5 v AA cells would work better.

    ?-)
     
  12. Greegor

    Greegor Guest

    Please post the make, model and source of this weather station.
    A link to it would be helpful if possible.

    Was it like this one?

    http://www.weathershack.com/la-crosse-technology/ws-8120u-it-br-t.html

    [...]
    -One TX61U-IT solar powered remote sensor included
    -High-efficiency solar panels maintains full charge with minimal light
    and stores solar power for continuous operation
    -Receiver rechargeable alkaline batteries can be replaced with
    rechargeable alkaline or regular alkaline batteries by changing switch
    from Solar to Battery
     
  13. Charlie E.

    Charlie E. Guest

    Dave,
    Make sure that this is actually six volts, and not 3 volts. My
    weather station has six batteries, but the are two batteries in
    parallel. You could buy a solar charger/supply for mine, and had two
    of them cook out in less than a few months. The manufacturer was in
    Canada, and I am in the low desert in CA. The system couldn't take
    the heat...

    Once I realized this, I just use good alkaline cells and go months
    without changing batteries. Helps to put the battery pack/transmitter
    in a relatively cool spot...

    Charlie
     
  14. Charlie E.

    Charlie E. Guest

    Make that FOUR batteries, in series-parallel... ;-)
     
  15. Jeff Layman

    Jeff Layman Guest

    There is something wrong with your weather station if AA cells last only
    a month.

    I have a LaCrosse WS2350 which takes input from a wired rain gauge and
    anemometer. It the transmits the data from those and the inbuilt
    temperature and humidity sensors wirelessly to a base station. The
    first set of 3 alkaline AAs lasted 20 months before they needed
    replacing (the manual states that the battery life is approximately 12
    months). The second set has already been going a year.
     
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