Another Newbie Ignorant Battery Question

SouthAfrica75
SouthAfrica75 Solar Expert Posts: 36
What type battery should I get to run a 10 watt light for approximately
6 hours ?

Could I get away with one of those lawn tractor or personal water craft type batteries or do I need something bigger.

Comments

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Another Newbie Ignorant Battery Question

    it must be deep cycle and not a starting type of a battery. most marine batteries are deep cycle, but some also allow for starting too. working this in reverse we have 10w x 6hrs = 60wh. now you need to double it so as to not drain the battery past 50% so this now is 120wh. because wh divided by volts is ah this is 120wh / 12v = 10ah and is the smallest battery you should get. that is small enough for even some other battery chemistries like nimh or nicd if you were to series parallel, but it's small for a deep cycle lead acid type to normally come in. you could get a higher ah rating lead acid type just for a buffer to allow for overuse or accidentally falling asleep with it on. just be sure the charging source can supply between 5% and 13% of the ah rating of the battery.
    i'm not sure what is locally available to you, but you may have to do some research there and ask retailers there what they have. you may get something from walmart too, but know that these don't usually last more than 4-5 years give or take depending on the care given to them. i wouldn't bother with an agm for something that small, but you could if you wish to spend that much $ for your battery. if you do then be sure to properly charge it and don't let it go over the manufacturer's max voltage spec.
    i know i keep updating it while you're reading it. i'll stop now.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,433 admin
    Re: Another Newbie Ignorant Battery Question

    It is also possible that some "D" cell or other form factor batteries in NiCAD or NiMH may work well for your application too...

    Problem is that every battery/chemistry has its strengths and weaknesses... Used to see NiCAD cells in surplus stores (from telephony applications?).

    In any case, depending on a lot of different issues (temperature, recharging time, self discharge time, peak current, spill proof, cost, etc.) may lead you to one chemistry over another.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Another Newbie Ignorant Battery Question

    stupid me as computer ups have batteries in about that range so you may want to check that option.
  • SouthAfrica75
    SouthAfrica75 Solar Expert Posts: 36
    Re: Another Newbie Ignorant Battery Question
    niel wrote: »
    stupid me as computer ups have batteries in about that range so you may want to check that option.

    Sounds like an idea...... One should last about 6 to 7 hours running those 10 watts
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Another Newbie Ignorant Battery Question

    see if you can find one rated for 10ah or more. if you can't then you could parallel 2 at 5ah or more to properly power your light. remember that you should not drain a battery beyond 50%.