Leisure batt, charger, split charger

Discussion in 'Mech Tech' started by rustbucket, Jul 22, 2018.

  1. With this hot weather I’m thinking about a 12v cool box for the back of my work van so I can keep drinks cool and then in winter I can keep milk in it for teas when I’m on site.

    I’ve got power in the back of the van but I’m wondering if a cool box will flatten the starter battery or if I will get away with leaving it plugged in all day.

    If needed because of the way I’ve run the power cables into the back it would be simple enough to just use a leisure battery instead of the starter. However then I’d need to charge the leisure battery, so at first I thought I’d just add in a split charge relay, but on reading a few things about leisure batteries they say not to trickle charge, so would I also need to buy a 240 smart charger. If so I don’t think I will bother as a split charger, battery and 240 smart charger is a bit of over kill for a bloody cool box.

    Having said that do you think I could buy a leisure battery and mains charger and just charge it over night when needed or would it be flat every couple of days with no alternator charge?

    I do already charge a fair amount of stuff in the back of the van like Gas analysers, torches etc so a leisure battery might be a batter idea long term.

    Cheer for any help or ideas.
     
    jivedubbin likes this.
  2. Normal peltier cool boxes are around 40 -50 watts 50w ÷12v = 4.166 amps so a 40ah leisure batt should get you around 10 hours continous use! Get a 120/140 ah and you'll be good for other uses! Check your alternator size to gauge how long it will take to charge said leisure battery through your split charge system!
     
  3. A peltirr cooler coolbox will kill you battery in about 2-3 hours
     
    paradox likes this.
  4. mikedjames

    mikedjames Supporter

    You need it all if you use a cheapo coolbox.
    Leisure battery and 10A or bigger 240v charger unless you run the engine above 2000 rpm for about 4 hours a day, split charge wont help if you dont use the engine.
    I have all the above.. and 2x100W hi efficiency solar panels with a proper (£40 at boat jumble, really £500) compressor coolbox ( average drain about 1-2A) ..

    I leave the fridge on 24/7, dont bother with hookup on the driveway so I can bulk buy cheese etc for lunch at work and keep it in the bus.

    Even then, a cloudy day or two and the battery shows signs of flattening. At a rainy April Techenders with a dodgy leisure battery, it was dead after 2 days.
     
  5. We had 3 running in the back of my brothers skoda octavia all day this weekend only after around 9 hours did the battery die
     
  6. Hmmmmmm thanks guys.

    So I need to have a rethink cos even with a split charger keeping the battery topped up I don’t think some days I will be driving enough to keep on top of the power drain.

    Short term I might just buy the battery and a 240 charger and just give it a zap overnight every few days and once it’s cooled down just disconnect it from the battery and keep the lid closed.
     
  7. Is it true that a leisure battery needs a smart charger and that a normal over night trickle charger will kill the battery?

    Isn’t a split charger just in effect trickle charging from the the alternator?
     
  8. mikedjames

    mikedjames Supporter

    Smart chargers get the battery to 100% charge when nothing else is connected.
    Trickle chargers or simpler current limited voltage regulated chargers work better than smart when you have a load on the battery at the same time as trying to charge it.

    Alternators are sort of current limited voltage regulated chargers. After a very long drive batteries would reach 100%
     
  9. You can get compressor chest fridges that use a lot less power and will run cooler than the peltior effect 12 volt cool boxes.
     
  10. Solar ?
     
  11. I've got a couple of counter top compressor fridges one rated at 40w the other at 50w also a absorbtion fridge they're silent but over 80w but they work considerably better than a peltier module cool box! Peltier cool boxes will cool max 20 degrees below ambient!
     

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