Adaptor for leisure battery

Discussion in 'Tech/Mech General' started by Dee Dee, Sep 27, 2014.

  1. Dee Dee

    Dee Dee Read Only Funster

    Joined:
    Sep 27, 2014
    Messages:
    5
    Likes Received:
    0
    Location:
    houston
    I just ordered leisure battery 100 Amps and a charge relay for my van. It's not a campervan, mostly work based van. I need the second battery for laptop mostly. Now, what adapter to use to connect the laptop to the battery? Apparently classical inverters are not very efficient as the current has to be transformed twice, from 12V to 220v and back to the laptop input standard. But little do I know. I never tried it before. Another option would be to convert from 12v straight to laptop via a dc to dc converter Is this a better option? I can charge my laptop from the cigar socket so thinking as well about just buying a simplified adaptop for a fiver that will simply take the current from the leads of leisure battery, and to which I can connect my laptop charger. What the best option would be here? Thanks
     
  2. pappajohn

    pappajohn Funster Life Member

    Joined:
    Aug 26, 2007
    Messages:
    29,443
    Likes Received:
    16,872
    Location:
    YO11 2BD
    If you can currently (no pun intended) charge the lappy via a fag lighter socket then thats all you need connected to your new battery.

    But......using the lappy while charging it will extend the charge time dramatically.
     
  3. Dee Dee

    Dee Dee Read Only Funster

    Joined:
    Sep 27, 2014
    Messages:
    5
    Likes Received:
    0
    Location:
    houston
    My bad, I don't have a laptop cig charger. I have one mini usb for my tablet. The tablet can charge, but don't know about laptop.
     
  4. icantremember

    icantremember Funster

    Joined:
    Sep 2, 2010
    Messages:
    5,040
    Likes Received:
    7,080
    Location:
    Nr Watton in Norfolk
    Ebay or Google .... just search for "laptop car charger" .... loads available and not expensive.
     
  5. Dee Dee

    Dee Dee Read Only Funster

    Joined:
    Sep 27, 2014
    Messages:
    5
    Likes Received:
    0
    Location:
    houston
    yep they are cheap allrighty. I will need to connect it to leisure battery. I can get a cig socket with jumper cables for a few pounds, if that's the most efficient option, or a more sophisticated dc to dc converter. How long do you think the laptop will run on this before depleting the leisure battery? How long does it takes to recharge it back again from alternator with the engine running? It's a standard laptop 15 inch with the input of 3 something Amps or so it says on the tin.
     
  6. Badknee

    Badknee Funster

    Joined:
    Aug 25, 2014
    Messages:
    3,640
    Likes Received:
    15,218
    Location:
    notloB
    The clue is in the name, 100 amp hour. I would imagine there is no such thing as a DC to DC converter but a good idea would be an inline fuse between the battery and the puter.
     
  7. Dee Dee

    Dee Dee Read Only Funster

    Joined:
    Sep 27, 2014
    Messages:
    5
    Likes Received:
    0
    Location:
    houston
  8. scotjimland

    scotjimland Funster Life Member

    Joined:
    Jul 25, 2007
    Messages:
    28,934
    Likes Received:
    25,574
    Location:
    .
    3amps is the current when powered from the mains.. not when supplied by a 12v battery ..let me explain..

    when calculating the time the battery will last you need to consider the power .. in watts .. check the laptop label.

    for example.. an 80 watt laptop powered by a 12v battery uses 80/12 = 6.66 Amps.. call it 7amps

    You battery is lets say 85 ah .. with a useful capacity of 45 ah (you don't want to discharge below 50% )
    divide 45/7 = 5 hours.

    Recharging time from the alternator is difficult to calculate, too many variables.. has to be checked with an amp meter while charging.. but roughly the same time as it took to discharge..

    Back to your question.. John and Brian both provided the solution.. an in-car 12v laptop adapter , you can remove the cigarette lighter plug and fit crocodile clips, preferably insulated ones, and if required a longer lead.. and clip onto the battery posts

    you may have to screw a self tapping screw into the battery post to get a place for the croc clip to attach .. or use a full size quick release battery clamps

    if you do this remember to fit a fuse near the battery end of the cable..

    quick release battery clamp
    [​IMG]
     
    Last edited: Sep 28, 2014
  9. scotjimland

    scotjimland Funster Life Member

    Joined:
    Jul 25, 2007
    Messages:
    28,934
    Likes Received:
    25,574
    Location:
    .
    ooops.. should have been 6.5 hours.. doh

    no matter you got my drift
     
  10. Dee Dee

    Dee Dee Read Only Funster

    Joined:
    Sep 27, 2014
    Messages:
    5
    Likes Received:
    0
    Location:
    houston
    thanks guys, I'll do just that, the clamps look alright. A bit disappointing how much power it can transfer in a session. I think 80 Watts or as it is case of my laptop 90W is the max power a laptop will use with the cpu going at full blast all the time, which hardly ever happens. I hoped to get at least 12 hours from 100 Amp battery.
     
  11. icantremember

    icantremember Funster

    Joined:
    Sep 2, 2010
    Messages:
    5,040
    Likes Received:
    7,080
    Location:
    Nr Watton in Norfolk
    "Houston we have a problem" ........

    .... I'm sorry but someone had to say it!
     
    • Like Like x 1
  12. pappajohn

    pappajohn Funster Life Member

    Joined:
    Aug 26, 2007
    Messages:
    29,443
    Likes Received:
    16,872
    Location:
    YO11 2BD
    I hope it isnt 3amps at mains voltage Jim.......thats 690watts.

    It will be 3amps from the chargers 19 volt output which is just 57 watts
     
  13. scotjimland

    scotjimland Funster Life Member

    Joined:
    Jul 25, 2007
    Messages:
    28,934
    Likes Received:
    25,574
    Location:
    .
    indeed John.. my mistake..

    however in my explanation I did say to calculate the amps when supplied from the 12v battery had to be made using the wattage on the label of the laptop.. and not what was on the mains power adapter
     
  14. Minxy Girl

    Minxy Girl Funster Life Member

    Joined:
    Aug 22, 2007
    Messages:
    8,491
    Likes Received:
    9,839
    Location:
    E Yorks
    Perhaps another option would be to look at getting a second battery for your laptop to supplement it's power range that way? You could then recharge them both at home and this could give you an extra couple or so hours, so maybe 4 hours in total for the laptop batteries - although this will depend on the efficiency of the laptop itself! Using 2 laptop batteries and your leisure battery, you won't get 12 hours but you might get near 10 if used carefully (ie by tweaking your power usage, lowering screen brightness etc). As for recharging your leisure battery itself it on the run, how long is a bit of string! It will depend on how much draw you are making for other things, like lights, wipers, radio etc, how far you travel. The only way to keep it charges would be to plug it in to the mains overnight at home.
     
Loading...

Share This Page