Laptop om 12 volts

Feb 22, 2011
5,863
8,405
Newcastle under Lyme
Funster No
15,397
MH
Hymer B544 A Class
Exp
Since 2015
I recently bought an adapter to up the 12 v to 19 v required by the laptop and have it plugged into a Hella socket, all works fine. I then bought an extension lead so I can position the lappy where I need it.
It lights up the battery light ok but shuts down a couple of seconds after switching on, I should add the lappy battery is knackered so it needs the external power source.
Seems like there is insufficient power getting to it with the extension lead ?
Does anyone know a why the extension lead seems to loose this much power to stop it working ?
Edit, extension lead is about 2 metres
 
Last edited:
Feb 8, 2014
1,555
2,439
Sheffield
Funster No
30,022
MH
Eldis Majestic 115
Exp
Vans and tugs since mid 70's
Maybe the extension lead is not heavy enough so a voltage drop may be the problem?
 

magicsurfbus

Free Member
Oct 11, 2010
4,685
10,158
NW England
Funster No
14,057
MH
Bessacarr Coachbuilt
Exp
Since 1997
When I use my 12v Chinese knock-off Mac laptop charger it takes a lot of oomph out of the leisure battery, I think because it's stepping up the voltage. In my last MH the leisure battery voltage (normally healthy) dropped some way below 12v whenever the laptop was charging.

If your leisure battery is already in demand from other items a laptop charger might not get enough power.

We had a similar thing with our old F&H 12v TV - we had to plug its power pack into the 12v socket then plug it into the TV set, otherwise it wouldn't work. You couldn't just leave them connected up overnight and switch on at the set.
 
Apr 27, 2008
9,302
8,445
Eastbourne East Sussex
Funster No
2,327
MH
A Class
Exp
Since 1972
If it works without the extension then the extension must have too high a resistance. You can get high wattage extension from ebay but they are usually long ones or make up your own.
 
OP
Figaro
Feb 22, 2011
5,863
8,405
Newcastle under Lyme
Funster No
15,397
MH
Hymer B544 A Class
Exp
Since 2015
I put the multimeter on this extension lead when I got home and the voltage shown was the same as that at the Hella socket.
Could it be that it`s the current it won`t handle ? The cable does look a bit lightweight.
The plug and socket on the extension lead do look like they will dismantle so I might try and wire it with different cable.
Should I order 0.5 mm, 0.75 mm or 1.0 mm ?

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Aug 6, 2013
10,985
14,007
Kendal, Cumbria
Funster No
27,352
MH
A Class
Exp
since 1999
I put the multimeter on this extension lead when I got home and the voltage shown was the same as that at the Hella socket.
Could it be that it`s the current it won`t handle ? The cable does look a bit lightweight.
The plug and socket on the extension lead do look like they will dismantle so I might try and wire it with different cable.
Should I order 0.5 mm, 0.75 mm or 1.0 mm ?
2.5 sq mm
 
Sep 17, 2017
1,712
2,848
Birmingham, UK
Funster No
50,575
MH
A-Class
Exp
2017
Depending on the model, the laptop is probably pulling 60w (and maybe up to 90w, check the PSU) as you power it up. That's 5A on 12v before considering losses in the transformer... Quite a lot of current to be pulling.
 
Dec 12, 2010
4,029
12,941
Cumbria
Funster No
14,651
MH
C Class
Exp
since 2011
I've just bought a 12 volt step up to 24 volt 12 amp adaptor to power a small 24 volt external fuel transfer pump rated at 7 amps. Under no load the adaptor outputs 24 volts on my multi meter, connect it to the pump and it drops back to 12 volt. Out of curiosity, I connected a 12 volt 21 watt bulb to it and the voltage dropped to 14 volts. Requested some action from the seller on ebay before I post feedback. There are lots of identical units listed, mostly coming from China, but I bought from a UK based seller for a few quid extra for piece of mind. :rolleyes:

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