get your self proper lappy charger. I got mine from exelby services bp garage a19 south bound. 14quid and works perfect in 12v. only use inverter for phone chargers etc
Quoting Mr Fibble “Sure, if you want to kill your batteries.”
Q says: He is Quiet correct
When obtaining a 12volt Supply (as discribed in my diagram)
That: Long term loading, and or deep uneven discharge
of just one of the twin batteries,
Will cause extra ware on both the un-discharged battery and its partner.
I obmitted to mention that fact 
** Original posting amended **
How-ever this is a system that I have used before to power
12volt devices which require a clean (electrical noise free) 12 volt supply
which only draw high (20Amp +) currents for short periods ( low duty cycle)
[ in my case Ham Radio Transceivers ]
It could be adapted to run other items which only require High Currents for short durations
(example kettles, micro wave cooker, etc)
** It is NOT Suitable for Long Duration, High Current Supply…**
Q agrees: That its far better solution is to obtain 24volt equipment and use existing wiring
Or to have an High Power 24 — 12 Volt converter ( or 24Vdc - 240vac invertor)
fitted and wired into the truck electrical system by a professional.
DoubleQ:
How-ever this is a system that I have used before to power
12volt devices which require a clean (electrical noise free) 12 volt supplywhich only draw high (20Amp +) currents for short periods ( low duty cycle)
[ in my case Ham Radio Transceivers ]It could be adapted to run other items which only require High Currents for short durations
(example kettles, micro wave cooker, etc)** It is NOT Suitable for Long Duration, High Current Supply…**
Remember also that the effect is ■■■■■■■■■■ (it adds up over time), so I’m not sure that I’d use it for kettles/microwaves either. A small device (e.g. a mobile phone charger) probably won’t draw enough current to have an effect, but then you could run that off a “normal” 12V outlet fitted in the cab.
Of course, you could always mitigate the effect by swapping your batteries occasionally. Alternatively, you could swap the feed to the other battery if you’re really sure you know what you’re doing, but you’d have to be very careful not to short out one of the batteries accidentally (as noted in your diagram).
Conor:
DoubleQ:
Excuse,But what everyone appears to have missed here,
is that the Lap -Top Changer is also NOT going to be 100% efficient
Likely somewere between 75 - 60%
and there-for could be drawing 120 - 150 watts from the 240Volt supplyI haven’t missed anything. It won’t draw more than is stated on the sticker on it. There’s not many lappy bricks more than 90W.
According to the OP the PSU “puts out” 90W max so 2xQ is quite correct that fully loaded it will draw more than that from the mains supply. It will be a switched mode supply though so probably in practice more like 80-90% efficient than the 60-75% suggested.
Paul
MrFlibble:
Alternatively, you could swap the feed to the other battery if you’re really sure you know what you’re doing, but you’d have to be very careful not to short out one of the batteries accidentally (as noted in your diagram).
The problem with swapping the feed to the other battery is that whilst its still a12V feed, the positive will be at 24V and negative at 12V, both with respect to the truck ground (chassis) which is far from ideal.
My money is on Mr Flibble on this one …he aint no duck egg take it from me folks 
thecoder0:
My money is on Mr Flibble on this one …he aint no duck egg take it from me folks
And your contribution is what?
squarepeg:
MrFlibble:
Alternatively, you could swap the feed to the other battery if you’re really sure you know what you’re doing, but you’d have to be very careful not to short out one of the batteries accidentally (as noted in your diagram).The problem with swapping the feed to the other battery is that whilst its still a12V feed, the positive will be at 24V and negative at 12V, both with respect to the truck ground (chassis) which is far from ideal.
I know, which is why I covered it in lots of advice not to do it…
" Alternatively, you could swap the feed to the other battery if you’re really sure you know what you’re doing, but you’d have to be very careful not to short out one of the batteries accidentally (as noted in your diagram)."
I also strongly advise AGAINST Doing that…
(Note warning about taking feed from poles labled “A” “B” in diagram)
Regards 2xQ
Steve-o I have pm’d you let me know if you have got it