# what size inverter, laptop, leisure battery, drain,



## wilse (Aug 10, 2007)

Hi all


Quick question...
I've had a look at the forum, but can't find the info I need.

I would like to power my laptop when in the "king" 


Laptop is rated:
Input 100-240v (1.5a), doing the "Watts = Amps x Volts), my laptop rates at 360 watts (if used 240v).
However if worked out on the 100v scale it's load is 150 watts.
Is it possible to work things out on the 100v scale? As I can change the plug to the US version.

As for output (if this is important) it's 18.5 volts 4.6 A.

I'm lost!!!

I have one leisure battery I think 80 Amp Gel.
Would it be a good idea to buy another?

How long could I run the inverter with my laptop when engine not running assuming everything is fully charged and in A1 condition?

hth?

wilse


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## dct67 (Sep 23, 2007)

Hi

Just taking the rating at it face value, if it draws 1.5A at 100V i.e. 150W, it will draw no more than 150W at 230V either.

If you want to maximise battery life, you might want to buy a 12V to 18V laptop power supply. This will mean you'll save having the losses due to the inefficiencies of going 12V to 230V back to 18V.

In terms of battery life, your battery can if fully charged deliver 80A for 1 hour at 12 volts (theoretically!). Worst worst case of using 12V to 230V to 18V conversion, you might draw as much as 180W (allowing for losses in the 12V to 230V inverter) - at 12V this is around 15A - i.e. around 5 hours of run time.

In reality, your laptop will use less (by far) then 180W. In fact it will probably draw less than 60W. And if you use a direct 12V to 18.4V inverter, you'll probably draw around 80W - or 7A at 12V - giving around 10 hours of computer use conservatively.

Kind regards


David


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## geraldandannie (Jun 4, 2006)

Hi, Wilse

I tend to use mine (laptop) off the internal battery until it runs out, and then charge it up using a small cheap 150W inverter overnight or when we're out.

Gerald


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## wilse (Aug 10, 2007)

geraldandannie said:


> Hi, Wilse
> 
> I tend to use mine (laptop) off the internal battery until it runs out, and then charge it up using a small cheap 150W inverter overnight or when we're out.
> 
> Gerald


Hi Gerald

I've actually got an inverter, but haven't had chance to fit it yet.
It's a cheapo 360w one.

I agree running it off battery then recharging overnight/driving.
Although I was static for 5 days last week, with no hook-up and with "dct67's" calculation, I could only have 2 hrs per day (which I probably wouldn't) plus this doesn't account for other electric uses, pumps, lights etc.

I'll check up on the laptop duffer

Can I presume adding another 80ah gel battery, would theoretically double my available "on tap" power?

wilse


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## 2kias (Sep 18, 2006)

Why bother with an inverter.
I bought one of these from Maplins Stock no L40BB
http://www.maplin.co.uk/Search.aspx?criteria=l40bb&source=15&SD=Y
Works extremely well. Check the voltage requirement on your laptop first.


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## wilse (Aug 10, 2007)

arrrh.... my mac ways have proved hard work to me again.

my laptop has a posh magnetic power lead, that when you walk past it when charging on your table, it detaches from the laptop rather than pulling your laptop on the floor, great but....

it doesn't use the standard din plug thing connections.

It's like this magnetic power lead

PS the other need for the the inverter is for the missus' to dry her hair!

wilse


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## vicdicdoc (May 14, 2005)

A totally agree with 2Kias, why bother converting from vehicle 12v to 240v via inverter to go back down to 18v ? . . . like him I have the gadget from Maplins . straight 12v to laptop power.



wilse said:


> PS the other need for the the inverter is for the missus' to dry her hair!
> wilse


Ho Ho,Ha Ha Ha . . . 
see the thread - http://www.motorhomefacts.com/ftopict-18434-inverter.html

your going to have some fun just like I did, my other half has this thing about washing her hair & drying it every day . . . better to convince her to have a crew cut ](*,)


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## 101316 (Oct 9, 2006)

Hmm, well if you can't find a power supply with the right connector to power your Mac you'll just have to go the inverter route.

My best *battery life tip *for anyone running any kind of laptop is to check out your laptop CPU power management settings.
My Acer for example has all kinds of energy saving features when running on its internal battery but when it thinks it's running on mains it runs the CPU on "high" setting and consumes a ghastly 6amps from the leisure battery. I switch CPU speed to "medium" (the lowest it will go) and consumption drops to around 3 amps - DOUBLING battery life at a stroke 

There, I just saved you the cost of another battery, with the savings you could send her to the local hairdressers to get her hair dried :lol:


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