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Author Topic: ELECTRICS question. Is a 130W/19.5V laptop in off-grid campervan possible?  (Read 1194 times)

LeeCooper

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Hello there!

We are planning a sprinter conversion, with an ideal outcome of being able to do freelance animation work whilst on the road.

The electrics seem to be the most daunting prospect, and we're waiting to buy the van until we can confirm that it's actually physically possible to use a fairly powerful laptop, without having to be constantly near a power hook up.

The laptop in question is a DELL Precision 5520, 2.90 GHz, 32Gb Ram with a 4Gb graphics card.
I know literally nothing about electrics but it says it's 130W and 19.5V on that small black box that goes between the laptop and the plug in the wall.   (inverter?  converter?)

I've watched countless hours of YouTube vids and have tried to learn the basic terminologies, but still can't confirm that it's possible to make use a powerful laptop for extensive periods of time.   My question to any-one out there is, is there a way to know how long a specific laptop will run for once you have chosen your battery setup?

If any-one has any advice on this, it would be greatly appreciated.   I would consider any set up at all if it allowed us the freedom to be away from a power hook up.  Solar, generator, big power bank, etc.

Thanks for any help.  :) 

Camper_Dan

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Greetings and Welcome!

In this case, the watts give us the important number.  So if we take 130 watts, and divide it by 12 volts, we get the amps that it will draw per hour.  That comes out to 10.8+ amps, so we'll just round that up to 11 to be safe.  So if we multiply the maximum number of hours per day that you plan on using it by 11, we should know about how many amp hours per day it will use.  You will want to get a car charger for it, so we can eliminate the use of an inverter, because they waste power. Whenever possible, we want to run everything on 12v.

Now, before we can figure out your whole system, we need to figure out what else you also plan on using, and then figure for a buffer so we know we're covered.

Charging while driving via an isolator, solenoid, or relay is always the most efficient way to charge your house battery(s).  The next best choice would be either a generator or shore power, and contrary to what all the solar sales people want you to believe, solar is always the worst choice, and comes in dead last for many reasons.  Provided we eliminate solar, everything gets much cheaper, simpler, and easier.

Cheers!
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LeeCooper

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Interesting advice!  Really appreciate your response, Camper_Dan.  :)

So if I were running my laptop for 10 hours, I'd be looking at 110 amp hours per day.
(I wonder if rendering or doing more intensive stuff on the laptop will draw more power?  when the fan and graphics card are churning away loudly?)   If I'm running off the laptop battery, the life will drop from 10 hours to about 2 hours once I've fired up my graphics programs.

A friend of mine has told me that an inverter is the way to go, and holy heck are they expensive!  So I'd be interested to see if there are alternative routes that are reliable.    Being less dependent on shore power is my ultimate wishlist, but I'm aware I might just be hoping for too much.

Sorry for the basic questions but isn't an inverter the same as a generator?   Or am I thinking of an "inverter generator"  (vs a conventional generator)      In my (basic) head, a generator is something that is filled up with fuel and is quite loud and placed outside the vehicle.   

Your stance on solar is really interesting, thanks for that.   I have been looking into lithium batteries, and lots of people seem really excited by them.   They seem very expensive also.

Really appreciate you taking the time to read my posts.

LeeCooper

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...also, I just realised I forgot to mention what other electrics we would need.  My girlfriend has a less powerful laptop which is far less power hungry and wouldn't be running it as much as me.

We have phones, a small portable wireless speaker, a hairdryer and would like a fridge with a small freezer compartment. 

In a perfect world, we would also consider bringing a very powerful Vitamix blender for short blasts, but that is way down on the list of priorities.  It's the laptop that we're focussing on.

Thanks again! 
Lee.

Camper_Dan

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Greetings!

Inverter: Converts 12v battery power to 120v AC house type power.  Inverters also come in multiple types, plain, modified sine wave, and pure sine wave.  Pure sine wave provides the cleanest power for electronics.  Using an inverter usually costs an extra 20%-25% more power from your batteries.

Inverter Generator: Fuel powered generator that produces both 12v DC and 120v AC power.  Typically these produce cleaner power than a normal generator, which is better for electronics.

Some people are calling power packs/banks generators, but they do not produce power, they only store it like a battery.

The hair dryer is probably out unless you go with a generator, anything like that involves heating is terribly taxing on batteries.  I'd also skip those expensive 12v fridge/freezers.  I've switched back to a plain old ice chest, and if I was going to go back to a powered fridge I'd probably go for a 3 way fridge that can be run mainly on propane, or with a little conversion either kerosene or even vegetable oil.  They will basically run on candle power, saving you a ton of power.  They can be found used really cheap at wrecking yards.

For the next part of the equation, deep cycle batteries don't like to be discharged farther than 50%, so you need at least double the maximum amp hours you're planning on using.  To be safe, and better for the batteries, I like to go at least 3x on amp hours just to be safe.

So first we need to figure out how much total power we'll need, then we'll figure how we'll recharge it.

Cheers!
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LeeCooper

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Hi there, Dan.

It's been a while.  Thanks again for your last responses. 
My concern with the deep cycle batteries is that I will need so many, (given the 50% charge rule).
Ideally, I will need a huge bank, as my work laptop alone will require as much as 150aH a day.
This is why a lithium bank seemed like a better choice.

Some-one I am in touch with is selling as 1000w pure sine wave inverter with a 30amp vehicle charger and a built in solar charger for only 229, but it's interesting that you're saying this will cost me up to 25% of battery space.  I suppose if I went lithium I could afford the extra battery space?

I've been looking at 3 way fridges, which as I understand them can be powered by two types of gas and/or electricity.  From what I hear, they need a lot of space for ventilation.   Obviously, I want to save on electrics, but also want to save space, too. 

I've seen some conversions get up to about 600aH battery banks with a huge budget! 

We plan on buying the van very soon now, and I can see that the electrics need planning in the initial stages, so am getting concerned that I have no idea what I am doing.  Do you have any preferred guides or reading material that you would recommend?

Thanks again for your time. :)




Camper_Dan

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Greetings!

Okay, with your laptop running full tilt (2 hour battery time), and continuing to run full tilt, and you plug it in, how long does it take for the battery to get fully charged back up while you're still using it?

Cheers!
« Last Edit: May 20, 2019, 02:24:15 PM by Camper_Dan »
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LeeCooper

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It takes about two hours.

Camper_Dan

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Greetings!

Uggghhh... That's bad news...  I don't really see this as being practical without shore power or running a generator all the time you're using that laptop.  Isn't there a way to use a less power hungry laptop? 

Cheers!
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LeeCooper

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Hmm....not even with a gigantic lithium power bank?