PV to run a laptop - recommendations

[MrG]

Mr G, which pub ?

If the panels are a really good deal then you can buy a dropper to convert 24v to 12v. They're not expensive, so buy two in case one breaks down.

Alternatively you can probably buy an adaptor to covert 24v DC to the voltage of your laptop. (Usually 19v)

Is it possible for him to sell me some panels at that price ?

Thinkit was called the Piper or something.. George Square.. not sure I went to a few pubs last night. Do you know Glasgow then?

I should imagine I can get you some panels yes. One guy is in Cardiff, the other in Bath... your in France.. would have to work that out of course!

[MrG]

Cheers both.. Adam yes my mate did say to me I should get a 24V battery I remember now. The dropper option looks potentially simpler than trying to find a 24V laptop adaptor though.

I'll look into it.

[hardworkinghippy]

MrG,

Glasgow, yep, I know it well - I was born there.

I'm serious about the panels - I'm looking for some right now (plus decent batteries) and I've a friend travelling down to our place in France at the end of the month....

[MrG]

Ok.. so where in the UK is your mate travelling from?

The guy in Bath is generally the more reliable and easy to get hold of.

[mikepepler]

A lot's already been covered here, so I'll just add a little bit...

1. Get a single plug power meter, and measure your laptop's consumption. It'll be a lot less than the maximum, and you can also measure the effect of changing the power settings. You can also measure kWh used over the day, usually with an accuracy of 0.01

2. I looked at 12 and 24V systems. In the end I went for 12V, simply because things running off 12V are a lot more common.

[hardworkinghippy]

MrG,

He lives in Mottingham in London SE9. He's a good pal so he might travel but not too far.

What's the deal, how do I get in contact with this guy. I want around 1KW of panels.

Mike, it's true it's easier to find lots of things like lightbulbs TVs etc. in 12v.

[MrG]

I'll give him a call later on tonight and find out what the score is. My phone's dead at the moment, need to get it charged. I'll pm you and let you know if he can sort it out. I don't see him travelling to London though he's really busy working out notice at the company he worked for and setting up own business at the same time.

Cheers Mike yeah I'm prob going for 12V I reckon if I can.. probably with a droper.

[Tarrel]

Hi folks. Newbie on this forum. I appreciate this thread is old now, but just came across it.

If you need a laptop for basic communication and office work (i.e. you don't need to use any specialist software), I'd recommend an ipad. They'll run all day (10-12 hours) on a charge, and they then charge from empty to full in less than two hours, using 2 amps. Hence, a full charge is 4 Ah, which equates to 48 watt-hours at 12 volts. Over, say, a day of 6 hours of daylight, and assuming a conservative 30% efficiency, it would take just 24 watts' worth of power from your solar array.

The other benefit is that the on-screen keyboard is excellent, meaning that you can use it in the dark. No ambient lighting required, unless you need to refer to books, paperwork, etc.

I've had one for a year, and it has completely replaced my laptop. I spend weeks away at a time, during which my hotel bedroom is my office, and I design and deliver training workshops. The ipad is now an indispensable tool.

Just my two pence-worth...

Tarrel

[mobbsey]

It is certainly possible to run a laptop from a PV and battery system, but for continous use may need a larger system than expected....

Quite correct, but why run at 12 volts?

Most laptops now run on somewhere between 18 and 22 volts. It's more efficient to design a 24 volt PV system and then regulate down to the required supply voltage rather than produce 12 volts and then almost double the voltage the required level.

I keep meaning to write-up the design for my home-brew charge controller. You can buy 24 volt charge controllers, although they're not as plentiful as the 12 volt versions intended for "leisure" use; a curious word given that "leisure" in this context seems to be all about maintaining high levels of energy consumption off-grid

Some of the laptop power supplies that boost from 12V to the required supply voltage are often inefficient. They're primarily designed for cars, and so are a little more profligate with the juice than the more expensive versions specifically designed for use with PV. Regulating down from 24 volts can be done quite efficiently using readily available components. See the briefing I wrote some time ago for details --
http://www.fraw.org.uk/projects/salvage ... ulator.pdf

That handout (produced from some off-grid power workshops I use to run for computing projects and free festivals) also covers battery technology. However it doesn't deal with PV because at that time PV panels were way outside the price range of the sort of groups I used to work with (many opted for pedal power instead -- e.g. Rinky Dink)

Quite strange to see more requests for this type of knowledge at the moment. Last week I was teaching my son how to design/build a simple switched regulator for his DT project and realised how much I missed all the hands-on simplicity of electrical engineering, certainly in contrast to my work over the last few weeks going around talking about shale gas.