12v to 19v for laptop

[ShoelessSmith]

Forgive me if I have posted this in the wrong place but I am new here, in fact new to motorhoming, and I have looked across hundreds of pages but I just can't find what I am looking for. I could quite easily be utterly blind.

 

Due to Real Life circumstances (i.e. my wife's condition with her disease) we are moving our motor homing plans five years ahead to now. I will still be working from the motorhome when we're out and so we're getting out whilst she's still able because who know where we'll be in five years when I had planned to retire.

 

So, that's the plan. Now when we're hooked up to the mains on a hook-up I understand that we have the normal 240v supply as I would have in my home office and things will be as normal in terms of power.

 

We're planning on going somewhat off-piste as soon as we can as this suits us both (my experiences at camping tend to be with a tend on rucksack or bicylcle) so being in a motor home is going to be alien to me.

 

I am thinking of getting a 240W (or thereabouts) solar panel to charge up the leisure battery which is good. That is what I will be running the laptop from. Now, I understand enough physics to know that going from a 12v battery through a 240v inverter to a 19v supply via a laptop transformer is as inefficient as they come.

 

So, what's the best way for me here? Is there a good way of powering up the laptop from the battery? Will there be 12v sockets around the motorhome or do I need a converter/inverter device?

 

Apologies for the long winded message but the local caravan and motorhome people don't seem to have enough grasp of things electrical to help me and living in the middle of nowhere there's no-one else to ask.

 

Any advice would be gratefully accepted.

 

Malc

[colin]

What 12v sockets the van might have would depend on the make/model or what has been added after, we have the standard 2 cab sockets which are only realy for use whilst driving plus two in the rear which have been fitted as after market items and work off the leisure battery. Have a 12v input multi voltage output charger which amongst others has 19v for a laptop.

[colin]

What 12v sockets the van might have would depend on the make/model or what has been added after, we have the standard 2 cab sockets which are only realy for use whilst driving plus two in the rear which have been fitted as after market items and work off the leisure battery. Have a 12v input multi voltage output charger which amongst others has 19v for a laptop.

[ShoelessSmith]

Thanks, our motorhome is new to us but I will inspect it tomorrow and crawl all over it then looking for 12v or 19v sockets.

 

That would make life a lot easier if we could find something but everything on this new motorhome is just alien to me -- it's even got central heating which we don't have here in the cottage, for example!

 

Malc

[Brian Kirby]

I think you may have misunderstood Colin. Most motorhomes only have 12V sockets on the dashboard, which usually only work with ignition on. However, some do have a 12V outlet of some sort for a low voltage TV, that might be usable. Look near the TV cupboard, if there is one.

 

If there is none, wiring a car cigarette type socket back to your leisure battery should be fairly straightforward. If you don't want to tackle the wiring yourself, find a suitable unit (Halfords probably, but other car accessory shops should stock them), install the socket where you want it, and then get an auto electrician to make a suitable, fused, connection. Shouldn't be that expensive.

 

Then, either buy from your computer manufacturer (usually expensive!) a dedicated 12V car charger for the laptop, or from Maplin (usually cheaper), a multi-voltage laptop charger. Either plugs into the 12V socket and gives a stable 19V (plus alternative voltages for the Maplin type) output. Unless you need a 240V supply for other purposes, such a 12V laptop charger should be a more efficient way to get from 12V to 19V than going from 12V to 240V and back down to 19V, although there will inevitably still be some small loss.

 

First, however, do make sure your leisure battery is in good condition and up to the task.

[manxli]

Hi Malc

 

First of all, best wishes and go for it! I have similarly just retired 5 years early, as my wife also has a serious condition and we will tour as much of Europe as we can between therapies and treatments.

 

You can get special adaptors for some laptops. e.g. For a MacBook:

 

http://www.amazon.com/Cybertech-MagSafe-Charger-Adapter-Notebook/dp/B006RAF0NY

 

Luckily my Chausson has 12v sockets in the storage cupboards which are powered by the leisure battery. I believe some solar setups can charge BOTH leisure and vehicle battery similutaneously, or to be safe you could have a separate small battery just for your laptop perhaps? My transit has space for an extra battery under the passenger seat for example.

 

All the best

 

 

Alan

 

 

[ShoelessSmith]

Thanks all for the warm welcome and the replies.

 

We've just come back from a test one night 'camp' in the gin-palace at Y Bala (close by so if there was a problem then we didn't have far to get home). I can report that despite having no hosepipe nor water in the tank it was a total success.

 

Yes, I fed off the umbilical cord so power wasn't an issue but the wife, being an ex-narrrow boat inhabitant, wants to get off piste as soon as possible.

 

Yes, it looks like laptop chargers are the way to go and we're going to go for the largest panel on the roof that we can afford (the TV aerial will just have to go) and then power up the battery from that. If we can get a second 110 Amp/h battery then all well and good.

 

But if I am correct a laptop drawing, say, five amps can last about 25 hours on such a battery. That should do me for a few days worth of work and there must be enough sun, even on the Llyn Peninsula, to charge the thing up for a fourth or fifth day of Welsh rain.

 

So I am going to go for one panel, the bigger the better, keep the one battery and then have a couple of cigarettte sockets by the table and then we're off and running. And by the fifth rain of rain on the Rhinogs we can either read by the laptop light or just come home.

 

Cheers

Malc

[Brian Kirby]

If you do decide to add a second battery, check your payload first. Batteries, especially proper leisure batteries, are very heavy. Regarding getting 25 hours use at 5A out of a leisure battery, I'm going to say "no Sir"!

 

First, 5 x 25 = 125 Ah, and your battery is only rated at 110Ah.

 

Second, it is probably not a true 110Ah battery.

 

Third, you should not discharge the battery (depending on type) by more than 60% of its capacity, so 75Ah, or you risk damaging the battery. Until you know what its capacity and type actually are, I'd suggest not taking down by more than 50% of its rated capacity. Sorry!

 

What will follow is a lengthy and learned discourse on the chemistry, and relative merits of different types of, and the advertisers' and makers' porky pies, that surround leisure batteries, which fortunately I am not competent to conduct. However, others on here are (seriously, not joking), and I'm sure will. :-)

 

BTW, I'd also ask a few questions about solar panels, and their controllers, and intergating both into your van's electrics, as well, as they are by no means straightforward either. I'd do this before engaging an installer, as they are not all quite as knowledgable as they should be, or sometimes claim to be. Sorry again! :-D

[manxli]

Hi

 

These 'Fuel Cell' Generators seem to be popular here in Switzerland, although pricey. The advantage seems to be full 240v power anywhere , anytime.

 

http://www.efoy-comfort.com/

 

Anyone had any experience? I've seen a few outside upmarket motorhomes on my travels.

 

Alan

[StuartO]

I'm pretty sure that an EFOY unit supplies only a charging current for a 12 volts battery, not 240 volts.

 

They are expensive to buy and they use high-purity methanol in a special type container (bought only from the manufacturer) which is also expensive. They do provide an alternative to plugging in on a campsite or using solar pannels to charge your leisure battery(ies) but (my experience) has been that even a modest sized solar panel is plenty enough for us. You certainly don't need to cover the MH roof in them.

 

The unique advantage of an EFOY unit is that it works any time, automatically and including overnight if necessary, to keep your leisure batteries well supplied.

 

For charging my laptol I manage well enough using a low cost, handy little 150 watt capacity inverter, plugged into a 12 volt socket, to which I connect the laptop's normal charger. This system won't cope with running the laptop at the same time as charging its battery but since I only ever need if if we've been off EHU for long enough to flatten the laptop battery. Since McDondalds restaurants all provide free WiFi and usually have a mains socket somewhere you can plug into, that's another contingency source which I rely on if necessary.

 

Bottom line: don't spend a fortune or clutter up your MH with unnecessary kit for what might be a small or non-problem.

[ShoelessSmith]

Thanks again for the replies.

 

The work that I have to do each evening is CPU intensive and it will involve about four or five hours of serious database bashing which uses up a fair amount of power more than, say, four or five hours of browsing the internet or replying to emails. Though there will be some of that as well.

 

I tend to start work at around five in the evening and then the machines can be going full tilt until about ten o'clock, five hours later.

 

This is why I have to sure that I have enough oomph to get those five hours worth of database bashing each evening and hence the reason why I am really seriously considering two batteries.

 

Okay, if I had a fag packet then on the back would be written the following.

 

110 Ah battery. Call it 100 Ah and if we look at only using 40% of the reservoir then we've got only 40 Ah.

 

My laptop uses 5A (4.89 A actually) at 12v which is about 8A at 19v. 8A into 40Ah is five hours.

 

This margin is too tight for my comfort so I can't see any alternative than a second battery.

 

Malc

[Brian Kirby]

But, and it is not an inconsiderable but, you then have to put back into the battery the 40Ah (plus what you use to run space or water heater, lights, etc. :-)) you took out, within the next 19 hours, to be able to repeat the exercise. IMO, whether you can safely to do that by relying on solar charging alone is highly debatable.

 

You'll first have to drill through the performance data provided by the panel manufacturers, and you'll then have to allow for the variability of output from the panels due to atmospheric phenomina (cloud, etc), local phenomina (shadows from trees, buildings, etc), diurnal factors (varying power output as the sun angle changes between sunrise and sunset), and seasonal factors (lower winter sun angles generally reduce solar output), and geographic factors (the further south you are sited, the higher the sun, better the panels will perform). Panels that will work well at mid-day on a clear summer's day in Alicante, for example, will deliver almost nothing at mid-day on a cloudy winter's day in Edinburgh. And of course, will produce nothing at all at night in either location. I think panels are a useful means to top-up if consumption can be reduced when external factors mean the charge rate is inadequate. But, in your case, that doesn't seem to be the case.

 

I'm not saying can't do, just that if you need a completely reliable system, you'll have to consider ways of charging your batteries that are fail-safe, and I don't think solar has that characteristic.

 

Of course, you can always take a night at a camp site with EHU if the batterirs are low, but it may cost you a day's work to find that out. Even there, you may be wise to augment the charger output so that your combined batteries (ideally a matched pair in terms of chemistry and age) will fully re-charge within that 19 hour window. Your options are, IMO, to fit the panels but accept the need to take an EHU as and when necessary; to buy a generator (the use of which may be limited by proximity to others - noise, fumes, etc); or to fit an EFOY or similar fuel-cell type charger (expensive, but you wouldn't need the solar panels, so can offset that cost).

 

All these options have costs, the cheapest probably being the generator which, if you are going for isolated places, should annoy no-one but yourselves. :-) You can also take it with you if you change vans. You would probably not need the additional battery if you do this, so would gain back a bit of payload, though you might want to substitute one of slightly higher capacity: say 125Ah. Most expensive would be the fuel-cell - but it would eliminate the need for EHU even when on camp-sites (silent), so the cost of EHU over time could also be offset in addition to the solar panels. Again, the comment above re battery bank with a generator seems relevant, and it would transfer to a different van. Solar, plus EHU when the solar falls short, looks to be possibly the most cost effective compromise if you think a generator might be unacceptable to others (or even to yourselves). But, the panels would be lost if you changed vans. It seems to me largely a matter of how many nights, at what time of year, in what latitudes, balanced against initial cost and costs in use. If using the van over extended periods, predominantly off grid, even the fuel cell might work out cheapst over your planned five years of use.

 

Hope these musings help.

[Robinhood]

....I'm not sure I can make too much sense of the maths in the last post. (edited to add : now previous to last as Brian was posting in parallel ;-) )

 

I also think that there is a factor being overlooked in the equation here, and that is that the laptop battery itself will (fully charged) keep you going for some time.

 

As you say you are likely to be working in the evening (when you are less likely to get significant re-charge from a solar panel), I would suggest a good starting point would be to buy one or several spare batteries for your laptop (of the biggest capacity available for the model - some models have significantly "oversized" batteries available as an option), and in conjunction with a dedicated 12V laptop supply, ensure charging of these during the daytime, whilst the panel is working at its optimum.

 

Any surplus over and above the requirement for the laptop batteries will then top-up your normal leisure battery(ies).

 

On a reasonably sunny day, with the panel capacity you envisage, it should be eminently possible to fully charge a couple of laptop batteries from a decent-sized solar panel in three or four hours (assuming typically about 60Wh capacity for each battery, and minimal losses). That would leave ample recharging capability for the habitation batteries.

 

Of course, this implies a certain discipline in changing the batteries over for charging (it's somewhat easier to remember to change them in use ;-) ) unless a separate dedicated charging cradle is available.

 

If I could afford it and had the payload, I would favour a combination of spare laptop battery(ies), augmented habitation battery capacity, and a reasonably-sized solar panel (though the capacity of this latter would also depend on what other electrical demand you expect to have - e.g. hours of TV watching, etc.).

 

Further edited to add:

 

to test the viability of this, check the rating of the battery in the laptop (either directly as Wh, or by multiplying the voltage by the mAh rating to determine capacity). You can then check how long you can work with a fully charged battery until it is (virtually) discharged.

 

Assuming a battery in reasonable condition, a bit of maths will then give you the required Wh for your desired working pattern, dividing by 12 will give you a "lossless" estimate of the Ah you will take out of your habitation battery for this working pattern - assuming you plan to use a dedicated 12v laptop charger, allow an extra 10% for losses.

 

Now, I don't know your machine, or the intensity of working, but for a laptop alone, I'd be surprised if that amounts to much more than 15Ah for 5 hours work (Chargers an power supplies generally quote the maximum current figure, not the nominal "in-use" value.

 

I'm happy to be corrected, though :-D

[ShoelessSmith]

Thanks again for the replies.

 

Yes, I understand the problems with the solar panels but that is going to be a better option than with generators -- at the moment. I can't stretch my funds to one of those fuel cell devices, though I wish that I could.

 

The thing about solar panels is that if there is no hook-up is that it may give me enough time to get to a hook-up on the second or third day. I can't use laptop batteries as my applications that I run use extensive database queries (maybe up to a quarter of a million on some days) and databases being databases are inefficient in terms of power consumption.

 

So even if I could get two nights out of this and then find a hook-up then this would be fine. The Memsahib and I don't watch telly, thankfully, so this isn't a drain. As we're not overly precious about hot water (we live in a cottage with a wood fuelled back burner so in summer we don't often have hot water unless we put the fire on low tickover). this need not be much of a drain.

 

The lights will be changed to LED to help shortly. But the way that I see it is that on this gin-palace a 200W solar panel should help even a little.

 

The thing is that I can't not do the work in the evenings (well, I get about three evenings a year off at the moment) but if I find that I have to get a Fuel Cell device then I will but not yet as buying a motorhome took a chunk out of my pot which I will want to rebuild up again.

 

Off to look at some more figures and to get some calculations done.

 

Cheers

Malc

[lennyhb]

Brian Kirby - 2015-06-17 7:17 PM

BTW, I'd also ask a few questions about solar panels, and their controllers, and intergating both into your van's electrics, as well, as they are by no means straightforward either. I'd do this before engaging an installer, as they are not all quite as knowledgable as they should be, or sometimes claim to be. Sorry again! :-D

 

Too true, I was going to install a panel on my mates Carthago, but as it was a brand new van he decided to get the dealer to do it. The dealer had their local expert do the job, biggest bodge I've ever seen. The panel brackets were mounted on inch thick uneven blobs of Sika looked dreadful, they wired the panel using 1.25 mm sq 3 core mains flex completely ignoring the 6mm solar cables that are pre fitted to Carthagos. Fitted the cheapest regulator possible (less 5 quid to buy), didn't integrate it to the CBE charging system or engine battery & charged my mate £500.

[zombies]

I have a Nikkai car 12v laptop charger which has various settings incl 19v, I bought it a few years ago and having changed laptops overtime the adapters do not fit one of them, am hoping I can buy extra bits for it.

Bought from Maplins approx £35

[zombies]

Just checked £23

http://www.maplin.co.uk/p/nikkai-12v-in-carin-air-laptop-adapter-with-usb-socket-1a-with-6-charging-tips-a19jt