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My partner and I work on our laptops as we travel in our cosy Hymer B594 motorhome, and we have a bit of an aversion to caravan parks, generally preferring to find our own secluded spots to stay, when we're in an appropriate region to do so.
We have a deep cycle leisure battery and a 300W inverter, but even when we've just come from a caravan park or a long drive, this setup only works for a maximum of six hours or so (even with just one laptop plugged in) before the inverter's low-voltage cutoff is beeping angrily and we're back to reading books. I doubt it's doing our leisure battery any favours, either!
We'd love to stay for days at a time when we find a good spot, and get some work done (usually for somewhere between 8-12 hours a day).
A generator is out of the question, really - we don't want to sound-pollute, which would make us very bothersome wildcampers - and we've been wracking our brains for an alternative solution. I'm thinking that we're probably dreaming, but I thought I'd ask anyway. You never know.
Our laptops use about 20-50W each (a big range, I know: It depends on our usage patterns, and whether the laptop batteries are charging). If I assume our 12V inverter wants 10A DC for every 100W AC (which this site suggests as a rule-of-thumb), that makes a max of 10A DC that we need, which makes something like 120 amp hours a day, not including lights, water pump, etc. That's quite a lot!
A solar panel sounds good in theory, but I think we'd need many £thousands worth of panel to come close to what we need. If I use the rule of thumb of 0.3 * rated watts = amp hours/day, a big 140W panel will only deliver 42 amp hours/day, a third of what we need.
We're thinking about getting a pedal-powered generator, which will apparently deliver somewhere in the order of 60W, and which we would presumably attach to the leisure battery - that's okay for running one laptop, or two charged laptops with minimal screen brightness, but would pretty much mean pedalling constantly, and possibly pedalling quite hard to aim for the 100W mark if the laptops are charging (which they will be - although that at least means a few hours' respite when their batteries are full). The form factor makes it unlikely to be very usable or ergonomic while using a laptop at the same time, although I'm sure our bodies would appreciate the exercise. Sounds like a bit of a pipe dream, though.
Are there any other options that we haven't thought of? Have my estimations gone awry, and I'm underestimating what I can achieve with a panel?
I appreciate any thoughts, even if they are just to confirm that we're just going to have to get better at finding pleasant and cheap caravan parks!
A few thoughts, although they may not be what you want to hear. The first step must be to fit a second leisure battery. We have 2 x 110 Ah and in winter, can last 3-4 days (but that's without drawing 10A per hour for 12 hours).
I have used my MacBook Pro with its 85 watt power pack via a 150W pure sine-wave inverter. I noticed that if I start with it fully charged, the current drain, as shown on the Hymer's meter above the door, is minimal. It will draw a lot more if re-charging and running the laptop at the same time.
You do not say what year your Hymer is, but if it is c. late 90's / 2000 or later, it will have a Schaudt Elektroblock charging system with a maximum charging current of 18 amps. So, you need to run it for almost 7 hours per day to put back your 120 amps used. That looks a tall order for anything other than mains hook-up, although you could run a small generator for that long. If the Hymer is older, you may have a different charging system, but I doubt the output will be very different.
You have already worked out that solar panels will not deliver enough in the UK during winter.
So where does that leave you?
1. You can modify your power usage (I would be surprised if two laptops are actually drawing 100W).
2. Don't discount a small generator. A Honda EU10i will power the Elektroblock charger and the laptops at the same time. They are pretty quiet - ours is just a background murmur when standing outside at the other end of the van.
3. Consider fitting a Sterling battery-to-battery charger and be prepared to move more often. This device increases the charging rate from the engine alternator. But beware, there can be some issues when fitted to vans with a Schaudt Elektroblock. Search for the Sterling Power website, or look at Roadpro or Vanbitz.
4. Use sites with a hook-up.
Finally, pay £10 sub and join this forum then you can search for loads of useful information and have access to a lot of experienced / expert motorhomers.
Philip
Last edited by JeanLuc on Wed Feb 17, 2010 3:41 pm; edited 1 time in total
Yes I agree with the last poster, We also went with a Stirling battery to battery charger, but we also have two house batteries. We run a 12v TV drawing 8A at 12v for 5 hours plus lights etc. The Stirling chragers are excellent and really look after your batteries. However, I would be tempted not to use an inverted but sort out a way to run your laptops directly from 12v, as you know it would be far more efficient.
Increase the size of your battery bank as a first step.
I suggest you power your computers using 12 volt chargers that will help eliminate the inefficiency of the inverter.
Solar will contribute a worthwhile amount in Summer, the rest of the year it is fairly insignificant but you will want at least a 100w panel.
The Sterling battery to battery charger is a good bit of kit but you would still need to drive every few days.
A small generator would do the job, the Honda is possibly the quietest, I had one and still found it too noisy and sold it. If you are not too close to other people and can stand the noise then that is the one. They are not very noisy but it did annoy me.
There is always a fuel cell, check Efoy on the net. That is very expensive electricity and would need to be running all day to do what you want.
Do not even think about wind power. I have done it with quite a big turbine but use it only rarely because believe it or not there is not often enough wind to make it worthwhile.
Make sure you do all you can to reduce your consumption, led lighting etc., Alan.
There is always a fuel cell, check Efoy on the net. That is very expensive electricity and would need to be running all day to do what you want.
Alan.
Good point Alan, I forgot about the silent Efoy option, even though we looked at them and discounted due to price.
Also worth considering the Self-Energy EG20 (LPG-powered built-in charger) from Conrad Anderson. Again, they have an internal combustion engine, so there is some noise.
Phillip, I met a proud owner recently and he demonstrated it to me I thought it was far too noisy (did not say that of course) partly because it is effectively in the van. The Honda is much quieter.
We have had an Efoy for several years and think it very good. As I said it is very expensive electricity but it does all we need and when it's life span comes to an end I will buy another or have this one refurbished, which I believe is an option, Alan.
I would put 2x 120w solar panels up. increase your batteries, and get some proper 12v laptop adapters from maplins. Inverters waste energy as they are inefficient.
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