# Advice on caravan-park-independent energy?



## Nettle (Jul 22, 2009)

Hello!

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!

Many thanks,

Michael


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## JeanLuc (Jan 13, 2007)

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


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## Antonia (Apr 27, 2008)

*charging*

Hi Nettle

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.

Regards

Antonia


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## erneboy (Feb 8, 2007)

I agree with Phillip. 

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.


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## JeanLuc (Jan 13, 2007)

erneboy said:


> 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.

Philip


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## erneboy (Feb 8, 2007)

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.


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## loddy (Feb 12, 2007)

I like the cosy Hymer bit

Loddy in his cosy Four Winds


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## Jezport (Jun 19, 2008)

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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## SpeedyDux (Jul 13, 2007)

Have you considered the cost of spare batteries for the laptops versus the other alternatives?


SD


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## teemyob (Nov 22, 2005)

*Laptop Work*

Hello,

When you say work, is that paid work?.

I would love to be able to travel and earn money form working on a laptop.


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## Spooky_b329 (Jan 24, 2009)

Much has already been mentioned, but:

1) Stop using the invertor, its inefficient as you are converting 12v to 240v, then the laptop power supplies are converting from 240v back to somewhere in the region of 16v. Get some car adaptor style power leads for the laptops, you can always chop the horrible cigar plugs off the end and buy some decent 12v sockets and plugs that don't keep falling out.

2) Check the battery isn't knackered...could be losing capacity due to heavy use. If its OK, add another. I have 170Ah and am expecting to add more.

3) Check battery is getting fully charged after an average drive via a volt meter. As a guide, after the engine has been off for a while to allow the battery to stabilise and no loads running in the van, a full charge would read around 12.7v, 50% discharged would read 12.2v. If its not getting fully charged except after a long journey, upgrade your charging system. Mine is based around a 100amp relay which means the full 55amps from the alternator is available to charge the batteries, although the charge rate will slow significantly as they get close to capacity.

4) Check how the inverter is wired...if its not connected directly to the battery, its very likely it is suffering voltage drop due to undersized cables. If you are running from a cigar socket this is very likely. Try running it direct from the battery, you may find it will go much longer before the low voltage warning.

5) Set the laptops so they have the power saving options turned on when running off 'mains' power.


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## Nettle (Jul 22, 2009)

Wow, what a great response! Thanks everyone, that's most helpful!

I have been thinking about getting a second leisure battery - it would be nice to be able to go another 6 hours or so before we're out of juice, although I'm not yet certain that capability will be worth the money. If we can extend the life of one battery by a bit longer (by skipping the inverter, etc), and we can thus increase our runtime by something approaching a full day, that'll certainly be worthwhile. Same goes for if we can decrease the charging time using a Stirling changer - great idea.

Our Hymer was born in 1993, so it may not have the Schaudt Elektroblock, Philip. I get your point though - although if I understand it right, when we use our laptops while charging, that long charge time should be lowered or eliminated (a net change of 8A, while using 10A for laptops).

I'm very curious about the Stirling charger - the product page suggests that the leisure battery should be changed 5 times faster - is this what others have experienced? That's pretty impressive. Does it work only with charging via the alternator, or with hookup/other energy sources (solar, etc) too?

That's a very good point about getting a 12V adapter - I should've thought of that. Looks like we can get them for our macbooks - we'll keep an eye out for Apple stores, or buy online.

Fuel cell! That sounds pretty damn space-agey. I'll have a peek at that as an option, as well as the EG20, although we are a bit reluctant to go with the noisy options, including a standard generator - we may have misconceptions about how much it matters though. What do others feel about generators (relatively quiet ones) + wildcamping?

2x120 panels - ouch! That sounds pretty pricey! Does anyone know what the resale price is like on those bad boys? If we were to kit ourselves out and resell in a couple of years when/if we decide to get a house of the non-driveable variety, could we expect much back?

I was thinking about getting some spare lappy batteries; they're a little pricey, though, at £100 a pop. Might as well just get another leisure battery!

Finally - yep, it is paid work; I run my own software company, A Tasty Pixel (atastypixel.com), writing Mac and iPhone apps. Katherine, my partner, is an artist who is gradually building up an online art business (nelliewindmill.com). We're still getting ourselves set up, but things are looking good - it's a great life (or at least the 7 months we've been at it so far have been great).

Thanks everyone, I'm very grateful for the assistance!

Michael


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## Nettle (Jul 22, 2009)

I have a little confusion about battery charge levels that I'm hoping someone can clear up - Spooky_b329, you mentioned that the battery should show about 12.7V when fully charged, and 12.2V when 50% discharged. We have a marine hybrid battery (a 113Ah Numax XV31MF) which apparently means we need to avoid discharging beyond 50% (presumably 12.2V).

Our inverter has a voltage cut-off that the guy we bought our Hymer from said would avoid discharging the battery beyond a safe level. However, the thing's beeping when our indicator panel shows about 10V (with no load on the battery)! Does that mean he was wrong, and we've probably stuffed up our battery? Is there a relatively easy way to tell if it's knackered?

Starting to wish I hadn't just taken his word for it and had read a bit more about battery care to begin with!


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## Losos (Oct 28, 2009)

erneboy said:


> 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.


What is the 'lifespan' I've tried to find this info on the EFOY site and can't. It's a big capital investment but I thought if I got say seven years out of it it might be worth it.

Cost aside it seems to tick all the boxes for me.


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## Losos (Oct 28, 2009)

Nettle said:


> Fuel cell! That sounds pretty damn space-agey. I'll have a peek at that as an option,


The EFOY fuel cell is the answer to your problems, it's a shame the cost is so high, probably because they are (So far) the only people making one in commercal quantities :roll:


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## autostratus (May 9, 2005)

SpeedyDux said:


> Have you considered the cost of spare batteries for the laptops versus the other alternatives?
> 
> SD


I love a bit of lateral thinking.


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## DABurleigh (May 9, 2005)

For your STATED requirements, mainly staying in one spot for several days at a time with no genny noise, no guaranteed sun or constant wind, running 2 laptops for ~10 hours a day (you estimate 120Ah per day) the EFOY is the only current solution.

However as soon as you RELAX those requirements, all sorts of other possibilities and combinations come into play. 

If you are not stuffed for payload, I'd recommend simply having 4 new leisure batteries connected together (I'd prefer 4 large 6V ones if not too big a £ premium), being as efficient and economical as possible with your 12V energy consumption (buy a battery monitor (NASA, Sterling, Victron, etc), and see how it goes.

Dave


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## loddy (Feb 12, 2007)

*Re: Laptop Work*



teemyob said:


> Hello,
> 
> When you say work, is that paid work?.
> 
> I would love to be able to travel and earn money form working on a laptop.


A few years ago I saw an advert in the Costa News for someone to collect and log English reg nos. for a client in UK (bet that was DVLA ) all you needed was a pen and paper and a computer

Loddy 8O


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## JeanLuc (Jan 13, 2007)

Nettle said:


> Our Hymer was born in 1993, so it may not have the Schaudt Elektroblock, Philip. I get your point though - although if I understand it right, when we use our laptops while charging, that long charge time should be lowered or eliminated (a net change of 8A, while using 10A for laptops).
> 
> That's a very good point about getting a 12V adapter - I should've thought of that. Looks like we can get them for our macbooks - we'll keep an eye out for Apple stores, or buy online.
> 
> Michael


Point 1 above. That's not quite what I meant. I was not referring to charging the leisure battery and laptop at the same time. Rather the difference in current drawn BY THE LAPTOP depending on whether the power pack is just supplying maintenance power to a full laptop battery, or trying to re-charge it and running the laptop at the same time. In other words, charge the laptop fully when you have mains, then don't let it run down before you plug into the inverter. The only way I have noticed the difference in those two conditions, was by looking at the current drain on the Hymer's meter whilst running my MacBook Pro from the inverter. If the leisure batteries were being charged whilst you were running the laptops, you would not see a current drain on the meter, just the charging current.

Point 2 above. Not sure what vintage your MacBooks are, but if they have magsafe connectors like mine, I have not found a direct 12V adapter to connect to the leisure battery source. Also, on mine, the output voltage from the 85W Mac power pack is 16.5V, not 12. I took the view that I did not want to risk an expensive laptop (or £100 power pack) so fitted a 150W pure sine-wave inverter.

Regarding the beeping and inverter low voltage cut-off. The cut-off is designed to prevent malfunctioning of the inverter as much as it is to protect the battery. Inverters are designed to work within a defined input voltage range, otherwise they output is compromised. I am fairly sure of my ground in saying that but no doubt DAB will correct me if I am wrong. The problem you may be experiencing is voltage drop between the leisure battery and inverter. That is a common problem and causes inverters to drop out. Inverters should be connected to the battery with heavy-gauge cables. Although mine was designed to plug into a cigarette lighter socket, I had that problem, so cut off the plug and connected directly to the batteries, via a relay (electric on/off switch). In the FAQ section there is a lot of stuff on Inverters (and loads of other useful info) and I put a paper in the Downloads section entitled 'Installing a small Inverter' which explains how I fitted mine.

I think you have to be a subscriber to get these.

Finally, two points. Firstly, I would strongly recommend the additional battery route. Secondly, note the point made by Erneboy (Alan) above. The EG20 is a great bit of kit, but in his view it is louder than a Honda EU generator.

Philip


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## coppo (May 27, 2009)

DABurleigh said:


> For your STATED requirements, mainly staying in one spot for several days at a time with no genny noise, no guaranteed sun or constant wind, running 2 laptops for ~10 hours a day (you estimate 120Ah per day) the EFOY is the only current solution.
> 
> However as soon as you RELAX those requirements, all sorts of other possibilities and combinations come into play.
> 
> ...


Hi Dave
Whats the advantage in 6v as opposed to 12v which most use?

Paul.


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## DABurleigh (May 9, 2005)

For a given battery capacity in a 12V system, battery life is extended by ensuring no parallel connections, but having the (only) charge and discharge current pass through all lead-acid cells. As soon as you parallel batteries up, then the currents are split according to the effective internal resistances of the batteries, and these can vary slightly according to type, design, age, other history of the batteries. When this happens, DIFFERENT charge/ discharge currents flow through each battery, curtailing the life of them both. Hence the received wisdom of not adding a new battery to an old one, but putting 2 new identical batteries in together.

So, for a given total capacity (total weight) at 12V, two 6V batteries are better than 2 12V batteries, and each should be just as manageable size/weight wise.

For 4 12V batteries, rather than splitting the current 4 ways, adding more chances for mismatches, in principle splitting it just two ways, with 2 6V in series and EACH of these pairs in parallel, is better.

In practice, the pricing due to supply and demand usually means that in Blighty, large 6V batteries are more expensive that 12V batteries. In the US, there is a larger market for 6V batteries. Most RVs use 6V batteries I believe.

Dave


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## coppo (May 27, 2009)

DABurleigh said:


> For a given battery capacity in a 12V system, battery life is extended by ensuring no parallel connections, but having the (only) charge and discharge current pass through all lead-acid cells. As soon as you parallel batteries up, then the currents are split according to the effective internal resistances of the batteries, and these can vary slightly according to type, design, age, other history of the batteries. When this happens, DIFFERENT charge/ discharge currents flow through each battery, curtailing the life of them both. Hence the received wisdom of not adding a new battery to an old one, but putting 2 new identical batteries in together.
> 
> So, for a given total capacity (total weight) at 12V, two 6V batteries are better than 2 12V batteries, and each should be just as manageable size/weight wise.
> 
> ...


Thanks, i,ve read about 10 times, think i,m understanding a little more.

Paul.


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