# Electricity Supply



## Daniel (Mar 28, 2008)

Hi all,

Please bear with me cos I am a novice.  My partner and I have recently bought our first van (a self build Transit LWB).  We are planning a long trip around Ireland so we will be doing an awful lot of wild camping.

The van appears to have a 60ah starter battery connected to a leisure battery (I don’t know the ampage of the leisure battery as it doesn’t say, it is a larger battery than the starter battery though).  These batteries are connected to a ZIG CF9 charging unit.  As I understand it they also charge when the engine is running.

I am planning on using a 300w inverter to power my laptop so we can watch DVD’s in the evening.  I shall also use a 12v fan heater when the weather gets really cold.

My question is really how long should I expect the power to last when I am wild camping.  Say for example I was parked up for 2 nights without running the engine or hook-up would the batteries last with me using the laptop each night through the inverter and using 12v lights and water pump etc.

Basically I am concerned because I haven’t got any of the following, a generator, solar panels (neither of which I can afford) or a battery charger.  I am hoping my batteries will stay charged due to driving around and the occasional hook-up over the summer months.  Does this sound feasible?

Any help/advice greatly appreciated.
Thanks
Daniel


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## Belgian (Mar 28, 2008)

*economize*

Hi Daniel,
It is feasible; but you'll have to economize your electrical consumption.
e.g laptop: when using an inverter you go from 12 V (battery) > 240 V (inverter) > 18 - 19 V (laptop adapter). The inverter and the adaptor are both consuming. Buy a simple adapter 12 > 18 - 19 V for your laptop (you have also a more stabilized power input - and they are cheaper than a 240V inverter). Moreover you can have the laptopbattery charging while driving. 
If possible change from bulbs to leds (20 W bulb = 1 W led).Only leds have a more bleuisher glow than bulbs for the moment (tomato soup will look brown-purple ) 
If you can afford it install solar cells, but bear in mind that they cannot provide 100% in our cloudy weather conditions.


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## GeorgeTelford (Mar 28, 2008)

Hi Daniel

First off a small 12v fan heater is not going to supply enough heat for you, secondly even if it did it would flatten your battery very very quickly.

Heating really requires a fuel supply namely Gas (LPG) diesel of petrol, solar panels? you couldnt actually fit enough panels on the roof to run an electric heater and a generator of the correct size would cost you over £1 per hour to run, gas by contrast would be pennies per hour

If you supply the laptop power supplies wattage, I can give you a rough guide to usage times.

Let us guess that the leisure battery is 110 amp hours, now for various reasons you will not be able to use the full 110 ah, the max you should use assuming fully charged is 55 ah you should not really discharge below 50% if you want the battery to last, unfortunately by driving around you never get more than 65-70% charged that leaves 22 ah useable.

Just for example let us guess that the laptop power supply is 84 watts, via an invertor that will lose 10% in conversion losses so lets say 90 watts that equates to 7.5 Amps so just for the laptop it would be 3 hours max followed by a good drive to recharge.

there are several ways to overcome this depending on how much money you want to spend.

George

PS whatever you do, do not use a 12v convertor these are terribly inefficient and use far more power than an invertor and power supply, charging the laptop via invertor while driving will give you a good head start.


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## Daniel (Mar 28, 2008)

Many thanks for the replies.

I would only intend to use the 12v fan heater for a max of 1 hour per night, are they really that greedy on electricity?  To be honest I'm not afraid of the cold, but unfortunately my partner is!!  I've been considering a 12v electric blanket as well.

Will the laptop power supplies wattage be displayed on the outisde casing of the laptop?  I like the idea of charging the laptop via inverter whilst driving, I might have been scared to try this before.

So if I assume after a good drive my battery is 70% charged how can I tell how many amps are being each hour?  I have a battery condition monitor but that only tells me the voltage.  If say the voltage goes down the 10v how discharged is the battery?

Sorry for all the questions, I'm desperate to be prepared for this trip and I'm on a steep learning curve as I've led a very untechnical life!!

Thanks
Daniel


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## wildman (Mar 28, 2008)

Daniel said:


> Many thanks for the replies.
> 
> I would only intend to use the 12v fan heater for a max of 1 hour per night, are they really that greedy on electricity?  To be honest I'm not afraid of the cold, but unfortunately my partner is!!  I've been considering a 12v electric blanket as well.
> 
> ...


Hi at 10volt the battery is discharged, if it is a standard lead acid battery rather than a dedicated leisure battery (i.e. one built and sold as such) then it will sulphate rather quickly and the battery will die on you. A one kilowatt fan heater will use approx 80amps per hour so forget it. You can measure how much current (amps) is being drawn if you connect a meter between the post and positive connector. Amps are a measure of current flow every item you use will add to the total. Batteries are marked in amp/hours so 110amp/hour battery will theretically run a 1 amp load for 110 hours or 110 amps for one hour but there are losses and no battery should ever be run flat so count on 50% of that. If you are short of cash the answer is to take an extra duvet and play games rather than watch TV, you know, I spy, strip poker, etc.
Do NOT use the cooker to provide heat unless you want to wake up dead from carbon monoxide poisoning!!!!!!!!!!!!!!!


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## AndyC (Mar 28, 2008)

Daniel said:


> Sorry for all the questions, I'm desperate to be prepared for this trip and I'm on a steep learning curve as I've led a very untechnical life!!


The problem with all these sorts of questions is that it's impossible to give a definite answer because everyone's use of 12v power is different.

To answer you question about the volt meter, if it shows 10v the battery is flat! 12.2v is about 50% charged, 12.7v is 100% charged (there is a table here other useful info too)

As a first step - *never* use the 12v battery for directly powering a heating appliance!! As others have said, if you think you are going to need heating get a proper gas or diesel powered job.

Second, check that your existing battery is in good condition, get it tested.

Third, increase your battery capacity, fit another battery the same size as your existing one and connect the two together with adequately sized cable.

Fourth, well before going off on your trip, see if you can try the van out for a few nights - that will show you any shortcomings.

AndyC


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## Don (Mar 28, 2008)

The thing that brought my son-in-law to earth was to walk him round the van, we listed all the electrical things and the Wattage the the item used when we had a complete list, we divided the total Wattage by the system voltage. Then we looked at the Battery (85Amph) and by dividing half of the 85 Amph (because you should never run more than 50% off your Battery)By the required Amp you arrive roughly at the time you get from your Battery.
He was trying to run an 800amp Microwave through an inverter with telly, DVD + lights etc and couldt understand why Battery was flat before he had made the Tea.
My own set up is a 130 Watt Solar Panel charging 2x 110 Bateries, running TV, Sky, Laptop and lights. Never run out yet. And they are long cold Dark nights at the moment.
The advice I was given re solar Panels was 50 Watt of panel and a 110 Amph battery per adult person.
I camp solo so I am on top (I hope).

Don


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## GeorgeTelford (Mar 28, 2008)

An average UK Battery that is fully charged would read 12.8 Volts (after standing unused/off charger for 12 Hours)

Each 0.1 V drop equals aprox 10% of charge ie the above battery would be at 50% discharged at 12.3 volts (settled voltage)

10 Volts is as near as dammit a scrap battery, with the right charger you may get some more service life out of it, but unlikely to ever achieve full capacity again.

The wattage will be on the laptop power supply.

There pretty much is no such thing as a real leisure battery, the fairy tale goes that a leisure battery has thicker plates to cope with deep discharge, now thicker lead plates would to me mean that the battery would be heavier than a standard automotive battery of the same ah rating, however if you check you will find that they weigh the same, the only increase I can find is in Pounds sterling charged not Lbs weight......


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## Don (Mar 28, 2008)

As are so many other speciality equipment.

Don


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## janeandbob (Mar 29, 2008)

Hi Daniel  We spend a lot of time in France and Germany. Empty the toilet in the aires or public toilets we have a spare cassette very handy. We also have fitted a second 85ah leisure battery and we can go 3/4 days no problem. We have a 500w inverter for the laptop but only try to use it when mobile. You have to use your power with care we do have a Kiper 1000kw gererator but only use it when we have to. If you move on every few days its fine we stay at France Passion site alot with no hook up or anything. And get our Water at the garage or cemetery and only drink bottled water.But I think one thing you do need is a Gas fire with a FLUE OUTSIDE. Enjoy your trip. Bob.


          check out.             http://www.francepassion.co.uk/


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## Daniel (Mar 31, 2008)

Thanks for all the fantastic replies!

I certainly intend to be prudent with my battery supply, especially in the summer months when we only really need to use the water pump.

I am considering buying new batteries for two reasons.  Firstly I am not happy with the arrangement i.e. the previous owner has fitted a 60ah battery and connected it to an 85ah battery (totally different makes and sizes).  I believe batteries that are connected together should be the same in size?  Secondly on my first outing I accidently left the fridge on 12v (I feel very silly about this!!) and drained both batteries.  I have re-charged them with a battery charger but I feel I have probably damaged them and won't get the best life out of them.  Are these batteries any good?  http://www.tayna.co.uk/L85-Numax-Leisure-Battery-2-Year-Guarantee-P1817.html  They also do a sealed version which is £69.99, don't know how much better they are?

I like the idea of listing all the electrical items and wattage used and dividing by system wattage.  I assume I should include bulbs in this?  Also I assume the system voltage is 12v?

I will  be trying the van out locally for a few nights before my trip.

Thanks guys!
Daniel


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## AndyC (Mar 31, 2008)

It's certainly not 'best practice' to connect together batteries of different capacities, but no harm will be caused. I had a 90Ah and a 110Ah battery connected together in our old motorhome.

Numax batteries are a pretty well known budget brand, no reason to think they are any better or worse than other makes.

I would never buy 'sealed' batteries (except for special applications), I like to be able to check the water level and monitor the cells with a hydrometer.

It's certainly a useful exercise to add up the consumption of all your electrical equipment, include everything that runs off the leisure batteries.

The system will almost certainly be 12v

Don't forget that the 'usable' Ah capacity of your batteries is only about half the quoted Ah capacity. 

AndyC


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## Daniel (Mar 31, 2008)

Thanks Andy,

I think I am learning slowly but yes I understand that if for example I have 2 x 85ah batteries I only have 85ah available when fully charged.

So are 'sealed' batteries the same as 'maintenance free' batteries?

Thanks again
Daniel


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## AndyC (Mar 31, 2008)

Yes, 'maintenance free' batteries will often be sealed. They are not designed for you to be able to top up, but sometimes you can get access to the cells by a bit of careful 'levering' of the cover...

AndyC


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## GeorgeTelford (Mar 31, 2008)

Hi Daniel

The fridge should NOT be connected to the leisure batteries, it should only run when the engine is running, this needs sorting asap.

George


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## Daniel (Mar 31, 2008)

Hi George,

My camper isn't a modern motorhome, in fact I think it is classed as a 'self-build' as it wasn't made by a recognised factory company.  This is probably why it has the facility to run the fridge from 12v.  I will never use it on 12v I will be sure of that.  I will possibly get it looked into when I take it to my brothers in June though.

Thanks


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## GeorgeTelford (Mar 31, 2008)

Hi Daniel 

The fridge should run from 12v just not from the leisure batteries 12v, it needs to be connected to the starter battery via a relay which turns it off when the engine stops.







More detail appear here on the excelent site by Kampin Gaz

http://www.kampenwagen.co.uk/fridge%20power.htm


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## Daniel (Mar 31, 2008)

All looks pretty scary, but I do understand what you are saying and why you are saying it.


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## guerdeval (Mar 31, 2008)

Just thought I should mention how important charging from mains is, we returned from Spain last week and I didn't bother to plug into mains, a week later we set off for St Malo for the weekend thinking the drive up would charge the batteries for the weekend (200 miles), not so, the generator cut in twice (automatically) over the weekend , normally it never runs except when I test it for just a weekend.             Also, can anyone say what is  the difference between 'GEL' batteries and normal ones. I have a sign in the locker saying use GEL only maximum 3 batteries, I think the ones in there are lead acid types as you can top them up with water, any ideas please.


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## AndyC (Mar 31, 2008)

Gel batteries are a special type of lead acid battery where the electrolyte is held in a gel form. They are fully sealed, and designed for special applications where topping up may be impossible or where severe inclination may occur which would cause a 'normal' lead acid battery to spill acid. There are also used in hazardous locations where the hydrogen & oxygen given off by normal batteries would pose a explosion risk.

They are pretty expensive and must not be charged above a voltage of around 14.4v (varies depending on manufacturer, some say no more than 14.1v)

AndyC


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## Daniel (Mar 31, 2008)

Found this on the camping and caravanning club website.  Quite useful for a beginner like me.

http://www.campingandcaravanningclub.co.uk/Documents/Looking after your leisure battery.pdf

Thanks guys
Daniel


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## AndyC (Mar 31, 2008)

Or, for more than you could ever possibly want to know about batteries there's: www.batteryfaq.org

AndyC


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## Trevor (Mar 31, 2008)

Don't forget if you link two batteries together and one of them is a bit duff it will pull the good battery down.


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## Daniel (Apr 1, 2008)

Trevor said:


> Don't forget if you link two batteries together and one of them is a bit duff it will pull the good battery down.



Will it pull the good battery down permanently or just whilst it's connected to the duff?

Cheers


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## wildman (Apr 1, 2008)

Permanantly, both batteries will sulphate and eventually die.


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