# Can I charge my battery and power 12v circuits?



## Dobloron (Jul 18, 2011)

Hi,

I’m in the middle of a camper van conversion and I’m planning on fitting a leisure battery to power a 12v fridge and lights etc. Charging the battery with a split charge relay arrangement and when available via a 240v hook-up and battery charger. 

From my investigations so far it appears as if the preferred type of charger (3 or 4 stage type) for 240v hook-up should be dedicated to charge the battery only and not power the 12v appliances at the same time. It seems that the output voltage of these chargers is greater than 13.6v, the highest voltage that most 12v appliances will tolerate without blowing up.

My question is: When parked up and plugged into a 240v hook-up, is there a charger/charger system which will happily charge the leisure battery and still allow the 12v appliances to work at the same time?

Cheers

Dobloron


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## Lorry Ball (Jul 18, 2011)

The battery is like a big water tank, the charger is like a hose filling it up, if you use a TV or fridge its like opening a tap to let water out, the closer the water is to the top of tank the hose slows down

Lorry      :drive:

when you are charging the battery up, the battery is powering the TV etc. with a little help from the charger
The battery will stop the voltage going over about 14-15 volts if everything is working properly


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## Dobloron (Jul 19, 2011)

Many thanks Lorry – that’s a relief. It would be a bit irritating if one had to wait for the battery to charge up before putting the lights on!!

It’s a micro camper conversion with limited space; the main electrical consumer will be a small 12v or 240v (with inverter) fridge at about 50W. If my calculations are correct it should draw no more than about 4 amps. 

Next question: If we put in a 100 Ah leisure battery what size and type of charger (there are so many to choose from - £45 on eBay and upwards) would be adequate to charge the battery and also power the fridge?

Many thanks

Dobloron


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## AndyC (Jul 19, 2011)

Dobloron said:


> From my investigations so far it appears as if the preferred type of charger (3 or 4 stage type) for 240v hook-up should be dedicated to charge the battery only and not power the 12v appliances at the same time. It seems that the output voltage of these chargers is greater than 13.6v, the highest voltage that most 12v appliances will tolerate without blowing up.


A 3 or 4 stage charger will not damage any 12v equipment which is designed for campervan use. 
There is a possibility that equipment that is meant to run from a 230VAC > 12VDC adapter (like some LCD TVs for example) may be damaged if run directly from the van's 12VDC sockets and the charger is running, because they are designed to run from a regulated 12VDC supply.

AndyC


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## Bigpeetee (Jul 19, 2011)

With limited power on battery, I wouldn't use an inverter to power your fridge, the inverter will need to be quite large to accommodate the initial surge of current but as they are not 100% efficient a 50w fridge could use upto 60w of power = 5A means your batt will be flat in about 8-10 hrs with no other appliances being used

Put very heavy cable to and from your split charger to reduce voltage losses, allowing the leisure batt to recharge quicker from alternator.

Can you get a gas/12v/240v powered fridge to save the battery?  I used to have a 12v fridge on a yacht, it would flatten the battery in no time, not what you want.


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## Dobloron (Jul 21, 2011)

*Ditch the fridge for a cool box?*

The fridge seems to be the main drain on the electrics – after all it’s only there to keep a couple of pints of milk, a lump of cheese and few cans cool - but can cost hundreds.

Ours is only a micro camper and probably we will be away in it for the odd week at a time. A state of the art fridge may do the job and consume the least electricity but it’s really a bit on the extravagant side. 

I quite like the idea of a well insulated cool box; starting out with plenty of frozen milk and cans to keep everything cool for a few days and if there’s a convenient hook up available plug in the Peltier cooler device to see us to the end of the trip.

Anyone done something similar?

Cheers

Dobloron


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## Hobbsy (Jul 21, 2011)

I have converted two vws now and take my advice, dont plan on using the fridge on 12v, you will eat a battery per night, you need to run the fridge on gas overnight! thats my biggest mistake not installing gas to my fridge


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## oldish hippy (Jul 21, 2011)

wel ihave well you might call it a micro camper use a mini fridge take litre carton of milk and butter runs off 12 or 240  got mine from freecycle argos sell something similar what ical kiddi frige hold hald dozen xcans pop and fitted a portaloo as well do want to do some more mod but carpentry skill are not good but will save and get the pieces done one at a time got the plans in my head


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## kangooroo (Jul 22, 2011)

I camp in a Renault Kangoo which is even smaller than a Doblo.  

IMO  a fridge takes up too much space and would drain a leisure battery (if I had one) too quickly.  I use a 12v powered coolbox while on the move and this is quite effective for keeping basics cool.  It's not as effective as a proper fridge however and I wouldn't entrust it to keep perishables such as fish or meat cold and is unlikely to run at the requisite 3 deg on a hot day.


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## Tony Lee (Jul 22, 2011)

Probably need to all talk about the same sort of fridge since they are not all created equal as far aas 12V power consumption is concerned.

An absorption fridge WILL use somewhere between 8 amps and 15 amps at 12V - and probably even more on 240V via an inverter off your batteries. 12V is ONLY for keeping things cold when you are on the move and have 12V available direct from the alternator.
If 240V mains is not available then running them on gas is the only sensible alternative for camping more than a few hours.

There are however, plenty of 12V fridges that are compressor fridges and these use far less power than the others. 3A average for a 60 litre unit is typical so running them for a couple of days off a couple of fully-charged leisure battery is manageable. Longer with a bit of solar input to help the battery.


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## spooker (Jul 22, 2011)

Be aware too - that the figures quoted for fridges are only approximations and can't allow for how you use them. As soon as you start putting warm items in it, opening the door and letting the cold air out - power consumption will rocket. I had a 60l compressor fridge in my last self build, lovely piece of kit, but in the summer with frequent use it would flatten x2 130 ah batteries in a couple of days - despite the 40w solar panel.


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## AndyC (Jul 22, 2011)

I reckon our 110l 12V compressor fridge averages around 40Ah per day.

AndyC


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## Dobloron (Jul 22, 2011)

*Anyone know anything about Peltier type coolers*

Thanks for all the replies – It looks likes electric fridges can be the chief drain on electrics and since space and budget prohibit anything gas driven or big (by our scale), I think we’ll be going down the homemade super insulated cool box road with emergency Peltier cooler. If we do this then the extent of the electrical system/storage can be hugely scaled down – sounds good.

Anyone know anything about Peltier type coolers and how to get the best out of them?

Cheers


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## chass (Jul 23, 2011)

I use one of these ticks all the boxes.  CTEK Multi MXS 7.0 Car Battery Charger - the smartest battery chargers in the world!


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