Power options for camper van (self build)

Hi folks,
I am a newbie to all things campervan but I am a seasoned camper and I would appreciate some advice on what to do for what I intend to use it for. I have bought a VW LT35 that i am converting into a camper for weekends, long weekends etc.
I want to power:
12V 80L compressor fridge
12V TV
maybe 12 volt microwave

I have bought a deep cycle VRLA AGM battery, 150amp hrs. Do I need to hook this up through my main battery, or can it run as a standalone unit being charged by 240 volt when available hrough battery charger. If so, what componentry do I need? I may even buy a second similar battery as the price was right.
How do they hook up to outlets? are they all cigarette lighter style connectors?
Any and all help much appreciated.
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Reply By: Member Al (Sunshine Coast) - Thursday, Sep 08, 2011 at 07:54

Thursday, Sep 08, 2011 at 07:54
Hi Erin, you have asked a biggie. Perhaps the best thing to do would be to read the information available in 'Topics, Power & Electrics' on this site. Look Here
Then come back here to the Forum with any specific questions. Good luck.


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AnswerID: 464475

Follow Up By: ezzmae - Monday, Sep 12, 2011 at 22:13

Monday, Sep 12, 2011 at 22:13
Hi Allan

Thanks for some really intersting and enlightening info there. The big message I am getting from a number of sources is work out what you wish to power and for how long, and design the system around that.

I have bought an AGM deep cycle 150ah battery. I also have a Matson 140amp dual battery isolator with smart solonoid and an anti spike protector. I want to locate the 2nd battery in a specially built box in the bottom of a cupboard in the van near the drivers side seat base. I would like to top up the AGM with the vehicles own battery through the alternator when it is running.
So it appears I still need: a heavy duty fuse located near the camper battery. a fuse box, a smart charger to top up the batteries when located near mains power if I haven;t moved in a while, a meter (?) and possibly a small inverter to convert 12V to 240V to charge/power laptops, phones etc.
My fridge is a 12 volt compressor 80L
My TV with inbuilt DVD is 12 volt (2-3 hours use per day?)
I have a small water pump that is 12 volts
3 x 42LED 12 volt lights
Sound system that I may have wired to work off the camping battery.

I will get it all wired up by a professional auto elec but I wanted input into whether the system is suitable for its purpose; overkill, underdone? do i need a second deep cycle battery? what size inverter? not every auto elec is an expert in these matters.

Thank you in advance for any tips or advice.

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Reply By: ezzmae - Monday, Sep 12, 2011 at 22:31

Monday, Sep 12, 2011 at 22:31
after my follow up to Allan and clarification of my needs, i am again wondering whether a standalone 12Volt battery system 150ah (possibly two) not connected to the main vehicle battery, and recgarged with a battery charger as required (as will mostly be in powered locations,apart from a day or two each trip) would suit my needs as detailed above.

Can any one give me any advice on how long a 12volt AGM 150ah battery wouold last using:
80L compressor chest fridge above freezing
12 volt Palsonic lcd tv (up to 3hrs per day)
Small water pump maybe 20 mins per day
3 x 42 led interior lights
Basic Sound system used a few hours per day

I am also considering running a small inverter for laptop charging.

All replies much appreciated.

AnswerID: 464861

Reply By: Member Al (Sunshine Coast) - Monday, Sep 12, 2011 at 23:48

Monday, Sep 12, 2011 at 23:48
Hi Erin, There are a lot of variables in estimating your power consumption. The fridge for example will vary dependant on ambient temperature and your usage. The other appliances will vary by their individual power ratings. However, taking a guess at your consumption, I would suggest the following. Other readers may have specific figures from experience but they may not mirror your appliances or usage.

For a 24 hour period:
Fridge, based on averaged continuous consumption of 2 Amps = 48 Ampere hours.
TV, say 8A for 3 hours = 24Ah
Water pump, say 3A for 20 min. = 1Ah
LED lights, say 0.5A for 4 hours = 2Ah
Sound system, say 2A for3 hours = 6Ah
Computer charging via inverter, say 3A for 3 hours = 9Ah
Giving a total of 90 Ampere hours.

With a 150 Ah battery this would be a drawdown to 40% remaining State of Charge. 50% being considered desirable for an AGM battery so a little more consumption than recommended but not too bad. Provided of course that you are able to replace that consumption by recharge the next day. You would need to do this by driving for several hours with the camper battery connected to the car alternator, or with a solar panel of perhaps 180W rating (assuming good absorption conditions), or with an adequate battery charger if mains power is available. Of course, if mains power is available, all those appliances could be supplied by the mains and a battery would not be needed at all.

Rule of thumb would also suggest that a 150Ah battery would satisfy the average conservative camp but the real issue is the ability to recharge that battery before it discharges below 50% SoC. The battery will also not always be 150Ah, with age its capacity will diminish.

Hope that helps.


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Reply By: Robin Miller - Tuesday, Sep 13, 2011 at 13:35

Tuesday, Sep 13, 2011 at 13:35
I would advocate a different approach Erin, which is simpler
and I think more effective for a single vehicle scenario.
It fits in better for the more isolated type of places we tend to go.

You need 3 elements for success.

1/ Larger capacity main vehicle battery. 2*80AH overlander type batteries should do you.

2/ Secondary means of charging batteries. E.G. Permanent roof mounted solar panel 80-120watt.

3/ Warning device for when batteries get low E.G. accurate Voltmeter with alarm.

From these 3 key elements you work on the efficiency of each attached device as you can and money allows.

Some key basic points about the above.

A/ The batteries are primarily charged by the car engine, and as such the batteries are spect to accept a high short term (>60 amp) charge rate.

As you get time - A selectable means of high idle speed (1000rpm) will assist.

B/ The solar panels contribute a little but there main purpose is to provide
a way to re-charge if your batteries somehow go flat.

C/ Low battery warning devices and low volts cut outs on fridge etc are there
to enable things to be turned off before its to late.

D/ Adopt a connection standard - I use 12v cig lighter plugs (copper plated lion
type) but only because I'm into this stuff and generally re-wire everything for better performance.
There are better (Hella) type items.

As time permits accessories such as a mains charger are useful if you spend time at CV parks.
This should connect straight into your battery , but I do not know your specific van and so cannot reccomend this without testing.

P.S. Forget the 12v microwave - they are just not efficent in your senario.

Robin Miller

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Follow Up By: Member Al (Sunshine Coast) - Tuesday, Sep 13, 2011 at 14:34

Tuesday, Sep 13, 2011 at 14:34
Blimey, I overlooked the microwave from the very first post. Forget it Erin, those things draw some 70 Amps which will turn your battery inside out! Some biggie motorhomes have them but they also have huge battery banks and generators.


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Follow Up By: Robin Miller - Tuesday, Sep 13, 2011 at 15:20

Tuesday, Sep 13, 2011 at 15:20
Hi Al

I have always wanted to re-design a microwave, They have ben $49 at local Kmart recently , but its a project to far for now.

Re-doing the little 12v stoves, and after the fight with Stanley and I got a genuine 24hr thermos our need for a microwave in the car sort of dissappeared , but one day if we get a vehicle with more internal room we might just make one more efficent for camping.

Robin Miller

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Follow Up By: ezzmae - Tuesday, Sep 13, 2011 at 17:09

Tuesday, Sep 13, 2011 at 17:09
thanks for that info Robin!! from your & Allan's comments, and reading the info on the forum I have decided to keep the microwave only for when I am at a powered site. Probably only 20% of the time. Otherwise rely on the little gas BBQ.

My trips will be mostly 3 day long weekends when I go to kitesurfing events and the odd 5-7 day trip. I already have the deep cycle AGM 150AH battery so would like to incorporate that. I can get another of these far below retail ($220, Eaton brand) from a friend in the boat building industry.

I am now thinking solar power would be a good idea although the cost and the fact it was not 100% reliable (in case of a run of cloudy days) had deterred me initially. I tend to travel based on a good forecast so usually when it's sunny! and I probably wont ever go more than a few days without access to power so am considering making my system totally independent from the main vehicle battery (easier to wire, less costly to install and simpler to maintain?)

Another friend has 2 x 120 watt solar panels almost new that they no longer need and may give me (a barter arrangement for some stuff i no longer need).

I need to do the sums, but am thinking now of a system like:

1. 2 x 150AH deep cycle batteries not connected to the main vehicle battery
2. 2 x 120 watt solar panels with a charge regulator recharging the batteries
3. voltage meter on the battery bank with some sort of automatic cutoff when they drop below 50%
4. backup electric battery charger to be connected manually if need be (my dad has a few of these because he is a caravaner so would not have to purchase immediately) hopefully not necessary on weekend trips

thank you all for your patience & help.

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Follow Up By: Member Al (Sunshine Coast) - Tuesday, Sep 13, 2011 at 18:21

Tuesday, Sep 13, 2011 at 18:21
Robin, my neighbour redesigned a microwave............he turned it into a letter box!


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Follow Up By: Robin Miller - Tuesday, Sep 13, 2011 at 19:44

Tuesday, Sep 13, 2011 at 19:44
I hope he left it unplugged Al - I once had to investigate a case in which the owner of a fast food shop removed the microwave door and jammed the over-ride switches on , he could toss a pie into it and quickly pull it out a bit later nice and hot - his hand only got slightly warm - well at least for the first year of using it.

Hi Erin

Hope it works out ok.
Your car alternator is the most powerful charger you will get and your carrying its weight anyway , so I would incorporate it into the system somewhere.
Robin Miller

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Follow Up By: Member Al (Sunshine Coast) - Tuesday, Sep 13, 2011 at 21:42

Tuesday, Sep 13, 2011 at 21:42
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Reply By: ezzmae - Wednesday, Sep 14, 2011 at 20:05

Wednesday, Sep 14, 2011 at 20:05
So, after considering a few options, i am going to go with:

1 x 150 ah AGM house battery
Ctek dual unit connected between house and cranking battery
2x 50watt solar panels on roof (as these have been given to me)

No microwave or hairdrier :) unless connected to 240volt

LED lights in camper, 1x80l compressor fridge, small water pump, invertor to recharge laptop every couple of days.

Running the engine for an hour or so if necessary to backup solar panels.

From research this seems to be feasible. Will an auto-electrician be able to install this for me or do i need to find a solar specialist i wonder?
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Follow Up By: ezzmae - Wednesday, Sep 14, 2011 at 20:09

Wednesday, Sep 14, 2011 at 20:09
Oh and 12 volt TV used for maybe 2hrs a day as well
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Follow Up By: Member - John and Val - Wednesday, Sep 14, 2011 at 21:04

Wednesday, Sep 14, 2011 at 21:04
Hi ezzmae,

It is possible to get a low voltage power supply for many laptops. Saves the cost of an inverter.


J and V
"Not everything that can be counted counts, and not everything that counts can be counted."
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Follow Up By: ezzmae - Thursday, Sep 15, 2011 at 21:00

Thursday, Sep 15, 2011 at 21:00
Thanks so much Val. You and Jjohn seem to be very respected on this forum particularly when it comes to power setups so always value your advice.
FollowupID: 739091

Reply By: ezzmae - Friday, Oct 07, 2011 at 18:17

Friday, Oct 07, 2011 at 18:17
Hi all

I have progressed a little in my plans for powering my camper and am ready to engage a tradesman to wire it all up. Advice needed on options for mains charging in conjunction with the ctek dual as my solar panels have turned out to be no good. Eventually i would like to buy a panel or two but cost prevents it at this stage.

I have a 150ah agm house battery, and a ctek dual to charge from the main battery while vehicle is running. My question is what mains charger to use to supplement this in case i am stationary for more than a couple of days? Can this be permanently connected to the battery? Would i be better off with another battery wired in a bank as the maximum i will be going without running the vehicle would be say 5 days? I have estimated with my usage a maximum of 3 days for the one 150ah battery without discharging it below 50%.

Many thanks for reading....
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