New Camper, 12v power questions.

Submitted: Sunday, Sep 13, 2015 at 22:18
ThreadID: 130279 Views:3060 Replies:4 FollowUps:9
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Hi all, so I've just bought our first camper trailer. Stoked...
It's second hand, come with 12v set up, well most of it. It's all wired up, got a 20amp hr battery that it came with from new, and a 105 amp hr battery that the guy i bought it from added. They are not linked. Small battery only runs water pump and 1 strip of led lights near kitchen area.
Has charger to charge from 240v and also a solar charger controller thingy lol? (I'm not very educated on this stuff)
The big battery is wired to run some 12v outlets.
I got an 80l waeco fridge with it, so will be running that plus some led lights.
It used to have an inverter but he kept that so would like to replace it.
So, my question/s, what inverter??? I got no idea about these. How many watts and how much $$$.
And how many watt solar panels will I need to keep things ticking over and again how much $$$
I realise these questions both have variables, so not asking for exact answer but ball park???

Thanks for any advice.

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Reply By: Member - John and Val - Monday, Sep 14, 2015 at 08:00

Monday, Sep 14, 2015 at 08:00

A few unknowns here, and a few things for your consideration.

1) If the 2 batteries aren't linked, the charger will only be connected to one of them. You'll have to somehow charge the other one. Maybe that's what the solar charger is for, maybe it handles charging from both solar and the vehicle? See if you can find a model number and we may be able to help there.

2) Depending on how you charge the bigger battery and how often, the fridge will be a pretty big load on that battery. You may have to consider adding more battery capacity or more charging. Maybe solar, maybe charging from the mains or the vehicle.

3) Inverters - depends what you want to run. Be aware that without adding a lot of batteries you cannot run big power stuff. Basicly that means you can't run any heating gear - jugs, toasters, irons..... You can use an inverter to power chargers for laptops, ipads, phones etc, but this is pretty inefficient and depending on just what you want the inverter to do it may be cheaper to buy 12 volt chargers for this gear.

If you do go for an inverter, it should be a pure sine wave type and 600 watt is probably a good size. Many smaller ones aren't much good, and if you need anything bigger than that then it's time to change your needs! (or add some more batteries.)

Hope that helps

J and V
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Follow Up By: Shane H9 - Monday, Sep 14, 2015 at 09:35

Monday, Sep 14, 2015 at 09:35
Thanks John.
OK, so, the charger just has alligator clips on the end so can be connected to either battery.
Big battery is a FULLRIVER DC 105-12.
The trailer has an anderson plug wired up for charging the big battery from car, and also an anderson plug wired to the solar charger regulator thingy. I will be getting an anderson plug wired up on my car, but would like to add solar for charging at camp.
Does this help with points 1 & 2 in your reply?

As for the inverter, I don't think it's going to be for us.
I think you're right, 12v laptop charger and other accessories / appliances would be better I think.

Thanks for your input.

FollowupID: 858347

Follow Up By: Member - John and Val - Monday, Sep 14, 2015 at 14:54

Monday, Sep 14, 2015 at 14:54

Your solar controller will handle 20 amps, so in principle you could attach up to about 240 watts of solar panels. I'd wouldn't push it beyond about 200 watts, which should be ample to handle your fridge and other minor loads.

I rather agree with Tony's suggestion of fitting a single larger battery - maybe next time. Alternatively, you could possibly connect the existing two batteries together in parallel (positive to positive and negative to negative), providing they are of similar type (either both AGM or both Gel.) Unless they are the same type, don't do it, as the voltages are sufficiently dissimilar to cause problems. You could also add another 100 Ah battery in parallel with the present one (it's only money!).

A few new worries - You have two anderson plugs, one to connect the solar panels, one to connect the big battery to the vehicle.

1) It is important not to inadvertently connect the solar panels directly to the battery - they must go through the solar controller. Anderson plugs are ideal for this sort of use, but can easily be used to accidentally connect the wrong things together.

2) You should not connect the van's battery directly to the vehicle battery (that would result in the vehicle battery helping to run the fridge.) You need a suitable relay to connect them only when the engine is running. In the simplest case this will be a relay to do the switching, operated by the ignition circuit. Better is a voltage controlled relay which only makes the connection after the battery voltage has built up after starting. Recent vehicles mess with them, so again, it's not as simple as we'd like!

3) A third factor that needs consideration is that most deep cycle batteries such as in your van require a slightly higher charging voltage than is available by simply connecting to the vehicle battery. This is particularly the case with "calcium" batteries. Losses are unavoidable in the long run of cable from up front to the van, compounding the problem. The answer is a dc-dc charger in the van, to accept the available voltage and increase it to suit the battery's requirements. I wouldn't do it at the outset, feel your way and rely on mains and solar charging to fully charge the battery. When next you have (another!) couple of hundred dollars to spare, suggest consider a dc-dc charger.

You might find this a useful read.


J and V
"Not everything that can be counted counts, and not everything that counts can be counted."
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Reply By: Tony H15 - Monday, Sep 14, 2015 at 09:47

Monday, Sep 14, 2015 at 09:47
Personally I’d ditch both batteries, buy a 150 or 200 AH AGM, and a 100 watt solar panel. I don’t know the current draw of your fridge but with a 105 AH battery I’d imagine it wouldn’t have a lot of juice left by morning. AGMs of this size (no name) can be had for around $300. Nothing wrong with no names either BTW, I’ve had mine for three years now - never touched it and never had any problems with it. Another alternative if you don’t want to ditch the batteries you have is a 100 watt panel and a backup battery charger like this one: .

I run a 200ah charged by a 80 panel at the moment and it runs my Engel, TV and lights and charges my phone, tablet and notebook without problems. I also carry an old Honda XD400 battery charger as a backup, haven’t used it for years but it is good insurance. 100 watt panels can be had for around $200 off eBay but the generator/battery charger I linked to are quite expensive - around $1400 I believe.

Cheapest option would be to keep your batteries, buy a solar panel, convert your lighting to LED and turn the fridge off at night! Converting to LEDs, if you haven’t already, should be top of your list: next to zero power consumption and far, far better lighting than incandescents. and fluros.

Pretty well everything you’ll need when camping can be bought in 12 volt so an inverter is pretty much a waster of space and money. Unless of course your wife demands access to a hairdryer, these of course require big wattages and big wattage inverters cost big $ and require lots of battery power to feed them. There are alternatives for everything though, my wife has a gas powered hairbrush/dryer she uses when camping.
AnswerID: 590344

Follow Up By: Bigfish - Monday, Sep 14, 2015 at 13:59

Monday, Sep 14, 2015 at 13:59
I agree. 1 large battery of 150-200 amp will do the job with ease. SSM make gel agm batteries that have good guarantee and reasonably priced. You should be able to sell the fullriver to help costs. One battery simplifies things and you can connect the 240 v charger and solar to it permanently. Your fridge will pull about 25 amp per day in about 28 degree weather and shaded. Hot humid days will see it use up to 40 amps if left in sun. So many variables. A deep cycle battery should never be taken past its 50% capacity. This will ensure a longer life and more reliability.
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Follow Up By: Tony H15 - Monday, Sep 14, 2015 at 17:03

Monday, Sep 14, 2015 at 17:03
Further to my first post, and sorry to disagree, I would not use an auto electrician, the job you end up with will cause no end of problem and if you do have problems you won't know where to start. As an example I used an auto electrician to install my electric brake unit and at the same time had him run wires through to the rear end for powering the fridge. For the fridge he ran a 5 core wire through, the wire gauge was woefully inadequate, the 7 pin plug was woefully inadequate, there were wires running everywhere (mostly just extras that were in the loom) and joins were just wires twitched together and covered with insulation tape. The terminals were crimped, broken and bare wires sticking out, but most of all it was just messy and untidy. I pulled the lot out and rewired myself - far better than the job I paid for.
Most campers who do their own electrical work started out just like you - knowing very little. Interest or financial considerations saw them designing and installing their own systems. It's the cheapest way and if something does go wrong you're in a pretty good place to diagnose and fix the problem.
Start with a simple system: single battery, solar panel, regulator, 240v staged charger, a few 12 volt sockets and a plug in digital voltmeter for monitoring purposes. As you learn more and your comfort demands more you can add more.
I started out of interest on motorbikes, then cars, then campers, then caravans. Having tried most everything I keep my system simple now, single large battery, solar panel with 12 volt genny for backup, hardwired, staged charger, LEDs throughout, enough sockets for everything, water pump, tank gauge and a hardwired, switched digital voltmeter.
FollowupID: 858366

Follow Up By: Member - evaredy - Tuesday, Sep 15, 2015 at 08:37

Tuesday, Sep 15, 2015 at 08:37
So by your comments, all auto sparkies are useless?

I had all my work done by an Auto electrician and they did a fantastic job.
This included wiring up a BCDC 1240 to my aux battery in the tub, wired in a 150W solar pane I have on the canopy, wiring anderson plugs to the rear of the Dmax, one for solar input, one for power from the aux battery.
They also installed and wired up the brake controller.

FollowupID: 858389

Follow Up By: Tony H15 - Tuesday, Sep 15, 2015 at 09:51

Tuesday, Sep 15, 2015 at 09:51
You can take it anyway you like. Presumably if you had all your work done by an electrician then you know little about electrical work, that being the case how do you know they did a fantastic job?

Common sense prevailing, if you get an auto electrician to do the job he's going to work to a price, if you do the job yourself, there is no price involved, no time involved. You can take as long as like or as short as you like, you can do the job properly or you can do the job as an auto electrician would - to a price - common sense really. The same applies in any field. I do all work myself, simply because I like to know what's behind the job, how to diagnose a problem and fix it if necessary. Nothing worse than spending hours out in the middle of nowhere tracing wires trying to find a problem when you are unfamiliar with the work. Been there, done that, won't do it again!

If you are happy using an auto electrician, that's fine use one - your choice! I'm not happy using an auto electrician, that's fine by me also - my choice.

What is your problem? Do you really think everyone has to agree with your ideals?

FollowupID: 858391

Follow Up By: Shane H9 - Tuesday, Sep 15, 2015 at 13:46

Tuesday, Sep 15, 2015 at 13:46
Thanks guys. I will be speaking to an auto electrician who is a mate of mine for guidance but doing the work myself. Best of both worlds i guess...
FollowupID: 858399

Reply By: Member - evaredy - Monday, Sep 14, 2015 at 14:23

Monday, Sep 14, 2015 at 14:23
If you are like me and know very little about electrics I would suggest you take the camper to an auto electrician and get them to look at it and explain everything to you.

Then you will know exactly what you need and it may prevent you wasting money on something you don't need.
AnswerID: 590353

Reply By: Shane H9 - Tuesday, Sep 15, 2015 at 13:16

Tuesday, Sep 15, 2015 at 13:16
Looking at 120w solar panel to start off and see how we go. Bedn speaking to ARB and their calculator thing says 105 amp hr battery and 120w solar panel shoukd be enough for fridge, led lights and charge a ph...
So, he has panels for $500 plus, then there's these ebay ones for $150,
I know you get what you pay for but are these ebay ones that bad? Comes with a 25yr warranty...
Can they be eired with an anderdon plug and plugged into my system???

Thanks again for the help here.
AnswerID: 590386

Follow Up By: garrycol - Tuesday, Sep 15, 2015 at 13:32

Tuesday, Sep 15, 2015 at 13:32
You no longer get what you pay for - you pay what the seller thinks they can get away with. The panels themselves are basically the same between ARB and ebay - will probably be made in the same Chinese factory.

There may be a difference in the quality of the regulators though - however I have a ebay set of 120w panels and the regulator works OK in make better than a later MPPT regulator I also have - the difference being that the MPPT regulator is a 3 stage charger but the sun goes down before it has been able to go through its program. The cheap basic version that was stuck on the panels is a simple charger and just whacks in as much juice as it can get away with.

So in my view I would no worry about the ebay panels but put some thought into what regulator/charger is attached.


FollowupID: 858396

Follow Up By: Shane H9 - Tuesday, Sep 15, 2015 at 13:45

Tuesday, Sep 15, 2015 at 13:45
Thanks Gary.
Camper already has a solar charger regulator installed, pictured.
Not sure if it's any good or not???
FollowupID: 858398

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