DC Power options for Camping?

Hi All,

I'm in the process of designing/building a teardrop camper for a Hobart>Melb.>Adelaide & return trip along the great ocean road and would like to know people's suggestions for DC power setups for campers etc.

I'd prefer something stand-alone from the car! Although we will be travelling more than a few hundred Km's on the great ocean road and that a DC-DC charger would make logical sense, We do live in Tasmania and any further trip's will most likely be on the island - so no more than 4hours to get to "camp" - additionally, I'd like the camper to be available for friends and family to use - so stand alone from a car setup with anderson plug's would be advantageous.

I currently have 2 brand new Fullriver DC85-12 AGM's sitting here and would like to use these. The appliances I see us using on the trip are 35L Waeco Fridge, 3 or 4 LED Caravan Lights, 300w 240volt inverter for charging laptop/camera, and possibly a car stereo for some music if ever needed.

We plan to stay at caravan parks on the great ocean road so connecting to mains to charge overnight will not be a problem, this is when we'd charge the camera batt's and laptop etc. also. Future camping in Tassie will all be free-camping at beaches, lookouts etc.


My Idea of a setup was:

-AGM Batt's runnning appliances daily - on the road or not.

-When in a carvan park, charge batt's from mains (additionally using mains for the fridge, and misc. chargers for camera's etc.)

When in a free camp situation, charge batt's from Solar Panels, and if necessary turning the fridge off overnight and stop/limit usage of the inverter.

any loopholes I'm missing here? or have I neglected to calculate something into the situation?






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Reply By: Allan B (Member, SunCoast) - Monday, Feb 03, 2014 at 23:00

Monday, Feb 03, 2014 at 23:00
Hi Thomas,

Your proposal to use use caravan parks on your trip to Adelaide and thereby using 230v mains to charge the batteries solves the issue for that trek. And you would have no need of an inverter for that section.

For free camping a solar could handle battery charging provided that you size the solar panels appropriately. It could be wise to provide for a connection from the car to charge batteries in the event of poor solar conditions. This does not need to be a permanent connection but carried and set up if needed.

Turning the fridge off overnight to save batteries is espoused by some but is something of a myth. The fridge does not use a lot of power during the cool of the night but if switched off it will warm up to some extent and require extra power when restarted to recover so effectively there is no benefit. In the meantime the fridge temperature will rise somewhat and possibly harm the contents.

Using 12v charge devices for charging laptop & camera will eliminate the need for an inverter, but it does mean acquiring these device chargers. An inverter does incur some losses but with a 300W inverter and small loads it does not amount to a great deal. I use a 360W inverter in this manner but run it from the alternator while driving.

Cheers
Allan

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Follow Up By: Thomas v - Tuesday, Feb 04, 2014 at 09:10

Tuesday, Feb 04, 2014 at 09:10
Thanks Allan - I thought as much with the fridge. Your theory is similar to the theory of turning a household reverse cycle heat pump off overnight - it's easier and more reliable to keep it running at idle overnight, and letting the smarts work out when to crank it up in the heat of the day!

With the temporary/emergency charge from the car, would you suggest something like an Anderson plug one end, and alligator clips the other, and running the car at fast idle for an hour or so?

Truth be told we are only in our mid 20's, and the car we are using is a 2014 Focus - so we're not exactly planning to head into the outback on 4x4 trips.... Ocean road aside, back in Tas we will be doing 3-4 night trips in one spot max.... And although an Anderson plug on the tow bar would be ideal for an "emergency", the converted jumper leads sounds more appealing if we were to change cars, tow it with my work vehicle, or lend the camper to someone else. Thoughts?
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Follow Up By: Allan B (Member, SunCoast) - Tuesday, Feb 04, 2014 at 09:52

Tuesday, Feb 04, 2014 at 09:52
Thomas, re the "emergency" charge from the car. You need to be careful to avoid discharging your cranking battery, so without appropriate devices installed you should not charge from it unless the engine is running. It could be done with clips and a fast idle but not really a good way to go. Better to install an Anderson plug, even close to the cranking battery, using a fuse of course.

It could well be that you would never need auxiliary power provided you have an adequate solar panel and enough sunlight. Is there sunlight in Tasmania? LOL

I will leave it to others more experienced in solar to comment on the size of solar panel appropriate to your situation.
Cheers
Allan

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Follow Up By: Thomas v - Tuesday, Feb 04, 2014 at 12:05

Tuesday, Feb 04, 2014 at 12:05
Thanks Allan,

so you're implying to wire a fused anderson plug to the crank battery, and then making an 'extension lead' anderson/anderson for emergency charging to the camper (obviously at fast idle, not to drain the crank batt.)?

If so this actually works well, as I could use this same extension lead for the solar panels should I want to park the camper in the shade....

and yes, we do get sun in Tasmania... and it bites pretty hard! I spent 12 days in FNQ, no sunscreen, no burn - less that 2 hour's in the sun in Hobart at the same temp. and I'm red like a lobster!

Hobart is actually the second driest Capital in Australia, after Adelaide.. Not a bad effort considering we have a 1200m mountain and it's own weather system towering over the CBD..

Back on track, I've spoken to local battery suppliers and they seem confident enough about the solar requirements to charge batteries efficiently - however I'm open to anyone's experiences/suggestions on here :-)

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Follow Up By: Allan B (Member, SunCoast) - Tuesday, Feb 04, 2014 at 12:53

Tuesday, Feb 04, 2014 at 12:53
Yes Thomas, as per your first paragraph. You could even have a short adapter with battery clips to Anderson for use with other vehicles. But you need to be careful with alligator clips, they can be dodgy... both for connection reliability and the risk of shorting if for example someone closes the bonnet.

Your idea of using the same Anderson extension for the solar panel is a smart thinking. Make sure that it is of adequate cross-sectional area, suggest no less than 16mm2 (5 B&S)

Our Queensland sun may have some UV filtered out by the smoke from all the coal-fired power stations. LOL I must remember the sun-screen when in Hobart!
Cheers
Allan

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Reply By: Tony H15 - Tuesday, Feb 04, 2014 at 09:22

Tuesday, Feb 04, 2014 at 09:22
I really don't see a need for an inverter: all the items you list can be charged and run from 12v.Inverters do use a little power and with two 85ah batteries you should have plenty of power for your meagre requirements.
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Follow Up By: Thomas v - Tuesday, Feb 04, 2014 at 11:54

Tuesday, Feb 04, 2014 at 11:54
Thanks Tony,

You're right about no need for the inverter - however I have one, albeit a couple of years old, so I was thinking of installing it for good measure. I wouldn't be using it for the great ocean road trip, more so if I need to charge the camera battery's somewhere remote at a later stage. I'm into photography, and my SLR camera doesn't have a 12volt charger available :-( - and I've already learnt from my experience of 3 flat batteries in my pocket! haha

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Follow Up By: oldtrack123 - Tuesday, Feb 04, 2014 at 13:11

Tuesday, Feb 04, 2014 at 13:11
HI
If that inverter is a few years old I would suggest YOU check if it is a FULLY isolated type
NON isolated were being sold up to a few years ago
IT may not be a non isolated & could be a potential death trap ,

PeterQ
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Follow Up By: pepper2 - Wednesday, Feb 05, 2014 at 09:59

Wednesday, Feb 05, 2014 at 09:59
Peter how do we determine what is a FULLY isolated inverter,what do we look for ????
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Reply By: Member - Bruce C (NSW) - Tuesday, Feb 04, 2014 at 13:53

Tuesday, Feb 04, 2014 at 13:53
Hi Thomas,
If thinking solar then I would get the biggest panel/s you can fit in the available space and wire them in via a good regulator. If you do this there will only be a few times when an inverter or even 240 will be required. Personally I never use an inverter. I just don't need one as I have 12 volt chargers for everything as they are inexpensive. Think about placing a panel or two on top of your teardrop van. 12 volt X 200 watt panels are cheap enough these days if you can fit them.

I have 280 watts of solar into 2 X 120 Ah AGM batteries and I never run out of battery power given my usage which includes a Waeco CF35 running at -03 24 hours a day, a 24 foot caravan running all mod cons and other devices including a laptop, all powered from the house supply. I never need 240 unless it is for the microwave or airconditioning. Main fridge is a three way on gas. I have not had to use the Anderson plug on the back of the car to charge the van either.

Your Anderson lead idea is a good one and will have many uses.

I have fitted Anderson plugs under each side of the van near the front section so that I can run a fridge outside or use them to run the other 12 volt gear I have.

Cheers, Bruce.
At home and at ease on a track that I know not and
restless and lost on a track that I know. HL.

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Follow Up By: Kevin.Hutch - Tuesday, Feb 04, 2014 at 18:39

Tuesday, Feb 04, 2014 at 18:39
Couldn't agree more with the "biggest solar array you can fit" even if you only put one panel on initially. Portable panels allow you to park the van in the shade and can be more efficiently angled in the lower latitudes than a roof mounted panel. Solar panel plugs are a little smaller than Anderson plugs and equally good for the currents expected. Just fit a 20 amp thermal breaker in the connection to your car battery connection.

Having said that the rooftop panel would charge when travelling. I have an 80 ltr and my 120 watt horizontal rooftop panel copes well 24/7 in Queensland. Planned an upgrade but haven't yet justified it, may just supplement it with a portable panel.

I too have 12v laptop adaptor and 12v phone/camera chargers and I carry a small sinusoidal invertor just in case.

I use a jump start battery pack (typical 20A/H) for additional loads such as fan, laptop, camera/phone charge and recharged it from the car cig lighter socket when on the road, thus dedicating the "house battery" to fridge and LED lighting.

For my money I would go for a 12v fridge as the gas fridge can not be left on gas when travelling and their 12v function is usually very heavy on power, requiring a mobile connection to the car.

Kevin
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Follow Up By: Member - Bruce C (NSW) - Tuesday, Feb 04, 2014 at 19:30

Tuesday, Feb 04, 2014 at 19:30
Hi Kevin,
We always turn the gas off when traveling and just leave the fridge door closed and have never had a problem with the it losing temperature too much. Drinks are always really cold even after a full days travel.

I have found that the larger full size 12 volt fridges require more power than they stipulate. The smaller Waeco style portable fridges consume a lot less.

Cheers, Bruce.
At home and at ease on a track that I know not and
restless and lost on a track that I know. HL.

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Reply By: Simon - Thursday, Feb 06, 2014 at 22:59

Thursday, Feb 06, 2014 at 22:59
Gday Thomas,
I have just had your same issues building up my camper, sounds like a very similar situation, but mine is a camper on the tray of a 4x4 ute, not a focus. But the principles are the same.
I have a redarc bms (battery management system), a bit of initial outlay for the unit, but it does EVERYTHING. Money well spent in my opinion. Everything is seperate from my starter battery, except a trickle feed when the engine is running. It takes 230v AC from mains, as well as dc-dc as said above. It is a MPPT solar regulator also. Has a neat little lcd screen which shows you how long your battery has left til its flat, plus heaps of other information.
I recently took the vehicle for a trial camp in the SW, near margaret river. Managed three days without worry. Everything ran off of a 90AH batt, I had a 60L engel on fridge mode (not freeze), a second car stereo which I installed for camp music, enough LEDs to light up the entire site and the camper ontop, a little 12v water pump, plus some other bits and pieces. I havnt installed my solar panel as yet, but as I said everythingan without fail.

I installed it myself, cos im a tight arse jew and couldnt afford an auto lecky. Plus its half the fun of a building project! First time I have built anything of anykind and I was quite impressed with the finished product.
If you want more information, PM me and ill shoot some pictures across.
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Follow Up By: Thomas v - Friday, Feb 07, 2014 at 20:42

Friday, Feb 07, 2014 at 20:42
Simon,

Tight Arse Jew? I'm Dutch - so we must be on a similar page, haha!

I'm not too concerned about using the Focus as the charge point, however I'd prefer not to modify the car, so that way the camper can be available to be towed by my van (Mercedes Vito) or anyone else's car if they wish to borrow the camper.

Plus making it stand alone is appealing to me and is what theteardrop camper was initially all about - With all due respect to the grey nomad's, If I wanted wank factor I'd get a 200 series landcruizer and a 20ft Jayco caravan.. but, I am dutch.... that will never happen no matter my bank balance when I retire!

I've done the following calculations, and think I can get it past without ever connecting to a car/DC-DC charge etc. Let me know (or anyone else reading) if I've missed something in my calculations?

Advertised current draw of accessories:

Waeco CFX35 Fridge - 0.77 Ah average
Narva 87644 Lamp's - 0.08 Ah each x 4 lamps = 0.32Ah

I've rounded them up for good measure, just like a financial budget

Fridge: 1Ah x 24hrs = 24 Amps
lights 0.4 x 3hrs =1.3 Amp's

Rounding them up more:

Adding these together, and an additional 30% for good measure = 31Amp's

To replenish this I've calculated I need to "repay" the daily usage (35 Amp's) with solar.

31amps x 12Volts = 420 Watt's

375 Watt's / 3 Hours Sunlight = 125 Watt Solar Panel?

180watt A-Frame solar panel's are within my budget - so I'm more than covered?

If I'm using 2x 85Ah Batt's, and Ideally don't want to run them past 2/3, that gives me 112Amp's, or just over 3 & 1/2 day's complete run time with no solar....

obviously the theoretical works out better :-) but am I on the right track???







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