12 volt inverter 12 volt sealed deep cycle battery system

Submitted: Saturday, Jan 11, 2014 at 17:49
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doing my trailer up for a trip to the red centre in April with the kids looking for advice in relation to which is the best inverter and deep cycle sealed batteries to install
regards Gizza
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Reply By: Notso - Saturday, Jan 11, 2014 at 18:28

Saturday, Jan 11, 2014 at 18:28
Plenty of advice on here mate, but you'll need to say what you want to do with the set up.
AnswerID: 524293

Follow Up By: gizza - Saturday, Jan 11, 2014 at 18:37

Saturday, Jan 11, 2014 at 18:37
inverter to run small tv light etc battery system to run 80 lt and 40 lt engels overnight or a couple of days without access to 240 power
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Follow Up By: Member - Frank P (NSW) - Saturday, Jan 11, 2014 at 18:39

Saturday, Jan 11, 2014 at 18:39
Will one of the Engels be used as a freezer?

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Follow Up By: Notso - Saturday, Jan 11, 2014 at 18:48

Saturday, Jan 11, 2014 at 18:48
So you won'thave solar. Just charging from the tow vehicle?
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Follow Up By: gizza - Saturday, Jan 11, 2014 at 18:52

Saturday, Jan 11, 2014 at 18:52
yes the 80lt engel will be the freezer
yes charging from tow vehicle and topping up from 240 every couple of days
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Follow Up By: Brian 01 - Saturday, Jan 11, 2014 at 18:58

Saturday, Jan 11, 2014 at 18:58
Are you driving every day between 240v top-ups, and if so, for how long?
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Follow Up By: gizza - Saturday, Jan 11, 2014 at 19:20

Saturday, Jan 11, 2014 at 19:20
near enough Brian but would like to go a bit over the top just in case
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Follow Up By: Idler Chris - Saturday, Jan 11, 2014 at 19:22

Saturday, Jan 11, 2014 at 19:22
80lt freezer seems on the BIG side. Do you really need such a big freezer? What is in it and for how many people?
Do both have insulating bags?
What other people think of me is none of my business.
Do unto others what you would have them do unto you.

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Follow Up By: Brian 01 - Saturday, Jan 11, 2014 at 20:33

Saturday, Jan 11, 2014 at 20:33
If you will be driving each day when not on grid power, then my suggestion would be:-
1. For the 240v stuff, a 300w continuous modified or preferably pure sinewave inverter.
2. 2 x 100 or 1 x 200Ah AGM battery.
3. A minimum 40 amp DCDC charger located adjacent to the battery for charging when travelling.
4. Separate cabling from the start battery to the DCDC charger plus separate cabling to the pair of fridges, run the fridges direct from the car when travelling and from the trailer when parked. A bit of magic with some anderson plugs or a rotary switch will achieve this.
5. Consider isolation for the fridges if you are going to stop for any length of time without switching the fridges to the trailer battery otherwise you may flatten the start battery, a VSR will do this.
6. Make sure the wire size is adequate, minimum 6AWG for both sets.
7. 240v intelligent charger, minimum 20 amp.
8. A decent alternator in the car to run it all.
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Follow Up By: Member - John and Val - Sunday, Jan 12, 2014 at 07:59

Sunday, Jan 12, 2014 at 07:59
To meet your present requirements, I'd agree with Brian, apart from maybe dropping the dc-dc charger back to 30A rather than 40A. It's a lot of gear and will cost. One very important element is the alternator - it's got a lot of work to do.

Suggest that you will save heaps by changing your requirements. You don't need all the comforts of home when away, in fact roughing it a bit is part of the experience. Why do you need 120 litres of fridge space, including an 80 litre freezer? If you must carry frozen stuff (and it's not hard to avoid or minimise that) use the bottom of a fridge as freezer space. (We've carried prefrozen vacuum packed meats and pre-cooked meals for weeks like this in our 40 litre fridge, with a loose cover over the "freezer" space to restrict convection, and regular fridge contents above it.)

As already suggested, I'd look at just why you need 240 volts - Do you actually need a TV? If it's a family essential, then maybe a little 12V one? (or a USB thumbstick TV for your laptop?). 12v chargers are available for cameras, torches, computers, phones...... 12v LED lighting is readily available. ( If you were thinking of running 240V hair dryers, electric frypans, jugs etc, forget it - you cannot carry nearly enough power!)

Recommend you follow Mick's suggestion and read Electricity for Camping . It covers a lot of this stuff and answers many questions that you haven't asked yet!


J and V
"Not everything that can be counted counts, and not everything that counts can be counted."
- Albert Einstein

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Reply By: Notso - Saturday, Jan 11, 2014 at 19:43

Saturday, Jan 11, 2014 at 19:43
On a different tark now. There are perfectly good 12 volt tellys and lighting solutions around. The extra complexity of an inverter could be avoided quite cheaply, probably for about the same as it'd cost you for an inverter.
AnswerID: 524298

Reply By: Ross M - Saturday, Jan 11, 2014 at 20:19

Saturday, Jan 11, 2014 at 20:19
G'day gizza
I would be using a 12v tv and LED lights so no inverter is needed, as mentioned above.
Also would use the 40L Engel as a freezer unless you really have a bullock to keep frozen. And have both the 80 and the 40 well insulated and a fresh air supply for the condensers to get rid of the heat. No good having fridges stewing in a pool of their own hot air or they will run all the time and still may not cool or freeze.

Do you have a decent high output charger to bring the batteries Back Up when on 240v?

Probably need two 100ah batteries because if used in hotter weather April will be 30 or a bit more, the fridges will still be eating battery power each night as well as the tv etc.
Inside the vehicle the temp will be more and that is the temp the fridges feel. So run times and overall amp use may be about 100ah/day. That is what two 100ah batteries would only like to deliver in a day. ie 1/2 discharge. 50 ah each.

Make sure you have a digital battery monitor which you can switch on, or leave on, most of the time to check the voltage of the batteries to see how it is all holding up and when you may need to charge them.

Ross M
AnswerID: 524302

Follow Up By: Member - Frank P (NSW) - Saturday, Jan 11, 2014 at 21:06

Saturday, Jan 11, 2014 at 21:06
So Gizza,

If you follow Ross's power consumption figures, and I think you should, your batteries will be flat, like REALLY flat, in two days. Ie, according to your planned schedule of "plugging in" every couple of days, you will have absolutely no reserves. At the end of day 2 your batteries will be dead. Think freezer warming up, lost food, etc.

Adding batteries is not the answer. You need to offset consumption with input. If you want to annoy everyone at your campsites all day every day you can run a generator. Please don't do that. Or you can add some solar. Based on your planned consumption and my own experience with a power-hungry setup I think you need about 240 watts of solar. Or you can have a decent charging setup from your car and run your car for a considerable time every day. For other campers' sakes, please don't do that either.

If you plan to charge while driving then you may need a decent DC-DC charger, but if relying on solar and 240, then as Ross says, a solid multi-stage mains charger is a necessity.

Let me tell you my experience ...

I have a 130 litre compressor fridge, 320 amp-hours of AGM batteries and 200 watts of solar on the roof of my camper. I only discharge my batteries to 50%. Running that fridge and minimum lights (LED), the batteries last about 3 days to 50% discharge with no sun. With all-day sun they catch up every day.

I also have a 55 litre car fridge which I run as a freezer at -10 deg for long remote trips. If I use that I have to deploy an additional 240 watts of portable solar (total 440 watts) if base-camped to keep up, and am good for only 2 or three days with poor sun, but indefinite in good sun. I carry a generator for backup and also charge while driving with a DC-Dc charger.

I think you need something to charge your batteries, or you need to reduce your consumption.

Just my opinion.



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Reply By: Mick O - Sunday, Jan 12, 2014 at 00:40

Sunday, Jan 12, 2014 at 00:40
Two things you need to do, both of them involve reading.

1. Read This;Electricity for camping

2. and this;Building a 12V DC power system

Cheers Mick
''We knew from the experience of well-known travelers that the
trip would doubtless be attended with much hardship.''
Richard Maurice - 1903

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Reply By: The Bantam - Sunday, Jan 12, 2014 at 01:28

Sunday, Jan 12, 2014 at 01:28
First as has been said......you may be able to avoid the inverter all together.

Second...as has been said many times before.....there are realities about off grid refrigeration that some people simply don't grasp...or don't want to hear.

Big fridges realy need large batteries and a solid sorce of supply...more than many people want to know......reduce your refrigeration and reduce your costs dramaticly.

Say the word "FREEZER" and the power consumption increases dramaticly....like by a factor of 4 to 6 times the consumption of the same fridge run as a fridge.
Realy consider the need to run a freezer....particularly a big freezer.

Contrary to what all the sales people will try and tell you AGM may have no advantage what so ever.....a good quialty wett cell battery will cost less and have better temperature tollerance.....AND a good wett cell battery will tolerate fastrer charge rates than some of the AGM batteries.

Again, contrary to what all the sales people will tell you....a DC to DC charger may have no advantage whatsoever..particularly if tyou are not running an AGM that has a limited charge current.

Remember people always underestimate how much battery capacity is required......considerably so.
All too often people complain that either their batteries Do not hold up their requirements long enough and/or their batteries have a short service life.....due to insufficient capacity for their needs.
100Ah is sufficient to reliably stand up a 40 litre fridge run as a fridge for a couple of days. ...a 100AH battery will not hold up a 40,litre fridge run as a freezer for 24 hours in a hot environment

In addition people frequently do not understand that it takes time to recharge batteries regardless of the size of the charger.
6 to 8 hours is required to recharge a battery fully ...from any source...from a deep discharge.....particularly once the batteries get some age.

because of all the above, a very large portion of people are running on insufficient battery capacity, cycling their batteries too deeply and failing to fully recharge them day after day...resulting in very short battery life.

AnswerID: 524320

Reply By: Racey - Sunday, Jan 12, 2014 at 10:28

Sunday, Jan 12, 2014 at 10:28
I agree with most of what has already been said. No matter what frigs or freezers and teles you are running, the important thing to remember is that the energy to run these appliances, ie taken from the battery(s) MUST be replaced. The battery(s) MUST be large enough to supply the overnight load with reserve. While you are driving charging not a real issue. However, would strongly support the use of a DC-DC charger, otherwise the batteries don't get fully charged. Being able to fully charge the batteries is most important.

I doubt that you will be driving every day. Therefore you will need some other other means of charging and/or running the load. Add 1 solar panel, the largest you can fit in your kit. 200watt min. Don't fall for those little 40watt units 'cause they'll do jack s**t.

My own experience started running a 40ltr engel as a freezer with a 75ah Thumper charged from the main battery. It would not run the unit overnight. In the morning I found the battery voltage below 10volts, dead flat. I then linked that with the caravan batteries for overnight which was OK to a point. After 2 years the thumper was bulging on the insides. Solution 130ah AGM charged via a 20amp dc-dc charger and topped up with a 140 watt solar panel when we a stopped for few days. In the event we have a few overcast days then we fall back to a 230v charger from the generator.

An Engel run as a freezer will draw 4-5 amps and it will run for around 20 hours in a day, particularly in the hotter weather, which means you need a minimum of a 100ah battery just to break even. As I said before that 100ah must then be put back into the battery.

AnswerID: 524335

Follow Up By: gizza - Sunday, Jan 12, 2014 at 14:46

Sunday, Jan 12, 2014 at 14:46
thanks for all the advise guys much appreciated, i like the idea of a 12 volt tv and lights and no inverter, in relation to the batteries i was contemplating running 2 sealed deep cycle trojan batteries for the fridges (any thoughts on make) by the treads it would appear these would be sufficient for my needs. i have thought about solar but given the cost of my set up so far this will have to wait a little longer. i was give a new second hand calibre 20 amp multi stage battery charger, has anyone had experience with this.
once again would love some feed back. by the way I'm not precious don't fully understand a lot of stuff regarding outback travel and set ups willing to learn. nice to be part of the oz explore family
cheers Gizza
FollowupID: 805963

Reply By: oldtrack123 - Sunday, Jan 12, 2014 at 16:00

Sunday, Jan 12, 2014 at 16:00
Avoid an inverter if you can
They waste what may be limited available energy from the alternator
They DO ADD the risk of ELECTRIC shock if more than one appliance /device requiring /fitted with, a THREE plug is CONNECTED.

AnswerID: 524363

Reply By: Member - 2517. - Sunday, Jan 12, 2014 at 17:01

Sunday, Jan 12, 2014 at 17:01
They are excellent chargers,have used 2 for 5years.
AnswerID: 524371

Follow Up By: oldtrack123 - Sunday, Jan 12, 2014 at 23:22

Sunday, Jan 12, 2014 at 23:22
What are excellent chargers???
FollowupID: 806023

Reply By: Sigmund - Sunday, Jan 12, 2014 at 17:27

Sunday, Jan 12, 2014 at 17:27
There's lots of good advice above.

My experience over 5 years of CTing has been to go entirely to 12v for reasons of efficiency and simplicity (and I can fix the faults myself - have had to learn).

As for batteries, I'm a fan of calcium hybrids. Got 5 years out of 2 x 100 aH units.
AnswerID: 524376

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