Charging up the batteries

Submitted: Tuesday, Nov 19, 2002 at 01:00
ThreadID: 2407 Views:2490 Replies:5 FollowUps:6
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I do a lot of 4Wd'ing with My 4wd and off road camper. The one problem I have is when I go bush for a few days I want to be able to keep my batteries charged to run my fridge and 12volt camp lighting.

I have three N70 batteries two connected to the car and one on the camper.
My problem is the camper as this is the one that stays put and would usually run the fridge.

I don't want solar panels to charge because of space and cost .

What I am wondering is could an inverter be used to run a 4Amp battery charger to charge the camper battery overnight.

The idea would be to run fridge lighting etc inverter off the car overnight while the charging was taking place. The next day fridges etc could run off the camper and the car's second battery would charge during normal vehicle use.

Is this feasible? or have I got it all wrong. I am afraid electrics is a new area for me and I think better left to the experts.
I know I could buy one of those new super quite Honda generator sets but they are a little out of the price range at the moment.

At the end of the day I am just looking for the cheapest way to keep the camper battery charged so that the tinny'e can stay cold while I am enjoying the 4wd country side. Obviously I could also just keep manually swapping batteries out of the car to the camper but this is just too 70infull for the back to keep doing every day.

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Reply By: paul - Tuesday, Nov 19, 2002 at 01:00

Tuesday, Nov 19, 2002 at 01:00
Try it, you can always use the inverter for other things. One thing you will notice is that although inverters quote 90% efficiency and stuff they are not and are terrible at sucking power out of 12 v batteries. That means it may run your Arlec charger but it may even overnight suck out most of the dual battery set up in the wagon. I reckon test it out at home, i'd be interested to see the result and the response. Another cheap sloppy maybe dangerous in the rain and not great for your battery option is to just get a bigger decent deep cycle battery (what doof put an N70 in your camper ?) and in the morning run jumper leads from your main battery to your camper battery.

Another problem with putting a 4amp arlec on overnight is that you run the danger of cooking your battery. Those battery chargers do not stop charging when the battery is fully charged and if this is the case it can lead to the boiling of the battery fluid resulting in the breakdown of the battery plates and you have one buggered battery. You can solve this by inserting a small solar battery regulator (like $20 at Jaycar etc) in the cable from the arlec unit to the alligator clips. I've done it, works well.
AnswerID: 8707

Follow Up By: David - Tuesday, Nov 19, 2002 at 01:00

Tuesday, Nov 19, 2002 at 01:00
Thanks Paul,
The reason for the N70 in the camper is that I have a Liemack fridge/freezer and they recommend not to use deep cycle batteries. In fact before I got the fridge I had deep cycle to run the camper but then had to replace it because of the problems with the fridge.

I also forgot to mention I have 6 kids from blending to families so we have to carry the fridge in the camper always as there just isn't any room in the back of the 4wd with all the seats folded down and in use. If If I could I would just run the fridge off the car as the N70 will power the lights in the camper for over a week.
FollowupID: 4251

Follow Up By: Oziexplorer - Tuesday, Nov 19, 2002 at 01:00

Tuesday, Nov 19, 2002 at 01:00
David, no wonder Liemack went as a business into the distance and belly up.
Liemack were a good fridge, but they consume more than twice as much power as any other battery compressor fridge. In a 24 hour controlled environment test, the average power consumption by Danfoss powered 12 volt compressor units averaged about 2 amps an hour over 24 hours. The Liemack used a whopping 5.6 amps an hour over 24 hours. The reason is the Liemack uses a Mitsubishi 240vAC powered compressor, and uses an invertor to convert the 12vDC to 240vAC. NO, one BP SX60 solar panel would not run your system. You would need three (shock horror). As for them not recomending a deep cycle battery is completely wrong. A standard cranking battery is *NOT* under any circumstances designed to be used like a deep cycle battery, and after probably 50 cycles of deep cycling, the battery would be ruined and giving you very poor performance.

Looking at the long term and how young your children are and how much longer you expect to go camping, I would highly recommend you sell your Liemack refrigerator, get rid of one of the batteries you currently have to take you down to two, install a proper deep cycle battery for the second battery and a proper charging system mounted in your vehicle to charge that second battery to full capacity. You then run a 6mm twin cable down to the back of your vehicle, and terminate it with a small Andersen plug. On your camper, you put a second Anderso/en? plug wired with 6mm cable into your camper electrical system. You then get a Danfoss 12vDC powered fridge like the evaKool which has *great* insulation, and is properly built in Australia for our climate and then get a BP SX60 solar panel that would run the evaKool fridge.

Overall, this would still be a cheaper option than buying a Honda EU1000 generator and running it.
FollowupID: 4254

Reply By: OziExplorer - Tuesday, Nov 19, 2002 at 01:00

Tuesday, Nov 19, 2002 at 01:00
David, you have most definitely got it all wrong.

What brand and model of fridge do you have?

Running an inverter and battery charger would be the most wasteful and innefficient system you could possibly do. The major issue is you have one to many batteries and probably none of them are getting fully charged correctly.

As for space and cost of solar panels. A BP SX60 panel at $576 incl GST and delivered to your door, would probably be sufficient to keep you going:

This is a substantially cheaper option to the Honda EU1000 generator and requiries no maintainence, no fuel and the solar panel should last 25 years. What is stopping you from mounting it on a removable frame on top of your camper? The panel dimensions are 1110 x 502 which would be less space than a Honda generator and fuel. You can then just remove the panel from your camper roof and place it in the sun to charge your battery. The kids would happily keep the panel moved about 3 to 4 times a day depending on the time of year.

With a proper deep cycle battery you could have a trouble free - no noise - virtually no maintainence system, and you could cut down to two batteries in total.

Look, I have all the toys including Honda generator, but have not used the generator camping now for over three years, I rely totally on the solar panel and my Yuasa deep cycle battery.
AnswerID: 8717

Follow Up By: Colin - Friday, Nov 22, 2002 at 01:00

Friday, Nov 22, 2002 at 01:00
Finally some one with common sense, totally agree, do your home work and you will find this is the most practicall way to go Col
FollowupID: 4360

Reply By: Member - Nigel - Tuesday, Nov 19, 2002 at 01:00

Tuesday, Nov 19, 2002 at 01:00
Gotta agree with the other replies - converting 12 to 2540 then back to 12 will waste so much current that it won't be worthwhile. There are dedicated "12v to 14.4v chargers" available from the 12 volt shop, this would be a better option.

Just to give you something to think about, I have a 95 Ah in my car that will run my EvaKool for at least 3 days (without dropping the battery below 11.5v) and a 75 Ah in the camper that will easily give me another couple of days while still running the lights and water pump. I live in the tropics and set the EvaKool to cycle between 1 and 4 volts.

!2 volt motors are generally more efficient than 240, and when you add the ineffeciencies of the inverter, it doesn't really make sense to use a 240v compressor fridge.

Also make sure the batteries are "fully" charged (don't rely on the alternator) before a trip - I use a LEAB automatic switch mode charger - it was expensive but it pays for itself in increased battery life/capacity.
AnswerID: 8731

Reply By: Janset - Wednesday, Nov 20, 2002 at 01:00

Wednesday, Nov 20, 2002 at 01:00
I agree with all that has been said, it is good advice. Just one thought that has not been mentioned that you may want to consider.

If you do consider a fridge replacement have you thought of a 3 way fridge? 240 at home and caravan parks, and your battery is still being charged via the inbuilt charger on you van. 12 volts while travelling and gas in the bush. And on that note whilst in the bush, all your camper battery would have to do is to keep up with the lighting, and that you can control your self to make the battery last.

Again, use a deep cycle battery as suggested.

AnswerID: 8761

Follow Up By: Oziexplorer - Wednesday, Nov 20, 2002 at 01:00

Wednesday, Nov 20, 2002 at 01:00
I had a Chescold 3 way freezer I used as a fridge for many years, and even in the middle of summer in the tropics never had any issues with it.
I had a bubble in the front of the vehicle, so when I pulled up I just made sure the vehicle was level.
When I travelled I had it on 12vDC through a relay so when I switched off the engine, the relay opened, and the fridge was disconnected. If I was stopping for any time I would just put it on gas. All civil and simple.
FollowupID: 4286

Follow Up By: Janset - Saturday, Nov 23, 2002 at 01:00

Saturday, Nov 23, 2002 at 01:00
I like the relay bit. Considerit pirated ; )

FollowupID: 4385

Reply By: David - Wednesday, Nov 20, 2002 at 01:00

Wednesday, Nov 20, 2002 at 01:00
You are probably right. I originally thgought of the 3 way but got told that they were not very efficient either on gas or 12v but were ok on 240v. As we go where there is no 240v supply I opted for what I did. It is too late to change now as the fridges are just too expensive to be changing over all the time. Everyone I talk to selling these fridges has a different story to tell.On seconds thoughts it is not different, they all tell you their's is the best and they have a different set of statistics and comparisons to go by. Maybe they are our future politicians!
AnswerID: 8776

Follow Up By: Janset - Thursday, Nov 21, 2002 at 01:00

Thursday, Nov 21, 2002 at 01:00
Very ture David.

Every one has 20/20 hind sight. In this case the longest way round may be the quickest way home. The translation :) you may be able to sell you existing fridge and get a few bucks, cut your losses and go 3 way.

I think you must never overlook the obvious and that is, I decent size deep cycle battery at trade price, I last paid $160. How many of these do you have to go though before you total up the price of a replacement fridge.

FollowupID: 4318

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