Fridge on just the one battery?

Submitted: Monday, Jan 23, 2006 at 23:00
ThreadID: 30041 Views:3318 Replies:14 FollowUps:26
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Just had to ask this question. Couldn't find the info on previous posts :-(

Is it possible to effectively run a fridge ie Waeco CF-35 on just the one battery providing it is managed well? (by running the vehicle every day or so if staying in the same spot for say 5 days) I only ask this question because I don't quite have the bucks for a duel battery system at this stage but have access to the fridge.

This may sound dodgy but would it work if I had another battery (not wired) handy and used that when required and simply charged it as I go.

Any feedback would be appreciated.
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Reply By: Member - David 0- Monday, Jan 23, 2006 at 23:07

Monday, Jan 23, 2006 at 23:07
You can make a pretty reasonable dual battery setup for not much more than the cost of the battery. My first homemade setup cost about $20 excluding battery and battery tray.
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Follow Up By: Damien - Monday, Jan 23, 2006 at 23:09

Monday, Jan 23, 2006 at 23:09
Wow! That's great David. What did it invole?
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Follow Up By: Member - David 0- Monday, Jan 23, 2006 at 23:13

Monday, Jan 23, 2006 at 23:13
Most commercial dual battery setups assume you are going to use the aux battery for high amp applications like starting the engine or winching. if you are just going to run a fridge (say 3 to 4 amps) then a very simple setup will do the job nicely.

Message me if you like, or if you have an auto electrician friend have a chat to them.
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Follow Up By: Member - David 0- Monday, Jan 23, 2006 at 23:19

Monday, Jan 23, 2006 at 23:19
It is simply a relay that connects the two batteries together whenever the ignition is on. The batteries are connected via a smallish wire (it doesn't have to be big to carry a few amps). It isn't a smart system like the $700 units, and you can't use the battery for starting (unless you use jumper leads). There are downfalls with this design -like don't leave the ignition on when the engine isn't running. But my first 4b used this system for several years.
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Follow Up By: Member - David 0- Monday, Jan 23, 2006 at 23:23

Monday, Jan 23, 2006 at 23:23
PS Yu are still running the fridge off one battery, the auxulliary, but at least the engine still has a battery to start it. I would suggest you take the vehicle for a good run each day or so. The battery will eventually run down unless it gets a good long charge, but at least you will be able to get home.
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Follow Up By: Muzzgit (WA) - Tuesday, Jan 24, 2006 at 02:40

Tuesday, Jan 24, 2006 at 02:40
And what he means by a good long charge is 5 hours minimum.
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Follow Up By: Member - Coyote (SA) - Tuesday, Jan 24, 2006 at 08:03

Tuesday, Jan 24, 2006 at 08:03
Thats fair enough but you have to be real carefull not to destroy both batteries this way.. a good battery managment system isolates both batteries from each other even whn the engine is running. if you have them set up to connect automtically when the engine is running, then for example if your Aux battery has dropped pretty low whilst running your fridge, the moment you trun your ignition, the dead or low battery will start to draw down your main battery. in essence the batteries will always want to even out whatever charge is avialibale between them... in the long run, this will destroy one or both batteries..
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Follow Up By: Member - David 0- Tuesday, Jan 24, 2006 at 08:34

Tuesday, Jan 24, 2006 at 08:34
That is correct, hence you need to use a smallish wire between the two, as this resistance "slows down" that exchange. It slows down the charge as well, but not by much becasue that is a pretty slow charge anyway- hence the need for a LONG charge anyway.

Just the normal couple of mm cross section auto wire is fine if running a few metres at most.

As I said, it does have some drawbacks, but it provides a simple way to run duals untill you can afford to do something better.
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Follow Up By: ro-dah-o (WA) - Tuesday, Jan 24, 2006 at 11:04

Tuesday, Jan 24, 2006 at 11:04
This can be overcome by running a relay off of the warning light on the back of your alternator. This was when the warning light is on on the dash, the batteries will be isolated.
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Follow Up By: HJ60-2H - Tuesday, Jan 24, 2006 at 19:53

Tuesday, Jan 24, 2006 at 19:53
Or the positive of your starter motor. An old trick shown to me by an auto sparkie 20 years ago when I had a dual battery in my HQ Holden.
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Reply By: rolande- Monday, Jan 23, 2006 at 23:09

Monday, Jan 23, 2006 at 23:09
If you travel every day, just set it to maximum while driving and then turn it off when the engine is switched off. You will need to be careful of what goes where in the fridge but other than that it should work O.K.

Other option is to get a cheap N70 battery and wire up a battery box, charge as you go then switch off when vehicle off. This should run the Waeco for a couple of days - but by doing this the battery won't last too long.

There are cost effective ways of dual battery'ing the vehicle. Mine cost $225 without the battery but still using quality bits.

Hope this helps

Rolande
AnswerID: 150470

Reply By: Motherhen - Monday, Jan 23, 2006 at 23:15

Monday, Jan 23, 2006 at 23:15
We set up our previous little caravan with 1 deep cycle battery, to run an Engel caravan (upright) fridge, and a couple of solar lights. We got a solar panel and made a stand for it. We put the panel out when we stopped in the afternoon, and left it facing east ready for the morning, and even though the sun was soon off it, it still charged up the battery much quicker than when driving. We couldn't readily mount the solar panel on the roof as it was a small windup van. We turned the fridge off at night if the night was cool - as much for a quiet night as for the battery levels. On our experience, i don't think running the car for a while each day would be enough. Depending on your camping outfit, you may be able to mount a solar panel on the roof of your vehicle. It was well worth the money for efficiency and peace of mind.
Motherhen

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AnswerID: 150474

Reply By: 4145derek - Tuesday, Jan 24, 2006 at 07:31

Tuesday, Jan 24, 2006 at 07:31
Hi Damien,

It is best NOT to use the main battery for the fridge.

5 days is 450 amp hours, about 5 full deep cycle batteries worth of power.

You would need about 15 hours driving time to just charge the fridge battery.

If you have a good second battery set up and drive for 3 hours a day you should be fine.

How do you intend to charge the 2nd battery ?

I manufacture 12v power packs that can take up to a 340mm wide battery with built in controller / isolator, surge protection and full set of cables.

Best to run your fridge of this unit and not your car battery.

Opp-lock also do one now similar to mine in a big grey box. Check last months 4wd mag.

Regards Derek

AnswerID: 150504

Follow Up By: gramps - Tuesday, Jan 24, 2006 at 09:59

Tuesday, Jan 24, 2006 at 09:59
Derek,

'5 days is 450 amp hours'

Interested in how you arrived at that figure?

Regards

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Follow Up By: Member - Omaroo (NSW) - Tuesday, Jan 24, 2006 at 10:08

Tuesday, Jan 24, 2006 at 10:08
...by running a 360 litre Westinghouse 2-door upright with ice-maker in the trailer....

;)
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Follow Up By: 4145derek - Tuesday, Jan 24, 2006 at 10:13

Tuesday, Jan 24, 2006 at 10:13
40deg heat, fridge in rear of 4wd.

3 - 4 amps per hour x 24 hours x 5 days

TOTAL 360 to 480 amp hours.

Do you sums before making remarks.
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Follow Up By: gramps - Tuesday, Jan 24, 2006 at 10:16

Tuesday, Jan 24, 2006 at 10:16
hahahahaha my thoughts exactly. Trying to reconcile Derek's statement with Damien's post. A 35l fridge using a consistent 3 to 4 amps/hour ? Sorry, I'd be looking for a more efficient fridge as a starting point.

But then again, I'm not a sparkie/fridgie, hence the question :))))
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Follow Up By: Member - Omaroo (NSW) - Tuesday, Jan 24, 2006 at 10:18

Tuesday, Jan 24, 2006 at 10:18
Hey Derek - pardon moi!

My 40L fridge never runs for 24 hours straight - even during the 47 degree days we had in Cooma over New Year. It cycles periodically - and doesn't draw anything near 4 amps while doing so. I have measured with Fluke shunted ammeter whislt cycling, and it reported 2.1 amps draw. Even during the heat of the day it cycled for around 2 minutes every 10. At night it maybe ran three times an hour for a couple of minutes.

I suppose you are trying to convince people to buy your wares by claiming absolute worst cases.... but tell you what - go buy a better fridge than the one you are making an example of! ... or better still...keep the door shut!
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Follow Up By: 4145derek - Tuesday, Jan 24, 2006 at 10:20

Tuesday, Jan 24, 2006 at 10:20
360L ! Well that would need my Honda eu20 and at 10h on 4 L that would be 48 L of Unleaded.

But that depends on if the door is open ! or how much ice you want.

:-)
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Follow Up By: gramps - Tuesday, Jan 24, 2006 at 10:24

Tuesday, Jan 24, 2006 at 10:24
Derek,

So in the end what are you saying? Your 450 amp hours is a worst case scenario for an inefficient fridge? Or what?

Regards
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Follow Up By: 4145derek - Tuesday, Jan 24, 2006 at 10:36

Tuesday, Jan 24, 2006 at 10:36
In the end I am saying, you can't be stuck with a main starting battery.

Worst case, worst fridge, it does not matter.

People die in the outback when their cars breakdown.

I don't sell batteries, Try Repco, Supercheap, Marshall etc.

I only sell the electrics and kits.

Regards Derek.
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Follow Up By: gramps - Tuesday, Jan 24, 2006 at 10:40

Tuesday, Jan 24, 2006 at 10:40
Derek,

Thanks for clearing that up. I agree with you entirely about the starting battery and it's possible implications.

Regards
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Follow Up By: Member - Omaroo (NSW) - Tuesday, Jan 24, 2006 at 10:48

Tuesday, Jan 24, 2006 at 10:48
For what it's worth - I also agree. My tourers both have managed dual battery systems, and I wouldn't go anywhere without them.

Point of the matter is.... that very few people on this forum (as a percentage of contributors) actually go to anywhere so remote where battery performance is actually a life-threatening consideration.....especially by themselves.
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Follow Up By: Member - Des - Tuesday, Jan 24, 2006 at 12:08

Tuesday, Jan 24, 2006 at 12:08
Mightn't the recharge time depend on the type of deep cycle battery used? An AGM battery should recharge from the car a lot quicker than other types. More so if the wiring to the auxiliary socket is upgraded.
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Follow Up By: 4145derek - Tuesday, Jan 24, 2006 at 12:14

Tuesday, Jan 24, 2006 at 12:14
Quite right. Now you understand what I am saying.
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Follow Up By: Member - Omaroo (NSW) - Tuesday, Jan 24, 2006 at 13:58

Tuesday, Jan 24, 2006 at 13:58
Des - the original question asked whether or not a single battery installation would do what he wanted. Given that a cars primary battery is a cranking type - deep cycle doesn't come into it... so recharge time is purely dependant on your alternator's output. In my Jeep's case - 140amps.
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Follow Up By: Member - Des - Tuesday, Jan 24, 2006 at 14:20

Tuesday, Jan 24, 2006 at 14:20
Omaroo,
Fair enough. Sounds like your single battery system in the Jeep works fine for you.
One thing that is obvious here is that there is no "one size fits all" solution.
Cheers,
Des
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Follow Up By: Member - Omaroo (NSW) - Tuesday, Jan 24, 2006 at 14:23

Tuesday, Jan 24, 2006 at 14:23
True mate.

Don't get me wrong though... both of my GQ's have dual battery systems that run 100+ A/H deep cycles. Winch runns off the cranking batteries. Everything else off the D/cycle including fridge, radios, spots and other stuff....
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Reply By: Member - Omaroo (NSW) - Tuesday, Jan 24, 2006 at 08:23

Tuesday, Jan 24, 2006 at 08:23
Damien - I have an rather larg-ish 105A/H cranking battery in the Jeep and successfully run an EvaKool RF47DT fridge for three days - and being a diesel (requiring a heck of a lot of oomph to start) it cranks over no problems. I wouldn't go more than that - and even then I keep checking the battery with a multimeter. I do drive around for at least an hour a day.

I run a dual battery system in my other fourbies.

I suppose that if you have a battery large enough it's not a huge problem. If you drive around each day (not merely idle) then you're just fine.

5 days without a drive - certain problems! Time for a duAl (duel is a gun fight) battery system....and an hour's drive every couple of days.
AnswerID: 150509

Reply By: desert - Tuesday, Jan 24, 2006 at 09:46

Tuesday, Jan 24, 2006 at 09:46
Damien, you could short-circuit (Pun intended) all this unnecessary work and just buy a Battery Pack, or power Pak, whatever you want to call it. Charge it via cig. lighter and run fridge from this. It is nothing more than a battery in a box anyway with convenient plugs and sockets included. But you will need to drive everyday to recharge it, at least 3 to 4 hours driving time.
AnswerID: 150518

Reply By: tdv - Tuesday, Jan 24, 2006 at 09:50

Tuesday, Jan 24, 2006 at 09:50
I have done this several times. Charge my 100 amp/hr battery before I leave home. Run the fridge from the car while driving and run from the spare battery while stopped. I can get 3 days from the spare battery on my 60l waeco on number 3 setting in 25-26 degree temp. I have run the fridge overnight from the car battery and if you are worried just set the auto cut out to Medium to ensure you don't drawdown the fridge too much. Best bet would be to run the fridge at home from your spare battery and see how long you can get.

Good luck

Terry
AnswerID: 150520

Reply By: howie - Tuesday, Jan 24, 2006 at 13:34

Tuesday, Jan 24, 2006 at 13:34
there are too many variables but,
before i had dual batts-(assuming low draw fridge and good battery to start with)
1) 3 weeks canning - no problem - moving nearly everyday,fridge on max during day and cold enough to switch off at night
2) 3/4 days was about the limit in summer with hot days and nights plus not moving much
you have to work out anything in between.

in the short term you could take a fully charged spare batt with a fused female cig socket to run the fridge at night, that way you would sleep better.
or, make a really long lead for the fridge and plug it into somebody else's car at night when they are not looking.
AnswerID: 150543

Follow Up By: Steve - Tuesday, Jan 24, 2006 at 20:25

Tuesday, Jan 24, 2006 at 20:25
"make a really long lead for the fridge and plug it into somebody else's car at night when they're not looking"

mate, you're a belter. Why didn't I think of that;>)
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Reply By: Damien - Tuesday, Jan 24, 2006 at 13:46

Tuesday, Jan 24, 2006 at 13:46
Thanks for all the feedback guys. I think I'm going to go for a good quality "Battery Pack" option for ease, convenience and portability.

Thanks again :-)
AnswerID: 150548

Follow Up By: Member - Des - Tuesday, Jan 24, 2006 at 14:41

Tuesday, Jan 24, 2006 at 14:41
Ah, Damien, but which battery pack? Waeco? Engel? Home made? AGM or wet cell? That's another thread's worth!

Here's my two bob's worth.

AGM batteries have lots of advantages: see Val Rigoli's discussion. And they are not tooo expensive. He has, for example, 60amp/hr battery for $170 or 80 amp/hrs for $220. Stick it in a good box (with connectors etc) and you have a good pack for $250 or $300. Only downside is weight: 60 a/h weighs 18kg, 80 a/h 28kg. Anything bigger and you should be in the weightlifting team.

You could instead get two smaller ones: eg 45 a/h $139 ea, 15kg. You can then have one running the fridge at your campsite and the other charging in the vehicle when you go off for the day.

Interesting to note that Waeco have gone this route. They used to sell Blue Apple Thumper etc, some of which were huge, v heavy and $600+. Now they have only one: Coolpower 36, 36a/h. Compact and not too heavy (13kg). If that's not enough, the idea is that you get two and put them together or charge one and use the other. But at $349 rrp ...!!.... the do it yourself battery box jobbies are looking more attractive.

Cheers,
Des
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Reply By: Outbacktourer - Tuesday, Jan 24, 2006 at 17:32

Tuesday, Jan 24, 2006 at 17:32
Yes it is possible.

Since having our fridge (Engel 39) for 6 years we have never used it off anything other than an N70 starter battery.

Use a $20 Projecta low voltage cut-out in circuit for safety. A battery in a box (same terminal configuration as truck) or a jump starter pack would be a good backup if travelling solo or remote. Also powers lights if vehicle goes for milk/bread/grog.

There is no doubt that having a dual battery system is popular but IMHO not a wise spend of dollars for you or 90% of those who have it.
AnswerID: 150589

Reply By: ferris - Tuesday, Jan 24, 2006 at 18:25

Tuesday, Jan 24, 2006 at 18:25
Hi Damien, Many of the replies so far are fairly expensive, and you are budget conscious. That's fair enough. I think most people on this forum have started with the basics and built up from there. It's amazing what you can do with a little bit of ingenuity. As others have already stated one battery hasn't a hope of doing what you are hoping to achieve. Perhaps the most cost effective way to get things to work is to throw a bag of ice in and only use the fridge sparingly, and when the engine is running. Other option is a $99 generator from Bunnings, even though we all hate them. Cheap battery systems don't work, and you are better off waiting until you are better positioned to get a good one. By the way, your local autoelec can probably come up with a good system far cheaper than the brand names. It may not have the bells and whistles, but it will work just as well.
Cheers Ferris
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Reply By: Exploder - Tuesday, Jan 24, 2006 at 19:20

Tuesday, Jan 24, 2006 at 19:20
Arr. Have you got a generator?? Because then your problem is solved.

We did this on one trip, we did have duel batteries in a patrol but the AUX battery was stuffed and we neglected to check it before we left.

So what we did was at night we would run the fridge on a High setting for 4Hrs or so on the Generator along with a few lights, then in the morning when we got up gave it a run for a 1or2 Hrs off the Battery, Or left it going until the Low voltage Cut out came on if we forgot it was running and we left for the day in one of the another 4WD.

Then the next day we would take the Patrol out for a run to get the charge back into the AUX Batt, This would work for you too but probably best not to forget the fridge is running, you could also top the battery up with the genny and a batt charger if going for a run every day or leaving the car idling for 30 or so minutes isn’t you thing

This worked for us but the longest we were in one spot was 3day's.

If you don’t have a generator then think about this a good duel set up will cost you $750 a good generator isn’t much more and it will serve you well for the next 15+ years, that’s how old mine is it’s a hand me down and it’s quiet, small and uses bugger all fuel.

AnswerID: 150614

Reply By: Willem - Tuesday, Jan 24, 2006 at 19:50

Tuesday, Jan 24, 2006 at 19:50
This is a non technical reply

I have a dual battery set up with a Century Overlander 700cca cranking battery as the auxilliary. The batteries are run in parallel through a simple $20 solenoid and a switch on the dash. When driving the switch is set to ON and both batteriers get charged. When stopped for the night the switch is set to OFF so that any other power is runnin g off the auxiliiary battery. On starting in the morning the switch is left OFF until the truck has warmed up.

If I stop at 4pm then I let the fridge run till 8pm and then switch it off.
I have a 32lt Engel fridge in a jacket which draws 2.7amps/hour

Cost? Do it yourself.

Battery $140
Battery holder ARB $90
Solenoid $20
Some wires and cables $10 = $260

Make the battery holder yourself and save $90 Cost = $170
AnswerID: 150624

Reply By: Mainey (WA) - Tuesday, Jan 24, 2006 at 20:10

Tuesday, Jan 24, 2006 at 20:10
Damien, your original question is; "Is it possible, to effectively run a Waeco CF-35 on just the one battery providing it is managed well?
By running the vehicle every day or so if staying in the same spot for say five (5) days. Would it work if I had another battery handy and used that when required and simply charged it as I go"

Yes, the key is "managed well" you should be able to run the fridge from the crank battery and by driving "every day" as you have stated, the crank battery would then be recharged.
The 'spare battery' should be used only as an emergency back-up, for when and if the original failed to start the car, then you would have to recharge the original by some serious driving to get charge back into it.
The spare should be periodically recharged if going away for long periods, but that's not what your post is about - or is it??

AnswerID: 150630

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