Powering 40Ltr Engel Fridge

It's always a bad day in the bush when people are running generators Geeko. Ever heard of a second battery and a fluoro light? Or even moonlight or firelight? Or even darkness?

Disagree with you Aandy,

A generator (and most are very quiet these days) used responsibly at appropriate times will cause less noise than flies.

The gentle hum of a four stroke generator or the rhythmic popping of a two stroke at the right time of day is far less irritating than the intermittent buzz of flies or the sound of some clown's blaring music.

I spend some time at Gembrook, Vic, which is a haven for motor bikes. They make plenty of noise but it is their bush to enjoy in their way as much as I enjoy it in mine.

Tolerance is the key. Allowing something else in the bush to spoil your experience just isn't worth it.

I don't use a genny because I have found my new love, solar. Not because it's quiet, just because it's convenient.

Anyway, each to their own.

Cheers,

Jim

Just for the record, I do not use the genny around other people or in camp grounds although they really are quiet, and I do have two fluoro lights and a gas lantern, we like the quiet as much as anyone else, however I do not like the idea of a battery run fridge when in the thick of it, even on my two battery system, and when alls said and done I at least offered an alternative, and not just my own two cents worth.

gecko i was told from bunnings not to run the the fridge or anythink sensitive off of the the generator direct as they give out spikes

Wrong jim. Tolerance is not the key. CONSIDERATION for others is the key. Blaring music, loud motorbikes or other inconsiderate behaviour do not make the sound of a generator any less intrusive. They only add to it! Caravan parks in towns and cities have strict limits on sound emissions but out in the bush where we are supposed to be able to "get away from it all" we have to put up with generators, motorbikes, chainsaws, and "heroes" trying to get through bog holes or 45 degree inclines. After my last trip to the Wonnangatta Station I was almost glad to get back to the peace and quiet of Melbourne. I am so happy that I have memories of being there in the sixties when the only people encountered there were true bushmen who enjoyed the simple pleasures of a yarn around the camp fire and the light of the moon and stars. Sad to say the modern vehicle has made it possible for all the sooks and softies who "must" have warm milk on their special high fibre, low cholesterol cereal and couldn't survive without a chilled chardonnay before dinner.

Aandy,

Wrong is a very strong word. I think you mean wrong in your opinion.

The bush belongs to all Australians to use it as they see fit, that is as long as they don't destroy it.

How someone enjoying a glass or two of wine, or eating All Bran with low fat milk, affects your enjoyment of the bush eludes me.

Mate, settle down, it's not up to you to decide how life in the bush SHOULD be. It's a personal choice.

I'm neither wrong nor right. Neither are you.

Cheers,

Jim.

One other consideration. If the batt pack is 17 amps you should not drain it completely or it will be stuffed in no time. Keep it to 50% if you want it to last; effectively 8.5 amps, bloody near useless for a fridge.

Cheers,

Jim.

Sorry to rain on your parade here but the maths above is not quite right.

A 40 litre Engel draws about 2 amps when its running.

Whether it's on freeze or chill won't change the current flowing in the circuit, it will remain around 2 amps.

What changes the length of time the battery lasts for is how long it draws 2 amps for.

Ampere Hours is a measure of current over time.

If the fridge is on freeze and it's a hot day and you forgot to close the lid so it runs for the whole hour it will use 2 Amps x 1 hour for that time.
This equals 2 Ah or Amp hour. At 2 Ah it will run of a 20 Ah battery for a bit under 10 hours (20/2 = 10) as the process isn't 100% efficent.

If the fridge is on chill with the lid closed and runs for 15 minutes in the hour (0.25 of the hour) then the usage will be 0.25 x 2A x 1 hr = 0.5 Amp hour.

In the second case it will run off a 20 Amp hour battery for 20/0.5 = 40 hours (a bit less again due to efficiency)

My Engel 40 running at about 4°C will run off my 75-80 Ah secondary battery for 3 days up the river without the vehicle running. Therefore it's easily going to last for 24 hours off a 20-25 Ah battery.

Lastly it is not the remaining Ah capacity that stuffs batteries, it is the voltage that they are discharged down to. And then it depends if they are deep cycle or not as to whether that's a problem.

A 20 Ah battery will give you 20Ah (or more usually off a new battery as they rate conservatively generally) before it gets to the stage where the voltage is getting low and you can go a little past that point before it gets to battery stuffing stage but not much, otherwise they would call it a 10Ah battery (and it's case and price would be half the size).

Now a suggestion. Your vehicle battery is probably between 60-80Ah. You probably have an 80 Amp alternator on it. Until you can afford to buy a dual battery setup you could run your fridge at around 1 - 2 on the dial or 4°-6°C and use about 12-18Ah of your capacity each day depending on duty cycle of the compressor (ie how much it runs in the hour) and top up by running the vehicle for a while each day.

Let's say conservatively without anything else (lights, stereo, air con fan) running at idle or just above you can probably get 10-20A of charge from your alternator. If the battery is being drained 20Ah per day, an hour running would top it up. But realistically the if you ran your vehicle for 20 minutes a day and camped in the same spot 3 days you won't have a problem starting it on day 3 to move on. THAT IS PROVIDING YOUR BATTERY WAS IN GOOD NICK TO START WITH! Get it checked before you go.

A good solar panel on the roof (pack it up before you drive off) will just about run the fridge on a sunny day and use nothing from the battery too.

Dave

Quite wrong geo. the fridge may be drawing 2 amps when it is running but the important figure is amp/hours. As a fridge on a very cold day it may consume 1amp per hour. As a freezer on a hot day it may consume 5amps per hour. This was the original question as to how long it would run.

With all due respect Geo,

Your post is grossly innaccurate on many grounds and is no way to treat any battery that you may expect reasonable life from.

As for your theory of current draw, I would seriously question that. There are many sights on the net that would differ from your views.

They are written by farmore knowledgeable people than you or me.

As I said, no disrespect intended.

Cheers,

Jim.

Quote:It will provide 17amps for 1 hour or 1 amp for 17 hours. Thus I can ise my CPAP (antin-snore machine) for 2 nights sleeping 7 hours and drawing about 1 amp per hour. You do the maths yourself for the fridge. Using it as a freezer i would expect a draw of 5 amps per hour so 2 maybe 3 hours would see the Jump start out. End Quote.

Aandy, if you draw 1 amp per hour you are using 1 Ah of your batteries capacity. If you do it from a 1 Ah battery it will be flat in an hour. You will take 20 hours to flatten a 20 Ah battery.

A fridge (or any device for that matter) that only draws 2 Amps with the compressor on can never use 5 amps per hour.

Jim,

Without getting personal you have no idea what I am qualified as so please don't imply I have no idea what I'm talking about.

If what I have described is unclear or you have criticism to make, please provide the figures or detailed explanation to explain to all the others on this very public forum just exactly why I am wrong, as opposed to criticising without any suggestion of what is correct.

No disrespect taken, but I wasn't always an Ambo & I've got no idea what you are qualified as either.

Dave

Geo,

A lot of what you have said is at complete odds with what the likes of Collyn Rivers have to say.

Also different to what is said on sites such as this;

http://www.windsun.com/Batteries/Battery_FAQ.htm#AGM,%20or%20Absorbed%20Glass%20Mat%20Batteries

Cheers Mate,

Jim.

Hi Jim,

Great site, I've bookmarked it. Bit complex for some people but I found it quite good.

This only leaves me with one question; it says what I said. The maths used for calculating Ah rates is exactly the same. I didn't specify 20hour rates for Ah cap of batteries as I was trying to give a reasonably simple explanation for a stop gap solution until they get a dual battery system but regardless of that; what I suggested is that 20Ah (be it 2 A for 10 hrs or 20A for 1 hour) for approx 20 hrs will flatten a 20Ah battery to it's safe end point. (Not as has been previously suggested kill the battery by taking it past the safe end point, which incidently is about 10.5 to 10.75 volts depending on battery construction.)

In previous posts recently I have recommended float charging as does the site referenced, and discussed uses and supply sources of cheap gel cells.

I didn't get into specifics of different constructions as it wasn't necessary.

What I have said in my original post is reinforced by the web link you have posted.

I'd be happy to help you solve any differences you may feel exist between the three (mine, yours & theirs) I'd be happy to help but maybe this is now best taken off line by sending a PM. I would even give you a ring if you PM a phone no. and suggest a time.

If you find something that I have overlooked I will happily print a correction or retraction.

Regards

Dave

Hi again Paul and Cathie, I agree with Patrol22.

If your not planning to stop more than 3 or 4 days in one spot, one large deep cycle auxiliary battery or even two small deep cycle batteries will probably meet most of your requirements and works out much cheap that most other options.

Solar panels can be beneficial for longer stops but cost heaps more than an extra large battery.

From reading through different forums, generators are band from a lot of parks now so this could be a problem.

It still all comes down to your intended use.
Cheers