Fridge/Freezer choices

[chris w]

Hi There

 

Live aboard for 1 year - now only 8 months a year.

If I was not moving I would run my engine for around 2 hours every day to heat the water and charge the battery's.

I think even Chris w would agree, that with a good charge controller and good battery's it should not be a problem, it isn't for me.

Replacing gas bottles has almost become a thing of the past.

 

Alex

 

Well if you have a fridge and TV and normal use of lights, pumps etc, you will consume about 100AH per 24 hours. To replace this needs around 150AH pumped back in (due to batery physics).

 

Let's assume you have an 80A alternator with a charge controller. You will get about 50A max out of it at NB revs, but not continuously due to the battery terminal voltage rising. In 2 hours you will probably put back somewhere in the region of 50AH (after allowing for charging physics)......... only about half that required based on the above consumption.

 

So your batteries will start off the next day with a deficit of about 50AH. This process will be cumulative over a few days. You would really need to run your engine for about 5 hours each day to get your batteries back up to full charge IMHO.

 

Chrs

[Orphiel]

Can you clarify "hammers".?

 

If you have a typical 3x110AH batteries set-up the actual (Peukert) capacity is 765AH. You can use half of this without damaging the batteries, so say 400AH is available. A 12v fridge will draw 4A and will be ON about 50% of the time. So over a day the total capacity used will be around 70AH (Peukert corrected). Thus the fridge will only sap about 20% of your batteries' available capacity.

 

If the fridge is "hammering" the batteries, then either its an old (higher current) fridge or your batteries are cream-crackered and need to be replaced.

 

Chris

 

Hammers as in they are full of lovely charge when I plug it in, then about a day or two later everything is flashing red and stopping working, even with the couple of hours running the engine. I don't really have longer than that to run it as am at work all day. I also keep meaning to get some kind of idiot's guide to batteries and electric, as I do find your handy calculations really difficult to understand, appreciated though they are.

 

Hmm. I will check what kind of fridge it is, I do suspect it's an older one, which might be the problem. You say it should only be on 50% of the time, well mine is definitely on all the time, to the point of freezing things inside to the back and making ice, so I suspect it stays on all the time as well. Might that be the problem? I must confess I am not as rigorous with my charging regime as I could be, but then I just stopped using the fridge and have barely noticed all winter, as I don't use many foods that need fridging. Would be handy in the summer though.

 

Cheers everyone for ideas on how much gas they use also, I might look into that.

 

Meg

[steelaway]

Well if you have a fridge and TV and normal use of lights, pumps etc, you will consume about 100AH per 24 hours. To replace this needs around 150AH pumped back in (due to batery physics).

 

Let's assume you have an 80A alternator with a charge controller. You will get about 50A max out of it at NB revs, but not continuously due to the battery terminal voltage rising. In 2 hours you will probably put back somewhere in the region of 50AH (after allowing for charging physics)......... only about half that required based on the above consumption.

 

So your batteries will start off the next day with a deficit of about 50AH. This process will be cumulative over a few days. You would really need to run your engine for about 5 hours each day to get your batteries back up to full charge IMHO.

 

Chrs

 

Thanks for that Chris

 

Its a 110 amp alternator and a sterling charge controler and I really dont have a problem.

I might run the engine a bit longer from time to time and I do use other stuff sparingly - like turning of lights.

Do you think my 6v semi traction battery's are a factor?

 

Alex

[chris w]

Thanks for that ChrisIts a 110 amp alternator and a sterling charge controler and I really dont have a problem. I might run the engine a bit longer from time to time and I do use other stuff sparingly - like turning of lights.Do you think my 6v semi traction battery's are a factor?Alex

 

If it's a 110A alternator, you will get about 80A into the batteries (initially). Over 2 hours I would estimate you are putting back around 120AH which will mean about 85AH actually absorbed back into the batteries. If you are being parsimonious with your use of electrics, then you may not be using the typical 100AH per day and the 85AH may be just about balancing what you do use.

 

But it must be a fine line......... Chris

 

Hammers as in they are full of lovely charge when I plug it in, then about a day or two later everything is flashing red and stopping working, even with the couple of hours running the engine. I don't really have longer than that to run it as am at work all day. I also keep meaning to get some kind of idiot's guide to batteries and electric, as I do find your handy calculations really difficult to understand, appreciated though they are.Hmm. I will check what kind of fridge it is, I do suspect it's an older one, which might be the problem. You say it should only be on 50% of the time, well mine is definitely on all the time, to the point of freezing things inside to the back and making ice, so I suspect it stays on all the time as well. Might that be the problem? I must confess I am not as rigorous with my charging regime as I could be, but then I just stopped using the fridge and have barely noticed all winter, as I don't use many foods that need fridging. Would be handy in the summer though.Cheers everyone for ideas on how much gas they use also, I might look into that.Meg

 

Some questions Meg:

 

1. How do you know the batteries are fully charged? How are you gauging that?

 

2. What size domestic battery bank do you have? eg: 3 x 110AH or what?

 

3. Can you hear the fridge motor running all the time? If it is, then over 2 days, that will heavily punish the batteries.

 

4. Do you run the normal lights, pumps, TV etc as regards other electrics.

 

5. What kind of charger do you have (eg: Make, how many amps, is it a multistage charger or a Halfords special?)

 

Chris

Edited February 29, 2008 by chris w

[blackrose]

If you have a shore mains connection, then a 12v fridge will be running from the charger, if it is a multistage variety, and not from the batteries. The charger acts as a 12v powerpack and doesn't even need the batteries connected to function in this mode. It will run the whole domestic side of the boat all the time you're connected to shore.

 

Chris

 

Yes, if you're on shore power fridges shouldn't be an issue, but then with a dual use 12v/mains fridge why not just run it off the mains?

 

I suppose it makes no difference really...

 

Mike

Edited February 29, 2008 by blackrose

[chris w]

Yes, but if you're on shore power & have a dual use 12v/mains fridge then why not just run it off the mains?

 

I suppose it makes no difference really...

 

Mike

 

C'est vrai mon ami.....

[steelaway]

Hammers as in they are full of lovely charge when I plug it in, then about a day or two later everything is flashing red and stopping working, even with the couple of hours running the engine. I don't really have longer than that to run it as am at work all day. I also keep meaning to get some kind of idiot's guide to batteries and electric, as I do find your handy calculations really difficult to understand, appreciated though they are.

 

Hmm. I will check what kind of fridge it is, I do suspect it's an older one, which might be the problem. You say it should only be on 50% of the time, well mine is definitely on all the time, to the point of freezing things inside to the back and making ice, so I suspect it stays on all the time as well. Might that be the problem? I must confess I am not as rigorous with my charging regime as I could be, but then I just stopped using the fridge and have barely noticed all winter, as I don't use many foods that need fridging. Would be handy in the summer though.

 

Cheers everyone for ideas on how much gas they use also, I might look into that.

 

Meg

 

Hi There

 

Sounds like your fridge is knackerd or at least the thermostat.

 

Alex

[sueb]

Hi Sue

 

We swopped our gas fridge for a 240v one.

We could not believe how long our gas bottles last now - probably 6 months.

Plus we have less condensation and a freezer that does.

We are glad we changed.

 

Alex

£re you on mains and how often do you run your engine? we go away for at least a week at a time and our batteries would't hold out that time. it is probabaly horses for courses. Sue

[steelaway]

£re you on mains and how often do you run your engine? we go away for at least a week at a time and our batteries would't hold out that time. it is probabaly horses for courses. Sue

 

Hi Sue

 

No I am never on mains (the mains lead is still in its bag after 3 years!)

It really sound like you need a better charging system for your battery's, its a common problem.

If you read the details from Chrisw - you should be able to meet that criteria.

 

Alex

[Eastern]

If you check the Miele web site

 

www.miele.co.uk

 

An undercounter size A++ rated larder fridge uses 83.9 KWh/annum and a icebox type A++ uses 124.1 KWh/annum.

These are, of course, 240v only.

[Yoda]

Sounds like a very good case for photo cells being installed. Anyone not having time to charge their batteries must have these fitted otherwise the batteries will just die.

[Keeping Up]

If you check the Miele web site

 

www.miele.co.uk

 

An undercounter size A++ rated larder fridge uses 83.9 KWh/annum and a icebox type A++ uses 124.1 KWh/annum.

These are, of course, 240v only.

Which is still about 25% more than a similar-size 12-volt icebox-fridge (assuming the same test conditions by the two manufacturers)

[Eastern]

Which is still about 25% more than a similar-size 12-volt icebox-fridge (assuming the same test conditions by the two manufacturers)

 

Interesting. The A++ energy rating is the lowest (i.e. best) rating of any fridges. The testing regime is independent of manufacturer and is applied to all white goods in the EU to allow a comparison of energy usage between different models.

 

 

On the Shoreline site a 12 v fridge (model RR155W) with freezer compartment running at 12v takes an average 1.3 amps/hour (15.6 W/h). Multiply this up comes to 137 KW/h per annum, and its more expensive than the Miele. The Miele is about 10% more efficient than the 12v Shoreline model.Of course its not an exact comparrison as the Miele is smaller at 131 litres agaist the Shoreline 150 litres. The Miele does however have a 4 star freezing compartment agaist the Shoreline 2 star, and auto defrosting.

http://www.boatfridge.com/index.asp?Col_Ca...mp;productID=81

[Keeping Up]

Interesting. The A++ energy rating is the lowest (i.e. best) rating of any fridges. The testing regime is independent of manufacturer and is applied to all white goods in the EU to allow a comparison of energy usage between different models.

On the Shoreline site a 12 v fridge (model RR155W) with freezer compartment running at 12v takes an average 1.3 amps/hour (15.6 W/h). Multiply this up comes to 137 KW/h per annum, and its more expensive than the Miele. The Miele is about 10% more efficient than the 12v Shoreline model.Of course its not an exact comparrison as the Miele is smaller at 131 litres agaist the Shoreline 150 litres. The Miele does however have a 4 star freezing compartment agaist the Shoreline 2 star, and auto defrosting.

http://www.boatfridge.com/index.asp?Col_Ca...mp;productID=81

It shows that size does matter, I was comparing it (from memory) with the Shoreline RR47 which takes only 0.94 amps, which is about 100 kWh/year (25% more efficient than the Miele). But looking at their site I see that it is slightly smaller than the Miele (97 litres).

[Eastern]

It shows that size does matter, I was comparing it (from memory) with the Shoreline RR47 which takes only 0.94 amps, which is about 100 kWh/year (25% more efficient than the Miele). But looking at their site I see that it is slightly smaller than the Miele (97 litres).

 

And of course the cheap model is built by a German manufacturer with a world wide reputation for quality products, and the other is badge engineered by Shoreline.

[wonderdust]

And of course the cheap model is built by a German manufacturer with a world wide reputation for quality products, and the other is badge engineered by Shoreline.

 

Shoreline also make laboratory and pharmacy fridges as well!

[smileypete]

And of course the cheap model is built by a German manufacturer with a world wide reputation for quality products, and the other is badge engineered by Shoreline.

 

The Miele is not built by Miele but is actually a rebadged Liebherr:

 

http://en.wikipedia.org/wiki/Miele

 

cheers,

Pete.

[David]

Hi

We have an Indel Isotherm with the added electronic gizzmo which turns the fridge on when it senses a voltage over 13.2v and fitted with the "colded plate". So when running the engine or charger to recharge batteries the fridge comes on and freezes the cold plate, this amperage is "free" as Chris has explained above the source of this supply is not from the batteries. In this mode the fridge also drops the temperature down to -14 degrees before cutting out and whilst the voltage remains above 12.7v cuts back in at -6 degrees, when it goes back into normal mode the cold plate acts as a store of cold just like freezer blocks.

When the fridge senses the voltage has dropped back to 12.7v , shortly after ceasing to charge the batteries, it goes back into normal mode and runs the fridge with a cut in at -1 and out at -6 degrees. It can also be switched to standard mode which acts just the same as other 12volt fridges, this mode must be used if conected to a landline and the charger is on 24/7 or you can freeze the whole fridge up. They have this system on fridge freezer models also.

The down side ours which is just a tad larger in the freezer box than a Shoreline is twice the price, but made a massive difference to power comsumption.

Insidentally compressor fridges with a lot of hours running get "tired" compressors which have to work longer to bring the temperature down to whatever setting so have a much higher power consumption.

If looking at Isotherm try Stone boatbuilding (they have a boat fitted with a Isotherm fridge/freezer in this months Waterways World), Tracy gave us a good discount on ours.

david

Edited March 3, 2008 by David