12v versus 230v fridge

[Jwelec]

New to boating! If I had a decent solar array, inverter, battery bank can I run a 230v fridge instead of 12v? Existing fridge is on it's last legs and 230v are much cheaper! Thanks for any advice. John

[mrsmelly]

Mains fridge every time. The new mains kit via a DECENT inverter is a no brainer.

[David Mack]

General consensus is that if you already have a suitable inverter to produce 230V ac from your batteries, it makes little difference to overall power use whether you have a 12V dc or 230V ac fridge. The latter does add inverter losses, but there is so much more choice of mains fridge models that you can choose a more efficient model to offset the inverter losses.

[Jwelec]

Thanks! What would be a decent battery bank in terms of Amp hours using standard lead acid?

[ditchcrawler]

17 minutes ago, mrsmelly said:

Mains fridge every time. The new mains kit via a DECENT inverter is a no brainer.

And the word DECENT is the most important. A crap invertor will use more power in 24 hours than the fridge does. The quiescent  current on mine is so low it doesn't show on my meter.

Edited March 8, 2022 by ditchcrawler

[TheBiscuits]

4 minutes ago, ditchcrawler said:

And the word DECENT is the most important. A crap invertor will use more power in 24 hours than the fridge does. The quiescent  current on mine is so low it doesn't show on my meter.

 

True, but it's worth noting that a well known brand name is not a guarantee of this, it has much more to do with the design of the inverter.

 

My deceased low-frequency inverter would draw over 4A continuously with no load, and the low power seek mode wouldn't switch it out of standby on small loads (phone chargers, radio etc.)

 

My replacement high-frequency inverter draws between 0.7A and 0.8A when not doing any heavy lifting and that's in active standby so small loads still work.  It gets left on 24/7 from March to October, but in the dark months gets more thrifty use.

 

 

 

 

[ditchcrawler]

5 minutes ago, TheBiscuits said:

 

True, but it's worth noting that a well known brand name is not a guarantee of this, it has much more to do with the design of the inverter.

 

100% 

[Tony Brooks]

27 minutes ago, Jwelec said:

Thanks! What would be a decent battery bank in terms of Amp hours using standard lead acid?

 

You tell us what you power audit shows and then we can answer, but that is only the tiniest bit of the requirements. of far more importance what is your charging regime throughout the year.

 

Typically we recon 12v fridges draw between 30 and 50 ah per day and rule of thumb says install four times the battery capacity of the consumption to allow for the loss of capacity so on that basis and without allowing naything to power the other equipment  between 120 and 200 Ah and fully recharge every day.

[OldGoat]

38 minutes ago, ditchcrawler said:

And the word DECENT is the most important. A crap invertor will use more power in 24 hours than the fridge does. The quiescent  current on mine is so low it doesn't show on my meter.

Very little that you do in today's boating world is 'simple'.  I well remember when boating was basic and folks were happy with that.

 

The 'problem' with running a 240v fridge on a 12v boat is not the consumption of power for the inverter and the fridge - it's the power that the inverter consumes while it's waiting for the fridge to run. (quiescent  current above) . You need a very good inverter that consumes verylittle while waiting - and such an animal is quite pricey.

IME inverters with a 'sleep' mode (often) don't react to the fridge switching on. The solution th that issue is a larger battery bank...

 

Edit: - not asked, but if you want reasonable modern comfort, consider a 3/4 height fridge freezer from a good manufacturer (I'm a Liebherr fan). It'll probably consume less power than an under counter unit and you'll have some space for frozen foods / ice for you g & t  and more importantly not having to go shopping quite so frequently.

Edited March 8, 2022 by OldGoat

[Alan de Enfield]

34 minutes ago, Jwelec said:

Thanks! What would be a decent battery bank in terms of Amp hours using standard lead acid?

 

Like all things electric it is not just 'what the appliance takes' it is how do you replace the electricty used.

 

I guess if you have not bought the boat then you do not know if the battery bank adequately supported the existing fridge - if it did, it will support a 240v fridge.

 

The size of battery bank depends on usage of the boat - if you are a liveaboard and moving once a week / once per 2 weeks then I'd suggest that 5x 110Ah batteries should be considered, if you are a leaisure cruiser (weekends and holidays) and will be moving every day then 2 or 3 x 110Ah batteries will be sufficient.

 

ONLY YOU know how demanding you are going to be, if you want a 'gaming PC', microwave, washing machine etc etc, you will need a very different electricity system to someone watching a bit of TV and just charging their phone.

[doratheexplorer]

I'll go against the flow:  I have a decent inverter (Mastervolt) but I'd still choose a 12v fridge every time.  The reason is simple, if my inverter goes pop, I can still console myself with a cold beer.

 

Second hand 12v fridges come up for sale fairly regularly.  I bought my boat with an old and slightly broken 12v fridge, which I sold for £50 and bought a barely used Shoreline fridge for £100. 

[TheBiscuits]

1 minute ago, doratheexplorer said:

Second hand 12v fridges come up for sale fairly regularly.  I bought my boat with an old and slightly broken 12v fridge, which I sold for £50 and bought a barely used Shoreline fridge for £100

 

That's fair enough, but to replace it new would cost about £700. 

 

At which point a more efficient mains fridge for £120 starts looking a lot more attractive - especially if your inverter is always on so the continuous draw is already part of your energy budget.

 

If I had neither a fridge or an inverter (new boat for example) I'd have to think quite a bit which way to go.

 

6 minutes ago, doratheexplorer said:

I'd still choose a 12v fridge every time.  The reason is simple, if my inverter goes pop, I can still console myself with a cold beer.

 

That's not a bad reason, but what do you do if it's the fridge that goes pop?

 

With a mains fridge you can get an alternative delivered tomorrow or even collect one from a shop today.  

 

Having both types for redundancy seems excessive!

[Alan de Enfield]

8 minutes ago, doratheexplorer said:

I'll go against the flow:

 

I'm getting splinters in my bum from sitting on the fence and having one foot in each camp.

 

I have a 230v AC Freezer, and a 12v Fridge (with small freezer compartment)

 

If the inverter goes 'pop' I still have cold milk and ice cream, but, both rely on batteries being kept charged.

[Murflynn]

surprising how many folk never check the secondhand market.

 

a bit like using charity shops, except that in charity shops you often find treasures that you didn't even know you were looking for.  my best buy was a Drizabone wax coat for £25 as good as new.

 

[OldGoat]

6 minutes ago, Murflynn said:

surprising how many folk never check the secondhand market.

 

a bit like using charity shops, except that in charity shops you often find treasures that you didn't even know you were looking for.  my best buy was a Drizabone wax coat for £25 as good as new.

 

I was amazed t'other day to receive an email from my local council offering very good pricces of items that folks had chucked out! (OK they have a scheme where they collect used items in good condition and advertise them on the council's website). 

[doratheexplorer]

17 minutes ago, TheBiscuits said:

 

That's fair enough, but to replace it new would cost about £700. 

 

At which point a more efficient mains fridge for £120 starts looking a lot more attractive - especially if your inverter is always on so the continuous draw is already part of your energy budget.

 

If I had neither a fridge or an inverter (new boat for example) I'd have to think quite a bit which way to go.

 

 

That's not a bad reason, but what do you do if it's the fridge that goes pop?

 

With a mains fridge you can get an alternative delivered tomorrow or even collect one from a shop today.  

 

Having both types for redundancy seems excessive!

If the fridge goes pop I'm buggered either way.

 

I don't leave my inverter on all the time.  Only put it on when I need to.

 

[beerbeerbeerbeerbeer]

2 hours ago, TheBiscuits said:

 

That's fair enough, but to replace it new would cost about £700. 

 

At which point a more efficient mains fridge for £120 starts looking a lot more attractive - especially if your inverter is always on so the continuous draw is already part of your energy budget.

 

If I had neither a fridge or an inverter (new boat for example) I'd have to think quite a bit which way to go.

 

 

That's not a bad reason, but what do you do if it's the fridge that goes pop?

 

With a mains fridge you can get an alternative delivered tomorrow or even collect one from a shop today.  

 

Having both types for redundancy seems excessive!

This is the dilemma I keep going through; should I spend my money on getting a decent inverter so I can power a 230v freezer that I can pick up reasonably cheap? Or should I spend on a good quality 12v freezer saving money on the need to buy an inverter?

And if I get an inverter then I should go the whole way and get the very best I can afford so I can use power tools too?

personally I want to stick with 12v all the way for simplicity

I would expect solar panels, combined with driving the boat, would provide enough power most of the year to keep batteries charged.

In the winter a fridge and freezer may not be needed so much so one or the other (or both) could be switched off.

 

I thought 12v freezers and fridges used more like 25Ah per day??
So one of each would draw perhaps around 50Ah per day.

Am I well out on this?

 

to add: just checked some figures I had done awhile back and I worked it out to be about 120ah per day to run both a 12v fridge and 12v freezer.

would that be closer ?

Edited March 8, 2022 by Goliath

[Alan de Enfield]

6 minutes ago, Goliath said:

I thought 12v freezers and fridges used more like 25Ah per day??
So one of each would draw perhaps around 50Ah per day.

Am I well out on this?

 

A very good quality, proper marine 12v fridge cost towards £1000 may use 25Ah per day. My £700,  80 litre Dometic uses 30Ah per day but the more you open the door the more leccy you will use.

 

A freezer will use a fair bit more than a fridge as it tends to be working much harder having to get the temperature down to -18C, whilst a fridge is only +5C. My 230v AC 'work-top' sized (£80) freezer uses around 50Ah per day - again depending on number of door openings and the amount of frozed food inside.

 

If you budget on 100Ah per day for both Fridge., freezer and inverter losses you should be on the 'high' side (safe-side)

[beerbeerbeerbeerbeer]

4 minutes ago, Alan de Enfield said:

 

A very good quality, proper marine 12v fridge cost towards £1000 may use 25Ah per day. My £700,  80 litre Dometic uses 30Ah per day but the more you open the door the more leccy you will use.

 

A freezer will use a fair bit more than a fridge as it tends to be working much harder having to get the temperature down to -18C, whilst a fridge is only +5C. My 230v AC 'work-top' sized (£80) freezer uses around 50Ah per day - again depending on number of door openings and the amount of frozed food inside.

 

If you budget on 100Ah per day for both Fridge., freezer and inverter losses you should be on the 'high' side (safe-side)

So I am in the right region with my corrected figure of 120ah for both.

 

I’ve a 2 way fridge which came with the boat.

and I’m now looking to buy a 95L 12v freezer, costing £525 which reckons ; Power Consumption:         1.8 Avg.AH/hr (12v)

 

 

 

[Tony Brooks]

1 minute ago, Goliath said:

Power Consumption:         1.8 Avg.AH/hr (12v)

 

That works out at about 43 Ah per 24 hours so 30 to 50Ah per day is about right.

[Alan de Enfield]

4 minutes ago, Tony Brooks said:

 

That works out at about 43 Ah per 24 hours so 30 to 50Ah per day is about right.

 

I bet that is the 'laboratory testing' where the door is not opened for the duration of the test, & no 'room temperature food' is put in.

 

"Perfect conditions"

 

 

You could run your engine (or plug into a shoreline) for a long time before you have spent that additional £400 over the price of a 230v (better insulation rated) freezer.

[doratheexplorer]

16 minutes ago, Goliath said:

So I am in the right region with my corrected figure of 120ah for both.

 

I’ve a 2 way fridge which came with the boat.

and I’m now looking to buy a 95L 12v freezer, costing £525 which reckons ; Power Consumption:         1.8 Avg.AH/hr (12v)

 

 

 

Prepare to use a fair bit more than that though.  That figure is under ideal circumstances (ambient temperature, not opening the door).  If the ambient temp is high, your fridge can easily use twice that amount.

40 minutes ago, Goliath said:

This is the dilemma I keep going through; should I spend my money on getting a decent inverter so I can power a 230v freezer that I can pick up reasonably cheap? Or should I spend on a good quality 12v freezer saving money on the need to buy an inverter?

And if I get an inverter then I should go the whole way and get the very best I can afford so I can use power tools too?

personally I want to stick with 12v all the way for simplicity

I would expect solar panels, combined with driving the boat, would provide enough power most of the year to keep batteries charged.

In the winter a fridge and freezer may not be needed so much so one or the other (or both) could be switched off.

 

 

If you don't need an inverter, don't get one.  In your situation, I'd get a 12v fridge and a small genny for the odd occassion I needed 240v (like power tools).

 

Think really hard about whether you really need a freezer though.  They will use twice the power of a fridge, and maybe even more important - you have to keep them on all year round.  A fridge can go off in the winter and food keep outside in a box.  This is VERY helpful when your solar is doing next to nothing.  Running a freezer 24/7 in winter will likely cost so much that it's really not worth it.  You'd save money by buying frozen food and chucking away what you don't eat straight away (not that I'm advocating that).

Edited March 8, 2022 by doratheexplorer

[beerbeerbeerbeerbeer]

26 minutes ago, Tony Brooks said:

 

That works out at about 43 Ah per 24 hours so 30 to 50Ah per day is about right.

👍

 

in theory then ;

allowing 120ah per day for a fridge and a freezer,

and with 3 batteries giving 330ah,

I should never go below 2 thirds of my power, or 60-70%

IF I fully charge my batteries everyday.

 

And there’s the big IF

the tricky part for me to work out is how long it will take to put the charge back in.

But with 200W solar panels and my engine it shouldn’t be a problem...

Edited March 8, 2022 by Goliath

[beerbeerbeerbeerbeer]

15 minutes ago, doratheexplorer said:

Prepare to use a fair bit more than that though.  That figure is under ideal circumstances (ambient temperature, not opening the door).  If the ambient temp is high, your fridge can easily use twice that amount.

If you don't need an inverter, don't get one.  In your situation, I'd get a 12v fridge and a small genny for the odd occassion I needed 240v (like power tools).

 

Think really hard about whether you really need a freezer though.  They will use twice the power of a fridge, and maybe even more important - you have to keep them on all year round.  A fridge can go off in the winter and food keep outside in a box.  This is VERY

I have thought and considered a genny for tools.

but for a number of reasons I want to avoid that one

 

the freezer will be seasonal, for March to September, maybe longer depending on weather.

 

the fridge I do switch off in winter and for weeks at a time throughout the rest of year if I’m not using it.

 

 

To add; I didn’t mean to high jack thread but maybe my questions have helped the OP.

 

 

 

 

Edited March 8, 2022 by Goliath

[Tony Brooks]

13 minutes ago, Goliath said:

👍

 

in theory then ;

allowing 120ah per day for a fridge and a freezer,

and with 3 batteries giving 330ah,

I should never go below 2 thirds of my power, or 60-70%

IF I fully charge my batteries everyday.

 

And there’s the big IF

the tricky part for me to work out is how long it will take to put the charge back in.

But with 200W solar panels and my engine it shouldn’t be a problem...

 

The times Alan gave for lead acid batteries are about as close as you will get but with battery monitoring using rested voltage you will, over time get an idea. the problem with solar is that the controller will likely drop into float well before the batteries are fully charged. In reality I am sure it has to be done by monitoring and experience. Just make sure that you can easily isolate the panes so you can run a load and then get a stab at rested voltage during daylight.