Marine Fridge 12V vs Regular 115V with inverter

[fishin Hatt]

Ok Guys, I discovered the fridge on my 38 convertiable was 115v only (must have been replaced by previous owner or maybe never was 12v) after my first year of use. I like to have my fridge working when im out and im not running the generator all the time to do it.

I can buy a bar fridge many places for cheap and put it on an inverter. The whole package might cost $450. When i looked at the dedicated marine 12v fridge they are like $1200 !!

Has anyone used a regular fridge on an inverter?? If so how does it work for you on battery power? Has anyone had both that they can compare. What are some of the more efficent models out there for in 12v.??

Cheers!
Marshall

 

[mobilemn1]

Hey Marshal,

I have looked at those pricey refridges my self . Haven't made a descision yet on what I am going todo. I can tell you this, during a hurricane I only had a Honda 400watt generator for emergency. It ran a double wide refrig, tv, and several lights all at the same time. Most of the newer refrigs are more enegy efficient than the one I had. You may get a post from some of the electrical genieus with the power formulas. But refridges don't run continuous any way. Also depends on usage. Wouldn't your generators keeping the batteries charging while you are running, keep a battery bank high enough to run inverter. the electrical gurus can do the math.

Daryl

 

[fishin Hatt]

Thanks Daryl ,
Yes the new fridges are pretty efficent but i still don't know what they will be like on an inverter. I read somewhere that you can add 5% more consumption when you use an inverter than just a 12v applience. Also a inverter is always using power when tied in the system so i have heard.

Im also wondering about using about three of the marine deep cycle batteries at costco in parallel instead of the big 8D mainly because they are deep cycle for the house bank. The 8Ds deep cycle are very expensive!

 

[GJH]

The 12 volt will be more efficient, especially if it is one of the cold plate designs. You will lose efficiency through the inverter. Those 12/120 volt reefers usually accomplish that by having an inverter built in.

That being said, I power a household Sub Zero side by side, amongst many other things with an inverter. If all you want to do is power the refrigerator, the 12 volt reefer may be lower total cost, however the inverter gives you access to so much more stuff.

 

[fishin Hatt]

The 12 volt will be more efficient, especially if it is one of the cold plate designs. You will lose efficiency through the inverter. Those 12/120 volt reefers usually accomplish that by having an inverter built in.

That being said, I power a household Sub Zero side by side, amongst many other things with an inverter. If all you want to do is power the refrigerator, the 12 volt reefer may be lower total cost, however the inverter gives you access to so much more stuff.

Good point George....... but how big is your battery bank to go powering multiple stuff like that. How long do you get out of your batteries??

 

[GJH]

I have a 400 amp hour, 24 volt bank. I think it is down to 300-350 amp hours now, in reality. It gets used very heavily, we have pulled 34,700 amp hours out of this bank in the last 14 months. I use four L16 deep cycle 6 volts in series. This will operate the Sub Zero and two wine-cooler type beverage fridges (one of which is used as a refrigerator, set at 39 degrees) over night, and an hour or two of watching TV, using the computer and blazing some lights. I have an automatic generator starter that kicks on when voltage gets to 24 volts; some times I will set it to 24.4 if I know that I'll need the generator sooner anyway.

A weak link in my system is that I do not have this bank charged by an alternator when underway; I intend to correct that in the coming year.

Truthfully, if I had to do it all over again, I think I would have put in an ultra quiet 6 or 7 KW second generator instead. I think I will end up adding one anyway. The boat is wired for it and the panel is set up for it too.

 

[REBrueckner]

There are several options: None cheap...

First, try a local refrigeration guy and see if he can replace your 120volt compressor with a 12volt....that might be doable....all use DANFOSS compressors, from Europe, I think, and knowing that can enable you to begin to make comparisons.....a water cooled compressor is nice, but the pumps have a lot of problems and overall are probably not worth it for occasional use.
I have the original 16 cu ft household Frigidaire side by side on my 1972 YF....the 120 volt compressor has never worked: I installed a 12 volt Adler Barbour refrigeration system in each side, two total, remote compressos, one is used as a frig, the smaller side (originally the freezer) is partioned off and I use as a freezer when fully stocked up. Not a cheap option, but you can get as used system on e-bay for maybe $500 each or less...

I have one water cooled unit powered by a puny little 1 amp 12volt pump....and the drive craps out every six months...a more robust pump might work better...I tried a number of options, none worked....I don't use it....I think it may be better on five know sailboats....at 11 knots water rotates the impeller and wears it out....too much hassle....

If you run a big fridge and freezer both from an inverter they'll use quite a bit of power....the inverter wastes about 15% when running to power the fridge and uses additional standby power 24 hours a day....quite a bit in total....With daily charging you'd likely need about 3 8D deep cycle of about 220 amp hours each...about $700 for the 3 8D's in the NY/CT area at retail....Likely you can also get an inverter from E-BAY, rebuilt maybe 90 day warranty, at perhaps 1/2 or less retail....Look for an inverter with low standby draw...TRACE was best when I looked, but I never found one and bought a Xantrex for other applications....

Also unless you can charge quickly you may incur extra genny run time...also expensive....you need charging capacity to match your daily use...

Inverters are most efficient when matched to normal use...if you need,say, a 600 watt inverter for a fridge but by a 2000 watt so you can power a microwave, for example, likely you'll use another 5% power daily.....maybe more I have not researched in years...check standby current ratings

 

[REBrueckner]

Here's a post I made from earlier today:
"...Any opinions on what a reasonable house-bank size would be if you wanted to run an inverter?..."

Depends on ambient temperature (for fridge/freezer) and hours of use of appliances, together with how often you want to recharge....You really should figure the daily amp hours of load, add about 15% for the inverter and then buy enough batteries to about triple or quadruple that daily use if recharging daily.

Most load is refrigeration and freezer...they use a lot of power....And fridge/freezer use is directly proportion to ambient temp difference: a fridge at 40 degrees interior temp and 70 degrees ambient (a thirty degree difference) will use TWICE the power on a 100 degree day (60degree difference).

Actual hours of use of power is critical: for example, if your normal daily load is 150 amp hours (rather modest) leaving just one 25 watt 12 volt light on for 24 hours means another 50 amp hours daily!!!!!....... an increase in load of about 1/3!!!! If a small TV pulls 5 amps, for one hour daily it's insignificant; at 10 hours, it's also 50 amp hours...quite significant....

Aboard my 48 YF my daily use in moderate temps is about 150 to 175 amp hours at 12 volts and I am aboard alone including a 12 volt fridge system inside a household fridge of abou ten cubic feet.....it goes to over 200 amp hours when I also run a separate small size freezer... Just one kid or a few guests opening a fridge repeatedly on a hot day could easily double that!!!!! An inverter system is a bit less efficient....

AGM vs lead acid battery type is also significant...

Check my "dc system design" for additional details....
http://www.samsmarine.com/forums/sho...=system+design

 

[fishin Hatt]

I have a 400 amp hour, 24 volt bank. I think it is down to 300-350 amp hours now, in reality. It gets used very heavily, we have pulled 34,700 amp hours out of this bank in the last 14 months. I use four L16 deep cycle 6 volts in series. This will operate the Sub Zero and two wine-cooler type beverage fridges (one of which is used as a refrigerator, set at 39 degrees) over night, and an hour or two of watching TV, using the computer and blazing some lights. I have an automatic generator starter that kicks on when voltage gets to 24 volts; some times I will set it to 24.4 if I know that I'll need the generator sooner anyway.

A weak link in my system is that I do not have this bank charged by an alternator when underway; I intend to correct that in the coming year.

Truthfully, if I had to do it all over again, I think I would have put in an ultra quiet 6 or 7 KW second generator instead. I think I will end up adding one anyway. The boat is wired for it and the panel is set up for it too.

George,
It sounds like i may be more comfortable with the lower power 12 volt fridge from what your saying. I kinda think wehn you run your battery bank down it must take a while to bring it back! All my batteries are also charged by the alternators and thats great if your going places .......not great on a mooring for a couple days!

I actually have a little Honda 2000EU portiable geny that i never really thought of using........its really quiet unless your really running a heavy load would keep a battey charger going for sure quietly!! Would also burn almost no gas and make less noise than the 7K Onan inboard!! Hmmmm put one of those little things on the swim platform of a big boat and you wouldn't even know it was there!!

Hmmmmm!!

 

[fishin Hatt]

Here's a post I made from earlier today:
"...Any opinions on what a reasonable house-bank size would be if you wanted to run an inverter?..."

Depends on ambient temperature (for fridge/freezer) and hours of use of appliances, together with how often you want to recharge....You really should figure the daily amp hours of load, add about 15% for the inverter and then buy enough batteries to about triple or quadruple that daily use if recharging daily.

Most load is refrigeration and freezer...they use a lot of power....And fridge/freezer use is directly proportion to ambient temp difference: a fridge at 40 degrees interior temp and 70 degrees ambient (a thirty degree difference) will use TWICE the power on a 100 degree day (60degree difference).

Actual hours of use of power is critical: for example, if your normal daily load is 150 amp hours (rather modest) leaving just one 25 watt 12 volt light on for 24 hours means another 50 amp hours daily!!!!!....... an increase in load of about 1/3!!!! If a small TV pulls 5 amps, for one hour daily it's insignificant; at 10 hours, it's also 50 amp hours...quite significant....

Aboard my 48 YF my daily use in moderate temps is about 150 to 175 amp hours at 12 volts and I am aboard alone including a 12 volt fridge system inside a household fridge of abou ten cubic feet.....it goes to over 200 amp hours when I also run a separate small size freezer... Just one kid or a few guests opening a fridge repeatedly on a hot day could easily double that!!!!! An inverter system is a bit less efficient....

AGM vs lead acid battery type is also significant...

Check my "dc system design" for additional details....
http://www.samsmarine.com/forums/sho...=system+design

Ok REBrueckner!

Lots of good stuff there I will be checking Ebay for DANFOSS compressors and Trace inverters.

I am thinking that the 12 compressor may be better for me than an inverter. I don't have the space for 3 extra 8D's and they would cost almost as much as the new fridge anyway let alone the inverter!

One thing i would like to ask .......is i have to replace an old 8D as it wont hold its full charge anymore. I was thinking of putting in 3 (and I already have one so 4) 12v marine/deep cycle 750cranking amps 115 amp hour in parallel on sale at Costco for 89.99 rather than another big 8D .The big 8Ds are hard to handle and the deep cycle ones i have never seen around here....if you can even get them??? This is the house bank so it really needs deep cycle to me. Would they do the same job as the 8D...........Anyone know?!?

Thanks
Marshall

 

[Boatsb]

First the interstate 8D marine deep cycle is about $185. The 3 costco batteries are usually not made as well and would cost more. Engines need high amperage to start. Diesels need higher amperage to start. could the batteries in parallel handle it? probably. Would the 4 sets of connections allow for more issues with corrosion? probably. Would it be better to buy a better quality battery? Most probably. Would charging be an issue? Possibly.

Sorry if I was not clear but I like the simplicity of one big battery.

Less things to go wrong. If one battery is dead in a group the rest may be good but will follow soon so where is the savings?