Running a Refrigerator Compressor on 12V or 24V and more

[onestepcsy37]

Originally Posted by DotDun

Not true. While plugged in your shorepower charger will pick up the load of the 12v refrigerator, not the batteries. The charger will maintain the batteries at ~13.3v in float mode, when the refrigerator kicks on, the charger will increase it's output in response.

i will defer to your better knowledge of shore power. i for one never plug in, preferring to live on my batteries. of course, with my old battery charger it's hardly worthwhile; it's a 10 amp 2 bank charger, meaning 5 amps per bank. although collectively on a 24 hour basis it would supply all my needs, when my adler barbour was running i would be on the deficit side and drawing from the batteries.

but the information i passed on about battery life being dependent on depth of cycles still holds. i read about it on the trojan website.

[ssanzone]

i am still in the middle of the 12v side of the wiring and have not fully worked out the 110 in my head.

i have a loosely formed plan of shore power direct into a converter and a switch to bypass the bank.

meaning... the entire boat runs on 12v and the power source to the panels are either the bank (with inverter) or shore (with converter).

an automatic switch that detects 12 vs 110 in a marine environment seems a recipe for failure especially when it relates to cold beer.

-s

[SV THIRD DAY]

Originally Posted by ssanzone

an automatic switch that detects 12 vs 110 in a marine environment seems a recipe for failure especially when it relates to cold beer.

-s

Buy this man a Beer....he GETS IT!

[skipmac]

Originally Posted by onestepcsy37

but the information i passed on about battery life being dependent on depth of cycles still holds. i read about it on the trojan website.

I don't think there is any disagreement on this point at all. A battery's life, assuming no defects or abuse, is primarily determined by the number of discharge/charge cycles including how deeply discharged, for how long and how long before recharging AND to what level the batteries are recharged, etc.

I think the point that a couple of us are trying to make is that when you're at the dock with a constantly on battery charger (or on any other system that is able to constantly supply more power than you consume) you are not cycling the batteries or at most some mini-cycles that have little impact on the life of a FLA battery. You are running on the power from the charger and having very little impact on your battery life.

[ssanzone]

Originally Posted by skipmac

You are running on the power from the charger and having very little impact on your battery life.

my only word of caution would be around over charging as is possible with leaving batteries connected to a charger for long periods of time.

-s

[Andina Marie]

BEWARE the problem of short cycling batteries at the same voltage.
For long stays at the dock supported by a smart charger there is a trick to saving your expensive house bank from premature aging.

See the trick at Hints and Projects

[Blue Agave]

Just replace yer battery's every other year for heavens sake, they're not THAT expensive lol

[Vasco]

My boat in Lake Ontario is tied to the dock all week. We are off the dock most weekends. I have four cheap deep cycle batteries, 2 house banks (this was done in 1988 when two banks over one was the prevailing wisdom.) Storage space allows for one bank of 2 group 27's and the other bank of 2 group 31s. The battery charger runs all the time at the dock and the fridge (EZ-Kold with Danfoss 12v compressor) is always on.

The battery banks have each lasted 6 years and I admit I have been a bit slow in adding water sometimes. I think 6 years out of these cheap batteries (about $100 each now, $80 each 6 years ago) is pretty good. I would not bother with an ac/dc fridge.

I should add that the batteries stay on the boat on the hard all winter with maybe one charging mid winter.

[TacomaSailor]

I'm having trouble with the "living aboard is hard on batteries" statements.

We've lived aboard most of the last 14 years. Our first set of 8-D gelcells lasted over 7 years, our 2nd set of T-105s lasted another seven years, and our third set is now four years old and in great shape.

We do have 500 watts of solar power, mostly live on the boat at 32 degrees N or further south so get good daily recharge rates and never pull the batteries down below 80% charge (-125 amp hours) and usually don't pull them below 90%.

Our solar controller is set to charge our lead acid T-105s to 14.5 V and they do reach that voltage almost every afternoon and then float at 13.65.

We have a 9 cubic refrigerator and run a Technautics CoolBlue ACC refrigeration system. That uses a BD-30 (I think) with a modified controller. The compressor pulls 3.5 amps at 14V.

We NEVER turn on the AC shore power battery charger.

It has never occurred to me that living aboard was hard on batteries!

[SV THIRD DAY]

Originally Posted by TacomaSailor

I'm having trouble with the "living aboard is hard on batteries" statements.

You are not trying to say that everything you hear on an internet chat room isn't gospel truth are you

But admit it....there are Live Aboards that maintain their boat and then...well there are the live aboards that give the rest of us a bad name..

[jonahmulski]

Thank you for all the input.
Take home message: Connecting an appliance (e.g. my refrigerator) to the DC side of the system while plugged into shore power will not harm the batteries because the battery charger will charge/float the batteries while also providing DC power to the house appliances. Thus, the refrigerator will be running off the battery charger and not cycling the batteries.
This is good... simpler is better.
Now I need to read up on my inverter/battery charger to see how many amps it will provide.

[deckofficer]

Think of your battery as a big filter for the charger, hence clean, almost zero ripple DC.

[CaptTom]

Originally Posted by jonahmulski

Now I need to read up on my inverter/battery charger to see how many amps it will provide.

That will help you estimate how long it will take to recharge from a given state of discharge (say, 50%). It is irrelevant if you're on shore power most of the time. If you're plugged in over night, it doesn't matter if it took one hour, or eight, to recharge.

One day after a long stay on a mooring I saw my charger pushing well over 90 Amps. Quite handy to replace a day's worth of discharge in an hour or two! Makes running the noisemaker to recharge possible, without disturbing the peace too much.

[californiakayak]

Originally Posted by djmarchand

The motor on a Danfoss compressor is actually AC. The controller takes DC input and inverts it to variable frequency AC to run the compressor. That is why it is so efficient compared to a straight DC motor.

And DotDun is correct as to how your shore power charger works.

David

I checked and this seems to be true. However, if it is true, doesn't seem like danfoss would create a lower voltage compressor ac or not to do this job. one would actually need to measure the voltages to see what is happening. However, I have seen several times that they have a dc to ac (inverter is the common name for that device) inside, and this video actually shows it and much more ! https://youtu.be/Vbvd0H3gnhI