New refrigerator, time for a new battery charger - advice?

Sorry to start yet another refrigerator thread, but our old Norcold DE 461 died. Original to the boat, 1996, so I guess I can't be too annoyed, worked for 25 years. I did try some of the advice on past threads for getting it working again, but I'm giving up, and it's rusting out around the edges anyway. By the time I add shipping and tax and incidental installation stuff I'm not in the mood to spend $1,500 or more on the DE 061, so I finally found a 110v AC household fridge that matches the cabinet size within an inch or two all around. The LG LRONC0705V, single-door, 6.9 cu ft. I can order it through Home Depot for $499, free shipping, delivered to my house. Door swings the wrong way and it can't be changed, but with our galley layout that doesn't matter much. The dimensions are very close to the Norcold but slightly smaller all around so I don't have to do a big carpentry project, maybe just some trim or retainer pads to hold the new one securely and make it look pretty. I'll also have room inside the cabinet to add a vent fan this time. But that brings me to power...

I can't find the draw (watts) for that LG anywhere, I'll have to figure that out when I get it, but the Energy Star label shows it's rated at 220kWh per year, which is relatively low. The 110v connection will be easy of course, for when we're on shore power. And then we'll need a DC to AC inverter for 12v operation, but all that's a lead-up to: As long as I'm doing all this, it's probably time to upgrade the battery charger. We have a Dytek "Marine Automatic" battery charger and I've pasted the spec plate below. Still works well as far as I know and we've never had any problems with it, but I assume it's at least 25 years old too (or 26 years old, if that date code means 1995). Although I get the basics, I'm really not good at electrical, my brain just doesn't work that way, so I defer to the many experts on here who know more about electricity than Nikola Tesla ever knew:

What new battery charger should I buy?

I think what you need is an inverter so you have AC for the fridge when you don't have shore power or the generator running.

You need to see what the maximum watts the fridge requires, plus any other AC loads you may want to have, and size the inverter to that.

For little extra cost over that of an inverter you might buy an inverter-charger. If you go this route you can keep your current charger and use both to charge your house batteries faster when on the generator.

I would guess that old battery charger is not anywhere near as capable as the newer generation chargers. I am happy with the Pronautic 50-Amp, variable power out charger I have. What size house battery bank do you have to support an AC reefer? I big monster inverter/charger is not required if all you are running is the reefer. I used an 850-watt inverter about the size of a couple of cartons of cigarettes to power my under-counter AC reefer and preferred a separate charger to avoid the possibility of have both my inverter and charging capability go down if the inverter/charger unit quit.

Slightly off topic but with such a close fitting new fridge is there enough space for cooling? Many new models need clearance around all sides not just the back

Cheers.

We have Promariner (3) in our current boat and have used them in previous boats also. Putting in a large inverter/charter can be a fairly involved installation. If all you care about powering is the refer then I would just put in a small dedicated inverter, much easier.

Thanks everybody so far. Quick reply on clearance just for the moment, installation specs on the LG say 2" for sides, top and back:

https://images.thdstatic.com/catalog/pdfImages/fc/fcca7067-d679-4407-97ca-fd32dbe6da42.pdf

I'll actually have more than that all around, since the LG is about 2" less in depth than the Norcold that's coming out, and about an inch and a half smaller height and width than the Norcold. There's also 3" of dead (empty) space inside the fridge cabinet on top, and a 16" x 3" ventilation louver in the top of the cabinet, so I'll be able to mount the fan there. I've researched this (way too long) so I think I'm all set. So you can see what I mean here's a photo of our galley -- not our boat, just grabbed it off a sales listing a second ago for convenience, but same make and model, nearly identical. I see these owners did the same thing we have in mind, removed the original Norcold and replaced it with what looks like a residential fridge. I see they also ran matching cherry trim around the edge (Mainship just ran the trim around the top), and we'll probably do the same thing. I have a pile of dark cherry at home in my wood shop.

So far no one has mentioned the size of your battery bank. Whenever you are unplugged, your residential reefer will be consuming all of its power through your soon to be new inverter, so your Energy Star rated 220 kw / yr will need to come from the house batteries.

Doing some of the math, 220kw/yr/365=602w/day. Your house batteries will new have to find a new 600 watts every day that you are not plugged in. Those watts, from 12v batteries, 600/12=50 new amp hours, every average day. With inversion losses, say 60, and on hot days, say 100 new amps.

Most Golf cart 6v batteries are rated at 220 amps. If you limit discharge to 50%. that gives you 110 new amps available from a new pair of Golf cart batteries. So you then end up with enough new capacity.

Now you need to know you have the charging capacity to put all those amps back into your house bank, so just buying a new, dedicated inverter to run the fridge is just the beginning.
Fridge
Inverter
Batteries
Higher capacity charger

I know I have over simplified, but when you figure in all the related costs there is a lot more to consider.

I'm not sure I see the connection between the new fridge and a new battery charger. My guess is that the new fridge will use less power than the old, and when plugged in you will be less reliant on your charger. If it's working good I'd suggest leaving it alone, at least until you're ready for new batteries or it starts acting up.

I'd be really surprised if that new fridge draws more than 500 watts. I ran a home fridge off a 1000w inverter for 10 years on my last boat without issue.

Since you are switching from a dc fridge to an ac one and you need to add an inverter anyway. Now might be the time to install an inverter/charger. While there are many good choices a Magnum 2000w pure sine wave inverter/charger would be a good choice.

kthoennes said:

Thanks everybody so far. Quick reply on clearance just for the moment, installation specs on the LG say 2" for sides, top and back:

https://images.thdstatic.com/catalog/pdfImages/fc/fcca7067-d679-4407-97ca-fd32dbe6da42.pdf

I'll actually have more than that all around, since the LG is about 2" less in depth than the Norcold that's coming out, and about an inch and a half smaller height and width than the Norcold. There's also 3" of dead (empty) space inside the fridge cabinet on top, and a 16" x 3" ventilation louver in the top of the cabinet, so I'll be able to mount the fan there. I've researched this (way too long) so I think I'm all set. So you can see what I mean here's a photo of our galley -- not our boat, just grabbed it off a sales listing a second ago for convenience, but same make and model, nearly identical. I see these owners did the same thing we have in mind, removed the original Norcold and replaced it with what looks like a residential fridge. I see they also ran matching cherry trim around the edge (Mainship just ran the trim around the top), and we'll probably do the same thing. I have a pile of dark cherry at home in my wood shop.

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The more ventilation the less power it will draw. If you can increase ventilation with vents at the back or the top of the cabinet it would help.

A charger/inverter is nice. But if you're paying someone to do it right on an old boat it gets expensive. It's not hard to spend 4k+ on an 2kw install starting from scratch. And after that you start to see the deficiencies in your battery and charging systems. It's a slippery slope.

I did some sleuthing and it sounds like your new fridge won't draw more than about 150 watts.

If the only need is supporting the new fridge a high quality very small inverter is a simple install, even for DIY. A $100 Victron 250w inverter could be hidden behind the fridge and powered from the existing DC breaker and wiring for the old fridge. It doesn't get any simpler than that, and from an overall wiring and power management point of view is completely plug and play.

Keep in mind that most residential refrigerators have automatic defrost cycles using an electric heating element that can be 400 watts or more. Be sure to size the inverter and battery bank with that in mind.

James

Comodave said:

We have Promariner (3) in our current boat and have used them in previous boats also. Putting in a large inverter/charter can be a fairly involved installation. If all you care about powering is the refer then I would just put in a small dedicated inverter, much easier.

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Amen to that. Installing a whole-boat inverter/charger requires heavy cables and switching to isolate the inverter power from shore power. It's a major system upgrade that probably doesn't make sense for just the fridge. Inverters are pretty inexpensive these days. I recently installed a Magnum 3.2kw hybrid inverter/charger that was around $1200 but the install was a LOT more due to cabling, switches, breakers, etc. A simple 1000W inverter can be had for $200 and might even come with short cables. Plug-and-play for a single appliance.

But I do want to encourage the OP to consider replacing the battery charger. These have come a long way in the past 25-years. Modern 3-stage (or 4-stage) chargers will extend the life of your batteries. In addition to coarse chemistry-selection (AGM, FLA, Lithium), some have user-programable settings so you can tweak the charge profile to the OEM's recommendation. For example, a larger bank will need a longer equalization period. Likely very easy to install in under an hour, it's time for a modern battery charger.

Peter

So quick of everyone to discount the consideration of the inverter/charger. No one asked the OP if a system wide inverter would add more utility to the OP. Never mind that an inverter/charger is a 100 amp battery charger. No, let’s just offer up a cheap inefficient hack with out considering the whole picture.

How about we consider the whole picture and then offer up an opinion.

tiltrider1 said:

So quick of everyone to discount the consideration of the inverter/charger. No one asked the OP if a system wide inverter would add more utility to the OP. Never mind that an inverter/charger is a 100 amp battery charger. No, let’s just offer up a cheap inefficient hack with out considering the whole picture.

How about we consider the whole picture and then offer up an opinion.

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How about we answer questions and take at face-value the OP's statements? The guy (presumably a guy) didn't want to spend $1500 on a DC/AC fridge, so went with a $500 home-grade appliance that opens the wrong direction and will need some carpentry but was installed in an afternoon (all reasonable decisions). That's the problem he was trying to solve. He didn't ask about powering the Mars Explorer or decorating a Russian Winter Palace. Just how to power his AC fridge. That's it.

A system-wide inverter/charger will need 1/0 cables, transfer switches (more complex if there's a generator), fuses, monitors, etc. $2k-$3k just for parts plus installation. No one ruled it out, just offered balanced advice that if fridge was the main objective, a dedicated 1000w inverter for a few hundred bucks would do the trick. And it will.

Hack or not (and I don't think a dedicated inverter is), I call it the fastest way to cold beer.

Peter

mvweebles said:

The guy didn't want to spend $1500 on a DC/AC fridge, so went with a $500 home-grade appliance that opens the wrong direction and will need some carpentry but was installed in an afternoon (all reasonable decisions). A system-wide inverter (the Magnum PSW/20002 Inverter/Charger is over $1k alone - no cables) upgrade with 1/0 cables, transfer switches (which might include integrating with generator if his boat has one), fuses, monitors, etc. would take multiple thousands of dollars and take weeks to get all the parts together and install.

Hack or not (and I don't think it is), I call it the fastest way to cold beer.

Peter

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I can support this logic. I just see a series of poor decisions being made.

tiltrider1 said:

I can support this logic. I just see a series of poor decisions being made.

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In practice, I'm with you Tiltrider. I strongly prefer a solid infrastructure backbone. Provides lots of flexibility and reliability in the long run. But upfront, it's an expensive and time consuming investment.

Personally, I think RV/household style fridges on boats are a poor choice as they are efficient at just one thing: launching contents into the cabin. Left to my own preferences, I would ask "why not just build a hyper-insulated box with remote 12VDC compressor, preferably water-cooled? No inverter needed" Of course, that's even more distance to cold beer.....

Peter

mvweebles said:

In practice, I'm with you Tiltrider. I strongly prefer a solid infrastructure backbone. Provides lots of flexibility and reliability in the long run. But upfront, it's an expensive and time consuming investment.

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Agreed. I have a large charger/inverter and dual voltage fridge on my current boat and spent a lot of time and money on wiring upgrades to support and protect the high DC loads.

Whatever is installed should be properly wired, with appropriate fault protection and wiring size. Accommodating a 20 amp dc device is trivial, but a 200 amp DC load will require some big mods on the OP's existing system. I'm not arguing against that, but realistically it could represent a work package that amounts to 20% or more of the boat's total value and eclipses the economics of the fridge decision.

QUOTE=koliver;1011898]

Doing some of the math, 220kw/yr/365=602w/day. Your house batteries will new have to find a new 600 watts every day that you are not plugged in. Those watts, from 12v batteries, 600/12=50 new amp hours, every average day. With inversion losses, say 60, and on hot days, say 100 new amps.
.[/QUOTE]

I think you are confusing watts and amps. 50A/hr/day thru an inverter (modern inverter/chargers such as Victron Multiplus are about 93% efficient) equals about 54AH from a battery. If the battery usable capacity is 400AH ( eg: four 8D AGM or four 100AH lithium), the fridge would be able to operate for a week on a single charge. Of course this doesn't take into consideration all the other loads on the boat Put another way, a 200A battery charger would take less than half an hour to replenish all the energy used by the fridge in a day, and a 150A engine alternator would take about 40 minutes.

" Put another way, a 200A battery charger would take less than half an hour to replenish all the energy used by the fridge in a day, and a 150A engine alternator would take about 40 minutes."

This is where numbers and reality chemistry collide.
Perhaps the new auto batts can be charged to 100% with a large charge rate , but it doesn't work for simple LA (lead acid) or even AGM.

Heat in the battery being charged is one problem, that can only be handled by a temperature control for what ever is charging the batt..

The other hassle is the chemistry of most batts , bringing them up to 85% or so can be done with a big charger , but the last 10% or 15% takes a far longer time.

If 100% charge is not reached often, the batt slowly looses capacity.

Many long term cruisers use larger batt banks , to be able to accept this slow death , from the not fully charged condition.

Today solar is a great help in getting that 100% required charge.

I think I am too late for you but my fridge died couple of years back and i took it to a truck shop that does major repairs, they also fix truck fridges. These truck fridges are close to marine ones. Anyway, my fridge hadn't died, was just over heating and not cooling. The cooling fins were dusty and was advised to add a 12 volt fan to exhaust the heat out the back. Bingo.
I'm in a different boat now. 14 years old and i can tell the fridge is working hard so plan to pull it out and dust the cooling fins. A little dust on the cooling pipes/fins makes a big difference. There is some magic formula something like fridge should run for 90 seconds and be off for 3-4 minutes before running again. (don't quote me go talk to the experts).

Thanks again everyone for all the replies. They were all very helpful in thinking through options and approaches. We finally had some time last weekend to pull out the old one and temporarily slide the new one into the cabinet (just fit, phew!), just plugged into 110v for now. So catching up:

Keith (koliver) asked about the size of the battery bank. I've got a total of four -- two starting batteries (one for each engine), a house battery (Interstate deep cycle, SRM-31, just 98 amp hours) and then a battery that just starts the genset and the operates the windlass. That last battery was added by the previous owner. You'll recall too that I have a relatively old 10 amp battery charger, probably original to the boat (1996). I could give you the specs on all the batteries now, but Jeff F's posts (recommending a relatively simple approach) got me thinking. He's right, the new fridge has to pull much less than the vintage Norcold and we had plenty of battery reserve for that one (for our use habits), so shouldn't I be okay with just an inverter for now?

So I bought a GB energy consumption meter, model PM3000, plugged it onto the 110v outlet inside the fridge cabinet, plugged the fridge into the meter, loaded it about halfway with drinks and food, and switched it on. Opening the door turns on the LED lights. The lights alone pulled 2-3 watts (fluctuated on the meter, tiny). I let it run for three hours and twenty minutes. I should have let it run for three hours even to make calculations easier, but lost track of time. During the test period I let my wife and kids open and close the door for drinks and snacks. Wanted to get a rough sense of normal use. After those three hours and twenty minutes, the inside was ice cold (I had to turn down the dial because it froze some of the food). Unlike the Norcold that hummed like a back massager switched on high, the LG was so quiet I had to put my ear near the compressor or touch it to feel any vibration to tell if it was on. So after 200 minutes (3 hrs, 20 min) the results were:

26 watts "dynamic average power" during the test period
.063 kilowatts hours consumed, total during the test period
.37 amps was the highest amp reading displayed on the meter during the test period, but that's an "at the moment" reading, in other words, that's not the max, unfortunately that meter just gives you the amp reading at the random moment you check the display.
117 volts (voltage of the power supply)
60 hz

I was really impressed by how efficient that new refrigerator is. Heck, the headliner in the salon and the berths originally used 20, 20-watt halogen bulbs to light the interior, those relatively common inset lights you can get at West Marine. I replaced all the G-4 bulbs with LED's years ago. Kind of amazing that the new refrigerator pulls about as much as a single one of those old halogen bulbs (that would also get hotter than the surface of the sun).

So in summary, if my relatively old battery charger is just 10 amps, and even though my battery bank is pretty wimpy, for now I may be okay. My to-do list is so long -- and we can't get anybody to do any boat work around here so I pretty much have to do it all myself whether I'd want to pay somebody or not -- that maybe I can defer a new battery charger and upgrading the battery bank to a later day. My next challenge though is to think through how to wire the fridge. Right now it's just plugged into the 110v plug inside the fridge cabinet. Have to think through the inverter and 12-volt wiring. Something like this maybe:

https://www.amazon.com/Xantrex-8080...ocphy=9020397&hvtargid=pla-570286925911&psc=1

"Have to think through the inverter and 12-volt wiring."

Install a 120V box that is just for the inverter , solves the movable ground hassle at almost no cost,and with little effort, and never fails.

Thank you, but I'm not sure I get that. I have a 110v AC household fridge sitting in the cabinet now, plugged into a shore power/genset AC box inside the cabinet. I have heavier gauge red and black 12v DC wires that I snipped off the Norcold flopping around loose (I did put wire nuts on the ends temporarily just for safety). I have two separate switches on the boat's electrical panel for the refrigerator, one on the DC side, and one on the AC side. So I get a 12v DC to 110v AC inverter, connect the DC wires inside the cabinet to the inverter, and then I'm not sure from there. That's why I'm thinking I need some version of that Xantrex switch linked above. As you can tell I'm no expert with electricity, but I assume I should definitely not wire the inverter output to the fridge's 110v box, but then hope nobody ever turns on the 12v and 110v refrigerator switches at the same time. The Norcold would automatically switch back and forth by itself, but the new fridge has no such ability. I'm an electrical bonehead as everybody can tell, but I assume I can't have the inverter's 110v output and shore power's 110v output wired into the same box without some kind of switch or lockout installed -- to duplicate the Norcold's previous ability. For example, we have a back-up generator at home and there's a lockout installed so we never have the power company's and the generator's power feeding the house at the same time. See what I mean?

(Yes, I would certainly hire somebody to do all this for me but we can't get anybody to do service work -- for this, or to weld a broken bow rail stanchion, or a minor fiberglass job, or anything else.)

That switch would work with a small inverter like the one I suggested earlier. Bigger inverters typically have a built in transfer switch, but a bigger inverter costs more and would need more robust DC wiring and fusing, which complicates the install in different ways.

Jeff F said:

That switch would work with a small inverter like the one I suggested earlier. Bigger inverters typically have a built in transfer switch, but a bigger inverter costs more and would need more robust DC wiring and fusing, which complicates the install in different ways.

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IF you are fortunate, the compressor IS 12vt and you have a step down transformer converting 120vt to 12vt. IF that be the case, all you need is a selector switch designating 120 or 12vt
On my installation, I have a manual switch moving the designated load (microwave) from house bus to inverter bus. 3x4D house batteries would support the microwave for more than the time to heat up a cup of coffee and then some.

The installed galley amp meter saves a few steps when I must do the "30amp dance." I have an electric stove, microwave and 4 outlets (one of which has the washer/dryer plugged into it) on the house bus. Trust me, the 30amp service will not support everything so, watching the galley amp meter allows to shed loads are necessary.
Naturally, first load shed is the HW heater. That gives me lots of "room."
I thought I was being smart by moving one of the saloon outlets to the inverter bus until my bunkmate plugged in her iron. LOL

Incidentally, installing a larger inverter is not the answer. Consider the inverter as a "straw" of a specific diameter. Increasing the diameter of the "straw" is no good unless one has the batteries to support the larger "straw".
The larger "straw" just sucks the batteries down faster.

I keep thanking everybody but I mean it, this discussion has helped me a lot. I have no natural talent with electricity. Other than the most rudimentary concepts I just don't get it. It's like playing cards, I've never been able to grasp poker or any playing card game. Spatial or conceptual games like chess, that clicks in my head, but electricity -- forget it. My brain simply works very well in some areas and I'm a moron in others.

Anyway, I do understand Dan's straw analogy, thank you, yep, I get that. Thankfully that new fridge drew 27 watts (average) according to the meter. Even if the starting wattage is ten times higher for a second, that size inverter is still pretty darn small. This whole project has me studying 12v/110v systems for boats and RV's in general, and now I see I can get a inverter with a built-in switch, like this. Pretty cool.

https://xantrex.factoryoutletstore....r.html?category_id=83096&catalogitemid=105589

Price at that link is $300-something, but I see it elsewhere for about $125.

kthoennes said:

Anyway, I do understand Dan's straw analogy, thank you, yep, I get that. Thankfully that new fridge drew 27 watts (average) according to the meter. Even if the starting wattage is ten times higher for a second, that size inverter is still pretty darn small. This whole project has me studying 12v/110v systems for boats and RV's in general, and now I see I can get a inverter with a built-in switch, like this. Pretty cool.

https://xantrex.factoryoutletstore....r.html?category_id=83096&catalogitemid=105589

Price at that link is $300-something, but I see it elsewhere for about $125.

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The simplest thing you could do to keep the fridge powered all the time is to use an inverter like you linked to, wire it up to the DC system properly, mount it behind the fridge then plug the fridge into it. Forget about switching it over to any other source. The inverter will most likely also have a 'low battery' shutdown which will shut it down if your house bank gets too low (would only happen when you aren't plugged into shore power).

However, if you do wire it that way, it does seem possible that your 10 amp battery charger will need to be upgraded to keep up with your current 12V house load needs in addition to keeping the fridge going all the time. A 20 amp charger would be relatively inexpensive to acquire and install and double your 12V capacity.

One thing to keep in mind with an inverter you intend to have on all the time is it's idle current draw. Just having it on and making AC power available uses some amount of power. Some cheap inverters are TERRIBLE and will use 40-100 watts of power just sitting there. The one you linked to claims 5W idle which is excellent, if it really meets that spec. The Victron Phoenix 12/800 is similar in spec (800 watts) and is a quality unit at a comparable price to the Xantrex you listed.

kthoennes said:

I keep thanking everybody but I mean it, this discussion has helped me a lot. I have no natural talent with electricity. Other than the most rudimentary concepts I just don't get it. It's like playing cards, I've never been able to grasp poker or any playing card game. Spatial or conceptual games like chess, that clicks in my head, but electricity -- forget it. My brain simply works very well in some areas and I'm a moron in others.

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You can take this analogy a lot further to help get electrical straight in your head, but shift it to water plumbing. Most people understand the basics of plumbing because it's relatable; you can see/feel the medium and most people are exposed to plumbing more often.

Think of wires as pipes. Batteries as tanks. Solar panels as water sources. Water as electricity itself. Lights/Fridges/appliances as things attached to spigots that use water.

Volts are equivalent to pressure. Amps are equivalent to flow. Watts are a measure of quantity.

A battery charger is a 'pressure regulator'. The regulator takes the high pressure (high voltage AC) and reduces it to the low pressure system (12V DC). The incoming water is high pressure low flow, water coming out is low pressure high flow. The total volume of water (watts) coming in and going out is roughly the same. The incoming electricity is high voltage, low flow and the output is high flow, low voltage.

An inverter is the opposite of a pressure regulator and functions exactly in reverse, boosting low voltage high flow to high voltage low flow. That's why the inverter will need much bigger wires on the low voltage (pressure) side, the flow is much larger (10X) while the AC side can use quite small wires because of it's low flow.

With most electrical devices there are some losses when doing these conversions, with quality devices that usually isn't much of an issue.

kthoennes said:

https://xantrex.factoryoutletstore....r.html?category_id=83096&catalogitemid=105589

Price at that link is $300-something, but I see it elsewhere for about $125.

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That's an old modified sine wave unit. I'd go with a high quality sine wave unit.

Even a thousand watts is overkill. Does the existing DC feed have its own breaker or fuse? If you're reusing that your straw size is fixed, and small. Probably 20a/250w.

As suggested, you could wire in the inverter and forget about switching. Run it on 12v all the time. I'd be tempted to do that.