12v refrigeration

[gonesail]

i would like to power my 12v adler barbour with an AC/DC transformer when plugged into shore power. has anybody done something like this?

[Vasco]

What's wrong with keeping the battery charger on?

[Maddog]

Get a Norcold that runs on both AC & DC. Internal inverter senses the source and powers appropiatly.

[Pblais]

You could but you probably need a 12 volt power supply that can put out close to 80 watts DC. The fridge draws about 5.5 DC amps that runs at about a 50% duty cycle but I'm not sure what the startup power is a bit higher rated supply would be better. Since you would still be plugged in it gives you all the bad part about being plugged in without draining the batteries. You would need a manual switch to transfer between this converter and ship battery power.

If you had a smart battery charger running off the batteries wouldn't be that bad and that would take nothing. It is using battery power so you need to watch the water levels if using flood batteries. If the charger is not a smart charger you can fry the batteries running the charger all the time. Some folks put the charger on a timer so it only runs for a few hours per day and lets the batteries discharge in between.

I don't like plugging the boat in all the time since the danger from stay current or lightning induction increases.

[Richard Kollmann]

Danfoss requires that there BD2.5 and BD3 compressors be operated direct from batteries and not supplied by power supply or charger do to module pulse feedback thus using battery as a large protective capacitor. The normal way to power these compressors from shore-power is to draw current from battery while it is being charged by battery charger. This method of charging battery will cause battery stress over time even with a smart charger.

If the compressor is a Danfoss BD 35 or BD 50 there is an AC/DC automatic switching device used by WAECO in their cabinet refrigerators that will solve your problem on new variable compressors. WAECO does sell these separately but there are two different sizes depending on which model compressor you have. Installation is simple disconnect power wires from Danfoss unit and connect them to the Cool Power MSP unit. Connect MSP output wires to Danfoss module and plug MSP 110 volt cord into boat’s 110 outlet. When AC power is available the MSP disconnects DC to module and replaces it with AC.

[btrayfors]

Originally Posted by Richard Kollmann

... The normal way to power these compressors from shore-power is to draw current from battery while it is being charged by battery charger. This method of charging battery will cause battery stress over time even with a smart charger. ...

Richard:

Can you explain why powering one of these compressors from a house battery bank, with a smart charger attached, would "cause battery stress over time"???

Thanks,

Bill

[Richard Kollmann]

Bill. I tested three inexpensive battery charges powering a Danfoss compressor connected to three group 27 deep cycle batteries. The constant voltage charger of course should never be left on continually. The automatic charger prevents battery gassing because it switches off when a safe full charge is reached but will click on exceeding safe voltage whenever compressor runs. The third smart charger after a few weeks seemed to cause only miner battery water loss. More on this listed under Battery Stress on my web site. The problem for even a good smart chargers like the Heart charger is they must remain at float voltage rate when battery is at full charge even when refrigeration is running. Smart chargers cause less off gassing but still require water maintenance which shortens battery life. I must quantify my experience on this to say I only worked with new lead acid batteries.

[btrayfors]

Richard,

Thanks for your answer. I see where you're coming from, but must disagree with the sweeping generalization re: battery damage and smart chargers.

Not all chargers are made alike, and I'd hesitate to call even the ubiquitous Heart chargers "good chargers" given modern advances.

Just two examples:

1. My house battery bank is maintained by a very high end Victron Multi-Plus charger/inverter. This is left on continuously at dockside (for several years now). It maintains a float voltage of 13.2, whether or not the Adler Barbour compressor is running (which is most of the time on my boat, 'cuz it's an old one and the frig is big and not too well insulated). It does not cause excess gassing or water loss.

2. The Iota pulsing chargers are unlikely to be affected by load, due to their design and performance with the IQ-4 smart controller option. I have two of them, one used maintain the golf-cart battery bank which powers all my radios at home. The radios put variable loads on the batteries from 1 to 90 amps or so (with a 500W linear amp). The batteries are now approaching 4 years old (Trojan T-105s) and still test like new with a sophisticated battery tester.

All flooded batteries will suffer battery loss, even with proper charging voltages. HydroCaps and WaterMiser caps can help reduce the frequency of adding water, but they must be checked periodically.

Also, it is chronic undercharging rather than overcharging or high voltages which typically cause battery deterioration over time. A credible case can be made that battery voltages needed to achieve a full charge and to maintain a decent float level are typically too low, not too high. Indeed, with flooded batteries periodic "equalization" using voltages exceeding 2.58 per cell (15.5VDC for a 12V battery) can help to maintain battery capacity and extend battery life.

All of which is to say that with a proper battery and charging setup, I wouldn't worry a whit about potential damage by a Danfoss compressor pulling 5-7 amps maximum periodically.

BTW, love your website and all the good info about refrigeration.

Regards,

Bill

[Richard Kollmann]

Bill, Stress factors are all conditions that either directly or indirectly contribute to ageing of the battery’s life. If the Victron Multi Plus charger eliminates off gassing and can control battery temperature that is an improvement over other units. Life of batteries operating at temperatures over 77 degrees lose capacity quickly. There are other stress factors than temperature like state of charge, voltage, age, and routine maintenance affecting battery’s life. I would be interested in knowing after equalizing what the current amp-hrs capacity of your four year old Trojan batteries is now. Four year old discount store gulf cart batteries will only indicate 40% if of original amp-hr capacity.

I still believe that running a Danfoss 12 volt refrigeration unit off batteries while connected to shore-power can shorten battery life. My recommendation in the past to this question is, to have a separate sacrificial battery when connected to shore power preventing stress to ships batteries.

[btrayfors]

Hi, Richard....

Well, I've gotta apologize for the age mistake: I looked up the date of purchase of the 8 T-105's on my boat, and found it was June 2006. So they're just over two years old. They test better than 80% of capacity, even without equalizing recently.

Six of these make up my house battery bank (675AH total). I can tell you that during my recent 8-day cruise they performed perfectly. And, as usual, after a few deep discharges and recharges they "regained" some capacity. This is evident from the very noticeable difference in voltage-under-load for a few hours after charging.

Batteries that haven't been exercised for awhile, or "equalized", will often show an alarmingly low voltage soon after a load is applied. For example, mine drop quickly from 12.6 to 12.4 within a few minutes when the batteries have only been kept on charge at dockside for a few months. However, once you exercise them, i.e., give them a few deep discharges and full recharges when cruising, the voltage-under-load stays up there much longer.

These are the batteries maintained by the Victron. They have only been equalized once in their 2-year life. The float voltage is set for 13.2, and absorbtion voltage at 14.4. I'm gonna up this soon...maybe to 13.6 or 13.8 and 14.8, respectively....and see what happens. The batteries, BTW, are fitted with WaterMiser caps, reducing water loss and making inspection and top-off very easy.

I have two -- actually three -- other battery banks of interest. One, also on my boat, consists of two T-105s which are dedicated to the windlass. They are maintained by an Iota DLS-55/IQ4 (PWM pulse charger) which is left on most of the time when at dockside, and which is used periodically away from the dock, powered by an onboard AC generator. These batteries are the same age as the house batteries, and test better than 80% of original capacity. Test instrument was a Midtronics 500/XL conductance/resistance tester ($600).

Similarly, I have a T-105 battery bank used at home to power all my radios: ham, marine, military, commercial. It is maintained by an Iota DLS-45/IQ4 charger, on all the time. I draw anywhere from a few amps to 90amps with the linear amplifier when transmitting. This bank is over four years old and tests better than 80% of capacity.

I have two other banks of interest. These are Gelled golf cart batteries which are almost 12 years old. At age 10, they were removed from a friend's sailboat and I used them for battery testing in a longitudinal study of pulsers for almost two years. Believe it or not, these four 12-year old batteries test 70-80% of capacity. And, being gells, they hold a charge for a long time without charging. Simply amaazing!

I hear you re: stresses on batteries. However, I would point out that few batteries are stressed any more than your average car battery in terms of vibration, shock loading, heat, cold, etc. Typically, even cheap car batteries subjected to extreme heat and extreme cold last 5 years or so.

So, I've gotta agree to disagree with you. IMO, there's simply no way a 5-6 amp periodic load on a healthy house bank is gonna stress a deep cycle battery bank, providing it is connected to a good charger and kept fully charged most of the time.

In fact, given the smart circuitry used in many battery chargers today, the batteries won't even "see" the load of a Danfoss compressor -- or even two or three of them -- the chargers compensate instantly for loads applied to the 12V system, with virtually no change in float voltage.

Bill

[lamarchea]

My 12 volt refregirator is not functionning ad it used to be. the compressor and the fan are going on and off everyu minute or so. The refregiratior is not very cold. There seems to be enough gaz in the system it has been refilled but the problem was not soved.

Any idea on the problem and the solution ??

Thank you

[Pblais]

For the most part they seem to last a long time then fail for assorted reasons. The compressor is not serviceable. It may have a leak but finding it may be hard and other leaks can still be there. I'm not sure how you can tell if it has enough "gaz". If it had a leak it might not. How old is it and what type is it?

[lamarchea]

Thank you.

It is about 6 years old and the compressor model is a Danfoss BD35F.

I tried to fill it up with new refregirant gas but it seems full.

[scotte]

If it's cycling every minute or so it could very well be a low voltage problem, as the electronics will shut down the unit if there is too much voltage drop. Check that every connector from the fridge back is not corroded. A voltmeter may or may not help, depends on how fast it will display before the electronics shut it down.

There's diagnostics you can do be wiring an LED in to the system (info on this is not too hard to find online).

Adding more refrigerant might not have been a good decision - if overcharged it also won't work...

[Richard Kollmann]

If cycling is frequent and there is some cooling of evaporator as you describe then the problem is one of the following reasons:

• Thermostat’s capillary tube is touching the evaporator where it should not. To eliminate thermostat place jumper wire across thermostat terminals on electronic module.
• Poor heat removal at condenser. Have you cleaned coils lately?
• Too much or contaminated refrigerant, this happens when someone tries to add refrigerant. To low on refrigerant will not cause fan and BD compressors to stop running but too much refrigerant or air in refrigerant will produce an overload signal at module and stop compressor.
• A fan load of over ½ amp will also signal module to stop compressor.

Many manufacturers are more interest in cost than quality and omit the $2 troubleshooting LED. The first thing I would do is go to Radio Shack and buy their smallest milliamp 12 volt red LED with red and black polarity wires attached. If you do not have my 12/24 volt book you can see a picture of where to connect LED on my Slide Show at my web site. Three flashes of LED indicate an overload. One flash of LED a voltage problem. Two flashes a fan problem.

Email me if you need help.