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Old 20-06-2011, 13:19   #46
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Re: Xantrex Battery Charger Overheating - Frigoboat Fridge

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Originally Posted by btrayfors View Post
DotDun,

Glad you did read it :-)

I was just about to post a short note re: smart chargers.

A modern smart charger, faced with a fully charged battery and in the float mode, can deliver a LOT of amperage without dropping back to the absorption or bulk charging modes.

In other words, it is fully capable of powering most/all onboard loads without affecting the voltage being maintained at the house batteries.

Examples:

1. My Iota DLS-45/IQ4 remains in the float mode (13.6V) even when powering my SSB radios and my SG-500 amplifier. The amplifier draws 50A or more during voice peaks in the SSB mode, and the transceiver draws another 30A during peaks. That's 80A or more during voice peaks....the Iota takes that in stride and remains in the float mode.

2. My Victron Multi-Plus charger/inverter easily maintains my onboard refrigeration (which draws 6A and runs much of the time because of its advanced age -- 23 years -- and a large poorly insulated box). In addition, it runs other onboard loads...computer, SSB and VHF radios, nav instruments, TV, etc. all the while remaining in the FLOAT mode.

It's the battery voltage which controls what the smart charger will do, in most instances.

I almost never disagree with Richard Kollman who is the acknowleged refrigeration expert, but I must take issue with his remark about compressors which run a lot throwing off the charger's calculus. NO, sorry, if this is happening then you've got a lousy charger.

Especially since, as earlier noted, the compressor in question draws only 3A when running.

I note also that we are 40-some posts into this vexing but resolvable issue.

PLEASE, Sailorman, get some instruments and MEASURE WHAT'S GOING ON.

Put us out of our misery :-)

Bill
I know guys .. this is painful but I'm working today and waiting for info from Xantrex and the tech that installed the charger.

I'm less concerned about the Xantrex unit putting too much charge into the batteries on float than my Cristec that came with the boat. I have replaced batteries twice on my boat due to venting problems. The first time we couldn't find a fault with the charger but 2nd time I'm not taking any chances. I was hoping the 40A Xantrex would be a simple fix. Now I have a problem with the Xantrex throwing off a warning that doesn't have a simple answer. Will be running these test soon and report back. Thanks for all the advice.
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Old 20-06-2011, 21:08   #47
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Re: Xantrex Battery Charger Overheating - Frigoboat Fridge

Perhaps a ground/neutral is missing on the refrigerator and the return path is through the charger. You can verify this by measuring the voltage at the refrigerator. This could also lead to rapid use of the boat zincs as this becomes another electrical path.
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Old 21-06-2011, 08:54   #48
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Re: Xantrex Battery Charger Overheating - Frigoboat Fridge

This has been a good discussion about small 12 volt refrigeration and battery stress. Mostly the opinions center around battery activity caused by a 5 amp refrigerator while battery charger is controlling voltage and amperage. As long as a new battery remains at rest it holds its charge for several months although it will lose some of its original amp-hr capacity. The same new fully charged liquid battery at rest connected continuously to a smart charger at a float voltage of 13.2 volts will keep plates clean and battery fully charged. During this float charge phase current interring battery is generally less than 300 milliamps. With less than three watts of activity in a large liquid battery it is unlikely its liquid will raise in temperature to cause outgas boil with a new battery.

When a quality smart battery charger operating at float voltage sees an increase battery activity of 30 to 60 watts power to operate refrigerator it may hold the float voltage level of 13.2. It is the movement of wattage through batteries and their age that causes their additional stress.
The reason some boaters experience less battery water loss has to do mostly with cooler battery temperature.

Most comments on this thread are good but beware of suggestion to power 12 volt refrigerator direct from battery charger without a battery, Danfoss compressor for one has warned against it. There is a new Danfoss compressor that does not need a battery it is designed to operate from 10 to 45 volts of solar power.

Remember that each day after a liquid battery is manufactured it loses amp-hr capacity and there is only a lifetime number of amp-hrs activities in a particular battery.
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Old 21-06-2011, 09:17   #49
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Re: Xantrex Battery Charger Overheating - Frigoboat Fridge

Richard,

Most respectfully, you are an expert on refrigeration, but your statements re: batteries and electricity as reflected in your last posts show significant misunderstandings.

1. When a smart charger is connected to a battery and that battery (bank) is fully charged and floating at, say, 13.2V, any additional load such as a very small compressor load WILL NOT PASS THRU THE BATTERY. The charger will provide the needed current directly to load.

2. A flooded battery floated at 13.2V WILL NOT keep its plates clean. This level is too low to avoid sulfation of the plates and to avoid stratification of the electrolyte. A periodic higher charge in the 14.4-14.8V range, coupled with occasional equalization, will do a much better job.

3. A new flooded battery doesn't have 100% of its capacity....not until it has been cycled a few times and, preferably, equalized. After that, the rate of deterioration in capacity depends very much on how it is treated -- charged and discharged and kept topped with distilled water and not contaminated, etc., etc.

4. A flooded battery in good condition will not boil or gas at normal float voltages ...13.2-13.6. My 10 T-105's are kept on charge 24/7 at a float level of 13.6 or more (the Victron has a "high" float level of 14.0 for a time, and reverts to 14.6 "periodic absorption level" every 2 days for a half hour.) This regime has actually IMPROVED the capacity to these batteries until they test as nearly new. They are five years old. By the way, this higher charge voltage has NOT resulted in greater water loss, and mine have Water Miser caps to help prevent any loss.

5. The last statement re: "there is only a lifetime number of amp-hrs activities in a particular battery" is patently false. Why, then, do some users get five-to-seven active years out of a set of flooded batteries while other manage to kill them in less than a year?

The relatively small amperage required by a Danfoss compressor (3-6A typically while running) is a tiny amount as seen by a large house battery bank. Even the starting draw is momentary and doesn't stress a healthy battery bank. A compressor running 80% or even 100% of the time 24/7, with a modern smart battery charger properly connected to the house batteries, should have virtually NO EFFECT on battery charging or longevity.

Bill
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Old 21-06-2011, 10:56   #50
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Re: Xantrex Battery Charger Overheating - Frigoboat Fridge

I have a similar setup, though instead of a frigoboat I have a Nova Kool, but it still uses a BD35. I have a 40A truecharge that has no problems with keeping the fridge running happily at 13.2-13.4 24/7. My draw with the compressor running is 5A. My ampmeter is not quick enought to catch the startup amps. I disagree with the suggestion of running the fridge directly off of the charger with no battery. The BD35 is designed to run off of battery voltage which is continious, whereas the charger manages voltage using pulse width modulation(PWM). Even the new solar only compressors are designed for a continious voltage source, not a PWM charger. The PWM charger actually puts out a much higher peak voltage, but essentially averages 13.2-13.4 at float. Without feedback from the batteries I'm not sure how the charger would regulate it's output. It might put out a high continious voltage. Between pulses the charger samples the battery voltage to decide what to do, without a battery it might try to put out bulk voltage or even equilization voltage. By the way you should disconnect your fridge during equalization. The voltage is too high for 12V and an undervolt condition for 24V. I've been told this is very bad for the controller.

It makes no sense to me that the unit should overheat at 20% load. Do you turn your refrigerator off with a breaker at the panel or with a switch at the refrigerator? My thought is that the problem may be in the wiring to the fridge. If you are turning it off at the panel you are killing the power to the entire circuit, but if you are using the switch on the fridge you would still be able to detect a draw from any problems in the wiring. I would think that any problem big enough to cause the charger to overheat would pop the breaker, but you never know.
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Old 21-06-2011, 11:18   #51
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When you suggest "measuring the voltage" what am I actually looking for and under what conditions. Can you be more specific.
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Old 21-06-2011, 13:07   #52
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Re: Xantrex Battery Charger Overheating - Frigoboat Fridge

Bill, I have never considered myself an expert on refrigeration or on liquid deep cycle batteries but I have more than 50 years maintenance and engineering experience with both. Experience in refrigeration ranged from a 4800 horse power set of compressors to the small 12 volt units of today. Having engineering responsibility for thousands of vehicle batteries including electrical vehicles I form your own opinions. I attended conferences on electrical vehicle power controls and battery application. I have read the same information you have and from experience formed my own opinions with why batteries are over stressed while running 12 volt refrigeration while being charged.

I believe Sailorman’s point was short battery life and how does he solve the problem?
If you lower float voltage below 13.2, battery will not receive full charge, I have tried that.
Move boat to a cooler climate.
Place a timer on battery charger. This method is reported to reduce higher battery temperatures.
Install WAECO’s converter so compressor will run on shore power direct switching 110 volt AC to 24 volt DC. His BD35 compressor will also run on 24 volts DC then auto switch back to 12 volts when AC power is lost.
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Old 21-06-2011, 14:07   #53
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Re: Xantrex Battery Charger Overheating - Frigoboat Fridge

Richard,

I have never seen -- either on my own boats or on client's boats -- evidence of house battery stress from running small compressors while being charged.

More to the point: it just doesn't make any sense at all, either from a practical or a theoretical/engineering perspective.

Smart battery chargers will maintain float-level voltage, despite having to furnish varying light-to-medium DC loads for onboard refrigeration, electronics, lights, etc.

What varies is the charging current which, at any given voltage, is controlled by the battery bank itself. It will take what it will take, and no more unless you raise the voltage.

There should be no need to:

"... lower float voltage below 13.2, battery will not receive full charge..." or
"Move boat to a cooler climate" or
"Place a timer on battery charger. This method is reported to reduce higher battery temperatures." or
"Install WAECO’s converter so compressor will run on shore power direct switching 110 volt AC to 24 volt DC."

None of these "remedies" are necessary. Nor, IMHO, are they desirable.

Smart battery chargers are voltage-controlled. It is the preset battery voltage levels which tell the charger what to do, i.e., when to go into
bulk, absorption, or float modes.

A well-designed modern battery charger may be left on 24/7. Mine are: three of them....two on the boat and one at home which maintains a T-105 bank. No overcharging. No excessive loss of water.

Altogether, with three separate chargers and three banks of batteries (totaling 10 Trojan T-105's), I have something like 20 user-years of service in this 24/7 mode. Only changes I've made recently -- after extensive battery testing for another project -- was to raise the float voltage and absorption voltages, and to increase the frequency of "repeat absorption" charges on the six-battery bank maintained by the Victron Mult-Plus. This has resulted in the past nine months in a very significant INCREASE in battery capacity...almost to new levels. Meanwhile, the other two banks which were maintained at 13.6V float levels have deteriorated over the past 5 to 6 years, and are at approximately 60% of their original capacity.

I think the OP has another problem which, in the absence of reliable objective data from onboard amperage and voltage measurements, remains obscured.

And, BTW, I DO consider you to be a refrigeration expert, even if you don't :-)

With best regards,

Bill
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Old 23-06-2011, 08:01   #54
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Re: Xantrex Battery Charger Overheating - Frigoboat Fridge

Bill, If your small 12 volt refrigerators maintain desired box temperatures 24/7 from battery chargers and do not need battery water added and batteries last more than six years I agree you are not adding much undo stress to batteries. My experience in the tropics is it is almost impossible even in winter to keep battery temperatures while connected to charger below 80 degrees. At 100 degrees and 13.2 continuous volts from charger new batteries out gas and need water at 6 weeks, if 12 volt refrigerator is left running at the dock.
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Old 23-06-2011, 08:24   #55
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Re: Xantrex Battery Charger Overheating - Frigoboat Fridge

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Originally Posted by Richard Kollmann View Post
Bill, If your small 12 volt refrigerators maintain desired box temperatures 24/7 from battery chargers and do not need battery water added and batteries last more than six years I agree you are not adding much undo stress to batteries. My experience in the tropics is it is almost impossible even in winter to keep battery temperatures while connected to charger below 80 degrees. At 100 degrees and 13.2 continuous volts from charger new batteries out gas and need water at 6 weeks, if 12 volt refrigerator is left running at the dock.
John,

Yes, I agree that charging voltages need to be adjusted according to ambient temperature. Trojan recommends a decrease of 0.28V for every 10 degrees F above 80F. So, for flooded batteries in 100F temperatures their recommendation for float voltage would be 13.2V minus (2 * .28) = 12.64V.

To my mind, all flooded batteries should be fitted with either WaterMiser or HydroCaps to reduce water loss. REDUCE, not eliminate. My batteries all have WaterMiser caps, and they DO require periodic watering, even at 70-80F ambient temperatures.

There's no way around this. Either you use adequate float voltages and carry out the needed inspection and watering periodically, or you reduce the float voltages to reduce watering intervals and as a result you promote faster sulfation of the plates, thereby shortening the life of the batteries. Take your choice :-)

Leaving the frig on and the boat on shorepower has little to do with this reality.

Cheers,

Bill
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Old 23-06-2011, 08:39   #56
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Re: Xantrex Battery Charger Overheating - Frigoboat Fridge

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Originally Posted by Richard Kollmann View Post
Bill, If your small 12 volt refrigerators maintain desired box temperatures 24/7 from battery chargers and do not need battery water added and batteries last more than six years I agree you are not adding much undo stress to batteries. My experience in the tropics is it is almost impossible even in winter to keep battery temperatures while connected to charger below 80 degrees. At 100 degrees and 13.2 continuous volts from charger new batteries out gas and need water at 6 weeks, if 12 volt refrigerator is left running at the dock.
A reason to use a smart charger that employs a battery temperature sensor. Mine has one and in hot weather the voltage will drop to 13.05v and cooler weather I've seen 13.3volts.
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Old 23-06-2011, 13:24   #57
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Update on Xantrex Charger Overheat Problem

Just a quick update on where I am with this.

1. I called Xantrex Support. Not a lot of help. They suggested I check if the refrigerator is connected directly to the battery (It isn't); and offered to send me a new (third) charger if I ship the old one to them. They seem to work on the basis that if there is any doubt, send out a new charger. Shipping the charger to Xantrex and getting the replacement will take time so I'm going to continue to investigate if there is a connection issue on the refrigerator circuit.

2. I took some initial voltage and amp readings off the house batteries and refrigerator with the charger on and off and didn't see anything unusual but need to run those tests again. Maybe someone here could share what exactly I'm looking for in these tests and what would be an indicator of a problem. I did see a drop off in voltage when I was on the batteries at the batteries but not sure if this would be expected if the fridge is drawing current off them. The amp flow seemed to be the same at the battery and refrigerator.

3. Nothing on the AC side appears to be a problem. Cords, outlet and connections all appear to be good.

If anyone could offer some specific instructions, let me know.
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Old 23-06-2011, 15:49   #58
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Re: Xantrex Battery Charger Overheating - Frigoboat Fridge

I know you asked about what to look for before, and I'm sorry for not answering. Just haven't had the time or energy to walk you thru all the tests and possibilities.

A thought just occurred to me, though: we don't really know for sure that the Xantrex is overheating, just that the temp warning light comes on. It's possible that the problem is a faulty temp sensor....these are frequently found these days, unfortunately.

You'll need to turn EVERYTHING off for these tests, except shorepower, battery charger, and frig.

What to check:

1. voltage at the house batteries with the charger on and the frig compressor running;

2. voltage at the terminals of the compressor while it's running and the charger is on;

3. amperage drawn by the compressor (you'll need a clamp-on ammeter for this) while it's running, measured close to the compressor;

4. amperage drawn by the compressor while it's running, measured at the batteries.

5. if your ammeter measures in-rush current, that would also be useful (measure during compressor startup).

Now, turn off the shorepower.

6. voltage at the house batteries with the charger OFF and the frig compressor running;

7. voltage at the terminals of the compressor while it's running and the charger is OFF; and

8. resting voltage at the battery terminals with everything OFF (after the compressor has run about 30-60 minutes to take the surface charge off the batteries.

If these tests don't turn up anything strange or unexpected, then I'd suspect the temp sensor in the Xantrex. Maybe, just maybe, you don't have a problem after all :-)

Bill
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Old 23-06-2011, 16:14   #59
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That's helpful. Thanks. One question though. What would be considered strange or unexpected? I realize there are many potential things that can go wrong but can you give me a few examples of things to watch out for.
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Old 23-06-2011, 16:54   #60
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Re: Xantrex Battery Charger Overheating - Frigoboat Fridge

Reverse polarity between charger and battery is a good place to start.
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