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Old 09-11-2015, 06:10   #16
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Re: Running Refrigeration Off Of Battery Charger?

I used to have a guest 6 amp charger......admittedly not a 10, but these things are meant to charge a trolling motor battery, without a load on it. Mine is still in use, but no longer on the boat. When I tried to use it like you are it was boiling my batteries (ok, not really boiling, but never getting into float and I went through a lot of water).
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Old 09-11-2015, 06:27   #17
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Re: Running Refrigeration Off Of Battery Charger?

Most 12V DC Evaporator Refrigeration units draw less than 5 - 6 Amps (some as little as 2.5 A), when running.
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Old 09-11-2015, 06:31   #18
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Re: Running Refrigeration Off Of Battery Charger?

Thanks for the all the feedback. At present I just have a couple hundred Ahours of AGM batteries. I'll be building a more robust system in the near future so mainly hoping to not wreck anything in the meantime.

Gord identified the correct charger. Also, when up and running the refrigerator only draws 3.5 amps.
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Old 09-11-2015, 08:22   #19
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Re: Running Refrigeration Off Of Battery Charger?

Running a charger direct to the reefer, and not through batteries, is the biggest issue. It might work without the batteries but it all depends. Your small bank of batteries would be fine. Your bigger concern would be what would happen if the AC goes out. We lost ours for about a week this winter already and the marina does not guarantee steady power.
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Old 09-11-2015, 09:17   #20
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Re: Running Refrigeration Off Of Battery Charger?

Quote:
Originally Posted by Delancey View Post
Battery charger powered by shore power connected to batteries, refrigeration connected to batteries. What is wrong with this?

How is it any different charging batteries from solar or the diesel? What exactly happens anyway? I have a Guest 10amp Pro Charge. Is it replacing electricity to the batteries as it is being used?

Thanks
Your charger will provide greater than 12V and it won't be smooth in a way that devices expect. Your batteries also act to dampen out the charger input which will vary greatly in terms of voltage, current and frequency.

The internal resistance of the batteries then provides relatively constant voltage that is very smooth. DC powered devices work most efficiently and last longest when provided with clean, smooth 12V power.

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Old 09-11-2015, 09:32   #21
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Re: Running Refrigeration Off Of Battery Charger?

If I may add a slight correction to this.

How smooth or clean the charger output can vary a lot from one model to the next. There are some that put out a very clean 12V and others that output a very nasty, pulsating DC.

Also, since 99% of the 12V powered devices are designed to work in cars, boats, etc they are mostly quite tolerant of DC voltages higher that 12V. A fully charged lead acid battery will be about 12.6V. Plus almost all the cars, trucks, boats, RVs and such have alternators that charge at 13.5-14.5V which is certainly taken into account by 12V powered equipment designers.

A charger going into EQ mode at over 15V might be an issue for some equipment but normal charging voltages I have never found to be a problem.

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Originally Posted by leftbrainstuff View Post
Your charger will provide greater than 12V and it won't be smooth in a way that devices expect. Your batteries also act to dampen out the charger input which will vary greatly in terms of voltage, current and frequency.

The internal resistance of the batteries then provides relatively constant voltage that is very smooth. DC powered devices work most efficiently and last longest when provided with clean, smooth 12V power.

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Old 09-11-2015, 20:53   #22
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Re: Running Refrigeration Off Of Battery Charger?

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Originally Posted by Delancey View Post
Battery charger powered by shore power connected to batteries, refrigeration connected to batteries. What is wrong with this?

Nothing, typical install.

How is it any different charging batteries from solar or the diesel?

It isn't. The battery doesn't know where the electrons are coming from

What exactly happens anyway? I have a Guest 10amp Pro Charge. Is it replacing electricity to the batteries as it is being used?

Yes. If you are running an icebox conversion with Danfoss BD-35 or equal, it is drawing about 5 amps from the battery when running. Your charger will be supplying the 5 amps back to the batteries that they are giving up to the fridge. (That's the oversimplified version, your battery charger may increase / decrease output depending on it's charge algorithm, but in the long run, you have it exactly right.

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Old 09-11-2015, 21:04   #23
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Re: Running Refrigeration Off Of Battery Charger?

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Originally Posted by Delancey View Post
From the manufacturer -

"Shore Power

A battery charger must always be connected to the battery, never directly to the refrigerator's electronic unit. The battery charger shall have a capacity of at least 10A. Another, better solution is to install our Power Pac converter which automatically switch from battery to shore power supply when shore power is connected."

We don't intend to spend a lot of time hooked up to shore power hence are not interested in shelling out the three hundred dollars the manufacturer is asking for the Power pac converter. I just want to understand why they consider it to be "another, better solution" than my current set up.

If you buy the Power Pac it means more money to the manufacturer, so definitely a better solution from their perspective. From you perspective, if you have the power pack, when you connect to shore power, your whole 10 Amps (very light charger BTW) will be recharging the batteries, instead of about half going to run the fridge.

I assume it is because it is converting shore power to 12v and supplying the refrigerator when available, but why is this better? Cycling the batteries less? But are you cycling the batteries when the charger is replacing energy as it is being used? Without the power pack, you are not really "cycling the batteries" BUT they are in a constant state of operation (meaning the chemical reaction is ongoing). If you have the power pack, and no other load on the batteries, they will be idle (more or less) when connected to shore power.
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Old 10-11-2015, 11:04   #24
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Re: Running Refrigeration Off Of Battery Charger?

I think the biggest danger to the fridge's electronics is the Ciggy plug and tiny wiring provided with the fridge.

If one looks at Danfoss BD35f manuals, it also says to wire directly to battery terminals, fused as close to the battery as possible, and not to share any busses with other devices. The gauge wire they recommend is much much thicker than what ampacity charts will say is acceptable to pass 2.2 to 6.5 amps that the Danfoss compressor can pull, depending on the rpm it is set to run at, 2000 to 3500 rpm.

Disregarding the significant voltage drop, which is not as much an issue with a sawafuji compressor compared to a Danfoss, the intermittent nature of a ciggy plug connection has got to wreak havoc when it is just on the cusp of connection/no connection.

Splice some Anderson Powerpoles into the provided cord so You can still use the horrible ciggy plug for the portable factor, but then have a solid 10 AWG wire from fuse panel, or directly from battery to power the fridge, and stop wasting battery power heating up spring steel used in ciggy plugs.

99% of the time when a portable fridge fails to operate properly, it is the dang power cord and ciggy connector causing too much voltage drop or just an intermittent connection.

All ciggy connectors will wear out at some point, and in my opinion should never be asked to pass more than 3 to 4 amps anyway
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Old 10-11-2015, 14:45   #25
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Re: Running Refrigeration Off Of Battery Charger?

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Delancey you may want to do as I do and that is to put both + leads to the house bank to get more output to the house and use the combiner switch to charge the engine bank on the rare occasion that is needed
It isn't a very good idea to hook up a two bank charger this way for the following reasons:

1. Two bank chargers have the smarts to deliver current to the battery that needs it most.

2. When one starts a small engine, it may draw somewhere around 60A for 15 seconds, or 0.25 Ahrs.

3. Even if the 10A charger devoted all of it's output to the starter battery, it would only take 90 seconds to put it back, except...

4. In reality, the starter battery state of charge is still so high, that only a very small percentage of the charger output would go to the starter battery.

5. The user may forget to recharge the starter battery.

6. The starter battery should be recharged immediately every time it is used.

7. If the starter battery is left discharged, the life expectancy will be decreased.

8. Disservice to anyone else who may need to use the system (guest, next owner, etc.) who wouldn't expect it to be wired like this.

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Old 11-11-2015, 07:27   #26
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Re: Running Refrigeration Off Of Battery Charger?

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Originally Posted by ramblinrod View Post
It isn't a very good idea to hook up a two bank charger this way for the following reasons:

1. Two bank chargers have the smarts to deliver current to the battery that needs it most.

2. When one starts a small engine, it may draw somewhere around 60A for 15 seconds, or 0.25 Ahrs.

3. Even if the 10A charger devoted all of it's output to the starter battery, it would only take 90 seconds to put it back, except...

4. In reality, the starter battery state of charge is still so high, that only a very small percentage of the charger output would go to the starter battery.

5. The user may forget to recharge the starter battery.

6. The starter battery should be recharged immediately every time it is used.

7. If the starter battery is left discharged, the life expectancy will be decreased.

8. Disservice to anyone else who may need to use the system (guest, next owner, etc.) who wouldn't expect it to be wired like this.

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His charger is only 5 amps on one leg,not really enough to charge and run the frig! My start battery is being charged any time the engine is running I'm talking about charging the engine battery, engine off plugged in at the dock. The charger manufacturer recommends both leads on one to double the output
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Old 11-11-2015, 08:52   #27
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Re: Running Refrigeration Off Of Battery Charger?

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Originally Posted by sartorst View Post
His charger is only 5 amps on one leg,not really enough to charge and run the frig! My start battery is being charged any time the engine is running I'm talking about charging the engine battery, engine off plugged in at the dock. The charger manufacturer recommends both leads on one to double the output
Well I believe that a 5 amp charger would run the fridge and charge his battery just fine at the dock. At the dock a 5 amp charger is capable of producing 120 ah ( 5 ampx24 hours=120ah) and using our fridge as an example right now it draws 3.5amps with a 4 hour run time per day (3.5 ampx4hours= 14ah per day) o on our boat a 5amp leg would charge the battery and run the fridge just fine. Your numbers will depend on total run time for your refer. YMMV
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Old 11-11-2015, 10:15   #28
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Re: Running Refrigeration Off Of Battery Charger?

Good point
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Old 11-11-2015, 17:19   #29
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Re: Running Refrigeration Off Of Battery Charger?

The charger sees the battery pack as a charge.

If other units are connected to batteries, the charging Amperage correspondingly grows up.

I was told batteries being somewhat transparent between charger and the final charge (absorbing unit)

Again, the charger sees them all at par.
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Old 29-01-2016, 21:32   #30
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Re: Running Refrigeration Off Of Battery Charger?

If the OP is using the battery charger as a 12v power supply with either no batteries or dead batteries, than likely to ruin the charger. Chargers are not power supplies.
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