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Old 08-11-2015, 07:44   #1
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Running Refrigeration Off Of Battery Charger?

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?

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Old 08-11-2015, 07:59   #2
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Re: Running Refrigeration Off Of Battery Charger?

I have seen an instance in which a boat is effectively running the refrigerator straight off the battery charger - reefer is hooked to one small battery which acts as a capacitor.

In my case, the reefer runs off the house batteries, which are charged with the battery charger if I were to plug in, or are recharged by solar and/or engine, if not plugged in.

The reefer only sees whatever the battery is delivering, and the charger only cares that it sees a need to charge the battery, that is to say.

Or am I not understanding the question?
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Old 08-11-2015, 08:10   #3
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Re: Running Refrigeration Off Of Battery Charger?

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.

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?
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Old 08-11-2015, 08:16   #4
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Re: Running Refrigeration Off Of Battery Charger?

Nothing wrong with it. Refer doesn't know or care if the power comes from a battery, charger, DC power supply or what.

The only possible negatives I can think of.

- You have a cheap, horrible charger (unlikely if it's any half decent marine charger) that puts out pulsed DC. The batteries in the system should smooth out that kind of power (IE like a capacitor) but potentially not good for DC powered appliances, especially if running direct without a battery in the system.

- If you do this for a long time at a dock your house batteries could be on their last legs and you wouldn't know it because the charger is doing all the work.

- Charger is programmed to do battery equalization at a high voltage say >15V. Some devices don't like this. You would have to check the specs on the refer and the programming on the charger.

The first is unlikely and the second easily dealt with if you pay attention to your battery's condition.
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Old 08-11-2015, 08:28   #5
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Re: Running Refrigeration Off Of Battery Charger?

Battery chargers vary considerably in the "quality" of DC that they provide to the electrical system. A battery installed as part of the system helps mitigate a poor quality charging voltage. Battery chargers and DC power supplies are really different animals.

Early on I was concerned that while connected to shore power and a charger, that the DC refrigeration switching on and off might trigger the charger into the bulk/ acceptance/ float modes over and over and thus cook the batteries. After 20 years and several small DC refrigeration systems it has not been a problem. 400 AH of GC batteries and Xantrex Freedom inverter/ chargers.

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Old 08-11-2015, 08:48   #6
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Re: Running Refrigeration Off Of Battery Charger?

Any decent battery charger is going to attempt to supply current until a certain voltage is reached, and then hold that voltage with a variable current for a set point until decreasing the current to hold a lower voltage.

Since the reefer is not a current storage device, this will wreck havoc with the battery charger, and it will be putting out voltage all over the place.

You could probably get away with a direct connection using an old-time ferro charger that just sits at one voltage.

The batteries in your setup are just acting as a ballast - the charger is happy and your reefer is happy. It is valid to think of it as the equivalent of power going directly from the charger to the reefer, although it technically is not.

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Old 08-11-2015, 09:36   #7
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Re: Running Refrigeration Off Of Battery Charger?

Simple battery chargers are trying to determine battery charge level, and adjusting output accordingly, by looking at how its output is being consumed. Putting even a constant load introduces some error into that type of measurement, putting a cycling reefer is going to confuse the hell out of it.

It kinda works because as you turn
on loads, the charger algorithm might see 'more acceptance' or perhaps 'lower voltage' and increase output accordingly, but without a charge system specifically isolating measurement of load current from battery charge acceptance, the charger will be a bit confused. Its making output decisions based on a baked in model of how the bank behaves, its model of the system will be innaccurate since it doesnt include these other loads. That means you'll likely end up chronically overcharging or undercharging.
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Old 08-11-2015, 11:50   #8
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Re: Running Refrigeration Off Of Battery Charger?

10a charger is pretty small. it'll be running hard all the time and might get hot and may not last too long. a 10a charger is for maintaining full batteries.


generally boats running off shore power have chargers in the 40-100a range. these have built in fans and are designed to output constantly.


every boat I work on is plugged into shore power 99% of it's life with things on the boat left on.
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Old 08-11-2015, 12:03   #9
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Re: Running Refrigeration Off Of Battery Charger?

"A battery charger must always be connected to the battery, never directly to the refrigerator's electronic unit."
Better translation: A battery charger is not the same as a DC power supply. You'll find that emphasized with Honda's portable gensets as well. The 12V power output is for charging batteries, NOT for powering electronics. This is usually because the "12 volt DC" power is not a pure ("clean") DC power source, but it has some AC components to it.
Somewhere on the web there's a well-illustrated article by a ham radio operator who has oscilloscope traces posted, showing exactly how "dirty" the DC output of a Honda actually is. Batteries don't care, and if there's a battery at the common junction, it usually "eats" the dirt. But electronics get insulted, sometimes mortally insulted, by getting DC that isn't clean. Sometimes it drives them nuts, sometimes it causes programming to be reset, sometimes it simply burns them out.
As a practical matter? You hope the big hungry battery "eats" all the problems before the electronics can notice it. Or you add in-line power filters or conditioners to protect the electronics a bit more.
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Old 08-11-2015, 12:52   #10
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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
Nothing wrong with it whatsoever. Yes, the charger will replace the power as its used. It is actually supplying the power, to speak more precisely, as the charger will ramp up the current to match the power draw when it feels the voltage sag from the load, maintaining the system at float voltage. Practically no power will be flowing in or out of the battery. You can easily check this yourself using a clamp meter.


I don't know why others are discussing direct connection of consumers to battery chargers, without a battery, which was not the question.

It's interesting, however. Battery chargers are different. Better ones are specifically rated to act as power supplies. My previous Newmar, and current Victron, specifically permit such usage.


"* Use as a power supply; can power loads without a battery in line"

Newmar | PT Series Battery Chargers | 24 and 32 VDC | 8 - 95 Amps
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Old 08-11-2015, 13:19   #11
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Re: Running Refrigeration Off Of Battery Charger?

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Originally Posted by smac999 View Post
10a charger is pretty small. it'll be running hard all the time and might get hot and may not last too long. a 10a charger is for maintaining full batteries.


.
I'm finding that statement hard to swallow.
Most 12 volt refers draw considerably on the south end of 10 amps. And not a constant draw. So as I see it the setup will work. An idea would be to put the ten amp charger on a timer to run a couple hours 2 or 3 times a day. To keep the batteries charged but not cooked.
Similar to this
Amazon.com: GE 15076 24-Hour Plug-In Mechanical Timer: Home Improvement
I have used them on several boats in the past
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Old 08-11-2015, 13:21   #12
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Re: Running Refrigeration Off Of Battery Charger?

Many years ago, we unintentionally did it for 2yrs with an AC/DC fridge before we realized the relay that kicks the fridge over to 110v AC when connected had failed, so it always ran off DC.








No harm but once I realized what was going on a $15 relay and it auto-selected the power source again.
Never noticed any battery issues but I think it was a bigger charger than 10amps.
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Old 09-11-2015, 04:08   #13
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Re: Running Refrigeration Off Of Battery Charger?

Delancy has a Guest 10A ChargePro (probably #2611) which is a 3-stage charger.
Stage 2 (Absorption) charges at a rate of 3 to 9 Amps, at 13.2 to 14.3 VDC.
Wired as he describes, this shouldn’t present a problem for the charger, batteries, nor refrigerator.
http://s3.amazonaws.com/szmanuals/f8...4b232edea758b9
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Old 09-11-2015, 05:31   #14
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Re: Running Refrigeration Off Of Battery Charger?

Yes, but, don't you love the buts

A 10 amp charger is rather small, if he has much of a bank, and it is discharged by not much at all, a 10 amp charger is going to take quite awhile to recharge it. There are other reasons to get a larger charger as well
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Old 09-11-2015, 06:10   #15
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Re: Running Refrigeration Off Of Battery Charger?

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
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