# Chest freezer on marine batteries. Help!!



## MOSTBCWT (May 5, 2016)

I am looking to run a 7 cubic foot chest freezer using an inverter and deep cycle marine batteries. I have two new interstate 100AH batteries, picking up a "decent" inverter and looking for info on how much solar panel I need to connect to the batteries to maintain operation.

I can figure 6-7 hours per day of sun year round average here in the southeast US. Freezer has a 12a start up and a 1.7a run rating. Want to run it completely off grid and stand alone. 

Wire batteries in series? Parallel? What solar panel size etc?

Any help out there? Thank you in advance.


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## wy_white_wolf (Oct 14, 2004)

All the calculations will be about the same as the mini frig thread so study that. 

First thing you need to do is figure out how much power it uses. Get a Kill-a-watt meter and run it for a week under normal usage. We can run the calculations from there.

2 100AH batteries. My guess is that won't even be close. Take a look at the mini frig thread and you'll see it took over double that. I'd guess you'll need More than it.

No you can not count on 6 to 7 hours a day for insolation. In any off grid system you need to plan for worst case scenario. That would be using the lowest monthly average for your location. In the SE that would probably be around 2.5 hours for December or January.

WWW


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## MOSTBCWT (May 5, 2016)

wy_white_wolf said:


> All the calculations will be about the same as the mini frig thread so study that.
> 
> First thing you need to do is figure out how much power it uses. Get a Kill-a-watt meter and run it for a week under normal usage. We can run the calculations from there.
> 
> ...



Thanks. Youtube has several videos of one or two batteries running a refrigerator/freezer combo or a heat freezer very easily with less battery than I have. Was hoping someone here could do the math. The killawatt meter is irrelevant with knowing the start up and running amps. Thanks again for your response.


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## GREENCOUNTYPETE (Jul 25, 2006)

Thats what the kilowatt meter does is the math , and it does it based on a duration run time.

it is keeping the number of watts used for the duration 

yes it will run on the batteries , the questions is will it run enough to be useful how often will your batteries need a charge 

make sure to fill the freezer with your normal frozen foods to get a read on what it would take with food in it


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## MOSTBCWT (May 5, 2016)

Thank you. I guess the specific thing I'm looking for is how much solar panel I need to maintain charge to those two batteries. Based on what I already know the batteries on their own EACH will run the freezer for a 24 hour period before reaching 50% discharge. If wired parallel I double the battery power. 

How do I figure solar panel wattage needed to keep these charged? Is this what the killawatt tells me? So whatever the killawatt says it's using in a 24 hour period is how much solar panel wattage I need? This stuff messes with my head. Lol


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## wy_white_wolf (Oct 14, 2004)

The Kill-a-watt meter will tell us 1 part of the equation to figure out panel size. Location (insolation) and type of charge controller are the other 2.

From the other thread:



> ...
> daily watt hour requirement *1.5 / minimum monthly sun hour average for a PWM controller or
> daily watt hour requirement *1.2 / minimum monthly sun hour average for a MPPT controller
> ...


 WWW


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## MOSTBCWT (May 5, 2016)

Thnks


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## gpforet (Dec 24, 2013)

Using your data about the battery running your freezer for 24 hours before reaching 50% discharge we can assume you've used 50ah of the 100ah capacity.

So, and this is a rough estimate: A single 100watt panel will replenish the 50ah in about 12 hours of sunshine. So a 200watt panel will do it in 6 hours. As was mentioned earlier, for off-grid applications, you'd have to plan for worst case, both in terms of battery capacity and panel sizing.

If you are using conventional flooded cell lead-acid, it's best to charge at a rate equal 1/10 their rated capacity to keep the electrolyte from statifying. In your case that would be about 10 amps.

My rig is 4-6v GC batteries in series running a 24v pure sine inverter with 2-250w panels and keeps my fridge and freezer running for 3 days without any solar input to a 50% discharge. The panels will top up the batteries in 5 hours.

Good luck.




MOSTBCWT said:


> Thank you. I guess the specific thing I'm looking for is how much solar panel I need to maintain charge to those two batteries. Based on what I already know the batteries on their own EACH will run the freezer for a 24 hour period before reaching 50% discharge. If wired parallel I double the battery power.
> 
> How do I figure solar panel wattage needed to keep these charged? Is this what the killawatt tells me? So whatever the killawatt says it's using in a 24 hour period is how much solar panel wattage I need? This stuff messes with my head. Lol


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## MOSTBCWT (May 5, 2016)

Thank u


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## frankieboy (Oct 16, 2007)

How are you guys determining the battery bank is drawn down to 50%, by remaining voltage or some other approach. If voltage, what voltage is it that you consider 50%?


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## MOSTBCWT (May 5, 2016)

I use a meter that shows % of charge.


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## TnAndy (Sep 15, 2005)

MOSTBCWT said:


> I use a meter that shows % of charge.



Which is a voltmeter with % of charge on the face instead of volts.

You can use a voltmeter (must read to two places right of decimal), or use a tester for specific gravity. Volt reading need to be take with no draw (open circuit), and an hour after the last charge applied to the battery.

For a 12v battery:

100% = 12.73v

80% = 12.50v

50% = 12.10v

http://www.trojanbattery.com/BatteryMaintenance/Testing.aspx

You also have to consider depth of discharge (DOD)......the deeper you discharge a battery, the less number of times you can do so before it is "kaput".


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## MOSTBCWT (May 5, 2016)

TnAndy said:


> Which is a voltmeter with % of charge on the face instead of volts.
> 
> You can use a voltmeter (must read to two places right of decimal), or use a tester for specific gravity. Volt reading need to be take with no draw (open circuit), and an hour after the last charge applied to the battery.
> 
> ...



So what are you trying to say as it relates to what I'm doing? I'm confused. Lol


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## TnAndy (Sep 15, 2005)

Sorry.....I meant that for Frankieboy, who was asking about DOD and voltage....not as a comment on what you're doing, which I think has been covered pretty well.


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## MOSTBCWT (May 5, 2016)

TnAndy said:


> Sorry.....I meant that for Frankieboy, who was asking about DOD and voltage....not as a comment on what you're doing, which I think has been covered pretty well.



That's why I asked since you quoted me. Lol. Thanks for contributing


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## Fire-Man (Apr 30, 2005)

MOSTBCWT said:


> That's why I asked since you quoted me. Lol. Thanks for contributing


MOSTBCWT, remarks like you gave wy-white-wolf to start with---- ""The killawatt meter is irrelevant with knowing the start up and running amps."" makes it sound like you know more than they----and appeared to be a "Insult" to his brilliant knowledge and Now you seem to be starting with TnAndy. These are two Smart guys and know their Stuff and they do not take kindly to insults. 

Do you realize a freezer does Not run 24/7 so knowing how much start-up and how much running amps will not Help you at all---Unless you can figure out accurately how many times per day it starts up and how many minutes it runs per day, but then you can not know that because how you use it effects all them numbers----you understand that?


Now your freezer---just a simple question or a few'

Are you going to be using it as a freezer?
Do you realize once frozen a freezer draws less power when kept full than empty?
Do you realize that how much power it uses will be according to how you use it----think on this----it stays full of frozen stuff compared to you adding large amounts of unfrozen things to it often will make it Draw a lot more than just keeping it closed, full of froze stuff all the time?

If you took a kill-a-watt meter and monitored your usage for some time then it will tell "them" how much wattage you need so the amount of panels/wattage and the size of the battery bank can be figured.


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## MOSTBCWT (May 5, 2016)

Fire-Man said:


> MOSTBCWT, remarks like you gave wy-white-wolf to start with---- ""The killawatt meter is irrelevant with knowing the start up and running amps."" makes it sound like you know more than they----and appeared to be a "Insult" to his brilliant knowledge and Now you seem to be starting with TnAndy. These are two Smart guys and know their Stuff and they do not take kindly to insults.
> 
> Do you realize a freezer does Not run 24/7 so knowing how much start-up and how much running amps will not Help you at all---Unless you can figure out accurately how many times per day it starts up and how many minutes it runs per day, but then you can not know that because how you use it effects all them numbers----you understand that?
> 
> ...



I appreciate your response as well as everyone else's. I'm not really concerned with how you perceive a text conversation as they have no emotion. I've graciously thanked everyone who has assisted so no need for an assumption of negative things that do not exist. Thank you for your contribution. Good evening.


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