Watt hour relationship

[cisumma]

I need to run a 115 watt hour fridge in a 450 ah 24 volt lead acid AGM vmaxtank battery; and, the two 355 watt PV rated in series at 110 v and 32 amps
Can this be possible?
I have yet to learn the watt hour relationship.
Thanks

 

[Bud Martin]

I need to run a 115 watt hour fridge in a 450 ah 24 volt lead acid AGM vmaxtank battery; and, the two 355 watt PV rated in series at 110 v and 32 amps
Can this be possible?
I have yet to learn the watt hour relationship.
Thanks

AGM batteries of 450Ah = 225Ah of usable Ah, so 225Ah x 24V = 5400Whr.
Is your your fridge 120VAC? If it is then you will need inverter which will also have conversion loss too that has to be factored in.
No your panel, two 355 Watts panels in series at 110V and 32Amps. Where did you get the 32Amps number from? What are all the spec the panel? What is Voc, Vmp, Imp of the panel? 355W panel at 55Vmp, the current will be only 355W/55VMP = 6.45A so your info are not correct. Please provide more details of what you have.

 

[cisumma]

The frig says 115v at 1 amp and the panels are rated at 48.7 v at 9.06 amps
Incidentally, the battery bank is 450 amp hours; so, 450/2 gets me 225 ah

Actually, I come up with 28.3125 amps. I was trying to fuse the 10awg homerun to a 30 amp fuse. At some point I ended out with 32 amps.
Thanks.

The MPP is all in one 2.4 kw 80 amp sys

 

[cisumma]

So, 5400wh/115w = 46.9565217391h , and that doesn't sound reasonable.


Also, I have 120v ,12 amp chest freezer.
120v*12a=1440w
; and,


5400wh/ 1440w= 3.75 h this is possible I suppose but I am not sure; because, during the day I will have roughly 3.3 hrs of peak sunlight and at least 10 hrs of light.

 

[iamrich]

You don't have enough panels. If your fridge uses 115w per hour (wh) and you run it 24 hours a day, you will be using 2760wh. So you need to generate at least that much from your panels everyday or you will run out of power (no matter how big your battery is).


Well I guess if you get 5 hours of sun and the panels put out max, and you don't have much loss in the LV2424 you might just make it (710wx5h=3550wh)

 

[iamrich]

So, 5400wh/115w = 46.9565217391h , and that doesn't sound reasonable.

5400wh/115wh = 46 hours. You can go 46 hours before your battery is at 50%, assuming no charging from the solar

Also, I have 120v ,12 amp chest freezer.

This is unlikely. I don't think I want to see a freezer that uses 35kw a day But if that is accurate you are going to need at least 7-8kw of panels which is well beyond the LV2424.

 

[wholybee]

To help with your original question. Watt hour is literally, Watts x hours.
A 115W fridge, run for 24 hours is 2760Wh.
Watts = Volts x Amps. The Fridge says it's 115V at 1A. So the Fridge is 115 Watts. NOT 115 Watt hours like you state in your first post.
So, your calculation of 5400Wh/115Wh is incorrect, because it should be 5400Wh / 2760Wh.

The same calculations can be made with your panels. 2 x 355W panels = 710W. Assume (guess) you will make power for 5 hours per day. 710W x 5h = 3550Wh. So you probably have enough to run your fridge. I would double check the specs on the freezer. But even if they are more reasonable(similar to the fridge) you will need a couple more panels.

 

[Bud Martin]

To help with your original question. Watt hour is literally, Watts x hours.
A 115W fridge, run for 24 hours is 2760Wh.
Watts = Volts x Amps. The Fridge says it's 115V at 1A. So the Fridge is 115 Watts. NOT 115 Watt hours like you state in your first post.
So, your calculation of 5400Wh/115Wh is incorrect, because it should be 5400Wh / 2760Wh.

The same calculations can be made with your panels. 2 x 355W panels = 710W. Assume (guess) you will make power for 5 hours per day. 710W x 5h = 3550Wh. So you probably have enough to run your fridge. I would double check the specs on the freezer. But even if they are more reasonable(similar to the fridge) you will need a couple more panels.

1) Wh/Wh = Unit Hour, since fridge is rated at 115V and consumes 1A, so power is 115V x 1A = 115W, so in 1 hour the fridge uses 115Wh of power or in 24 Hr (1 day) it will be 2670Wh/Day. So as to how long the load will run in Hour will be about 46.95 Hour (5400/115) or 1.96 Days (5400/2760).
2) The fridge compressor will never run 24/7, it will cycle on and off depends on how well the insulation is, room ambient temperature, amount of cold mass inside the fridge. Typical compressor will be running 50% per hour, if the compressor runs 24/7, that will be bad news, so average out Wh or Wh/Day will be less than the calculated value above.
3) When you use inverter to convert DC to AC there will be conversion and system loss, so to get 115W of power on the AC output of the inverter, the inverter will use about 15% more power than it puts out, that means the input power will be about 132W to produce 115W on the output of the inverter.

 

[cisumma]

Thanks ,
I will have to digest this info.
In the real world I am temporarily attempting to hook up two panels temporarily, I need to maintain the battery because grid power is of [ as part of my savings plan, go figure ,right?]

I have 6 panels all together and my goal is to have basic refrigeration. I will have to run the 12 amp or 1 amp appliance according. Probably with a bag of ice .
But lights and charging and 5 hrs of refrigeration is an attempt at luxuries of basic survival.
Thanks again.

 

[iamrich]

With six panels you should be fine. 2130w per hour off the panels (best case) puts you at almost 6kw a day in winter (3 hours of sun). You will be able to replenish what you use off your battery each night with the solar.

 

[cisumma]

Thanks so much, now I have to find a ground mount rack. I ve been calling " Unbound solar "; but, they don't want to call back.
I guess I could get 2 inch service 40 steel and electricion steel and put one together.
Thanks again.

 

[MisterSandals]

I need to run a 115 watt hour fridge

How did you come up with this number? Its seems a little high.
I have a 27cuft (big!) energy star fridge that runs at 125w for about 1/3 of the time and 20w the remaining 2/3 of the time.
(125w x .33h) + (20w x .66h) = 54wh per hour. x24 = 1307wh daily.

Are you measuring the watts when it is running? Do you know what percentage of the time its actually running and what is uses (for display and other wasteful things) when not running?
The tricky bit of this is the defrost cycle and ice maker cycle are REALLY hard to measure and account for.

 

[iamrich]

You could probably use pressure treated posts and unistrut from Home Depot (or similar). I would run the panels 2S3P and face them in slightly different directions to extend your day (say Southeast, South, Southwest). You will get less power per hour, but will get power flowing longer. You would need to fuse/breaker each string, but I think it would be worth it. You might start making power as early as 9am and keep it going until 5-6pm this time of the year.