Double juice & quad up reserve

[THDLink]

I will be setting up two 100 watt panels, one mono the other poly(just cuz). There will be four 6 volt 220amp batteries with 300 max inverter. All 12 volt. There will be a mini fridge running on this setup and/or pumps ect. Pics going up soon 
Any comments on the balance of power? Chime in, I haven't bought batteries yet.
It gets real cloudy here for like days at a time, I think the large reserve should do it for a mini fridge.

[southpaw]

We need specs on the mini fridge to make informed comments. Some mini fridges use more energy than full size fridges.

[THDLink]

The mini fridge should be 0.9 amps. I read most are. This is the sweet spot of efficiency on my inverter which maxes out at 2.5 amp 120ac. I didn't mention I haven't  bought the fridge

[THDLink]

Should I dump load in solar? Sometimes my mechanical relay heats up from switching when system is full. Only switches every 3 seconds but still heats up in the evening of a sunny day. Thanks for your response southpaw.

[PaulJ]

Need to know the av daily power use of the fridge, guessing will just get you into trouble.
0.9A x 120V x 24 hrs = 2.6kWh if the thing runs continuously - way more than your panels will make on average.
If the compressor runs intermittently you will use substantially less than that, ~50% or so, maybe less. Still not going to cut it with 2ooW of panels if it's in use 24/7.

As southpaw said, a full size fridge may use less power if you get an efficient one.
Spending money up front on efficiency will pay for itself very quickly in an off-grid setup.

Chest freezers converted into fridges can be extremely efficient.

[THDLink]

yes! this is important. Sometimes i forget the basics having put down the alternative energies for a while. good input. I think I'll be able to get one off the college kids hopefully it won't run all the time. On the other hand i could get a new one for a hundred dollhairs' with it's daily  use info and no funk. looks like a 2.4cuft (smaller) style mini fridge uses an average:

e-star rated .75 KWH/day.

2 panels = 200 watt max

so. 2 panels at average 50% output for 10 hours= 1000whrs = 1KWHr average,

4 days of darkness = -3kwhrs
220ahr battery
.22KAhrs x 12volts = 2.64KWhrs
x2batteries..
5.28KWhr reserve
3/5.28= ~60% battery

in theory would take twelve days to recover. but it doesn't get Totally dark here like 0%.
is this a safe number though, factoring in snow cover?

note it's either super bright or super cloudy here and o.m.g. the snow and sleet and freezing rain.

this is my first time "around"...
any winter weather tips would be great


edit- forgot 30% loss in recharging the bank

[Mary B]

You won't get full output for 10 hours unless you are using a tracker! More like 3-4 hours of full output then it tapers off.

[PaulJ]

"note it's either super bright or super cloudy here and o.m.g. the snow and sleet and freezing rain."

Put the fridge outside / in an unheated room in winter and it will use very little power.

[Judd]

Hello everybody,
            I am new to fieldlines, I applied yesterday and got to join today. I have lurked here in the past and learned quite a bit from the members posts. Some of the members are extremely knowledgeable in electronics. I wish I could say the same for myself but i only decided to go off-grid in 2002 and it has been a steady learning curve since then. I am no expert but ,i did manage to set up our own off-grid system of 4kw of pv and a turbine which supplies the house and shed quite easily. I have a good weight of forklift batteries to store the energy and I have been pretty lucky with some of the decisions and buys that I have made.
             Let me also add,that I am a fan of Oztules and I commend him for all his fantastic advice on transformers, etc. I just happened to pop in as the thread of the transformers was getting going. It was so interesting that my wife downloaded the whole thread and sometime in the future, I intend to give it a go.
  PaulJ  happened  to mention that chest freezer converted to fridges are extremely efficent, Let me second that statement, it is indeed very true. You can do it the simple way with a timer or buy the conversion kit which is simple enough to install. The Chest freezer does not lose all its cold air the moment you open the door, so it has a good head start on the upright version from the word go.
                                                                   Judd

[THDLink]

That's a good fridge idea. The chest fridge point makes sense. Hi Judd!

[Mary B]

I recently converted a 7 cu foot chest freezer to a fridge. Used a PID controller, solid state relay, and a transfer switch to drop it back on grid if I power down the inverter

[Johann]

If you got only 200 watts of solar panel, I am afraid that this is not enough power.
Those mini fridges use about 1,000 watts a day with usable sun power of 4-5 hours per day and not to forget losses of charging and discharging batteries and that those 200 watts  of panels are putting out about 160 watts instead.
A 300 watt inverter is a little bit small for an fridge, since the start-up power can be 4-5 times higher than the name-plate rating. So 120 volts times 0.9 amps =108 watts times the start up power = times 5 is over 500 watts. If your inverter is an modified inverter then the inverter may use even more power since the efficiency is lower.
Remember, you have to put the power back into the battery again that you take out. So, basically you still have to run your mini fridge and also have to charge your battery bank at daytime.


You also mentioned some pumps? power consumption?

[DamonHD]

1,000 watt *hours* a day.

Let's please be careful with the difference between power and energy.

Rgds

Damon