Should get deep-cycle because they are built for continuous power.
For discharge rates, 5-hour (0.2C) and 20-hour (0.05C), the battery performs best when discharged slowly; the capacity readings are substantially higher at a slower discharge than at the 1C-rate.
Rated capacity vs available or practical capacity:
Reserve Capacity (RC) is the number of minutes a fully charged battery at 80°F will discharge 25 amps until the battery drops below 10.5 volts. For example, "Reserve Capacity Minutes: 130".
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How many hours could a 100 W fridge run, per day, given a 120 W solar panel
attached to a 40-60 Ah battery?
I see 4-6 hours of peak sunlight, but it's still absorbing rays for the other hours of the day. I don't get why those hours aren't also factored in.
5hrs*120W = 600 W-hrs
600W-hrs/100 = 6 hours of time the fridge could run?
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Technically a solar panel will output some voltage at all hours, but little current. Anything except full sun is practically nothing. And a panel "rated" for 120W is under ideal circumstances - they never reach this in reality. My gut is saying that the battery will eventually cycle near empty.
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Cycle near empty meaning destroy the battery?
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Depends on the battery chemistry. Some types, like lead-acid cannot take being completely discharged. All battery types - the deeper you discharge and recharge them, the shorter they will last.
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Yes, but I mean lead-acid.
Probably will be that anyway:
Hmmm, 18 V
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If you don't already own the fridge, you might do better (efficiency and run time wise) to get a mini fridge made to run on 12V. That saves you the losses in the inverter, and reduces the current drawn from the battery.
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I have an energy star rated mini-fridge. I also have a bunch of reflectix and think buying some insulation will be better than buying another mini-fridge.
If it's "Energy Star" rated, then there ought to be information on its energy consumption available. Energy star rated appliances are supposed to tell you the energy consumption for one year of operation. From that you can find the average energy for one day.
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Example
319 kWh/year
(319000 Wh)/365 = 874 Wh/24h
874 Wh/day or, with 80% efficient inverter and assuming 12 V, that's (874/12V)*1.2 = 88 Ah.
Therefore, at least two 75 Ah batteries are needed.
https://www.batteriesplus.com/productdetails/battery/marine-and-boat/deep-cycle/bci-group-24m/sli24mdc
$90 for 65 Ah
https://www.batteriesplus.com/productdetails/battery/marine-and-boat/deep-cycle/bci-group-24m/sli24mdp
https://www.directenergy.com/learning-center/how-much-electricity-does-my-refrigerator-use
This calculator spits out that for a ??? W fridge (running off AC power), given 5 hours of direct sun--needs ??? watt PV system!
| Min | Max | |||
| Spec (per) | Quantity | $ 356.00 | $ 429.00 | |
| 70 Ah | Battery | 2 | Total | |
| $ 150.00 | ||||
| Charge | controller | 1 | $ 14.00 | $ 24.00 |
| 100-150 W | PV cells | 2 | $ 137.00 | $ 200.00 |
| 750 W | Inverter | 1 | $ 55.00 |
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