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food:refrigeration:power [2024/05/09 17:32] frater_secessus [charging from alternator] |
food:refrigeration:power [2024/05/09 17:55] frater_secessus [power and duty cycle] |
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===== TL;DR ===== | ===== TL;DR ===== | ||
- | * compressor fridges are a part-time load; as a rule of thumb we can assume the compressor will be running 1/3rd of the time. | + | * [[food: |
- | * but they will consume Wh (Watt-hours) over a 24-hour period | + | * they will consume |
- | * you must make power to recharge the bank | + | * you must have at least enough charging capacity |
- | * and have enough bank to make it through periods where charging is absent | + | * and have enough |
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60w x 0.33 duty cycle x 24 hours = **480Wh** required each day to run the fridge. | 60w x 0.33 duty cycle x 24 hours = **480Wh** required each day to run the fridge. | ||
+ | ==== why think about it 24hr terms? ==== | ||
+ | |||
+ | * offgrid power consumption is often considered in terms of daily cycles | ||
+ | * solar power occurs in daily cycles | ||
+ | * overlanders and others who travel often (and for whom alternator charging is practical) think of driving in hours per day | ||
===== battery bank capacity ===== | ===== battery bank capacity ===== | ||
- | The battery bank capacity is dependent on a few factors: | + | The battery bank capacity |
- | * how deeply the chemistry can be discharged (~50% for lead, ~80% for LiFePO4) | + | * how deeply the chemistry can be discharged (~50% for [[electrical: |
* nominal voltage (12.0v for lead, 12.8v for LiFePO4) | * nominal voltage (12.0v for lead, 12.8v for LiFePO4) | ||
* days of " | * days of " | ||
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==== charging from solar ==== | ==== charging from solar ==== | ||
- | Charging from [[electrical: | + | Charging from [[electrical: |
- | You will need to [[electrical: | + | You will need to [[electrical: |
December in Belle Fourche has only 1.52 hours of FSE. It would take ~375w of panel((flat-mounted, | December in Belle Fourche has only 1.52 hours of FSE. It would take ~375w of panel((flat-mounted, | ||
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Average 1378 | Average 1378 | ||
+ | table based on the PVwatts link above | ||
==== charging from multiple sources ==== | ==== charging from multiple sources ==== | ||