This shows you the differences between two versions of the page.
Both sides previous revision Previous revision Next revision | Previous revision Next revision Both sides next revision | ||
food:refrigeration:power [2024/05/09 17:42] frater_secessus [battery bank capacity] |
food:refrigeration:power [2024/05/09 17:55] frater_secessus [power and duty cycle] |
||
---|---|---|---|
Line 6: | Line 6: | ||
===== 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: |
* they will consume a given number of Wh (Watt-hours) over a 24-hour period | * they will consume a given number of Wh (Watt-hours) over a 24-hour period | ||
* you must have at least enough charging capacity to replace at least that amount of Wh | * you must have at least enough charging capacity to replace at least that amount of Wh | ||
- | * and have enough bank to make it through periods where charging is absent | + | * and have enough |
Line 20: | Line 20: | ||
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 requirement is dependent on a few factors: | The battery bank capacity requirement is dependent on a few factors: | ||
- | * 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 " |