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food:refrigeration:power [2024/05/09 16:52] frater_secessus [charging] |
food:refrigeration:power [2024/05/09 17:42] frater_secessus [battery bank capacity] |
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* 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. | * 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. | ||
- | * compressor fridges don't take a lot of current | + | * they will consume |
- | * but they will consume Wh (Watt-hours) over a 24-hour period | + | * you must have at least enough charging capacity |
- | * you must make power to charge the bank | + | |
* and have enough bank to make it through periods where charging is absent | * and have enough bank to make it through periods where charging is absent | ||
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The compressor only runs as needed. | The compressor only runs as needed. | ||
- | 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. |
===== 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 lead, ~80% for LiFePO4) | ||
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* ≥**47Ah of LiFePO4** (480Wh / 0.8 depth of discharge / 12.8v nominal) | * ≥**47Ah of LiFePO4** (480Wh / 0.8 depth of discharge / 12.8v nominal) | ||
+ | In practical terms 100Ah of LFP is cheaper by the Ah than 50Ah, so we would probably round up to 100Ah. | ||
==== days of autonomy ==== | ==== days of autonomy ==== | ||
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* fully charging every third day = 141Ah | * fully charging every third day = 141Ah | ||
* etc | * etc | ||
+ | |||
+ | Many folks will round up from 141Ah of LFP to 200Ah since that is a common size (and even less expensive by the Ah). | ||
+ | |||
Note: the math is simple with LiFePO4, since it is not affected by [[electrical: | Note: the math is simple with LiFePO4, since it is not affected by [[electrical: | ||
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The simplest case will be charging LFP from [[electrical: | The simplest case will be charging LFP from [[electrical: | ||
- | Charging LFP [[electrical: | + | Charging LFP [[electrical: |
Assuming there is enough time (usually 5-6 hours) a lead bank can be charged by DC-DC alone. | Assuming there is enough time (usually 5-6 hours) a lead bank can be charged by DC-DC alone. | ||
+ | |||
==== charging from the ciggy port ==== | ==== charging from the ciggy port ==== | ||
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==== charging from solar ==== | ==== charging from solar ==== | ||
- | Charging from solar is predictable((on average)) if one knows where/when one will be camping. | + | 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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The good news is there would be excess solar harvest in the other months of the year: | The good news is there would be excess solar harvest in the other months of the year: | ||
- | '' | + | |
- | Month Daily Wh Avg | + | Month Daily Wh Avg |
- | Jan 574 | + | Jan 574 |
- | Feb 806 | + | Feb 806 |
- | Mar 1329 | + | Mar 1329 |
- | Apr 1658 | + | Apr 1658 |
- | May 1865 | + | May 1865 |
- | Jun 2298 | + | Jun 2298 |
- | Jul 2324 | + | Jul 2324 |
- | Aug 1983 | + | Aug 1983 |
- | Sep 1562 | + | Sep 1562 |
- | Oct 1010 | + | Oct 1010 |
- | Nov 641 | + | Nov 641 |
- | Dec 485 | + | Dec 485 |
- | Average 1378 | + | Average 1378 |
- | '' | + | |
+ | table based on the PVwatts link above | ||
+ | ==== charging from multiple sources ==== | ||
+ | Often [[electrical: | ||
+ | Adding 30mins of 30A DC-DC charging a day would drop the panel requirement to ~236W. | ||
+ | And since the solar would be handling higher-voltage / longer duration charging duties one could fall back to a less expensive [[electrical: | ||
+ | Or one could use [[electrical: | ||