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12v:bank-sizing [2023/05/17 13:42] frater_secessus [charging predictability] |
12v:bank-sizing [2023/12/29 09:57] (current) frater_secessus [charging] chargig |
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+ | DRAFT | ||
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====== sizing a house battery bank ====== | ====== sizing a house battery bank ====== | ||
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- | Everything in this article assumes you have already assessed your [[electrical: | + | * Everything in this article assumes you have already assessed your [[electrical: |
- | + | * We will think in terms of 12v systems and 100Ah batteries. | |
- | We will assume lithium = the common LiFePO4 | + | |
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=== usable capacity === | === usable capacity === | ||
- | * lead-chemistry batteries (FLA, AGM, GEL) are typically [[electrical: | + | * lead-chemistry batteries (FLA, AGM, GEL) are typically [[electrical: |
- | * lithium batteries are typically nominal 12.8v and discharged to 80% DoD. A 100Ah LFP battery holds 1,280Wh, of which 1,024Wh are usable (1,280Wh x 0.8). It would take **98Ah of LFP** to give us 1,000Wh usable. | + | * lithium batteries are typically nominal 12.8v and discharged to 80% DoD. A 100Ah LFP battery holds 1,280Wh, of which 1,024Wh are usable (1,280Wh x 0.8). It would take **98Ah of LFP** to give us 1,000Wh usable. |
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* AGM 0.20C (20A for every 100Ah of capacity) | * AGM 0.20C (20A for every 100Ah of capacity) | ||
- | If we cannot meet minimums the bank should be downsized (or charging increased) | + | If we cannot meet minimums the bank should be downsized (or [[electrical: |
Note: Lithium has no minimum charging current | Note: Lithium has no minimum charging current | ||
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* FLA 0.20C (20A for every 100Ah of capacity) | * FLA 0.20C (20A for every 100Ah of capacity) | ||
* AGM 0.33C (33A for every 100Ah of capacity) | * AGM 0.33C (33A for every 100Ah of capacity) | ||
+ | * LFP 1.0C (100A for every 100Ah of capacity) | ||
- | If the alternator can only safely provide 50A of charging to the house bank this would limit us to a 166Ah AGM bank (166Ah x 0.33 = 50A). | + | If the alternator can only safely provide 50A of charging to the house bank this would limit us to a 166Ah AGM bank (166Ah x 0.33 = 50A). If the alternator has excess capacity then a larger bank can accept more current. |