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electrical:12v:alternator_charging_rates [2023/09/10 13:13] frater_secessus [estimating DC-DC charging] |
electrical:12v:alternator_charging_rates [2023/09/10 13:25] (current) frater_secessus [estimating combiner charging] |
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- | ====== How much will by battery charge by alternator? ====== | + | ====== How much will my battery charge by alternator? ====== |
This should be easy, right? | This should be easy, right? | ||
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We know the time part because we're the ones driving. | We know the time part because we're the ones driving. | ||
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===== TLDR ===== | ===== TLDR ===== | ||
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===== estimating DC-DC charging ===== | ===== estimating DC-DC charging ===== | ||
- | DC-DC charging rates are more predictable because of how they work. A 20A DC-DC will likely pump 20A into the bank most of the time. So 3 hours driving x 20A = 60Ah returned to the battery bank. The price of this predictability (and other features) is... price. | + | DC-DC charging rates are more predictable because of how they work. A 20A DC-DC will likely pump 20A into the bank most of the time. So 1/2 hour driving x 20A = 10Ah returned to the battery bank. The price of this predictability (and other features) is... price. |
- | If you need predictable charging then DC-DC is likely the answer. | + | If you need predictable charging then DC-DC is likely the answer. There are [[electrical: |
- | ==== estimating combiner charging ==== | + | ===== estimating combiner charging |
This is the tough one. We know roughly where the charge rate will start out for discharged batteries (≤0.33C) but the taper complicates things. | This is the tough one. We know roughly where the charge rate will start out for discharged batteries (≤0.33C) but the taper complicates things. | ||
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* **FLA** taper is steep; | * **FLA** taper is steep; | ||
* 100Ah x .12C = 12A. | * 100Ah x .12C = 12A. | ||
- | * 0.5hours of driving x 15A = 6Ah replaced. | + | * 0.5hours of driving x 12A = 6Ah replaced. |
* **AGM** taper is more gradual, so charging currrent stays higher on short drives. It might only taper to 0.15C by the end of the drive. | * **AGM** taper is more gradual, so charging currrent stays higher on short drives. It might only taper to 0.15C by the end of the drive. | ||
* **Lithium** has an odd taper because the charging voltage curve is not linear. | * **Lithium** has an odd taper because the charging voltage curve is not linear. | ||
* in the broad " | * in the broad " | ||
+ | ==== in the real world ==== | ||
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+ | In most installs this variability isn't a major issue: | ||
+ | * combiner charging is commonly paired with solar charging (also highly variable!) | ||
+ | * alternator charging is often a backup or "nice when you can get it" charging source. | ||