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electrical:12v:alternator_charging_rates [2023/09/10 13:05] frater_secessus [charging method] |
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? ====== | + | DRAFT |
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+ | ====== 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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**NOTE**: | **NOTE**: | ||
- | * **FLA** taper is fairly linear and steep; | + | * **FLA** taper is steep; |
- | * **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. | + | * 100Ah x .12C = 12A. |
+ | * 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. We might use 0.175C as our average rate. 8.75Ah replaced. | ||
* **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. | ||
- | * when deeply discharged((the "lower knee" | + | * in the broad " |
- | * then quickly come to the broad, " | + | |
- | * if the bank is nearly charged the current may be 0.1C | + | |
+ | ==== in the real world ==== | ||
+ | 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. | ||