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opinion:frater_secessus:charging_faster [2021/12/16 19:22]
frater_secessus [lithium] |
opinion:frater_secessus:charging_faster [2025/10/11 14:21] (current)
frater_secessus [lead-acid] |
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| **Lead batteries** have a **maximum amount of current** they will accept, typically [[electrical:12v:battery_capacity|C/3]] for AGM and C/5 for flooded. So if you have 100Ah of AGM the most it will want to take is something like ~33A. Once the battery's limit is hit throwing more charging capacity at it can't charge it any faster.((it may help run loads, though)) | **Lead batteries** have a **maximum amount of current** they will accept, typically [[electrical:12v:battery_capacity|0.33C]] for AGM and 0.2C for flooded. So if you have 100Ah of AGM the most it will want to take is something like ~33A. Once the battery's limit is hit throwing more charging capacity at it can't charge it any faster.((it may help run loads, though)) |
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| ** Deep-cycled lead batteries have a lengthy [[electrical:12v:charging|Absorption]] stage** that cannot be sped up((at least not more than a few percent, see below)). Depending on use, Absorption typically requires several hours.There is a saying that "it takes 9 months to make a baby, but two women cannot make a baby in 4.5 months". Same with absorption - it takes what it takes and you cannot hurry it in the normal sense. | ** Deep-cycled lead batteries have a lengthy [[electrical:12v:charging|Absorption]] stage** that cannot be sped up((at least not more than a few percent, see below)). Depending on use, Absorption typically requires several hours.There is a saying that "it takes 9 months to make a baby, but two women cannot make a baby in 4.5 months". Same with absorption - it takes what it takes and you cannot hurry it in the normal sense. |
| MaineSail found that | MaineSail found that |
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| * charging AGM at C/2.5 (max rate) resulted in the battery being 63.3% "full"((amp-wise)) at Vabs and being fully charged in **5hrs, 30 minutes** (20min Bulk, 5hr 10mins Absorption) | * charging AGM at 0.4C (max rate for that particular battery) resulted in the battery being 63.3% "full"((amp-wise)) at Vabs and being fully charged in **5hrs, 30 minutes** (20min Bulk, 5hr 10mins Absorption) |
| * charging AGM at C/5 (min rate) resulted in the battery being 77.4% "full" at Vabs and being fully charged in **5hrs, 42 minutes** (76min Bulk, 4hr 26mins Absorption) | * charging AGM at 0.2C (min rate) resulted in the battery being 77.4% "full" at Vabs and being fully charged in **5hrs, 42 minutes** (76min Bulk, 4hr 26mins Absorption) |
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| Note that the **using 2x the charging current only sped up the whole process by 12 minutes (3.6%)** due to Vabs starting earlier but taking longer. | Note that the **using 2x the charging current only sped up the whole process by 12 minutes (3.6%)** due to Vabs starting earlier but taking longer. |
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| **Lithium batteries** can slurp up current wildly, but shouldn't for their own health. Lithium lasts longest in sub-C use (ie, less than 100A for a 100Ah Li bank). C/2 (50A) is a more common manufacturer recommendation, and folks [[electrical:12v:drop-in_lifepo4#an_approach_to_greater_longevity|striving for added longevity]] might limit it to C/5 (20A). . In commercial examples the BMS will limit current to protect the cells. A small [[electrical:12v:b2b|DC-DC charger]] can help protect bare cells from their own greediness. | **Lithium batteries** can slurp up current wildly, but shouldn't for their own health. Lithium lasts longest in sub-C use (ie, less than 100A for a 100Ah Li bank). 0.5C (50A) is a more common manufacturer recommendation, and folks [[electrical:12v:drop-in_lifepo4#an_approach_to_greater_longevity|striving for added longevity]] might limit it to 0.2C (20A). There is some evidence that 0.4C rates are acceptable for long life when combined with gentle charging voltages like 3.45Vpc.((FIXME - insert Rod's testing of 2011 bank here)) |
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| | In commercial examples the BMS will limit current (typically to 1C) to protect the cells. A small [[electrical:12v:b2b|DC-DC charger]] can help protect bare cells from their own greediness. |
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| Limiting charging current also makes it easier on alternators when they are used to charge Li. | Limiting charging current also makes it easier on alternators when they are used to charge Li. |
