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opinion:frater_secessus:charging_faster [2020/04/18 13:30] frater_secessus [charging faster isn't always better] |
opinion:frater_secessus:charging_faster [2020/10/11 19:48] 127.0.0.1 external edit |
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There is a common misperception that charging one's battery banks //faster// is //better// or worth throwing more money at. Here are some reasons it is not always true: | There is a common misperception that charging one's battery banks //faster// is //better// or that having more charging capacity guarantees faster charging. Here are some reasons it is not always true: |
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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. Throwing more charging capacity at it can't force-feed the battery 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. 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. | ===== 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)) |
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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. |
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| However: |
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| > charge current affects the SOC transition point from bulk to absorption charging - MaineSail((https://marinehowto.com/how-fast-can-an-agm-battery-be-charged/)) |
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| 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 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) |
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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. Getting to Vabs faster could be [[electrical:solar:pwm_tweaking|preferable on PWM controllers]]. |
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| Also note that for simple, timer-based Absorption configurations((like 180 minutes)) the slower charging regiment would actually complete more Absorption.((180/266mins rather than 180/310mins)) |
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| ===== lithium ===== |
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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 limit to keep from stressing them. 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). C/2 (50A) is a more common limit to keep from stressing them. 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. |