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electrical:12v:directcharginglfp [2022/10/28 10:44] frater_secessus [assessing your own setup for direct alternator charging] vehicle loads |
electrical:12v:directcharginglfp [2023/01/10 15:30] frater_secessus [current demands of DC-DC chargers vs isolators] |
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There is an [[electrical: | There is an [[electrical: | ||
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- **overcharging** (holding Vabs after reaching 100% SoC) is actually a bigger concern, particularly if one drives for hours. | - **overcharging** (holding Vabs after reaching 100% SoC) is actually a bigger concern, particularly if one drives for hours. | ||
- | So this article will focus on current demand by LiFePO4 house banks. | + | This article will focus on current demand by LiFePO4 house banks. |
===== the formula in 60 seconds ===== | ===== the formula in 60 seconds ===== | ||
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{{https:// | {{https:// | ||
- | The average max current drawn from the alternator is **0.33C**, or 1/3rd of what the warnings predict. | + | The average max current drawn from the alternator is **0.33C**, or 1/3rd of what the warnings predict. |
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This crude and fictional graph illustrates the //general patterns of current demand// on the alternator from both isolators (purple) and DC-DC chargers (green). | This crude and fictional graph illustrates the //general patterns of current demand// on the alternator from both isolators (purple) and DC-DC chargers (green). | ||
- | The isolator starts out high at 85A and current starts falling off immediately. | + | The isolator starts out high at 85A and current starts falling off immediately. |
The DC-DC holds a steady 60A until the 14.4v setpoint is reached around 50 minutes. | The DC-DC holds a steady 60A until the 14.4v setpoint is reached around 50 minutes. | ||
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- make the first test run a brief one and with the Li fairly well charged.((higher states of charge will typically lessen current demands to some degree))((if you have paralleled batteries you might want to do this step with just one in place to get a feel for the draw.)) | - make the first test run a brief one and with the Li fairly well charged.((higher states of charge will typically lessen current demands to some degree))((if you have paralleled batteries you might want to do this step with just one in place to get a feel for the draw.)) | ||
- test it with a drive. | - test it with a drive. | ||
- | - repeat the last two steps with the Li bank at lower and lower states of charge, down to the lowest | + | - repeat the last two steps with the Li bank at lower and lower states of charge, down to the lowest state of charge you expect to recharge from alternator. |
- disconnect the isolator with a switch when you come to the desired SoC | - disconnect the isolator with a switch when you come to the desired SoC | ||