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electrical:solar:charge_controller [2024/06/01 21:58]
frater_secessus [sensors] |
electrical:solar:charge_controller [2024/07/01 22:48]
frater_secessus [sizing your charge controller] |
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| * battery voltage will read [[electrical:12v:voltage_sag|falsely high during charging]], and | * battery voltage will read [[electrical:12v:voltage_sag|falsely high during charging]], and |
| * temperature will read high because of the controller's own heat from electronics | * temperature will read falsely high because of the heat the controller generates from its own electronics |
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| With lead-chemistry batteries both conditions cause [[electrical:12v:psoc|chronic undercharging]], a key cause of [[electrical:batterycide|premature battery failure]]. Many LiFePO4 batteries have [[opinion:frater_secessus:agm2lifepo4#wait_lfp_can_be_damaged_by_charging_in_cold_weather|low temperature charging cutoff]] but those that do not must rely on the charger to disconnect when battery temps are ~freezing. | With **lead-chemistry batteries** both conditions can cause [[electrical:12v:psoc|chronic undercharging]], a key cause of [[electrical:batterycide|premature battery failure]]. Many **LiFePO4 batteries** have their own [[opinion:frater_secessus:agm2lifepo4#wait_lfp_can_be_damaged_by_charging_in_cold_weather|low temperature charging cutoff]] but those that do not must rely on the charger to disconnect when battery temps are ~freezing. |
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| [[electrical:12v:multipoint_charging|Multiple controllers (with separate arrays) can be used to charge a common bank]]. The controllers should be configured with similar charging setpoints for the greatest efficiency.((http://www.morningstarcorp.com/parallel-charging-using-multiple-controllers-separate-pv-arrays/)) | [[electrical:12v:multipoint_charging|Multiple controllers (with separate arrays) can be used to charge a common bank]]. The controllers should be configured with similar charging setpoints for the greatest efficiency.((http://www.morningstarcorp.com/parallel-charging-using-multiple-controllers-separate-pv-arrays/)) |
| ===== sizing your charge controller ===== | ===== sizing your charge controller ===== |
| As with [[electrical:inverter|inverters]], sizing the controller correctly will help system efficiency and save money. An oversized CC will have unnecessarily high parasitic drains as it powers itself and will cost more. An undersized CC will not be able to put all the rated solar wattage to use and will leave no room for expansion. | |
| For PWM controllers, the formula is something like (panel wattage / 13) * (1.2 oversize for safety) = charge controller amps.((https://www.altestore.com/howto/sizing-pwm-solar-charge-controllers-a91/)) | NOTE: in no case can the panel voltage limit be exceeded. |
| MPPT controllers have more leeway in sizing since they can [[electrical:solar:overpaneling|control the output of the panels]] independently of battery voltage. | |
| See also [[electrical:solar:sizing|Sizing a Solar Installation]] | As with [[electrical:inverter|inverters]], sizing the controller correctly will help system efficiency and save money. An oversized CC will have unnecessarily high parasitic drains as it powers itself and will cost more, weigh more, and take up more space. An undersized CC will either not perform well (MPPT) or be damaged (PWM). |
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| | ==== PWM ==== |
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| | PWM controllers are sized based on the **maximum input power** they will ever see. |
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| | One formula is something like (panel wattage / 13) * (1.2 oversize for safety) = charge controller amps.((https://www.altestore.com/howto/sizing-pwm-solar-charge-controllers-a91/)) A faster, cruder method is (panel wattage / 10) = charge controller amps. |
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| | ==== MPPT ==== |
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| | MPPT controllers are sized based on the **average power** they will see. |
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| | The approach is different because |
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| | * MPPT are expensive |
| | * MPPT can trim incoming power to avoid exceeding their output rating |
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| | So MPPT controllers generally have [[electrical:solar:overpaneling|more panel put on them than their rating would suggest]] ("overpaneling"). |
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| | There are a few ways of calculating this. The Victron MPPT calculator is quite good. It will generally suggest 10-30% overpaneling. |
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| | You can ballpark it manually by dividing *panel wattage / 14.25v((this appears to be the constant used in the Victron calculator))). Example: |
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| | ''400w / 14.25v = 28.0702A'' |
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| | * 28.0702 / 25A candidate = 3.0702A. (3.0702A / 25A) = **12.28% overpaneled**. On the lower end of Victron's overpaneling recommendation. |
| | * 28.0702 / 20A candidate = 8.0702A. (8.0702A / 20A) = **40.35% overpaneled**. This exceeds Victron's overpaneling recommendation. 40% overpaneling might be fine at higher latitudes like Canada or Alaska, but the controller would be maxxed out quite often elsewhere. |
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| | **Conclusion**: 25A is appropriate for 400w of panel. |
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| | 25A? 20A? |
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| | - (28.0702A - 25A) = |
| ===== overpaneling ===== | ===== overpaneling ===== |
| this section [[electrical:solar:overpaneling|has been moved]]. | this section [[electrical:solar:overpaneling|has been moved]]. |
