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electrical:solar:nonessential [2019/06/23 08:36] frater_secessus [how much surplus current is there?] pwm heat |
electrical:solar:nonessential [2019/10/01 13:05] frater_secessus [when to run opportunity loads] |
**During Absorption** the charge current is tapering down as the battery accepts less; the more it tapers down the more is available for loads.((agaom. normal + opportunity)) At the very beginning of Absorption ~0% of "bonus" output is available. At the very end of Absorption ~99% is available. Mid-way through Absorption((judging by current not time)) ~49% of the panels' output is available for loads. | **During Absorption** the charge current is tapering down as the battery accepts less; the more it tapers down the more is available for loads.((agaom. normal + opportunity)) At the very beginning of Absorption ~0% of "bonus" output is available. At the very end of Absorption ~99% is available. Mid-way through Absorption((judging by current not time)) ~49% of the panels' output is available for loads. |
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There will generally be more "surplus" power available when using MPPT charge controllers v. PWM,((http://forum.solar-electric.com/discussion/comment/372165#Comment_372165))((http://forum.solar-electric.com/discussion/comment/250746#Comment_250746)) though the difference is smaller in Float and late Absorption we one would run opportunity loads anyhow. Siphoning off power can actually help PWM controllers run cooler by reducing the ON-OFF switching activity that generates heat. | There will generally be more "surplus" power available when using MPPT charge controllers v. PWM,((http://forum.solar-electric.com/discussion/comment/372165#Comment_372165))((http://forum.solar-electric.com/discussion/comment/250746#Comment_250746)) though the difference is less dramatic during periods one would run opportunity loads (see [[electrical:solar:nonessential#when_to_run_opportunity_loads|below]]). Siphoning off power can actually help PWM controllers run cooler by reducing the ON-OFF switching activity that generates heat. |
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It is for the same reason MPPT provides more current in Bulk: panel voltage (Vmpp) is not constrained to output voltage ([[electrical:12v:electrical_notation|Vabs]] or [[electrical:12v:electrical_notation|Vfloat]]) and excess voltage is converted into extra current. | |
===== when to run opportunity loads ===== | ===== when to run opportunity loads ===== |
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At the start of Absorption the controller still needs near-Bulk levels of current for charging. At the end it needs almost no current. **Halfway through Absorption about half of the system's peak power will be available for loads.** See the image at the top of the page for an example of how current demand drops in Absorption. | At the start of Absorption the controller still needs near-Bulk levels of current for charging. At the end it needs almost no current. **Halfway through Absorption about half of the system's peak power will be available for loads.** See the image at the top of the page for an example of how current demand drops in Absorption. |
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For [[electrical:12v:lifepo4_batteries_thread|LiFePO4]] set the LVD to Vfloat; there is no actual Absorption stage _per se_ in fractional-C charging. We use these setpoints only because our traditional lead-acid controllers work that way. | For [[electrical:12v:deep_cycle_battery#lithium_chemistries|LiFePO4]] set the LVD to Vfloat; there is no actual Absorption stage _per se_ in fractional-C charging. We use these setpoints only because our traditional lead-acid controllers work that way. |
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===== timing opportunity loads ===== | ===== timing opportunity loads ===== |