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electrical:solar:nonessential [2019/06/23 08:38]
frater_secessus [how much surplus current is there?] |
electrical:solar:nonessential [2020/01/13 11:16]
frater_secessus [opportunity loads] |
| ====== opportunity loads ====== | ====== opportunity loads ====== |
| {{ :electrical:solar:discretionaryv5.png?direct&400|based on http://www.chargetek.com/basic-information.html}} | {{ :electrical:solar:discretionaryv5.png?direct&400|based on http://www.chargetek.com/basic-information.html}} |
| Solar power installations are generally [[electrical:solar:sizing|designed]] as if the load[s] will be steady around the clock. | Solar power installations are generally [[electrical:solar:sizing|designed]] as if the load[s] will be steady around the clock. This can lead new folk into buying [[opinion:frater_secessus:beginner_mistakes#too_much_battery|too much battery]], a waste of money, space, and needless weight. |
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| In practice, actual loads may be heavier in the daytime (as when working with power tools) or at night (as when watching movies or running a forced-air furnace). | In practice, actual loads may be heavier in the daytime (as when working with power tools) or at night (as when watching movies or running a forced-air furnace). |
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| Due to the nature of battery charging there are better times and worse times to run non-essential loads. If done attentively (or automatically) **one can run electrical loads that do not affect the battery's | Due to the nature of battery charging there are better times and worse times to run non-essential loads. If done attentively (or automatically) **one can run electrical loads that do not affect the battery's |
| [[electrical:depth_of_discharge|State of Charge]]** at all. | [[electrical:depth_of_discharge|State of Charge]]** at all. This is especially true for Lead-Acid chemistries that do not take much current in [[electrical:12v:charging|Float or late Absorption stages]]. |
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| This is especially true for Lead-Acid chemistries that do not take much current in [[electrical:12v:charging|Float or late Absorption stages]]. | |
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| ===== how much surplus current is there? ===== | ===== how much surplus current is there? ===== |
| **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 less dramatic during periods one would run opportunity loads (see [[http://rvwiki.mousetrap.net/doku.php?id=e#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. | 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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| ===== when to run opportunity loads ===== | ===== when to run opportunity loads ===== |
| 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 ===== |
