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electrical:solar:pwm_tweaking [2017/11/26 18:20] frater_secessus [set Vabs and Vfloat relatively high] |
electrical:solar:pwm_tweaking [2018/04/18 16:52] frater_secessus [the controller's achilles heel] |
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====== Tweaking a PWM controller for maximum power ====== | ====== Tweaking a PWM controller for maximum power ====== | ||
- | PWM controllers are inexpensive and durable, but typically they cannot extract as much power from a given panel as the more expensive | + | [[electrical: |
- | Note: much of this information also applies to [[electrical: | + | Note: much of this information also applies to [[electrical: |
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During charging with a PWM controller **the solar panel will be running at the voltage of the battery bank**. | During charging with a PWM controller **the solar panel will be running at the voltage of the battery bank**. | ||
- | This affects charging in all three [[electrical: | + | This affects charging in all three [[electrical: |
{{ http:// | {{ http:// | ||
- | 17.8v x 5.6A = 99.68w < | + | 17.8v x 5.6A = 99.68w < |
+ | 17.8v x 5.6A = 94.70w <-- MPPT running at 95% efficiency | ||
14.8v x 5.6A = 82.88w <-- power at a high Absorption voltage, as with flooded lead acid \\ | 14.8v x 5.6A = 82.88w <-- power at a high Absorption voltage, as with flooded lead acid \\ | ||
- | 14.4v x 5.6A = 80.64w <-- power at a lower Absorption voltage, as with AGM \\ | + | 14.4v x 5.6A = 80.64w <-- power at a lower Absorption voltage |
+ | 14.2v x 5.6A = 79.52w <-- power at a low Absorption voltage | ||
13.8v x 5.6A = 77.28W <-- power at high Float, as with deeply cycled banks \\ | 13.8v x 5.6A = 77.28W <-- power at high Float, as with deeply cycled banks \\ | ||
13.2v x 5.6A = 73.92W <-- power at low Float, as with lightly cycled banks \\ | 13.2v x 5.6A = 73.92W <-- power at low Float, as with lightly cycled banks \\ | ||
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12.1v x 5.6A = 67.76W <-- power at 50% state of charge; | 12.1v x 5.6A = 67.76W <-- power at 50% state of charge; | ||
- | This last number shows how far off PWM output can fall when battery voltage is at its lowest. | + | This last number shows how far off PWM output can fall when battery voltage |
===== the plan ===== | ===== the plan ===== | ||
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During the bulk charging stage the battery needs every bit of power it can get. Any loads applied during this stage slow down charging and, more importantly, | During the bulk charging stage the battery needs every bit of power it can get. Any loads applied during this stage slow down charging and, more importantly, | ||
- | Wait until your bank is well into Absoroption | + | Wait until your bank is well into Absorption |
==== set Vabs and Vfloat relatively high ==== | ==== set Vabs and Vfloat relatively high ==== | ||
Since the panels make more power at higher voltages((up to Vmp)) cranking up Vabs and Vfloat to higher-but-still-sane levels will result in more power being harvested. | Since the panels make more power at higher voltages((up to Vmp)) cranking up Vabs and Vfloat to higher-but-still-sane levels will result in more power being harvested. | ||
- | ==== battery: maintain | + | ==== battery: maintain |
This may seem obvious, but remember: | This may seem obvious, but remember: | ||
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- **Cycle less deeply** - Instead of cycling to 50% state of charge (12.2v) consider cycling to only 75% SoC (12.4v). | - **Cycle less deeply** - Instead of cycling to 50% state of charge (12.2v) consider cycling to only 75% SoC (12.4v). | ||
+ | - [[electrical: | ||