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electrical:solar:pwm_tweaking [2017/11/22 10:05] frater_secessus [delay loads until after Bulk] |
electrical:solar:pwm_tweaking [2023/11/19 16:18] frater_secessus [PWM'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: |
- | ===== the controller's achilles heel ===== | + | ===== PWM's achilles heel ===== |
- | 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**.((or close enough for the purposes of this discussion. |
- | 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 = 100w < |
+ | 17.8v x 5.6A = 94.70w <-- MPPT running at 95% efficiency | ||
+ | |||
+ | PWM harvest | ||
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 \\ | ||
12.7v x 5.6A = 70.61W <-- power at 100% state of charge (SoC) \\ | 12.7v x 5.6A = 70.61W <-- power at 100% state of charge (SoC) \\ | ||
12.4v x 5.6A = 69.44W <-- power at 75% state of charge; bulk charging \\ | 12.4v x 5.6A = 69.44W <-- power at 75% state of charge; bulk charging \\ | ||
- | 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; |
+ | 10.0v x 5.6A = 56.00W <-- battery bank accidentally run flat | ||
- | 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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==== delay loads until after Bulk ==== | ==== delay loads until after Bulk ==== | ||
- | During the bulk charging stage | + | 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 Absorption before using [[electrical: | ||
==== 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. | ||
- | ==== battery: maintain | + | Using the above panel as an example, Vabs of 14.7v will yield 3.5% more power than a Vabs of 14.1v. |
+ | Note: consult the battery manufacturer' | ||
+ | |||
+ | DO invest in the $10 temperature probe option. | ||
+ | ==== battery: maintain | ||
This may seem obvious, but remember: | This may seem obvious, but remember: | ||
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* keeping your bank as charged as possible will let the panels produce the most power for conditions | * keeping your bank as charged as possible will let the panels produce the most power for conditions | ||
- | In other words, the lower your battery voltage gets the worse the system | + | In other words, the lower your battery voltage gets the worse the pwm charging |
- **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). | ||
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