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opinion:frater_secessus:adding_dc-dc_charging_to_solar

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opinion:frater_secessus:adding_dc-dc_charging_to_solar [2020/05/11 18:03]
frater_secessus created 		opinion:frater_secessus:adding_dc-dc_charging_to_solar [2020/05/11 18:06]
frater_secessus
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 ====== Opinion:  adding DC-DC charging to solar ====== ====== Opinion:  adding DC-DC charging to solar ======
  
-**Devil’s advocate proposition:**   when combined with nontrivial amounts of solar,  **DC-DC charging is a decreasing return expense**.  Normal isolator charging would do the Bulk-style heavy lifting adequately and much more cheaply.+When combined with nontrivial amounts of solar,  **DC-DC charging is a decreasing return expense**.  Normal isolator charging would do the Bulk-style heavy lifting adequately and much more cheaply.
  
 **Reasoning:**  normal isolators raise the bank to  alternator voltage (Valt,  something like 13.8v, maybe higher).  The primary value of DC-DC charging is that it DC-DC upconverts voltage to reach Vabs (Pb) or to induce top-balancing via overcharge (Li).   Let’s look at the cost/benefit, assuming the 300Ah lead bank AGM absorps at 14.4v. **Reasoning:**  normal isolators raise the bank to  alternator voltage (Valt,  something like 13.8v, maybe higher).  The primary value of DC-DC charging is that it DC-DC upconverts voltage to reach Vabs (Pb) or to induce top-balancing via overcharge (Li).   Let’s look at the cost/benefit, assuming the 300Ah lead bank AGM absorps at 14.4v.
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   * a $25 constant duty solenoid would get the bank up  to Valt, at which point 70% of the current needed to charge Pb and 100% of the current needed to fully charge Li has already been  provided.  Solar would have to lug voltage up 13.8v -> 14.4v for Absorption/balancing.   * a $25 constant duty solenoid would get the bank up  to Valt, at which point 70% of the current needed to charge Pb and 100% of the current needed to fully charge Li has already been  provided.  Solar would have to lug voltage up 13.8v -> 14.4v for Absorption/balancing.
   * a $100 voltage sensing relay would do the same.  Cost more for the autoswitching magic and possible crude overcurrent protection via internal autoresetting breaker   * a $100 voltage sensing relay would do the same.  Cost more for the autoswitching magic and possible crude overcurrent protection via internal autoresetting breaker
-a $200-400 DC-DC charger (CTEK, Renogy, Sterling, etc) would bring battery voltage right up to Vabs (14.4v).  +  * a $200-400 DC-DC charger (CTEK, Renogy, Sterling, etc) would bring battery voltage right up to Vabs (14.4v).  
   * Solar would just handle the high voltage, decreasing current Absorption proper.   * Solar would just handle the high voltage, decreasing current Absorption proper.
  
opinion/frater_secessus/adding_dc-dc_charging_to_solar.txt · Last modified: 2020/10/11 19:48 (external edit)

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