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--- electrical:12v:diysmartpass [2022/08/23 13:51]
frater_secessus [50A DC-DC combo chargers: $265-$328]
+++ electrical:12v:diysmartpass [2022/09/10 12:51]
frater_secessus [how it works]
@@ Line 18: / Line 18: @@
 The D250 provides staged (boosted) charging and the Smartpass provides Big Current during Bulk charging.((until battery voltage == alternator voltage))  The setup is pricey;  as of Aug 2022 the D250 is $328 and the Smartpass 120 is $326.  Total $654.  There are other features in this setup((jumpstarting, starter battery maintenance)) but these main features might be replicated by the approaches described below.
-There may an additional benefit of using a small DC-DC charger + isolator:  charging current will be very high only at first when the alternator temperature is lowest and most able to handle it.((just started the engine))
+There may be an additional benefit of using a small DC-DC charger + isolator:  charging current will be very high only at first when the alternator temperature is lowest and most able to handle it.((just started the engine)) And even a giant DC-DC is "wasted" when current acceptance falls.
 ===== challenges =====
@@ Line 40: / Line 40: @@
   * [[https://amzn.to/3pCW5eY|Renogy 20A DC-DC]], $104. [[https://amzn.to/3QGwihC|Cole-Hersee continuous duty solenoid]], $55. [[https://amzn.to/3AhdNti|High voltage disconnect]], $13.
-The HVD mentioned here is actually LVD/HVD.  You can use it to make the isolator a [[electrical:12v:alternator#voltage-sensing_relays|VSR]], turning on at 13.2v (engine running) and turning off at 13.8v (just under alternator voltage). If you wanted to [[electrical:12v:self-jumpstarting|self-jumpstart]] set the connect voltage much lower so the two are connected anytime the key is one.  Or wire a separate momentary ON to energize the isolator.
+The HVD mentioned here is actually LVD/HVD.  You can use it to make the isolator a [[electrical:12v:alternator#voltage-sensing_relays|VSR]], turning on at 13.2v (engine running) and turning off at just under alternator voltage, if Valt > Vfloat.((and it probably is)) Alternatively, the HVD might turn off >Vfloat.
+If you wanted to [[electrical:12v:self-jumpstarting|self-jumpstart]] set the connect voltage much lower so the two are connected anytime the key is one.  Or wire a separate momentary ON to energize the isolator.

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