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--- electrical:12v:alt_and_solar [2020/05/11 12:35]
frater_secessus [how solar helps]
+++ electrical:12v:alt_and_solar [2020/05/24 12:00]
frater_secessus [gotchas]
@@ Line 36: / Line 36: @@
 ===== gotchas =====
-A bare solenoid doesn't know/care about the state of either battery, only that the ignition is in the ON position.
-When
+==== general issues ====
-  - solar is charging/equalizing higher than ~15v; and,
-  - the house and batteries are connected
+**When the chassis and house batteries are connected**, deep cycle **charging voltages** (Vabs) from solar or other sources **will be passed to the chassis**.   Since charging voltages differ((lithium typically the lowest ~14.2v, around ~14.4v, and flooded the highest ~14.8v) this could be an issue if house batteries were flooded; flooded starter batteries would require more frequent watering.  "Maintenance-free" sealed flooded batteries might be expected to fail earlier due to water loss.  AGM starter batteries might be overcharged by flooded charging voltages, though voltage drop across the relay and inter-battery wiring may serve to attenuate that possibility.
-the chassis' electrical system can be damaged by the overvoltage. When manually equalizing ensure the systems are not connected.  If your charge controller does automatic EQ try to disable that feature.  You may also want to [[electrical:12v:alternator_charging_hvd|automatically disconnect alternator charging]] when house battery voltage rises beyond a given setpoint.
+If overvoltage is a concern, one can use one of these workarounds:
+  * disable automatic [[electrical:12v:charging#equalization|Equalization]] (EQ); or
+  * decrease EQ voltage((Vequal))/duration; or
+  *  [[electrical:12v:alternator_charging_hvd|automatically disconnect alternator charging]] when house battery voltage rises beyond the starter battery's preferred charging voltage.
+==== voltage sensing relays ====
+[[electrical:12v:electrical:12v:alternator#voltage-sensing_relays|Voltage sensing relays]] can [[http://bdp.mousetrap.net/index.php/2018/10/27/side-effect-of-solar-alternator-charging/get "stuck connected"]] if the alternator and solar were charging the same time.  This situation would exist until the sun when down and house voltage dropped below the VSR's disconnection setpoint.
+It is effectively the same issue as the issue above.  Workarounds:
+  * any a workaround from the list above; or
+  * use [[electrical:12v:alternator#constant-duty_solenoid|a plain solenoid]] that would disconnect when the vehicle's key is turned off

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