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electrical:12v:alternator_charging_hvd

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electrical:12v:alternator_charging_hvd [2017/10/11 15:25]
frater_secessus [diode based isolators] 		electrical:12v:alternator_charging_hvd [2022/07/31 00:33] (current)
frater_secessus [solid state isolators]
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 ====== Disconnecting alternator charging at a voltage setpoint ====== ====== Disconnecting alternator charging at a voltage setpoint ======
  
-There are scenarios where one might want to prevent an isolator from combining the house and chassis 12v systems:+There are scenarios where one might want to prevent a [[electrical:12v:alternator|battery isolator]] from combining the house and chassis 12v systems:
  
-  - the house battery needs less voltage than lead-acid (lithium, for example)+  - the house battery might be a chemistry that could get overcharged by the alternator (lithium, for example) 
 +  - the house battery might have a resting voltage high enough to trigger the house side of a dual-sensing relay (LiFePO4)
   - the combined circuit can feed higher-than-optimal voltages back from solar charge controller to the chassis' electronics.   - the combined circuit can feed higher-than-optimal voltages back from solar charge controller to the chassis' electronics.
 +  - a [[electrical:12v:b2b|b2b charger]] in parallel with an [[electrical:12v:alternator|isolator]] could have the same backfeeding result
  
  
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 [[electrical:12v:alternator|Isolator/relays/solenoids]], etc, use mechanical or electrical means to combine the chassis and house 12v systems.   These mechanical or electrical means will require a small amount power to operate.((latching relays excepted))   [[electrical:12v:alternator|Isolator/relays/solenoids]], etc, use mechanical or electrical means to combine the chassis and house 12v systems.   These mechanical or electrical means will require a small amount power to operate.((latching relays excepted))  
  
-If the device's own power source is disconnected it will turn off and 12v systems will be separate again.((again, latching relays excepted))  Using a High Voltage Disconnect to kill power to the device will stop the alternator from charging the house battery at a given voltage setpoint.+If the device's own power source is disconnected it will turn off and 12v systems will be separate again.((again, latching relays excepted))  Using a [[electrical:12v:hvd|High Voltage Disconnect]] to kill power to the device will stop the alternator from charging the house battery at a given voltage setpoint.
  
 Shutting down the device will require different approaches, depending on where it gets the power to operate itself. Shutting down the device will require different approaches, depending on where it gets the power to operate itself.
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 Power to these devices is disrupted by interrupting power to the trigger+, which is one of the small lugs.((or the only small lug in the case of 3 lug relays)) Power to these devices is disrupted by interrupting power to the trigger+, which is one of the small lugs.((or the only small lug in the case of 3 lug relays))
  
- 
-**Note:**  three-terminal isolators that ground through the base of the unit may not be practical to use with HVD. 
  
 ===== voltage sensing relays ===== ===== voltage sensing relays =====
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 Power to VSRs is disrupted by cutting the ground wire. One way to reestablish the ground (thereby turning the device on) is HVD --> relay NO contacts --> ground wire in/out Power to VSRs is disrupted by cutting the ground wire. One way to reestablish the ground (thereby turning the device on) is HVD --> relay NO contacts --> ground wire in/out
  
-===== diode based isolators ===== +===== solid state isolators ===== 
-FIXME+ 
 +It is unlikely you will need an HVD with a diode-based isolators because: 
 + 
 +   - the isolator can't backfeed voltage back to the starter battery, and 
 +   - voltage drops up to 1v in the diodes when passing alternator --> isolator --> house bank
  
 +But it is theoretically possible alternator voltage is so high that even with the drop you might want an HVD.  Some solid state isolators have a trigger or exciter input;  control with HVD as with solenoids and relays.  
  
 +Three lug isolators without exciter input might not be usable with HVD.
electrical/12v/alternator_charging_hvd.1507749945.txt.gz · Last modified: 2020/10/11 19:48 (external edit)

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