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electrical:12v:alternator_charging_hvd [2017/10/11 14:26] frater_secessus [how it works] |
electrical:12v:alternator_charging_hvd [2020/10/11 19:48] 127.0.0.1 external edit |
====== Disconnecting alternator charging at a voltage setpoint ====== | ====== Disconnecting alternator charging at a voltage setpoint ====== |
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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: |
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- 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)) |
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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. |
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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. |
===== disconnecting isolators and simple relays ===== | ===== solenoids and relays ===== |
| {{ https://images-na.ssl-images-amazon.com/images/I/51tg8FDT67L._SX466_.jpg?200}} |
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| Purely Mechanical devices like solenoids and relays use 12v //trigger// or //exciter// voltage((usually from the accessory circuit)) to operate. They will either have 4 lugs or 3 lugs; in the latter case grounding is done through the base of the device. |
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by 12v trigger. Example: 12v source that's only active when the key is in the RUN position. These have 4 lugs: starting+, house+, trigger+, trigger-; or, | 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)) |
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| ===== voltage sensing relays ===== |
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===== disconnecting voltage sensing relays ===== | Voltage sensing relays (VSR) typically take power from the chassis battery and have a thin ground to complete the circuit. |
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These usually have 3 lugs: starting+ in, house+ out, starting-. The starting- "ground" is only used to complete a small circuit so the relay can run itself. So it's usually very thin. | 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 |
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| ===== solid state isolators ===== |
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| Some solid state isolators have a trigger or exciter input; drive with HVD as with solenoids and relays. |
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| Three lug isolators without exciter input might not be usable with HVD. |