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electrical:12v:alternator [2024/04/16 11:31]
frater_secessus [disabling alternator charging] delay |
electrical:12v:alternator [2024/06/06 12:36] (current)
frater_secessus [constant-duty solenoid] constant/continuous |
| * In many situations, it is possible to use a simple/inexpensive battery [[electrical:12v:alternator#combiners|combiner]] or [[electrical:12v:alternator#proper_isolators|isolator]] between the house batteries and the vehicle battery. These will allow the house battery to charge when the vehicle is running, but will prevent the vehicle battery from being drained when the engine is off. | * In many situations, it is possible to use a simple/inexpensive battery [[electrical:12v:alternator#combiners|combiner]] or [[electrical:12v:alternator#proper_isolators|isolator]] between the house batteries and the vehicle battery. These will allow the house battery to charge when the vehicle is running, but will prevent the vehicle battery from being drained when the engine is off. |
| * Some situations may benefit from or [[electrical:12v:mandatory_dcdc|require DC-DC chargers]] in between the vehicle batteries and the house batteries. | * Some situations may benefit from or [[electrical:12v:mandatory_dcdc|require DC-DC chargers]] in between the vehicle batteries and the house batteries. |
| | * charging is //triggered// by a 12v signal(("D+", "IGN", "ACC")) and/or by voltage-sensing((monitoring of the actual voltage coming from the chassis)) |
| * Idling the engine while parked for long periods of time just to recharge the batteries is possible, but generally a bad idea. | * Idling the engine while parked for long periods of time just to recharge the batteries is possible, but generally a bad idea. |
| * Pulling a lot of power from the alternator causes it to generate a lot of heat. When the vehicle is moving there's enough airflow to keep the alternator cool, but when parked the heat will build up and can damage the alternator. | * Pulling a lot of power from the alternator causes it to generate a lot of heat. When the vehicle is moving there's enough airflow to keep the alternator cool, but when parked the heat will build up and can damage the alternator. |
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| See [[electrical:12v:alternator_details#heat|this sub-article]] on alternators and heat | See [[electrical:12v:alternator_details#heat|this sub-article]] on alternators and heat |
| ==== charging current patterns ==== | |
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| | ==== alternator current rating ==== |
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| | In general, vehicles with higher-rated alternators (150A, for example) will handle a given load better than vehicles with lower-rated alternators (60A, for example). The rating in Amps will be listed on the window sticker, often on the alternator housing itself, or can be looked up using a VIN decoder for your automaker. |
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| | see [[electrical:12v:alternator_details#current|this related article]] on assessing how much current you can safely take from the alternator |
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| | ==== fuel consumption ==== |
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| | Fuel consumption for power generation will be greatest when the vehicle is idled. When charging loads are imposed on a vehicle that is already driving the added cost can be minimal. |
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| | Using the 3.6L [[rv:ram_promaster|Promaster]] with a 40A [[electrical:12v:b2b|DC-DC charger]] as an example, ObvB estimates: |
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| | >> In terms of cost, an average USA price of gas at $3.36, **idling** for 2 hours to produce 1kWh with a 40A DC-DC charger would burn 2 * (2/3 + 0.074) gal = 1.48 gal = **$4.97 / kWh**. If you were going to be **driving** anyway, then the additional cost of turning on a DC-DC charger (using my assumptions) would be about **50c/kWh**.((https://www.promasterforum.com/threads/fuel-consumption-at-idle.103939/post-841876)) |
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| | ===== charging current patterns ===== |
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| * charging lead chemistries directly from the alternator tends toward | * charging lead chemistries directly from the alternator tends toward |
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| ''23A x 20 minutes / 60 minutes in an hour = 7.666666667Ah'' | ''23A x 20 minutes / 60 minutes in an hour = 7.666666667Ah'' |
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| ==== alternator current rating ==== | |
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| In general, vehicles with higher-rated alternators (150A, for example) will handle a given load better than vehicles with lower-rated alternators (60A, for example). The rating in Amps will be listed on the window sticker, often on the alternator housing itself, or can be looked up using a VIN decoder for your automaker. | |
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| see [[electrical:12v:alternator_details#current|this related article]] on assessing how much current you can safely take from the alternator | |
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| ===== fuel consumption ===== | |
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| Fuel consumption for power generation will be greatest when the vehicle is idled. When charging loads are imposed on a vehicle that is already driving the added cost can be minimal. | |
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| Using the 3.6L [[rv:ram_promaster|Promaster]] with a 40A [[electrical:12v:b2b|DC-DC charger]] as an example, ObvB estimates: | |
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| >> In terms of cost, an average USA price of gas at $3.36, **idling** for 2 hours to produce 1kWh with a 40A DC-DC charger would burn 2 * (2/3 + 0.074) gal = 1.48 gal = **$4.97 / kWh**. If you were going to be **driving** anyway, then the additional cost of turning on a DC-DC charger (using my assumptions) would be about **50c/kWh**.((https://www.promasterforum.com/threads/fuel-consumption-at-idle.103939/post-841876)) | |
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| ==== constant-duty solenoid ==== | ==== continuous-duty solenoid ==== |
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| [[https://amzn.to/2RgAFUw|{{https://m.media-amazon.com/images/I/41zFkQ0pUIL._AC_UY218_ML3_.jpg?75 }}]]A [[http://amzn.to/2fZCfEr|constant-duty solenoid]] is an electromechanical device which uses an electromagnet to complete the charging circuit when the engine is running. The basic idea is the relay uses a low-current circuit((typically from the vehicle ignition)) to activate a higher-current circuit.((from starter battery to house battery)) | [[https://amzn.to/2RgAFUw|{{https://m.media-amazon.com/images/I/41zFkQ0pUIL._AC_UY218_ML3_.jpg?75 }}]]A [[http://amzn.to/2fZCfEr|continuous-duty solenoid]] is an electromechanical device which uses an electromagnet to complete the charging circuit when the engine is running. The basic idea is the relay uses a low-current circuit((typically from the vehicle ignition)) to activate a higher-current circuit.((from starter battery to house battery)) |
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| Note: some solenoids only have three terminals: 2 big load terminals and 1 small control terminal. This type gets the "ground"((return circuit)) through the body of the solenoid. The pic above is of a "three post" solenoid -- the case is grounded to the chassis through the metal feet. | Note: some solenoids only have three terminals: 2 big load terminals and 1 small control terminal. This type gets the "ground"((return circuit)) through the body of the solenoid. The pic above is of a "three post" solenoid -- the case is grounded to the chassis through the metal feet. |
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| === starter relays vs constant duty relays === | === starter relays vs continuous duty relays === |
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| While they may be externally identical, starter relays and constant duty relays are built differently inside.((https://aviondemand.com/insider/starter-solenoids-and-continuous-duty-solenoids/)) | While they may be externally identical, starter relays and continuous duty relays are built differently inside.((https://aviondemand.com/insider/starter-solenoids-and-continuous-duty-solenoids/)) |
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| The **starter relay** needs to switch huge currents for brief amounts of time. The switching has to be very fast and powerful to minimize arcing. To achieve this the solenoid will pull several amps to run a powerful electromagnet. The solenoid will not overheat because it is only "on" for a few moments. The control terminals typically have resistance of 3-4 ohms. | The **starter relay** needs to switch huge currents for brief amounts of time. The switching has to be very fast and powerful to minimize arcing. To achieve this the solenoid will pull several amps to run a powerful electromagnet. The solenoid will not overheat because it is only "on" for a few moments. The control terminals typically have resistance of 3-4 ohms. |
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| The **constant duty relay** is used for much longer periods of time and is rated for less current. The lower current means the connection doesn't have to be slammed closed as fast with a powerful electromagnet. As a result this relay type typically draws <1A and the control terminals have resistance of 15-30 ohms. | The **continuous duty relay** is used for much longer periods of time and is rated for less current. The lower current means the connection doesn't have to be slammed closed as fast with a powerful electromagnet. As a result this relay type typically draws <1A and the control terminals have resistance of 15-30 ohms. |
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| Note that per Cole-Hersee even a CD relay will get hot: | Note that per Cole-Hersee even a CD relay will get hot: |
| - use [[electrical:12v:b2b|a DC-DC charger]] to get at least the correct charging voltage | - use [[electrical:12v:b2b|a DC-DC charger]] to get at least the correct charging voltage |
| - if charging by relay only, use Crtical size wire to get the most voltage and current to the lead house battery | - if charging by relay only, use Crtical size wire to get the most voltage and current to the lead house battery |
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| | ==== triggering ==== |
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| | The setup needs to be //triggered// (told when to start/stop) so that it isn't connected all the time. There are two main methods: |
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| | - use of an ON/OFF 12v trigger signal ("D+", "IGN", "ACC"). When the 12v signal is present the charging circuit is operational. Caveat: in this kind of setup leaving the key in the ACC position without starting the engine can drain the starter battery. |
| | - voltage-sensing - 12v is always being provided to the charger. The batteries are connected when the chassis voltage is above a voltage setpoint (often ≥13.4v) and disconnected when the chassis side measures below a setpoing (often ≤13.2v). |
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| | In some cases both are combined for particular installs. Ex. smart alternators. |
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| ===== alternator hacks ===== | ===== alternator hacks ===== |
| ==== workaround: heavier wiring ==== | ==== workaround: heavier wiring ==== |
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| It's also possible to run a separate and heavier cable from the TV to the trailer; this would minimize voltage sag. If a plain isolator is used with heavier wiring the voltage will still be insufficient to fully charge lead batteries. | It's also possible to run a separate and (much) heavier & more expensive cable/connector from the TV to the trailer; this would minimize voltage sag. |
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| Heavier cabling + a DC-DC charger could provide correct voltage to the trailer battery. | |
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| ===== isolator without a house battery ===== | ===== isolator without a house battery ===== |
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| This setup would be: starter battery -> isolator -> inverter -> 120vac devices | This setup would be: starter battery -> combiner((A $25-$40 VSR (often marketed as a smart battery isolator) might be easiest. Could go even cheaper with a regular relay but you'd have to hunt for a D+/IGN signal.)) |
| | -> inverter -> 120vac devices |
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