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electrical:12v:alternator [2020/06/23 13:10] frater_secessus [limitations] |
electrical:12v:alternator [2020/07/12 20:47] frater_secessus [gotchas] |
Alternator charging is generally only practical for the [[electrical:12v:charging|bulk charge stage]] due to relatively low voltage output and the [[electrical:12v:charging|long time periods required for absorption]].(([[electrical:12v:b2b|DC-DC chargers]] can help with the voltage)) It is unlikely to get the house battery completely charged unless one is driving significant distances. This can have an impact on [[electrical:batterycide|battery longevity]]. If one drives often [[electrical:12v:alt_and_solar|a combination of the alternator doing bulk charging and a small solar doing the rest]] is good match. | Alternator charging is generally only practical for the [[electrical:12v:charging|bulk charge stage]] due to relatively low voltage output and the [[electrical:12v:charging|long time periods required for absorption]].(([[electrical:12v:b2b|DC-DC chargers]] can help with the voltage)) It is unlikely to get the house battery completely charged unless one is driving significant distances. This can have an impact on [[electrical:batterycide|battery longevity]]. If one drives often [[electrical:12v:alt_and_solar|a combination of the alternator doing bulk charging and a small solar doing the rest]] is good match. |
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Vehicles with //smart// (variable voltage) alternators may not be suitable for charging with normal isolators.((https://www.redarc.com.au/how-do-i-know-if-i-have-a-variable-voltage-smart-alternator)) See [[electrical:12v:b2b|DC-DC chargers]]. | Vehicles with //smart// (variable voltage) alternators may not be suitable for charging with normal isolators.((https://www.redarc.com.au/how-do-i-know-if-i-have-a-variable-voltage-smart-alternator)) See [[electrical:12v:alternator#smart_alternators|below]]. |
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See [[electrical:12v:mandatory solar|Is Solar Mandatory?]] for ideas on how to charge primarily by alternator. | See [[electrical:12v:mandatory solar|Is Solar Mandatory?]] for ideas on how to charge primarily by alternator. |
Anecdotally the problem appears to be worsened with **excessive idling**, although this may be a subset of situations where "the engine doesn’t run long enough or hard enough to get hot enough to burn any of the carbon off."((https://automotiverepairphoenix.com/ask-car-guy-can-carbon-build-impact-engine/)) | Anecdotally the problem appears to be worsened with **excessive idling**, although this may be a subset of situations where "the engine doesn’t run long enough or hard enough to get hot enough to burn any of the carbon off."((https://automotiverepairphoenix.com/ask-car-guy-can-carbon-build-impact-engine/)) |
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| ===== smart alternators ===== |
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| Traditional alternators typically try to hold a set voltage. //Smart alternators// talk to the vehicle's ECU (compuuter) vary output voltage depending on present conditions. It might unload the alternator during heavy acceleration to reduce parasitic losses, or run the alternator at high voltage just after starting to speed up the recovery of used energy.((https://www.redarc.com.au/alternator-vs-fixed-alternator)) |
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| The use of plain isolators with smart alternators may result in the rapid cycling of the isolator's circuit (with voltage sensing types) or the discharge of the house battery into the starter battery (solendoid type). |
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| [[electrical:12v:b2b|DC-DC chargers]] and/or isolators with an awareness of smart alternators may be required. |
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A [[http://amzn.to/2gsDtNc|manual battery switch]] normally has 4 positions: A, B, A+B, and Off. A would be for the starter battery and used during starting. B would be used for house use when one is not driving. A+B could be used to combine both sets for starting or for charging while driving. This kind of setup is prone to user error. A manual switch has no current or voltage losses. | A [[http://amzn.to/2gsDtNc|manual battery switch]] normally has 4 positions: A, B, A+B, and Off. A would be for the starter battery and used during starting. B would be used for house use when one is not driving. A+B could be used to combine both sets for starting or for charging while driving. This kind of setup is prone to user error. A manual switch has no current or voltage losses. |
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| ==== misc ==== |
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| [note from secessus: "not sure what's inside these solid state isolators"] |
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| [[https://amzn.to/3fVuKh0|{{ https://m.media-amazon.com/images/I/51XoShK5uIL._AC_UY218_.jpg?125}}]] |
| The [[https://amzn.to/3fVuKh0|Magnum Energy ME-SBC]] is notable for some unusual features: |
| * configurable connect/disconnect setpoints |
| * ability to drive a solenoid, which allows for much greater current |
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| Xantrex makes [[https://amzn.to/3eKhkEc|a 15A Digital-Echo Charge isolator]]. |
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===== sizing an isolator ===== | ===== sizing an isolator ===== |
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Alternator charging may bring some battery chemistries (like lithium) to **unsuitably high voltages**. A [[electrical:12v:hvd|high voltage disconnect]] can [[electrical:12v:alternator charging hvd|restrict alternator charging to lower voltages]]. [[electrical:12v:b2b|DC-DC chargers]] can also regulate voltage provided to the house battery. | Alternator charging may bring some battery chemistries (like lithium) to **unsuitably high voltages**. A [[electrical:12v:hvd|high voltage disconnect]] can [[electrical:12v:alternator charging hvd|restrict alternator charging to lower voltages]]. [[electrical:12v:b2b|DC-DC chargers]] can also regulate voltage provided to the house battery. |
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| Voltage-sensing regulators can be [[http://bdp.mousetrap.net/index.php/2018/10/27/side-effect-of-solar-alternator-charging/|triggered or "held closed" by voltage from the solar-charged side]] in some scenarios. Address with HVD as above if desired. |
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**Idling the engine** to charge house batteries **can seriously overheat the alternator**. It is usually cooled by wind from the vehicle's forward motion; a fan may help cool the alternator. | **Idling the engine** to charge house batteries **can seriously overheat the alternator**. It is usually cooled by wind from the vehicle's forward motion; a fan may help cool the alternator. |