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electrical:12v:alternator [2020/04/11 11:39]
frater_secessus [voltage-sensing relays]
electrical:12v:alternator [2020/07/04 14:06]
frater_secessus [limitations]
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 ====== Alternator charging ====== ====== Alternator charging ======
 +
 +aka Split Charging for our European friends
  
 In a dual-battery system((starter battery and house battery)) some of the alternator output is used to charge the house batteries when the engine is running.  When the engine is not running **the house battery is electrically isolated** from the starter battery to keep from draining it and leaving you stranded.  So the devices that handle the isolating/combining duties are called //battery isolators// There are several different types.  In a dual-battery system((starter battery and house battery)) some of the alternator output is used to charge the house batteries when the engine is running.  When the engine is not running **the house battery is electrically isolated** from the starter battery to keep from draining it and leaving you stranded.  So the devices that handle the isolating/combining duties are called //battery isolators// There are several different types. 
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 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.
  
-See [[electrical:12v:mandatory solar|Is Solar Mandatory?]] for ideas on how to charge primarly by alternator.+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]]. 
 + 
 +See [[electrical:12v:mandatory solar|Is Solar Mandatory?]] for ideas on how to charge primarily by alternator.
  
  
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 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/))
  
 +===== smart alternators =====
  
 +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))
 +
 +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).
 +
 +[[electrical:12v:b2b|DC-DC chargers]] and/or isolators with an awareness of smart alternators may be required.
  
  
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-Power from the alternator is shared with the house battery using an isolator of some sort.  This allows the [[electrical:12v:intro|house battery]] to charge but does not allow the house battery to pull power from the starter battery.+Power from the alternator is shared with the house battery using an isolator ("Split charge relay" / SCR) of some sort.  This allows the [[electrical:12v:intro|house battery]] to charge but does not allow the house battery to pull power from the starter battery. 
 + 
 + 
 + 
 + 
 + 
  
 ==== constant-duty solenoid ==== ==== constant-duty solenoid ====
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   - DC-DC isolators (aka //[[electrical:12v:b2b|b2b]] isolators//) that boost alternator voltage to [[electrical:12v:charging|more appropriate levels for lead chemistries]] and can do multistage charging. These have [[electrical:12v:b2b|their own page]].   - DC-DC isolators (aka //[[electrical:12v:b2b|b2b]] isolators//) that boost alternator voltage to [[electrical:12v:charging|more appropriate levels for lead chemistries]] and can do multistage charging. These have [[electrical:12v:b2b|their own page]].
  
-==== diode-based isolator ====+==== solid state isolator:  diode-based ====
  
 Note:  this type of isolator is no longer common for our uses.  Note:  this type of isolator is no longer common for our uses. 
  
-[[http://amzn.to/2gVwmKw|Solid state isolators]] are electronic devices which use diodes to prevent depletion of the starter battery.  **Isolators are generally brick-shaped**.  Diode-based isolators have a **0.5v - 1v drop** between the alternator and house battery. This may be desirable if the house battery is a wants lower-voltage charging like [[electrical:12v:lifepo4_batteries_thread|LiFePO4]].  Some solid state isolaters use FETs and diodes in tandem to reduce voltage drop. \\ Note:  solid state relays can't combine batteries for self-jumpstarting.+[[http://amzn.to/2gVwmKw|These isolators]] are electronic devices which use diodes to prevent depletion of the starter battery.  **Isolators are generally brick-shaped**.  Diode-based isolators have a **0.5v - 1v drop** between the alternator and house battery. This may be desirable if the house battery is a wants lower-voltage charging like [[electrical:12v:lifepo4_batteries_thread|LiFePO4]].  Some solid state isolaters use FETs and diodes in tandem to reduce voltage drop. \\ Note:  solid state relays can't combine batteries for self-jumpstarting.
  
 +==== solid state isolator:  FET-based ====
  
 +This type of isolator is similar to the diode-based one above, except that FET components are used instead of diodes, preventing voltage drop.  
 +
 +Example:  [[https://amzn.to/2Cwjkln|Victron Argo 200A FET Battery Isolator]]
 ==== manual switch ==== ==== manual switch ====
  
 +[[https://amzn.to/2VaL8SG|{{https://m.media-amazon.com/images/I/81n-ap+0lPL._AC_UY218_.jpg?125 }}]]The simplest and least-featured isolator is a //manual switch//.
  
 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.
 +
 +==== misc ====
 +
 +[note from secessus:  "not sure what's inside these solid state isolators"]
 +
 +[[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
 +
 +Xantrex makes [[https://amzn.to/3eKhkEc|a 15A Digital-Echo Charge isolator]]. 
 +
 +
 +
 +
 +
  
 ===== sizing an isolator ===== ===== sizing an isolator =====
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 ===== gotchas ===== ===== gotchas =====
  
-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]].+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.  
 + 
 +**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 run the alternator can seriously overheat the alternator.  It is usually cooled by wind from the vehicle's forward motion;  fan may help cool the alternator.+In early morning when house battery voltage is lowest, **a plain solenoid may unintentionally allow depleted batteries to pull down the starter battery**.  Workarounds:  use VSR, or start the vehicle immediately after inserting the key((ie, do not leave in the Accessory position which would drain the starter battery)) 
  
-==== wiring ====+===== wiring =====
  
 2 gauge copper wire connecting the coach and house is recommended for most alternator charging installs.  SternWake recommends attaching at the alternator rather than the battery.((http://www.cheaprvliving.com/forums/Thread-Charge-house-batteries-with-DC?pid=110652#pid110652)) 2 gauge copper wire connecting the coach and house is recommended for most alternator charging installs.  SternWake recommends attaching at the alternator rather than the battery.((http://www.cheaprvliving.com/forums/Thread-Charge-house-batteries-with-DC?pid=110652#pid110652))
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 Note that you will only have to run the POS+ leg of wire to the house battery as the chassis ground is the other leg. Note that you will only have to run the POS+ leg of wire to the house battery as the chassis ground is the other leg.
  
-==== alternator hacks ===+===== alternator hacks =====
  
 There are ways to get the alternator to pump out more power: There are ways to get the alternator to pump out more power:
electrical/12v/alternator.txt · Last modified: 2020/11/14 14:07 by frater_secessus