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electrical:12v:alternator [2020/05/21 07:46]
frater_secessus [isolators]
electrical:12v:alternator [2020/07/12 17:47] (current)
frater_secessus [gotchas]
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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 ("​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. 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.
 +
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 +
  
 ==== 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]]. ​
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 ===== 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.  
 + 
 +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.  
 + 
 +**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; ​ ​a ​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.1590072384.txt.gz · Last modified: 2020/05/21 07:46 by frater_secessus