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electrical:12v:alternator [2019/06/23 17:43]
frater_secessus [alternator hacks]
electrical:12v:alternator [2020/05/24 09:08]
frater_secessus [alternator hacks]
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 ====== Alternator charging ====== ====== Alternator charging ======
  
-In a dual-battery system((starter battery and house battery)) some of the alternator output is used to charge the house batteries.  ​Since the house battery is electrically isolated from the starter battery ​when the ignition is off((or house battery voltage is below a given setpoint)), these are sometimes ​called //battery isolators//​.+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
  
  
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   * when batteries are deeply discharged   * when batteries are deeply discharged
   * when [[electrical:​12v:​alt and solar|combined with solar]] or some other higher-voltage charging source   * when [[electrical:​12v:​alt and solar|combined with solar]] or some other higher-voltage charging source
-  * when used with battery chemistries like [[electrical:​12v:​lifepo4_batteries_thread|lithium]] that do not need [[electrical:​12v:​charging|staged charging]].+  * when used with battery chemistries like [[electrical:​12v:​deep_cycle_battery#​lithium_chemistries|lithium]] that do not need [[electrical:​12v:​charging|staged charging]].
   * when used with a [[electrical:​12v:​b2b|battery-to-battery boosting charger]] that can produce correct charging voltage   * when used with a [[electrical:​12v:​b2b|battery-to-battery boosting charger]] that can produce correct charging voltage
  
 ===== limitations ===== ===== limitations =====
  
-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]]. ​ It is unlikely to get the house battery completely charged unless one is driving significant distances. This can have an impact on 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. 
 + 
 + 
 +===== effect on alternator ===== 
 + 
 +Charging the house batteries from the alternator increases the load on the alternator and can be expected to contribute to somewhat earlier failure. ​ The shortened life may be trivial if alternator charging is done thoughtfully,​ and may be sudden if done without considering the effects of higher alternator loading. ​ If/when the OEM alternator fails a higher output one can be installed for not much more than it would cost to replace the original.  
 + 
 +SternWake reports **idling while charging causes a sharp increase in alternator temperature**.((http://​www.cheaprvliving.com/​forums/​Thread-Longer-alternator-life-when-used-to-charge-house-batteries?​pid=182096#​pid182096)) To avoid this, do your alternator charging while driving. ​ This will ensure airflow over the hot alternator.  
 + 
 +===== effect on GDI engines ===== 
 + 
 +High-performing engines with Gasoline Direct Injection can experience carbon fouling on the backside of intake valves, which can cause "​drivability woes... misfires"​ and dislodged carbon flakes can cause "​turbocharger issues... catalytic converter damage."​((https://​www.autoguide.com/​auto-news/​2015/​01/​is-carbon-buildup-a-problem-with-direct-injection-engines-.html)) 
 + 
 +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/​)) 
 + 
 + 
  
-Charging the house batteries from the alternator increases the load on the alternator and can be expected to contribute to earlier failure. ​ SternWake reports **idling while charging causes a sharp increase in alternator temperature**.((http://​www.cheaprvliving.com/​forums/​Thread-Longer-alternator-life-when-used-to-charge-house-batteries?​pid=182096#​pid182096)) So don't idle it!  
  
-Also see [[electrical:​12v:​mandatory solar|Is Solar Mandatory?​]] for ideas on how to charge primarly by alternator. 
  
 ===== isolators ===== ===== isolators =====
  
  
-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 ==== 
 + 
 +[[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. **Solenoids are generally cylindrical**. Energizing the solenoid will cause a **0.5A - 1A current drop** between the alternator and house battery. Exception:  
 + ​[[https://​amzn.to/​3egI27C|Latching isolators]] use latches((surprise!!!)) instead of electromagnets to hold the circuit closed, eliminating that vector of power consumption.  
 + 
 +((http://​www.cheaprvliving.com/​forums/​Thread-Questions-about-continuous-duty-solenoid?​pid=229761#​pid229761)). ​ SternWake recommends the [[http://​amzn.to/​2fZLFzs|Blue Sea 9012]]((http://​www.cheaprvliving.com/​forums/​Thread-Questions-about-continuous-duty-solenoid?​pid=229761#​pid229761)) although [[https://​amzn.to/​2NLVwg0|non-marine units in the $20-$50 range]] are more common in vans. \\ Solenoids can be used for [[electrical:​12v:​self-jumpstarting|self-jumpstarting]] //if// the chassis battery has enough juice to engage the solenoid.  
 + 
 +==== voltage-sensing relays ==== 
 + 
 +[[https://​amzn.to/​2Ri2jQV|{{ https://​images-na.ssl-images-amazon.com/​images/​I/​418qcncjT0L._AC_US218_.jpg|}}]]voltage sensing relays are solenoids with a bit of extra logic to know when to connect/​disconnect. ​  The VSR does not get trigger voltage from the fuse panel but rather reads the voltages of one((vsr)) or both))dvsr)) batteries to know when to switch on.  \\ This kind of isolator may have a "​combine"​ override function to enable self-jumpstarting. 
 + 
 +    - [[http://​amzn.to/​2h2tDxp|single voltage sensing]] - this type reads the voltage of only one battery. ​ In the case of an RV it would read the voltage of the starting battery. ​ When it is high enough above resting voltage (ie, being charged by alternator) it connects the starting and house batteries. ​ \\ [secessus says: "IMO the practical benefit (if any) to charging the starter battery "​first"​ is keeping the load on the alternator reasonable. ​ In practice, the isolator generally connects the two within a few seconds."​] ​  \\ Examples: [[http://​amzn.to/​2h2tDxp|Sure Power 1314]], [[https://​amzn.to/​2tEGp1e|BlueSea BatteryLink]],​ [[https://​amzn.to/​2Ri2jQV|Battery Doctor]]. ​  
 +    - [[http://​amzn.to/​2gVmLFU|dual voltage sensing]] - this type reads the voltage from both batteries and when either is high enough it connects the batteries. ​  This may or [[electrical:​12v:​alternator_charging_hvd|may not be what an RVer wants]] \\ Examples: [[http://​amzn.to/​2gVmLFU|Sure Power 1315]], [[https://​amzn.to/​37gcdIv|BlueSea SI-ACR]], [[https://​amzn.to/​2RFaXI7|JayCorp Smart Dual Battery 140A Isolator]]((bonus points to the Jaycorp for printing the connect/​disconnect setpoints right on the isolator!)) 
 +  - 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 ==== 
 + 
 +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. 
 + 
 + 
 +==== manual switch ==== 
  
-  - [[http://​amzn.to/​2fZCfEr|constant-duty solenoid]] switch - an electromechanical device which uses an electromagnet to complete the charging circuit when the engine is running. **Solenoids are generally cylindrical**. Energizing the solenoid will cause a **0.5A - 1A current drop** between the alternator and house battery.((http://​www.cheaprvliving.com/​forums/​Thread-Questions-about-continuous-duty-solenoid?​pid=229761#​pid229761)). ​ SternWake recommends the [[http://​amzn.to/​2fZLFzs|Blue Sea 9012]].((http://​www.cheaprvliving.com/​forums/​Thread-Questions-about-continuous-duty-solenoid?​pid=229761#​pid229761)) \\ Solenoids can be used for [[electrical:​12v:​self-jumpstarting|self-jumpstarting]] //if// the chassis battery has enough juice to engage the solenoid.  +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.
-  - [[http://​amzn.to/​2gVmLFU|{{ https://​images-na.ssl-images-amazon.com/​images/​I/​418qcncjT0L._AC_US218_.jpg|}}]]voltage sensing relays - this kind of isolator is **installed between the house and starter batteries**. ​  It does not get trigger voltage from the fuse panel but rather reads the voltages of one or both batteries to know when to switch on.  \\ This kind of isolator may have a "​combine"​ override function to enable self-jumpstarting. +
-    - [[http://​amzn.to/​2h2tDxp|single voltage sensing]] - this type reads the voltage of only one battery. ​ In the case of an RV it would read the voltage of the starting battery. ​ When it is high enough (ie, charged or being charged by alternator) it connects the starting and house batteries. ​  ​Example:​ [[http://​amzn.to/​2h2tDxp|Sure Power 1314]]. ​ [secessus says: "IMO the practical benefit (if any) to charging the starter battery "​first"​ is keeping the load on the alternator reasonable."​] +
-    - [[http://​amzn.to/​2gVmLFU|dual voltage sensing]] - this type reads the voltage from both batteries and when either is high enough it connects the batteries. ​  This may or may not be what an RVer wants, as it could consume some solar power to to engergize the solenoid and charge the starter battery. It would also backfeed excessive [[electrical:​12v:​charging|equalization]] voltages to the coach system. Example: [[http://​amzn.to/​2gVmLFU|Sure Power 1315]] +
-  - DC-DC isolators (aka //​[[electrical:​12v:​b2b|b2b]] isolators//​) that boost charging voltage to [[electrical:​12v:​charging|Absorption]] voltages +
-  - [[http://​amzn.to/​2gVwmKw|solid state isolator]] -  an electronic device which uses 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 lower-voltage chemistry 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. +
-  - 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.+
  
 ===== sizing an isolator ===== ===== sizing an isolator =====
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 If an isolator is **oversized** it will cost more for no benefit and will self-consume somewhat more energy to hold the combining circuit closed.((an electromagnet holds the parts of the active circuit together. ​ When power to the inolator input is cut the electromagnet can no longer hold the circuit closed. ​ The circuit is open and the batteries are isolated from each other.)) \\ If an isolator is **oversized** it will cost more for no benefit and will self-consume somewhat more energy to hold the combining circuit closed.((an electromagnet holds the parts of the active circuit together. ​ When power to the inolator input is cut the electromagnet can no longer hold the circuit closed. ​ The circuit is open and the batteries are isolated from each other.)) \\
 If an isolator is **undersized** (less common) it will not be able to carry enough current, resulting in overheating and/or [[electrical:​12v:​alternator#​sudden_disconnection|sudden shutdown]]. If an isolator is **undersized** (less common) it will not be able to carry enough current, resulting in overheating and/or [[electrical:​12v:​alternator#​sudden_disconnection|sudden shutdown]].
 +
 +Most AGM will pull about C/3 (33A for a 100Ah bank) but premium brands may do more.  Flooded lead-acid batteries tend to pull less current (C/5, 20A per 100Ah of bank). If your flooded back will only pull ~40A, or your AGM bank 70A then there is little reason to spend more money on a 150-200A isolator. ​
 +
 +
 +Lithium in particular has low internal resistance and can pull [[electrical:​12v:​battery_capacity|1C]] (100A for an 100Ah bank) or more.  Victron posted [[https://​www.youtube.com/​watch?​v=jgoIocPgOuga|a video]] showing it is possible to "​smoke"​ an alternator while charging lithium. ​ Since lithium does not care much about [[electrical:​depth_of_discharge|state of charge]], **there is little reason to go for maximum force lithium charging**. ​ Some Li bank owners use [[electrical:​12v:​b2b|DC-DC isolators]] which limit themselves to a particular output (20A, 60A, 100A, etc).((https://​shop.pkys.com/​Alternator-Lithium-Battery.html))
 +
 +Reasonable charging rates can also be easier on the alternator when charging suddenly stops, whether by completion((same reason headlights are turned on at the donor car when jumpstarting)) or BMS intervention. Blue Sea makes an [[https://​www.bluesea.com/​resources/​91|alternator field disconnect]] which shuts down alternator power just before disconnecting the load, but this may be chiefly applicable to marine alternators. ​ Others have discussed installing a small lead-acid battery parallel to the Li bank;  in theory this could soften the blow from Li leaving the circuit. ​ Other sources suggest the presence of the starter battery would be sufficient.((https://​shop.pkys.com/​Alternator-Lithium-Battery.html))
  
 ==== flooded lead-acid ==== ==== flooded lead-acid ====
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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; ​ ​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.txt · Last modified: 2020/06/25 08:49 by frater_secessus