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electrical:12v:alternator_details [2022/05/20 23:39]
frater_secessus [DUVAC] 		electrical:12v:alternator_details [2022/12/19 11:52]
frater_secessus [current]
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   * **heat**, which is the destroyer of alternators   * **heat**, which is the destroyer of alternators
  
-There is no way to know the actual number of amps you can pull from the alternator in any given condition.  A general rule would be that **if the output voltage is lower than normal the alternator is stressed**.  + 
 +In the absence of further information one might use these rules of thumb.   House loads here means both house bank charging and any loads demanded by the user.  
 + 
 +  * **at idle** house loads **≤25% of rated output**.  Note:  this is about stopping at red lights or in traffic;  idling the engine to charge batteries is not recommended.  For our 140A alternator this would be 35A. 
 +  * **while driving** loads ≤33% of rated output.  For our 140A alternator this would be 47A.   
 +  * if **alternator output  voltage drops below normal** the alternator is overloaded 
 + 
 + 
 +The accurate way would be to  
 + 
 +  - acquire the output chart for your alternator 
 +  - use a clamp meter to see what current the chassis draws with blower on, lights on, etc at a given engine  rpm 
 +  - do the math:  [output rating at that rpm / 2] to get continuous output rating at that rpm.  Subtract chassis loads.  The remainder is what you have left over to use.  
 + 
 + 
 + 
 +There is no way to know the actual number of amps you can pull from the alternator in any given condition without .  A general rule would be that **if the output voltage is lower than normal the alternator is stressed**.  
  
 While paying attention to the above rule, you might use some other rules of thumb: While paying attention to the above rule, you might use some other rules of thumb:
  
-  * **at idle** loads should be ≤25% of rated output.  Note:  this is about stopping at red lights or in traffic;  idling the engine to charge batteries is not recommended.  For our 140A alternator this would be 35A. 
-  * **while driving** loads should be ≤50% of rated output.  For our 140A alternator this would be 70A.   
  
  
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-===== types of alternator =====+==== regulation ====
  
 **Standard alternators** are the simplest model like the 14.0v model in the example above.  They are called //internally-regulated// because the voltage regulator is built into the alternator itself.  **Standard alternators** are the simplest model like the 14.0v model in the example above.  They are called //internally-regulated// because the voltage regulator is built into the alternator itself. 
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 **Smart alternators** are designed to support fuel mileage efforts.  Voltage might plummet during full accelleration (to free up engine power) then spike quite high in other conditions.  This wide variance means a DC-DC charger is required.  Note:  some smart alternators have a setting that allows them to be function like a standard alternator.  **Smart alternators** are designed to support fuel mileage efforts.  Voltage might plummet during full accelleration (to free up engine power) then spike quite high in other conditions.  This wide variance means a DC-DC charger is required.  Note:  some smart alternators have a setting that allows them to be function like a standard alternator. 
  
-**Heavy duty / high output alternators** - any of the above alternators can be build in heavy duty configuration, which typically connotes:+ 
 + 
 + 
 +===== Heavy duty / high output ===== 
 + 
 +Alternators can be built in heavy duty configuration, which typically connotes:
  
   * higher current rating   * higher current rating
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   * ability to make more power in idling scenarios, which is useful for police vehicles, ambulances, and other vehicles that need to idle for long periods of time.    * ability to make more power in idling scenarios, which is useful for police vehicles, ambulances, and other vehicles that need to idle for long periods of time. 
  
-HD alternators for any particular vehicle are typically bolt-in with no modifications required.  They do cost somewhat more.   The labor cost would remain the same so some people choose to upgrade the alternator when/if the OEM one fails. +HD alternators for any particular vehicle may be bolt-ins with no modifications required.  They do cost somewhat more.   The labor cost would remain the same so some people choose to upgrade the alternator when/if the OEM one fails.  
 + 
 + 
 +===== large case / small case ===== 
 + 
 +Alternator cases come in two general sizes:  large and small.  Most vehicles come stock with small case alternators because they are easier to "package" (fit into the available space).  Semis, boats, and other vehicles with fewer space limitations may use large case alternators, allowing for more internal cooling, larger or more separated components, ease of repair, higher constant duty outputs, etc.   
 + 
 +One is not //better// than the other;  they are meant for different applications.   
 + 
 +The mounting bolt pattern may be the same or it may  require a different mount.  Pulleys, belts, and/or belt lengths may need to be changed.   
 + 
 + 
 +Further reading: 
 + 
 +  * [[https://www.youtube.com/watch?v=Kw17G76JnWQ|Small case vs Large case alternators. Know your application!]] (youtube) 
  
 ===== DUVAC ===== ===== DUVAC =====
electrical/12v/alternator_details.txt · Last modified: 2024/03/29 19:48 by frater_secessus

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