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--- electrical:12v:alternator [2022/06/07 14:09]
frater_secessus [effect on alternator]
+++ electrical:12v:alternator [2022/06/23 11:16]
frater_secessus [effect on alternator]
@@ Line 46: / Line 46: @@
 ===== effect on alternator =====
-{{ https://img.mousetrap.net/misc/transit250alternator.jpg?150}}Charging the house batteries from the alternator increases the load on the alternator and can be expected to contribute to somewhat earlier failure.  In practice it's usually a non-issue if one avoids overheating((as when idling)) or overloading((as with giant AGM or lithium banks)) the alternator;  alternator failures from aux battery charging are quite rare.
+Charging the house batteries from the alternator increases the load on the alternator and can be expected to contribute to somewhat earlier failure.  In practice it's usually a non-issue if one avoids overheating((as when idling)) or overloading((as with giant AGM or lithium banks)) the alternator;  alternator failures from aux battery charging are quite rare.
 > I have created hundreds of designs and installed around 100 systems, many with isolators or solenoids. In four plus years not one customer has come to me saying that their alternator failed. I do tell them not to sit in a hot parking lot idling their engine to charge their batteries. -- jimindenver((https://vanlivingforum.com/threads/new-wiring-sketch.43877/post-544396))
@@ Line 56: / Line 56: @@
 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// so airflow over the hot alternator will help cool it.   Other measures included additional alternator cooling or pulley size tuning to alternator RPM at idle.
+==== alternator current rating ====
+In general, vehicles with higher-rated alternators (150A, for example) will handle the extra charging duties better than vehicles with lower-rated alternators (60A, for example).  The rating in Amps will be listed on the window sticker, often on the alternator housing itself, or can be looked up using a VIN decoder for your automaker.
+There are no firm rules on how much power you can extract, but these are commonly-observed limits:
+  * draw no more than 1/2 of rated amps while driving at normal road speeds
+  * draw no more than 1/4 of rated amps while driving at slower speeds
 Note that alternators put out their rated current at higher RPM.((typically highway speeds))  See chart on the right for a Ford Transit 250A alternator.

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