SchwarzeEwigkt Posted July 24, 2020 Share Posted July 24, 2020 Hey! Since my battery died last year and I replaced it, I’ve had a little digital voltmeter/USB charger plugged into my cigarette lighter socket. I’ve noticed that my system voltage is like 14.7V when I first start the car up and it’s cold out, usually 14.5V or so when it’s warmer. Once I drive the car for a few miles and everything gets up to temp, it settles at 14.3-14.4V. According to the manual, it’s in spec, though on the higher side. Most cars I’ve measured — with healthy alternators — usually made 13.5-13.8V. I’m curious to see what other folks tend to see. I freely admit that I haven’t measured the output voltage with a multimeter recently, so it might be that my cheap little socket-meter is a little overenthusiastic. I seem to recall doing that when I first got it and the readings jibed, though. I may be making that up. My memory’s like a steel sieve, you see. So, yeah. What kind of voltage are you guys making? Just want to make sure I’m not about to overcook everything. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
Alexmed2002 Posted July 24, 2020 Share Posted July 24, 2020 That sounds pretty normal. When I had my legacy it ran around 14.2V-14.5V. Link to comment Share on other sites More sharing options...
FLlegacy Posted July 24, 2020 Share Posted July 24, 2020 Mine stays around 14.4-14.2 Sent from my SM-G965U using Tapatalk Link to comment Share on other sites More sharing options...
DugsSin Posted July 24, 2020 Share Posted July 24, 2020 Pretty sure we run an 14.1 Link to comment Share on other sites More sharing options...
poconoracing Posted July 24, 2020 Share Posted July 24, 2020 (edited) My JVC head unit says ~14.4V on startup and falls to 14.0-14.1 driving around. I have seen 14.5+ in the dead of winter on a cold start. For comparison, My Goldwing reads 14.1 on startup and usually 13.8 or so after riding a while. My understanding is anything between 13.7 and 14.4 running is generally considered a healthy charging system Edited July 24, 2020 by poconoracing Link to comment Share on other sites More sharing options...
SchwarzeEwigkt Posted July 25, 2020 Author Share Posted July 25, 2020 Sounds like I’m a little high, but not out of the realm of normalcy. Thanks! Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
Alexmed2002 Posted July 25, 2020 Share Posted July 25, 2020 Sounds like I’m a little high, but not out of the realm of normalcy. Thanks! Sent from my iPhone using Tapatalk Do you have a lot of things plugged in by chance? Link to comment Share on other sites More sharing options...
SchwarzeEwigkt Posted July 25, 2020 Author Share Posted July 25, 2020 Do you have a lot of things plugged in by chance? I don’t think so. Just USB charger in the center console that’s usually not being used and the USB charger/voltmeter in the plug in the dash in front of the shifter. Why? Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
Alexmed2002 Posted July 25, 2020 Share Posted July 25, 2020 I don’t think so. Just USB charger in the center console that’s usually not being used and the USB charger/voltmeter in the plug in the dash in front of the shifter. Why? Sent from my iPhone using Tapatalk I was just wondering if you may have been drawing a lot of power or something. It sounds like you should be fine. Link to comment Share on other sites More sharing options...
Scubaboo Posted July 26, 2020 Share Posted July 26, 2020 Your alternator looks pretty enthusiastic! But yeah, could be your voltmeter. I'd compare it with voltage off OBD if you want to look more into it. Link to comment Share on other sites More sharing options...
pseudonym Posted July 27, 2020 Share Posted July 27, 2020 Damn, figures the car i decide not to install a wild stereo into has the best alternator. Link to comment Share on other sites More sharing options...
DrD123 Posted July 30, 2020 Share Posted July 30, 2020 Service manual says the output from the alternator is regulated at 14.1 to 14.8V, so I think you are good to go. Link to comment Share on other sites More sharing options...
YeuEmMaiMai Posted July 31, 2020 Share Posted July 31, 2020 I have seen on my 2010 outback 3.6R voltage range from 13.2 to 14.8. The ECM uses PWM (pulse width modulation) to control the alternator duty cycle to only charge the battery as needed. The readings are no different on my 2014 2.5i Legacy. Link to comment Share on other sites More sharing options...
SchwarzeEwigkt Posted July 31, 2020 Author Share Posted July 31, 2020 I have seen on my 2010 outback 3.6R voltage range from 13.2 to 14.8. The ECM uses PWM (pulse width modulation) to control the alternator duty cycle to only charge the battery as needed. The readings are no different on my 2014 2.5i Legacy. Does it really? Neat! How does it interrupt the alternator charging? There’s no clutch on the alternator pulley besides the overrun clutch that I’m aware of. Does it collapse the field in the exciter coil or something? My only rough understanding of the physics involved would indicate to me that decoupling the coils like that would reduce the drag the alternator would generate so you’re not wasting horsepower, and as long as your battery was healthy, it would fill in the dip. I think. Either way, it sounds like the electric equivalent of a variable displacement pump. I know how those work, but this is new to me! Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
YeuEmMaiMai Posted August 4, 2020 Share Posted August 4, 2020 There is a wire that command alternator on and off every modern car since the early to mid 1990's does this Link to comment Share on other sites More sharing options...
SchwarzeEwigkt Posted August 4, 2020 Author Share Posted August 4, 2020 There is a wire that command alternator on and off every modern car since the early to mid 1990's does this I just looked into it. It turns out that wire you’re talking about is the field or exciter coil. It works exactly like I thought it did. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
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