Timeline for Loss of engine power when using headlights
Current License: CC BY-SA 3.0
17 events
| when toggle format | what | by | license | comment | |
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| Jun 12, 2017 at 11:20 | comment | added | mongo | Let's say one has a failing voltage regulator. Then the battery disconnects, and there is nothing to buffer an overvoltage. How much? 16 to 19 volts perhaps. Do you want to risk your electronics: the ECU, the radio, the airbag box, the ABS box, etc. Disconnecting the battery on a running engine is simply not best practice in diagnosing. | |
| Feb 9, 2016 at 0:56 | comment | added | user5626466 | @HandyHowie: The voltage drop depends on the type of rectifier used. Most car alternators use a bridge rectifier with six diodes, resulting in this voltage curve: commons.m.wikimedia.org/wiki/… The residual ripple is ~ 0,21 U_eff. | |
| Feb 9, 2016 at 0:07 | comment | added | Tobin S | Less sophisticated systems will run power off of the alternator as components are cheap and tolerant of the output from the alternator. More delicate sensors and controls need consistent and constant power. A lot of the oscillations that are occurring are incredibly fast. Microseconds. Oscilloscopes would greatly improve auto/motorcycle electrical diagnostics as well as speed up the process. But they are expensive. | |
| Feb 8, 2016 at 15:50 | comment | added | HandyHowie | @IhavenoideawhatI'mdoing Electronics is an expertise of mine, but I did make a mistake in that comment, forgetting that the alternator has 3 phases, so I deleted it. I don't know off the top of my head how much the voltage will drop from the peaks, I will have to do some research. It is still a fact that the battery plays an important role in smoothing the wave from the alternator. | |
| Feb 8, 2016 at 15:26 | comment | added | I have no idea what I'm doing | @HandyHowie alright, you just removed the comment where you said that you guarantee that it is exactly like in the previous tutorial because you're an expert in electronics. So what is the alternator output, 0-12V oscillation or a much smaller oscillation near 12V with a slight drop? Now you're confusing me as well. | |
| Feb 8, 2016 at 15:20 | comment | added | I have no idea what I'm doing | @HandyHowie bcae1.com/charging.htm - rectifier for each alternator winding phase. When you sum them up - smooth-ish DC. Are you saying this is absolutely wrong? | |
| Feb 8, 2016 at 15:20 | comment | added | HandyHowie | @IhavenoideawhatI'mdoing Just though. The alternator has a 3 phases so when they are bridged, the overlap will mean that the output voltage will not drop to zero, but there will still be a significant drop in voltage from the peaks - see bcae1.com/charging.htm | |
| Feb 8, 2016 at 14:05 | comment | added | I have no idea what I'm doing | @HandyHowie oh, you mean the nodes. Well, the output still should not be as displayed in the tutorial, as each phase is rectified separately, so nodes wouldn't be at zero volts. It's definitely not smooth, but can't be on-off. | |
| Feb 8, 2016 at 13:54 | comment | added | HandyHowie | @IhavenoideawhatI'mdoing The diodes i mentioned are arranged in a bridge. A bridge rectifier flips the negative side of the wave to the positive side. Everywhere the wave passes through 0 will still be zero after the flip. See for example - electronics-tutorials.ws/diode/diode_6.html | |
| Feb 8, 2016 at 13:39 | comment | added | I have no idea what I'm doing | The battery acts as a filter against spikes, as far as I know, but I find it hard to believe that without it the current is "turning on and off". | |
| Feb 8, 2016 at 13:37 | comment | added | I have no idea what I'm doing | @HandyHowie Honestly, I always thought that a bridge rectifier is used. Unlike a single diode the bridge rectifier will convert the alternating components into continuous current, not just cut out the backwards component. | |
| Feb 8, 2016 at 13:29 | comment | added | HandyHowie | @IhavenoideawhatI'mdoing There is a regulator to control the voltage, but there would need to be some large capacitors to smooth the wave from the rectified AC. If you look inside an alternator, there are coils, brushes, diodes and a voltage regulator. The battery acts as the capacitor. | |
| Feb 8, 2016 at 12:53 | comment | added | I have no idea what I'm doing | @HandyHowie isn't there any kind of filtering? There usually is a voltage regulator on the alternator, doesn't it smooth the current? | |
| Feb 8, 2016 at 5:50 | comment | added | Tobin S | Also, check the various ground points. The one from the battery will be black, the one from the engine to body/frame ground will more than likely be a braided flat ribbon type cable, and sometimes one from the alternator to the body/frame. What to look for is if they are frayed, cracked, discolored(burned), and corroded. Aluminum looks white and powerdery, steel/iron is rust or reddish type, and brass or copper will be a greenish or white-ish powder. More than likely all three will be grounded to the same spot to save space and keep things in one place. | |
| Feb 8, 2016 at 5:43 | comment | added | Tobin S | I do understand that. There are some systems that only take voltage from the battery for that very reason. It is a very low cost troubleshooting measure. Forgot to point out that the multimeter could be used when the car is on, lights off, lights on. The voltage should not be below 13vdc. | |
| Feb 7, 2016 at 20:33 | comment | added | HandyHowie | It is not a good idea to run an engine without a battery. The output from the alternator is rectified AC, in other words, the current is turning on and off. The battery smooths this pulsing current, so without it, you could experience strange results, or possibly even damage. | |
| Feb 7, 2016 at 18:47 | history | answered | Tobin S | CC BY-SA 3.0 |
