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Not abnormal Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Mon, 2 Feb 2004 10:25:20
In Reply to: voltage drop/drain...., kooch, Sat, 31 Jan 2004 08:33:55 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The voltage regulator, well, regulates the alternator voltage. The VR is temperature compensated - it outputs more voltage when cold than warm. That's because charging a battery creates heat. On a hot day, you don't want to charge a battery fast, because it can't dump the heat. But on a cold day, you can charge the battery fast, because it's not about to overheat. But the VR doesn't measure battery temp - it's just got a sensor built into the VR, and assumes the alternator and battery are living in about the same environment. So on a very cold morning, 14.5 is reasonable.
As the engine warms up, the VR output will fall. It should be in the 13Volt range when the engine is above idle, with most reasonable loads. I can see a warm engine dropping below 13.0 at idle with a bunch of electrical loads - headlights and brake lights. Older Saabs have LOTS of brake lights, and you can easily pull 80 watts just hitting the brake. The voltage shouldn't drop below 12.8 or so at idle, even warm with most loads. Just because you moved your battery to the trunk, the VR doesn't know that. And the VR just controls alternator voltage.
What are you using to reference your meter for a ground? I ask because you show the Wolf EMS as consistently having a higher voltage than the battery or alternator. Unless the Wolf is creating power, it can't be at a higher voltage than the source. But if you're using different grounding points, all bets are off.
Looking at the voltages, I see nothing wrong. With the engine running, you have voltages in the low 14 volt range. This is fine, in fact, maybe just a bit high, but OK as long as they don't go higher. The only time you report a voltage below 13.0 is "engine warm, not running." If the engine isn't running, you're only going to see battery voltage. Nothing else is producing voltage. A battery voltage of 12.9 is a fully charged battery-perfectly normal. The reason you see voltages ABOVE 12.9 when the engine is running is that for the alternator to charge the battery, it must provide a voltage higher than the battery voltage - that way current flows into the battery to charge it.
I don't see anything wrong with your voltages. Yes, you are seeing a couple of hundred millivolt difference, which is probably more about where you are grounding your meter. In an ideal world, all the voltages would be the same, but we don't live in such a world. A couple of hundred millivolt drop is no big deal.
posted by 192.249....
, Mon, 2 Feb 2004 10:25:20 <-- Viewing This Message, Mon, 2 Feb 2004 11:23:46
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