Smart Alternator?

fixedintime · #1 10-03-2008, 04:14 PM

I noticed something on the way home from work this afternoon and thought I'd ask if this is normal.

Basically as I'm driving down the road, engine on, I noticed that the batter voltage was at 12.5. I had expected to see something like 14.5. As I drove on I notice at times it was 12.4, 12.5 or up at 14+, but it never seemed to drop below 12.4. I have had no problems with the battery/alternator recently. I did replace the battery three months ago. So it is relatively new. SG reports no trouble codes.

So the question is, is this normal, does Honda have a smart voltage regulator built into the alternator that decides based on some algorithm when the battery needs to be charged, and only charges it at certain times.

The car is a 2005 Accord, MT.

xcel · #2 10-03-2008, 05:10 PM

Hi Fixedintime:

___I have never seen that on my 05 w/ AT while Scan Gauged and the 12V display is up 75% of the time too.

___Good Luck

___Wayne

kendan · #3 10-03-2008, 05:19 PM

Sounds to me like the voltage regulater is working just fine. The new battery may be contributing to it showing 12.5 vs 14(it may stay charged longer). As long as the voltage doesn't drop below 12, you are fine.

SilentLou · #4 10-04-2008, 09:57 AM

I noticed this very thing on my 99 Civic after installing the SGII, I would see the voltage jump between 12 and 14 volts. I like to watch the voltage so I can catch an alternator failure in time before I'm stranded. I realized eventually that it is a smart alternator, which is great. If you see 12 volts, just turn on the headlights to increase the battery load and you then should see the voltage jump to 14 volts.

This may be the reason the car doesn't have a voltage gauge in the dash, it may be confusing.

fixedintime · #5 10-05-2008, 04:36 PM

Tnx all. I have been watching it the last two days and all seems normal. I just had not realized that the voltage regulator cuts back on charging the battery at time.

rweatherford · #6 10-05-2008, 11:15 PM

I think many manufacturers are doing this now. My radiator fan is variable speed on the Mazda5.

chilimac02 · #7 10-09-2008, 05:19 PM

Yep, I've noticed the same stuff on my '01 accord. In fact, you can watch a direct correlation between when your alternator comes on (giving you a 14volt reading) and your MPG dropping. I noticed this when running the A/C for my wife on my last trip. I decided that if I could hook in some extra deep cycle batteries, I could probably turn the alternator off and get a little more MPG.

hobbit · #8 10-09-2008, 07:41 PM

Yeah, but for how long? You've still gotta recharge the 12V
battery sometime ... and on long hauls it isn't really feasible
to wall-charge it.
.
_H*

rationull · #9 10-10-2008, 08:28 PM

The question has already been answered but I wanted to chime in anyway. I notice the same thing on my normal commute in my 07 Civic. By the time I get close to work, the voltage runs around 12.4-12.5 volts on the highway at steady state, and at idle when I get off. If I turn on the lights, the fan, or anything then it'll go back up to 13-14 volts.

No new information there, but I recently had my car at the dealer and had them run a charging system test for unrelated reasons, and everything came back fine. So, I'd say we can be confident this is in fact not a problem.

Kacey Green · #10 10-12-2008, 09:17 AM

I haven't looked at the HCHIIs behavior but I'll watch it on my daily commute a few time to see what happens to the voltage levels.