GM Regulated Voltage Control (RVC)

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While killing time on the internet, I came across some information about GM's RVC system. It has been around for almost 10 years, so I am late to the party in discussing it. I did not realize how complex battery charging has become in the last decade. My 2005 Subaru has a "dumb" voltage regulator in the alternator, with no intervention from the ECM. But GM's RVC has six charging modes, including desulfating. Voltage can range from 11.5V to 15.5V. In contrast, the voltage range I see on my Subaru is 13.6V to 14.9V.

The RVC keeps the battery around 80% SOC, instead of 95%, as I understand it. This, of course, enhances battery sulfating. In the link below I read that typical battery life in a recent GM is around 3 years. Is that what you GM owners are seeing?

http://www.agcoauto.com/content/news/p2_articleid/350
 
Originally Posted By: SubLGT
In the link below I read that typical battery life in a recent GM is around 3 years. Is that what you GM owners are seeing?



2008 Pontiac G5. 65K, pretty much summer use only.

Original battery is still in the trunk.
 
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Chrysler has had ECM battery charge control since 1985 (on EFI models) and temperature compensation.
 
I don't see why the alternator has to be more expensive, the BCM runs the field control and just commands energizing/ de-energizing like any other remote voltage regulator (eg Mopar).

I always figured the crude temp compensation was more than adequate. I've witnessed low 15s for startup voltage which pretty much does what that article claims. It's just a softer ramp-down to regular running mode.
 
I dont get the 80% SOC bit. Is this due to a smart alternator wanting to recover energy on slowdown?
 
Originally Posted By: JHZR2
I dont get the 80% SOC bit. Is this due to a smart alternator wanting to recover energy on slowdown?


As you know, the purpose of all these smart or intelligent charging systems is for better fuel mileage. I recall reading they can give about a 1% improvement in a conventional car. But if you are going to shut down the alternator for part of the driving cycle, that means less charging time is available to the battery. The industry seems to believe a target of 80% SOC is adequate. At least that's my impression.

And for vehicles with start-stop, the figure I have seen is 70% SOC. For those vehicles, there will usually be some kind of energy recovery, and that requires a low battery SOC to enhance charge acceptance during the recovery phase. Industry spokesmen are telling consumers that we need to accept the idea of having to buy a battery more often, especially for a start-stop vehicle, as a tradeoff for better fuel mileage. For now, that battery is still lead-acid chemistry, and as AGM or EFB construction.
 
Originally Posted By: stevejones
Originally Posted By: SubLGT
In the link below I read that typical battery life in a recent GM is around 3 years. Is that what you GM owners are seeing?



2008 Pontiac G5. 65K, pretty much summer use only.

Original battery is still in the trunk.


That's impressive. GM and Remy have done a good job with their charging algorithm, it seems. That 3-4 minutes spent at 15.5V must be effective at slowing down sulfation, if your example is typical.
 
Here is what Honda is doing in the 2016 Pilot SUV:

"...The Pilot engine makes use of a powerful 130-amp alternator that charges in two different ranges— a low 12-volt range and a high 14-volt range. By controlling the alternator charge voltage range, BMS works to keep the battery in a specific charge range, which can extend the service life of the battery by more than 25 percent. With BMS keeping the battery in a specific charge range, the alternator can run more often in the low range, which generates less drag on the engine resulting in improved fuel efficiency. Application of numerous electrical power reducing items (such as the use of efficient LED lighting and a special humidity control system that has an automatic air conditioning "off" function) allows the BMS to operate the alternator even more frequently in the more efficient low charge mode…"
 
Originally Posted By: JHZR2
I dont get the 80% SOC bit. Is this due to a smart alternator wanting to recover energy on slowdown?


Looks like GM's system can do that:

"...Referring to the RVC graph in Fig. 2 on page 44, you can see how much thought has gone into tailoring the alternator’s charge output to suit various scenarios. An interesting sidebar note would be the ramp-up in field current that the RVC systems sometimes introduce on deceleration. When you’re cruising in Fuel Economy Mode (lower charge voltage), you can charge harder during a brief period of deceleration without sacrificing fuel economy or overcharging the battery. In fact, when there’s a greater alternator load on the engine during deceleration, that load contributes to engine braking—something that’s good for brake pad life as well. Think of this as a mild form of what hybrid vehicles do with regenerative braking…"

http://www.motor.com/article.asp?article_ID=1606
 
Originally Posted By: George7941
I wish the RVC system would maintain at least 80% SOC on my battery, the best it does is 73%….


Are you still using the OE battery?
 
No, the battery quit at seven years of age. Here is my post on it
http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3690165/Re:_Abrupt_Battery_Failure,_No#Post3690165
 
Originally Posted By: SubLGT
While killing time on the internet, I came across some information about GM's RVC system. It has been around for almost 10 years, so I am late to the party in discussing it. I did not realize how complex battery charging has become in the last decade. My 2005 Subaru has a "dumb" voltage regulator in the alternator, with no intervention from the ECM. But GM's RVC has six charging modes, including desulfating. Voltage can range from 11.5V to 15.5V. In contrast, the voltage range I see on my Subaru is 13.6V to 14.9V.

The RVC keeps the battery around 80% SOC, instead of 95%, as I understand it. This, of course, enhances battery sulfating. In the link below I read that typical battery life in a recent GM is around 3 years. Is that what you GM owners are seeing?

Just replaced the original battery on my friend's 2004 Venture. Low mileage, but still excellent battery life!

http://www.agcoauto.com/content/news/p2_articleid/350
 
My older 92 Civic VX with the lean-burning D15Z1 engine had a Electronic Load Detector so that helped with the charging system relative to stop and go or high revs vs. highway cruise speed. I'm sure it helped fuel economy mostly, but I believe it was built into the alternator.
 
The German cars do this as well, frequently now cars have freewheeling clutches in the alternator pulley (I've had a couple of them fail)
 
That's interesting, I have to wonder what advantage might that have given that an alternator with zero field current would only have drag from the bearings and a bit of windage?

My new VW with Euro6 engine has every economy trick in the book, but not this.
 
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