[rpreston]

I just bought a 2011 535 and have some questions on regenerative braking and can't seem to find a lot of literature on the specifics of the system in the 535. Perhaps some of the folks in this forum can help

I notice the eye-candy on the MPG gauge going into the blue "efficient dynamics" when I take my foot of the gas and coast with the transmission engaged. If it disengage the clutch (man trans) and/or coast in neutral, then the eye-candy drops back out of the blue but remains maxed out at 40+

Now I suspect the eye-candy is really just that and not a true indication of charging/discharging but it leads to a few questions.

1. I know the alternator has it's own clutch (or is at least supposed to). But how/where is it connected? Is it belt driven off the engine or connected to the transmission? Are they using the starter motor as a generator or is there a separate unit.

2. Does anyone have any experienece with the battery being not kept reasonably well charged by the regenerative system. My normal commute is just 10miles, a lot of which is stop and go on hilly terrain. My normal inclination is to let gravity do a lot of the work for me so I tend to creep forward in neutral or with the clutch disengaged on downhills and when stopping on the uphills, I similarly tend to disengage the clutch early and try to coast to a stop rather than using a lot of engine or braking. Is this robbing the system of a chance to charge the battery?

3. I had read that the 5 series was using a glass-mat battery to allow but higher charge rates and a larger number of deep draw cycles. Is that true and does anyone have any experience with lifetimes and replacement costs?

[gatoman39]

yes it's an AGM battery and it's huge. If you don't drive much get a smart charger and charge the battery periodically.

[Needsdecaf]

Originally Posted by rpreston

1. I know the alternator has it's own clutch (or is at least supposed to). But how/where is it connected? Is it belt driven off the engine or connected to the transmission? Are they using the starter motor as a generator or is there a separate unit.

2. Does anyone have any experienece with the battery being not kept reasonably well charged by the regenerative system. My normal commute is just 10miles, a lot of which is stop and go on hilly terrain. My normal inclination is to let gravity do a lot of the work for me so I tend to creep forward in neutral or with the clutch disengaged on downhills and when stopping on the uphills, I similarly tend to disengage the clutch early and try to coast to a stop rather than using a lot of engine or braking. Is this robbing the system of a chance to charge the battery?

3. I had read that the 5 series was using a glass-mat battery to allow but higher charge rates and a larger number of deep draw cycles. Is that true and does anyone have any experience with lifetimes and replacement costs?

1. Connected just like normal. No trick starter / generator, etc. It's just a clutched alternator.

2. There have been multiple issues with batteries not being fully charged. Doesn't seem to be rampant, but not uncommon. Don't coast de-clutched. Bad practice in general.

3. TJP answered this for you. Replacement cost is expensive, about $500 as it has to be programmed to the car.

[Losco]

it's not a true "regenerative braking" as in prius and hybrids do. what it does is when there's enough charge in the battery, clutch at alternator will decouple, so you get more power from engine to the wheels, and when you coast/brake from high enough speed, alternator clutch will kick in and charge the battery. when this happens you will see the ED bar go to blue.

[yogi799]

I wonder what sort of (minimal?) fuel savings that mechanism produces (really? alternator putting so much resistance on a 300HP engine that momentary disconnecting it makes significant fuel savings? Gimme a break). Sounds like a complex beast, definitely with high parts replacement cost in case of a failure (battery - $500...). I hope it's not as dubious as the start-stop thingy.

As I've said before, I only hope one failure of any of these components does not wipe out your entire savings obtained over a span of several years. I fear that is precisely the case. BMW is probably cool with it, though. Extra profit can't hurt, especially it if looks great on marketing pieces and appeals to the green movements out there at the same time. Win-win for them for sure.

[EV0LVE]

That's how BMW makes their money down the road, install expensive parts that are bound to fail. My battery was replaced within 6 months of ownership, and I drive 30 miles to and from work, so I know the battery had plenty of time to charge in between start.

This regenerative braking is BS, marketing BS so they can come up with "Efficient Dynamic" crap.

To the OP, sorry for ruining your excitement about your ED car, I'm just not as excited about this failure-waiting-to-happen-ED.

[MBrown1003]

FWIW, my E90 M3 had regenerative braking. My commute is about 3.5 miles (to the train station) most days; if I drive into the city, it's about 26 miles on the way in, much of it in heavy traffic, and light traffic on the way home. Weekend driving is typically around town within a few miles from home -- lots of short trips.

I never had a problem with the battery holding a charge, or having enough power to turn over the engine, and I am an avid user of parked-car ventilation in the summer and residual heat in the winter.

[Jon D]

There's a brief description on the BMW Tech website but it doesn't really tell you anything more than you already know or what other posters have already said, but for what it's worth, here's the link: http://www.bmw.com/com/en/insights/t...y_regeneration
With regard to repeated short journeys, which don't allow the engine to reach and sustain normal operating temperature for a good few miles, I'd be more concerned about engine internal corrosion, due to condensate acids not being burnt off and remaining in the oil.

[gatoman39]

Originally Posted by Jon D

I'd be more concerned about engine internal corrosion, due to condensate acids not being burnt off and remaining in the oil.

Right. Which is why here in the States the dealer will do a free complementary oil change for you after a year, even if your car isn't asking for one. They swap the oil but don't reset the light. You have to ask for it though, they don't offer it.

[raleedy]

Originally Posted by Jon D

With regard to repeated short journeys, which don't allow the engine to reach and sustain normal operating temperature for a good few miles, I'd be more concerned about engine internal corrosion, due to condensate acids not being burnt off and remaining in the oil.

Is there a difference in this respect compared to not driving at all for extended periods?

[Needsdecaf]

Originally Posted by gatoman39

Right. Which is why here in the States the dealer will do a free complementary oil change for you after a year, even if your car isn't asking for one. They swap the oil but don't reset the light. You have to ask for it though, they don't offer it.

In my case, they changed the oil but didn't reset the light. So then 6 weeks later I brought the car in to reset the light...and they changed the oil again.

Dopes.

[gatoman39]

Originally Posted by Needsdecaf

In my case, they changed the oil but didn't reset the light. So then 6 weeks later I brought the car in to reset the light...and they changed the oil again.

Dopes.

why doesn't this story surprise me? Honestly, I'd prefer they reset the light, then give me the oil and filter. I'd rather do it myself.

[pauls]

Originally Posted by raleedy

Is there a difference in this respect compared to not driving at all for extended periods?

raleedy, absolutely a difference. In a cold engine you have hot combustion gases entering a cold crankcase with cold oil. Moisture condenses there just like on a cold beer on a hot day. Ideally if you start the car you want to drive far enough to get the oil up to complete operating temp to evaporate that moisture, if you don't moisture remains. The condensation issue never happens if the car isn't started and just sits.

[pauls]

Originally Posted by Losco

it's not a true "regenerative braking" as in prius and hybrids do. what it does is when there's enough charge in the battery, clutch at alternator will decouple, so you get more power from engine to the wheels, and when you coast/brake from high enough speed, alternator clutch will kick in and charge the battery. when this happens you will see the ED bar go to blue.

I think its even worse that that, been perusing threads on "increased battery discharge". It appears that the charging system only asks for the battery to be charged to 80%. The so called regenerative braking, given enough use will charge it to 100%, if not the battery is at 80% when parked for the night. Its hardly regenerative "braking" as it as nothing to do with the brakes. It would appear they've put a nanny in the system that monitors your driving habits because several in the above thread have had the service adviser tell them their battery died because they drive it on long enough trips so not covered by warranty. My interest arose because after sitting for 5 months with a high end float charger connected upon first start got the discharged warning, not possible since the charger was attached. I believe but don't know that the nanny decided I was not driving it frequently as it thought was healthy for the battery. So they're now telling us how we need to drive the car?