I'm confused--batteries 101
 

In another thread there was a reference to the R56's method of charging the battery. In it the statement was made that the battery only charges when decelerating. So...does this mean when your foot is off the pedal and you're slowing down in gear? Does it include any time you're out of gear and coasting, too? Hubby commonly coasts in neutral--does this mean he's not recharging the battery? And how much of a drive does it take to recoup the amount needed to start the engine?

Was that reference for 2007 MINIs? There is something like that coming in 2008. I wasn't aware we had such a system on the current MINIs.

I thought it was on the '07s. Maybe I'm mistaken?

Hey Deb,
I've heard it's not our cars currently, but the upcoming BMWs (Euro '08 MINIs was one generic story I heard) cars that will benefit from a new series of changes including a smart alternator that watches for the right times to charge (ie when decelerating and in gear, making better use of engine braking), shuts down the engine when the car is stopped and in neutral, and restarts itself as you disengage the clutch. Since the cars will be expected to be using the starter so often, expect it to be a different starter technology with a more robust charging system.

One of the feature of this new system, is that fuel efficiency is raised when the alternator is not working constantly against the engine. Traditionally alternators (and generators) require force to turn the rotor in the stator. This is converting kinetic mechanical energy into electrical energy. If you build a smart generator, you can let it freewheel when not needed to gain efficiency. You can also make it a more powerful generator (which requires more force, but generates more current more quickly). I would guess the engineers will allow the new alternator to kick in when it's most appropriate for efficiency, but without any need to worry about accidental discharge. If they see you're not allowing for their optimally efficient time opportunity to charge, they'll fall back to engaging it at a less opportune time. Either way, you'll save fuel in stop and go traffic if the engine doesn't idle at lights.

I think you may have read that particular tidbit in a thread about the changes for the '08 model. I don't recall any such "feature" for the '07.

You might be right, mauberly. I was totally confused about the origin of the statement. It makes total sense to do it this way, IF you don't have the habit of coasting, as my hubby does.

Interestingly enough, I had a '68 SAAB Sonett which went into neutral whenever it was decelerating. At the time it was the only pollution control "device" needed at a time when the engineering for most cars was pretty iffy. Made for interesting and fun driving in hilly St. Louis.

More on traditional alternators:

Because alternators always strive for a constant voltage output, they rely on an internal voltage regulator to measure load (how much power is the car's system asking for) and the present output which will be a factor of engine speed and thus alternator rotor speed. Then it will adjust the current given to its own field coil to compensate.

What all this mumbo jumbo means is that if you were to measure how hard it is to turn the alternator on your car when it's operating, the answer is, that the mechanical drag created by a traditional semi-smart alternator is constantly varying.

This new type of smarter alternator will try to think past the immediate here and now and make decisions about when to place drag on the motor with the use of the alternator. But unlike an air conditioner compressor, which needs an electronic clutch to engage and disengage the unit from dragging against the engine, the smart alternator should be able to rely on the computer and all its knowledge about when you're braking, accelerating, etc. to simply command the alternator when to direct current back to the field coil and transform from smooth freewheeling to active duty.

Note that hybrid cars can make use of their big ole electric go-motor to act as an alternator when either a) the gas engine's whirling away or in some cases b) when the car knows you're braking and a controlled use of that alternator as a braking effect against the transmission. b) is called regenerative braking.

Sounds like a reasonable plan. Hope they save a dime for their $10 idea.

There are more cars coming up with this feature. It's basically a micro hybrid design, letting the battery power the various electrical accessories by itself while cruising and there is not much of a electrical demand. On deceleration, the alternator kicks in and pumpps in more current than it would have been normally to make up for the off time. There is not much needed to implement this feature, and it can add close to 1mpg in everyday driving. Not bad for a tweak of existing hardware and software. Downsides are almost nonexistent.

Here's a press release
http://www.mini2.com/article450-incr...ear-2008-.html

Interesting. But what happens with marginal batteries--those in service a few years--or when cruising extended periods as we do here in the U.S?

I got 8 years out of my last BMW's battery. Something tells me I'll be lucky to get 2 or 3 out of this new design when it comes out. That's gotta figure into energy consumption...

I'm sure the controller knows when the battery needs "bumped" during cruising.

I'd think the battery gets a bit more of a workout. Maybe a better (more costly) design. I'm sure it'll take a while to figure whether battery expense goes up, real fuel savings, etc.

I'll bet the dealerships hate that press release. Heck, if I hadn't already purchased my car I'd have waited for the 2008. I'm definitely impressed.

Oh man. They have cars on the lots, and $4 gas in the country. Must be a disaster. I hadn't thought about that...

I have a different take on it. If ever there was a reason to wait while the bugs are worked out, this is it, IMO. The R56 as we have it now will look like the "good 'ol days."

Daffodil, coasting will not prevent the battery from charging, as it depends on the engine being on. However, the load of the engaged alternator would probably cause the computer to increase throttle, to prevent a stall. Thus, any economy your husband thinks he is getting by coasting (if that's why he is doing it) will be lost. That aside, one should not coast in neutral. It defeats the active safe handling of the vehicle. Plus, in all I have read on the subject, the idea that coasting and braking prolongs clutch/trans/engine is not bourne out in the real world.

The battery itself takes a much bigger hit than in a typical application. In most cars, the battery gets hit with a short burst of starter current draw and then basically has a free ride from there as the alternator replenishes that lost during the startup and whatever drain occurred from standby losses. Some cars (especially current MINIs) let the battery fill in for the times the alternator is overwhelmed such as idling with the a/c on, lights and wipers running, rear defroster grid heating. The 'smart' alternator setup will compensate for high draw by running in conventional mode. Batteries themselves would need to be beefed up a bit, but that is not a problem. A typical deep-cycle battery like what is available from Optima in the Yellow Top series would do well (I have one of these in my '03 MINI now) in the new application. The typical current ECU can have some additional code installed that would monitor the battery condition much closer than in the past, and tailor the charge control accordingly (and be able to warn of a failing battery well before you would have any direct issues with it - a bonus).

Many GM products currently (no pun intended) come with charge control circuitry. Expect to see it everywhere in just a few years at most.

As a matter of fact, on fuel efficiency, I have tested this in my 1990 Legacy and my 2000 MX-5 a few times and found that fuel consumption is equil or just a little better when rev-matching and downshifting for engine braking. It's also excellent heel-toe practice. :cool:

Not beefed up but AGM technology.

The GM system uses a mostly conventional-appearing battery but it's rated for deep cycling. The difference most outwardly apparent is a small red box with the main positive battery cable passing through it with a separate cable attached. This box contains a current measuring device that is used to keep tabs on current being pulled from the battery as well as that being pumped back in. The technology is not much different than what a typical laptop battery uses to keep a running tab on the available power in the battery. The most visible clue to the system's operation is the voltmeter moving around much more than in a standard charging setup. Old-timers would immediately say there's something wrong with the generator. :lol:

Expect also to see more things such as variable-displacement oil pumps showing up in more engines soon. It's a simple, proven technology that should have been implemented years ago. Also, a lot more accessories like power steering and water pumps will be electrified.

Lynn, it's a wasted breath trying to convince him. Our mechanic of many years has told me (and him) the same thing, but...

What's worse is when he does it in the automatic 530i. Supposedly he asked someone at the dealer if it would hurt the automatic transmission and was told no. Our mechanic disagrees.

This sort of thing always makes me wonder how mechanics and service providers keep all this information in their heads without it overflowing... :grin:

Very interesting thread, btw. I've learned a lot!

From a mechanic's perspective, it can be daunting, to say the least. There is so much to learn (and retain) compared to even ten years ago. I try to keep up with various system and technologies as I come across them, but unlike 25 years ago, the sheer amount of subsystems in the cars is unreal. Luckily, the more things change, the more they stay the same. Engines still have oil and pistons, transmissions have gears, brakes have not changed at all save for ABS, etc. The aforementioned charge control stuff is basically using the same parts overall, but slight tweaks in their design and the cheap availability of monitoring and control via the electronics allows an interactive control to take place that can squeeze all the efficiency possible out of those typical parts. A piston engine retains the same basic design it originally began with. It's just that over time subtle (and not so subtle) changes have progressed over time along with the available technology to make them more powerful, efficient and clean. The new R56 engine is chock full of newfangled tech, but the same basic design is there. ANd this is only the beginning. There is going to be a huge push soon to increase efficiency even more, and more novel ideas will be showing up.

Do you have a reference on that?

These tweaks have a downside alright...MONEY...You can buy an alternator for any old 350 chevy engine for less than $30.....now every new car uses a different fancy design making each one cost $200-$300 ....no telling what this will add to the cost of parts.