I have been long thinking about starting a series of posts about news in the automotive industry that have no direkt link to Saab or NEVS but could have an effect on the way we look at future products from Trollhättan [sorry guys I don’t want to start a discussion about the brand, so till next notice I will call the cars this way]. So if you like it I will try to deliver a “Not SAAB related” post each week.
My first post is about a,quite funny in my opinion, article about the BMW i3 in the USA. The original article is from consumer report although I’ve found it somewhere else.
The guys at consumer report summarise the problem with this sentence
Relying on that gas engine when the main battery is depleted works well in most cases, including high-speed steady cruising, but not, we’ve discovered, if you demand more of it.
They’ve discovered? C’mon even some BMW manager talked about the drawbacks of such a range extender configuration at its presentation in Munich.
So let us talk about range extender and its problems.
A EREV, or REX-EV according to BMW, is a normal Battery EV with a small IC-Engine and a small tank that acts as a generator in case the Battery levels are too low. There is no mechanical connection between the generator and the wheels, so the wheels will always get the power from the e-motor. The VOLT was also an EREV, but the managers at GM decided to add a fallback solution in case the driver fully depletes the battery before letting the generator do its job, more on that later.
So on the i3 you have a generator that produces 34 kW of power that is delivered to an e-motor that can produce up to 125 kW of peak power. If you are cruising at steady speed, the car may not demand the full energy coming from the generator, so most of the electric power produced by the generator is used to keep the car moving and the rest to charge the batteries. If you press the pedal to the metal running on the generator, and the battery is still not ready to deliver the extra power needed, the car will handle as an 39-44 hp car [this is 34kW with an effectivity of 85% – 95%], no more and no less.
How will BMW approach this problem?
It [the i3] will include a battery state-of-charge indicator, an early alert prior to potentially experiencing a temporary loss of power, and a proactive boosting of the battery level based on the car’s navigation prior to encountering hilly terrain. This enhancement will also be available as a retrofit for existing i3 owners.
As you see the BMW guys have no magic. The only thing they can do is to put a lamp on your instrument panel, so you know if you will have the full power to overtake the cars in front of you and rely to your GPS to start the range extending generator sooner than expected to have enough battery charge in the mountains, so you always have to tell your car where you want to go, so it can decide what is the best range extending strategy for your drive.
Taking the drama from my words, the i3 is an urban car, and in the cities you are constantly using the brakes and the demanded speed and acceleration are lower, so I think most of the people would do well with the i3 REX, but if you decide to take a short trip outside town, remember that you have a less powerful car when the small generator starts making noise.
At the end of the day a EREV will help you reach that charging station that is couple of kilometres away from your max range, but it has its drawbacks and the car will handle quite differently running on batteries than running on the generator.
Back to the VOLT. The VOLT has a direct connection between the IC-Engine and the wheels, but although many talk about the VOLT as an PHEV (Plug-In Hybrid) it is a real EREV. Why? The car will 99.9% of the time rely on electrical power, when the battery charge is too low the generator will start and the batteries will recharge, still running only on the e-motor. Only in the case the batteries are completely depleted then the IC-engine would drive the wheels till the batteries have once again a minimum of charge that allows the e-motor to drive the wheels.
I hope you liked it, and that I can write “Not SAAB related” technical articles till I can write “SAAB related” technical posts.
I like the idea of such articles here. Keep them coming.
Love this kind of articles, and in the current situation I think it is related to Saab – the future of Saab. We all need to be updated about developments in the car business. Bring it on Red!
Interesting stuff!
This is a good idea as it will broaden our minds. I have been sharing other car brand inovations with friends for several years now as there are so many interesting points of view. Remember when we drive our Saabs on the road we share them with people who are in other marques.
Agree with all the others. It’s good to be better informed.
No Red, totally Saab related! Great article and I should get back to posting some like this too.
Jeff, as I’ve said, the post will talk about something not Saab related, that somehow has a link to the products we could see in the future coming from Trollhättan.
So, yes I do also se this as totally Saab related. 🙂
I’d rather take 39-44 hp from a range extender than 0 hp from an EV relying purely on batteries. At least you get home without having to push the thing…
Well, that’s just the point of an range extender. I just wanted to make people understand, that running on range extender is more of a limp mode than an equivalent to the “normal” battery powered mode.
I agree that the point is valid. There is a good chance folks really believe buying an iBMW they’re getting a hybrid when it’s not one.
I’m just still really “annoyed” the new owner of Saab cars initially even considered selling pure EV’s as their only product. A vehicle that can leave you stranded if there is the slightest hiccup in preparation (charging) or execution of the trip.
Obviously they’d never heard of Murphy’s Law which they now must be very familiar with. Sorry.
Great initiative Red.
not only for our particular interest here, being open minded, curious and well informed about others around (even if we consider it not being the right solution for a Saab), is always learning something what is suitable or not. very important for us.
Red J.: I loved this read too and agree with Aeronils. I think the Volt comes closest to what an EV should be—-or at least comes closest to an EV for today’s needs for many of us. It’ll be interesting to see what the 2nd generation Volt looks like.
I agree. Keep these articles coming. I am currently leasing a Volt. I got it a few months ago with the hopes that the NEVS electric Saab would be in the US by the time my lease was over. I really like it. It feels like I’m driving the future and almost like a Saab engineer or 2 had something to do with it.
The volt basically has 3 motors and 3 clutches. The main electric that drives the wheels through a 7:1 gear reduction, a smaller motor/generator, and the gas engine. The car runs on the main electric motor at lower city speeds. There is a clutch (more accurately a brake) that keeps the main electric motor’s casing stationary. At higher speeds, the smaller motor/generator connects to the main electric motor’s casing with a clutch, and the other clutch/brake releases allowing the casing to spin. This allows the MEM to operate at a lower speed while keeping the output speed the same. The gas engine kicks in once the batteries are depleted, it connects to the motor/generator with a clutch. At lower city speeds, the clutch between the motor/generator and the main electric motor is disengaged and is only providing electricity. At higher speeds, the motor/generator also connects to the main motor’s casing. So, effectively, when the gas engine is connected by the clutches, it is still only physically turning the casing for the main eclectic motor.
Here is the You Tube video that I found last week where I got all of that. It’s pretty interesting.
http://youtu.be/AX5ZwzNwTc4
Big thumbs up, RedJ!