MG5 EV Poor Range

[jonathanhoey]

(bit of a tangent here, sorry)

The mk1 Jazz is a great car (we've got one) with some truly strange design decisions.

The most obvious one is that they put a CVT in it, but then gave it fake numbered gears anyway - seven of them, with paddle shifters on the wheel. And the revs don't sit at the optimal range (which is kind of the point of a CVT) - they rise and fall with the throttle. I can only assume they thought it would be too unintuitive if the driver couldn't hear the engine note rising.

 

[jonathanhoey]

Back on-topic, I've never really understood the theory that turning the regen down would somehow be MORE efficient. I mean, you're going to be decelerating anyway - you're just either harvesting some of that energy back, or you're choosing not to.

 

[Jocko]

Back on-topic, I've never really understood the theory that turning the regen down would somehow be MORE efficient. I mean, you're going to be decelerating anyway - you're just either harvesting some of that energy back, or you're choosing not to.

If you are going down a steep hill, then KERS 3 will maintain your speed and recover the maximum energy. However, if it is a long shallow descent, then KERS 3 would slow you down too much, and you would have to use the throttle to maintain your speed. KERS 1, on the other hand, would let you maintain speed with no throttle. As the recovery of energy can never be 100%, it is best not to use it than to recover it.

 

[Cocijo]

Back on-topic, I've never really understood the theory that turning the regen down would somehow be MORE efficient. I mean, you're going to be decelerating anyway - you're just either harvesting some of that energy back, or you're choosing not to.

Yes interesting point that you make. Like most things there is balance and compromise here. Your driving style is obviously very important. On regen 3 i sometimes find that i can slow down too soon if I’m anticipating ahead, that means that I can either leave it later to lift off or have to apply the power again for a short while. Your approach speed is also important. For some drivers regen 1 or 2 might suit their particular style and approach. I do agree - on the face of it why wouldn’t you just want max regen all the time to get juice back in the battery? In reality depending on different scenarios this may not work out. If you travelling down a long steep hill - yes max regen all the way will be the most efficient way to go.

 

[Petriix]

The KERS mode is just a tool to help you balance your use of energy. You can achieve similar levels of regen through controlled use of the accelerator and brake pedals regardless of the mode.

KERS 3 will give you more regen by default, so you'll lose more speed in the interim between coming off the accelerator and onto the brake. There are times when that will save you energy by recovering it where you would have ultimately ended up wasting it (either by using the friction brakes later in the sequence, or by arriving at a bottleneck too soon so ultimately having to slow more).

But there are times when KERS 3 will waste energy by slowing you down too much. This is especially true when driving at speed. The recovered energy is always going to be significantly less than the energy used to accelerate again.

So it's advisable to change the KERS mode to be appropriate for the situation. I tend to flick into 3 when approaching a junction and keep in 1 most of the time. Sometimes 2 feels just right on a bendy country road.

 

[Jocko]

The KERS mode is just a tool to help you balance your use of energy. You can achieve similar levels of regen through controlled use of the accelerator and brake pedals regardless of the mode.

Do the brakes on the MG5 work by regen and only act as friction brakes in the final phase of stopping?

 

[NellieEV]

Do the brakes on the MG5 work by regen and only act as friction brakes in the final phase of stopping?

I believe no...but yes... tiny amount of brake pedal seems to increase the KERS regen slightly, but then any further applies the friction brakes... from my experience anyway.

 

[jonathanhoey]

Do the brakes on the MG5 work by regen and only act as friction brakes in the final phase of stopping?

I don’t think it’s that sophisticated.

Lift off the gas pedal, you get regen braking. Press the brake pedal, you get friction braking (and regen as well, naturally).

It doesn’t appear to blend them intelligently like (sorry for going on about it) an i3 does, for example.

 

[NellieEV]

Equally I believe that ECO/Normal/Sport just remap the sensitivity of the throttle pedal (although ECO is also supposed to reduce/limit the AC ).

 

[Jocko]

Thanks. Petriix's post gave me the impression that it did.

 

[jonathanhoey]

Thanks. Petriix's post gave me the impression that it did.

I should stress that I am only speculating from my (couple of weeks) experience in the MG5 so far, and extrapolating to some extent based on my much greater experience in the previous car. Plus a little bit of technical knowledge, but I’m a layman really.

Certainly the car possesses the capability to autonomously control braking force AND throttle to each wheel independently - that is central to how Electronic Stability Control works, which all cars are obliged to have, so that much is not in question.

What we don’t know (and are collectively trying to figure out by trial, error, observation and informed guesswork) is to what extent it does it during normal driving.

 

[Petriix]

I'm fairly certain that the brake pedal increases regen. Just look at the power flow screen when in KERS 1 then press and release the brake pedal and see the difference.

 

[Petriix]

I'm fairly certain that the brake pedal increases regen. Just look at the power flow screen when in KERS 1 then press and release the brake pedal and see the difference.

Just to confirm the obvious: KERS 1 was giving me ~ -20A; when I applied the brakes it went up to over -50A (minus meaning energy gained). That's how most (if not all) hybrids and EVs work.

 

[Cocijo]

Do you know why the additional regen is applied when the friction brakes are used?

 

[Petriix]

Do you know why the additional regen is applied when the friction brakes are used?

I don't really understand the question. Why wouldn't you want to maximize regen rather than losing the energy as heat?

 

[NellieEV]

I'd guess the designers/engineers have the following thought process is: If you have it in KERS1 you only want very slight 'coast down', KERS2 'let's make this a bit firmer', KERS3 'Let's give some good engine braking'.... brake pedal 'SH!T LET'S GIVE THEM ALL WE'VE GOT +THE REAL DEAL BRAKES'

 

[Kithmo]

Do you know why the additional regen is applied when the friction brakes are used?

I always thought it was like the Prius, the braking (foot pedal) is done mainly by regen all the time except on heavy braking and below a certain speed (5 mph IIRC), where the friction brakes kick in.

 

[Petriix]

I always thought it was like the Prius, the braking (foot pedal) is done mainly by regen all the time except on heavy braking and below a certain speed (5 mph IIRC), where the friction brakes kick in.

And, of course, when the battery is fully charged; which is why I advocate only charging to full infrequently unless you really need the full range.

 

[Valiant5]

And, of course, when the battery is fully charged; which is why I advocate only charging to full infrequently unless you really need the full range.

What do you make, Petriix, of the advice in the manual to do the balance charge once a month? Must admit, it was never something I did with the Leaf I had before, but in the MG community it seems to be de rigeur. I've just done it a second time, but a full charge at the moment is lasting me the best part of the month, whereas with the Leaf I'd just charge a bit here and a bit there, as and when...

 

[Jocko]

What exactly is this Balance Charge, and how do you do it?