Mild Hybrid Cars

7 Jan 2014
Reaction score
West Glamorgan
United Kingdom
I have one. I'm a passable clever bloke, but I have absolutely no idea what it's doing for me or the environment. On the latter point, I've gone from a V60 diesel 55mpg to a newer petrol/mild hybrid 40mpg (25 around town).

So folks, any ideas?

My only theory is that it lets Volvo in my case, to get round a ban on ICE cars.
Sponsored Links
It's doing very little.

Mild hybrids are a petrol engine car with a tiny battery and an electric motor which also acts as a generator. The electric motor can assist the petrol engine in some situations to reduce fuel consumption, and is used when braking to recover some of the energy which can be stored in the battery for use later. The electric motor cannot move the car on it's own.
Their main use is so that car manufacturers can continue to sell internal combustion engines with very minimal extra effort while claiming the vehicle is somehow better for the environment.

The next variety is a hybrid car, which is similar in principle but the battery is larger and the electric motor can move the car for short distances on it's own without using the petrol engine. The Toyota Prius and other Toyota hybrid vehicles are the main examples of such vehicles. They are sold under the misleading label of 'self charging hybrid'. 100% of their energy is obtained by burning petrol in the internal combustion engine.
When introduced 25 years ago, these vehicles were a reasonable improvement in fuel economy compared to other vehicles available at the time.
Today they are just an excuse for Toyota to continue selling the same old technology under a different name and claiming it's somehow better for the environment.

Plug in hybrids are hybrid cars in which the battery inside can also be charged by connecting it to an electricity supply. They can drive for longer distances on electric alone, typically a few 10s of miles, and might have a use for those people who often drive for very short distances but at the same time also do excessively long journeys in regions which have little or no electric vehicle charging facilities. Many such vehicles have been sold with big tax incentives or grants for their 'green' credentials and then never actually plugged in anywhere, making them the same or worse as a standard hybrid car where 100% of the energy is obtained from burning petrol.
Our sons Fiesta ST has it. I think he said it’s only used to boost power on acceleration. It is a bit nippy.
I can't add to Flameport's excellent summary. They're a cynical "workaround" to get a few environmental brownie points, but basically, you're lugging a small battery and a motor round with you all the time, which is ultimately powered by the engine.
Sponsored Links
They reduce your emissions fractionally, it's the next step up the scale from stop/start engines.

They should be the legal minimum.

I have always wondered, does it help with turbo lag at all?
Suzuki- and probably other manufacturers - use the alternator as an electric motor to boost performance, reduce emissions et al on their mild hybrid vehicles. This is effective to some degree.
Naturally this won't have any effect on turbo lag whatsoever but with the variable vane / ultra small and high speed turbochargers used these days turbo lag has more or less been eliminated.
Gone are the days when you had to wait for the turbo to spool up (Saab 99 etc) before you got anywhere!
John :)
OK, so this is the experience of a week (500 miles). New car, swopped out for a Hybrid version of previous car - petrol powered Auto.

New car feels to accellerate quicker, smoother. ICE starts for a few min's morning when 'cold' in urban areas but have NO direct drive from ICE until +100KPH. Once warm car is using 'traction' battery only around 25% of the time on the usual daily run. On the long journey it's about the same maybe a bit more of the time.

Fuel consumption - Old car averaged 53mpg, presently new one is at least 12mpg better.
I have a Toyota Corolla 'self-charging' hybrid, 1.6 litre. Does about 75mpg (winter) to 80mpg (summer) if you're not lead-footed. It replaced an old 1.4 litre Corolla auto, which averaged only 32.2mpg. Acceleration with the new car is impressive, as the ICE kicks in to augment the EV drive.
Don’t think I’d ever get a fully electric car but I’d certainly consider a hybrid.
The "Mild Hybrid" using a 48V motor is, in my opinion a total waste of time. The tiny battery is incapable of propelling the vehicle without the assistance of the petrol engine (except downhill!). I own a Kia Niro self-charging hybrid which has a 1.56 KWh 240V battery, and that can drive the vehicle short distances unaided. The PHEV model has an 8.9KWh battery at 480V which is capable of around 30 miles electric use. Sorry to say I agree that the Mild Hybrid is merely a ploy by the manufacturers. Moreover, there have been reports that the engines of mild hybrids have failed seemingly due to cross-technology conflicts!
The automated 'Manual' box (circa 2009) was OK but hesitant at changing at low speeds. Later models box is CVT, we haver had any problems with those boxes.

I had a 2006 Accord with CVT box - I gather that is still going well (the car was in the dealers at the same time as I was for a service) at 170000 miles.
Gone are the days when you had to wait for the turbo to spool up (Saab 99 etc) before you got anywhere!
John :)
You had to keep the turbo spinning all the time - so basically the only way to drive them was to go like a bat out of hell whenever you could. Judging where to put the welly down coming out of a roundabout in the wet was art form!
Sponsored Links