[peppercorn]

When you take your foot off the throttle, the carburettor / injectors / fuel pump on a diesel return to the throttle opening that corresponds to tickover.

Just to note, this is not the case for the majority of modern vehicles in all circumstances:  Under some operating conditions a car's engine-management computer can 'decide' to cut fuel off entirely to the injectors.  This should be carefully monitored by the car's ECU to avoid the revs dropping below its stall speed and will only occur if no input for throttle sensor (ie. no pressure from your right foot) is present. On some vehicles light pressure on the brake pedal will indicate to the ECU that the driver wishes to go to this 'no-fuel slow-deceleration' mode.
The easiest situation to imagine where this is advantageous is where a driver is approaching a red traffic light or stationary traffic. If the driver is doing 15mph in 2nd gear, putting the clutch in will allow the car to coast (hardly slowing at all) but at the cost of a small amount of fuel to maintain tick-over.  Alternatively, keeping in gear can allow the car to slow fairly gently (through the additional 'drag' of engine pumping losses) but without a single drop of fuel being burnt.
Apologies if this is repeated - I've not read the whole thread.

[Geezer]

Good point PC. So that would mean you might do slightly better if you do stay in gear. Mind you, if you are going to stay in gear, you have to keep changing down if you don't want to stall the engine.

I have a suspicion that most people, if they think are going to come to a complete stop, either disengage the clutch, or stick it in neutral (except during their driving test, of course.)

[CliffordK]

I have a suspicion that most people, if they think are going to come to a complete stop, either disengage the clutch, or stick it in neutral (except during their driving test, of course.)

My Electric Vehicle has a clutch and flywheel that will spin quite well without any power.  I find it is actually best to bring the car to a stop in gear, so I can start again from zero, rather than slipping the clutch in first gear.  But, popping it out of gear as one approaches a stoplight is a hard habit to break.

[Geezer]

What does the flywheely thing? Is that the motor?

I've never driven an electric vehicle (other than dodgems {bumper cars} of course) but I thought the general idea was to leave it in gear and drive it only with the thingy that controls the motor power.

[CliffordK]

My EV Ranger has a 5 speed manual transmission, connected to the Electric Motor.  With a clutch.

Many people recommend a clutchless setup.  In my vehicle, there seems to be very little motor speed drop when free-wheeling in neutral.  Engaging the clutch while the motor is freewheeling will make the vehicle jump forward.  I'm not sure if it is the weight of the motor armature, or a flywheel, but it would be difficult to shift without using the clutch.

I can accelerate from zero...  but the different gears do actually make a difference.  I generally start in 2^nd gear, and work up through the gears. 

I have an ammeter, but not wattmeter, or miles/watt meter. 
I seem to get maximum power at about 200 Amp draw.
If I have it in too high of a gear, I get a lower amp draw, and less power.
If I have it in too low of a gear, I get a lower amp draw, and less power.

So, yes, the transmission does help.

Unfortunately, I am not an electrical engineer, and did not do the initial build on the vehicle.
I think one can vary power somewhat by varying voltage.  So, perhaps one could increase the system voltage from 144V to 288V, and get a wider power range.  Also, some DC motor controllers use pulses of power rather than a true variable voltage, although perhaps they use capacitors to remove ripple, and give true variable voltage.

[peppercorn]

Good point PC. So that would mean you might do slightly better if you do stay in gear. Mind you, if you are going to stay in gear, you have to keep changing down if you don't want to stall the engine.

Correct - it should be possible to return a very slight improvement in MPG if staying in gear, but as you infer there is a fairly limited rev range that this will mode support. The need to change gear at any point during deceleration would likely negate the gains anyway as the ECU would drop out of the 'fuel-off' mode in the change.  However a semi-auto gearbox might be able to handle the changes whilst staying in an efficient envelope.

I have a suspicion that most people, if they think are going to come to a complete stop, either disengage the clutch, or stick it in neutral (except during their driving test, of course.)

This is probably exactly the sort of behaviour the DVLA, in their rather clumsy way, are attempting to change through the pamphlet that Chris was sent []


Clifford, I've always suspected that IC vehicles converted to battery-electric end up with somewhat more gears than are actually required, due to the wider torque range generally available from an EM.  Of course, since your truck falls into the good-for-towing category of vehicle that you Yanks are so keen on I guess the more gears the better []

[Geezer]

Of course, since your truck falls into the good-for-towing category of vehicle that you Yanks are so keen on I guess the more gears the better

It's Ford Ranger! (I think they have them in the UK too). I had a four-banger Ranger, and it couldn't pull the skin off a rice pudding. It could barely tow my little tin boat.

[CliffordK]

It's Ford Ranger! (I think they have them in the UK too). I had a four-banger Ranger, and it couldn't pull the skin off a rice pudding. It could barely tow my little tin boat.

Aw, Heck, my old 4-Banger Ford Ranger was a towing/hauling machine. [8D]
If it only had overload springs. []

I could get one car loaded in the bed, and pulling another on a trailer   []

The EV Ranger has a very nice tow hitch.  However, it is very very gutless  [xx(]
I'm also having range problems.  I was getting 35-40 miles this summer.  But, this winter, the range seems to be plummeting to under 20 miles  []

[Geezer]

I'm also having range problems.  I was getting 35-40 miles this summer.  But, this winter, the range seems to be plummeting to under 20 miles 

Are you running the heater, or do you think the battery capacity is reduced by the cold temps? Is it lead-acid?

[CliffordK]

Lead Acid...  or AGM.

It should have an option to heat off of the motor, but it doesn't. 
Sometimes I'll hit the electric heater for a few minutes to help defog the windows, but generally don't drive with it on.

I think it is reduced battery capacity from the cold weather.  We'll see what it is like next spring.  I do need to try to equalize the batteries sometime.

[Geezer]

Can you monitor the voltage on each battery during charge and discharge?

I'm wondering if you might have a couple of dud cells, although, it that were the case, I would think you would see the charge current drop-off too quickly.

[neilep]

If ewe turn the engine off then this helps to save fuel too whilst coasting !..........which is nice !

[CliffordK]

If ewe turn the engine off then this helps to save fuel too whilst coasting !..........which is nice !

I've done it a few times.
Make sure you don't lock your steering, or are at least careful to unlock it.
Power steering will loose its assist, but may not be a problem at high speeds.
One gets one chance to pump the brakes before one also looses the power brake boost (but can still brake with more force).
If you have a manual transmission (with synchros), it s easy enough to pop the clutch to restart the engine. 
If, on the other hand, you have an Automatic Transmission in the USA, you may need to stop your vehicle and put it in park to restart, which is a big pain, and wouldn't be worth it, except for the biggest of hills.

A Hybrid does it all for you  []

[chris (OP)]

200 amps; that's a serious current - surely that's not maintained during steady speed...?

[CliffordK]

200 amps; that's a serious current - surely that's not maintained during steady speed...?

It is serious current.

200A x 144V.

I generally pull just over 200A while going uphill, and on hard acceleration. 
I avoid the freeway whenever possible, but I've been on the freeway for short hops at times.  Fast driving, but high power consumption.
I prefer to cruise somewhere around 80A. 

In about an hour of driving, I can essentially go from full to empty on 24 batteries.

If you consider power this way.
for conversions, 1KW (VA) = 1.34 HP.

So..
200A x 144V = 28.8 KW.

So...  My Ranger has a max of about 40 HP.  That puts it about the same as the old VW Bugs.

[Geezer]

200 amps; that's a serious current - surely that's not maintained during steady speed...?

It's relatively small compared to the energy consumed when you burn gasoline.

Clifford's electric Ranger is consuming around 6.5kW while cruising (80x144=6544) which sounds about right. If his Ranger was gasoline powered the engine would produce about 6.5kW under the same conditions.

However, as the engine would likely be around 25% efficient, it would be burning gasoline to produce 26kW.

The equivalent current for a voltage of 144V at that power level would be 181 amps, and if the engine was working hard, the equivalent current could easily be ten times greater.

[peppercorn]

I'm also having range problems.  I was getting 35-40 miles this summer.  But, this winter, the range seems to be plummeting to under 20 miles  []

I think all battery techs. suffer from reduced efficiency in the cold (something to do with increased internal resistance perhaps?).
What you need is some nice low-value fuel (in terms of capacity to do useful work at cost) that is onboard simply to warm the batteries and the cabin.  The simplest vs cheapest heater would probably be Propane, but it's hardly in keeping with the electric 'values'.
I reckon Torrefied Wood (think efficiently produced charcoal) is a pretty interesting and underutilised source of cheap heat (and even mech work) especially if you want to move said source around (ie. vehicles).

[CliffordK]

What you need is some nice low-value fuel (in terms of capacity to do useful work at cost) that is onboard simply to warm the batteries and the cabin.

It turns out that I have one of these laying around the house.
 [ Invalid Attachment ]
I hate to think what the covering might be made of.

[peppercorn]

I hate to think what the covering might be made of.

Oooo! Dreaded asbestos!

[wolfekeeper]

Good point PC. So that would mean you might do slightly better if you do stay in gear. Mind you, if you are going to stay in gear, you have to keep changing down if you don't want to stall the engine.

Correct - it should be possible to return a very slight improvement in MPG if staying in gear, but as you infer there is a fairly limited rev range that this will mode support.

I'm possibly the only person in this thread that has actually done this with a real-time MPG meter.

On an old BMW I had the engine had this kind of fuel cut-off. The cut-off works over almost the whole rev range; the only conditions for activation was being above a thousand RPM or so and with your foot off the throttle; and I don't think it did it on a cold engine, because the automatic choke was trying to keep the engine running and warming up.

So all you do to activate it is change down and use engine braking. The fuel MPG just wacks off up to infinite when you do that, and you get better engine braking than you would if it hadn't... until you get low enough revs and then it feeds the fuel back in again to stop the engine stalling, and you get a slight lurch- it's not possible to stall it this way on an automatic.

I'm pretty much certain that the same system is present on very many manual gearbox cars, it's cheap to install for the manufacturer and it improves engine braking performance as well as mileage, you just have to change down and use engine braking to use it.

As others have noted you get slightly better mileage than if you just used the brakes to stop; if you did that, because it was an automatic gearbox, the engine would drop to idle and the fuel wouldn't get cut; you had to deliberately select low gear to pull the revs up to use it.