Running on empty

[mellwaters100]

A recent "senior" moment resulted in an interesting experience I thought I would share!

I have a 130 mile round trip journey to work - started with full EV charge (guesstimate of 28 miles range) and a bit of petrol. Total range was about 70 miles. Plan was to fill with petrol at work. All fine and dandy until I get to work and realise - no wallet, so no means of getting fuel, argh!

The 2nd refuel warning had come on about 10 miles shy of work; the last 5 miles through city traffic the car switched to series mode. After trying to figure out best approach I decided on trying to make it back home. I took a rapid charge at work which took EV range to 22 miles and total range showed 32 miles. The next rapid charger was 47 miles away so, knowing the accuracy of the range guesstimator (!), I was banking on there being an extra 15 miles in the tank. Oh, and the last 33 of those 47 miles are motorway! And, from experience the 22 mile EV range lasts about 16 miles on that journey (a couple of long uphill drags), just as I hit the motorway.

So, all-in-all, I was reckoning I needed about 30 miles ICE range out of the remaining 10 being reported. What the hell, it was a sunny day so I decided to go for it! Sure enough, EV expired just as I got to the motorway, but I had a plan. As I have a 4HS with adaptive cruise control, set it to 58mph with minimum gap and sat behind a wagon all the way up the motorway.

Interestingly, for the entire 33 mile motorway section, the car ran in series mode without a break. EV range showed a constant 1 mile but, other than that, nothing untoward happened. Except, when I got to the next rapid charger (Ecotricity) it didn't initially work and there was an non-EV BMW sat in the other bay! I had already consigned myself to paying over the odds for the charge but reckoned it was a small price to pay to get home. When it didn't work, rang the call centre and they told me there was an error but press a button and I would get a free charge - bonus!

In the end, the EV ran out again about 4 miles from home but still made it back. Charged the car completely and refilled with fuel - took a total of 45.7 litres.

This got me thinking (quite apart from making sure I have an emergency tenner in the car for my next senior moment) - would it be more efficient for the car to run in series mode rather than parallel when cruising? With fuel in the tank, cruising at 58mph the car operates in parallel mode which then seems weird when, with minimal fuel, it runs in series to - as I have seen stated elsewhere - to maximise range. Surely, you want to maximise range irrespective of the amount of fuel you have?

Prior to this adventure, when the 2nd fuel light comes on I know the tank takes about 42 / 43 litres so was reckoning I had about half a gallon leeway. Normal ICE driving I get about 42mpg so was reckoning about 21 miles so, all told, I should have run out of fuel - but didn't. This suggests to me that the continual series mode was more efficient and so, why doesn't the car do that all the time?

Anyway, hope the above tale helps others experience range anxiety!

 

[ThudnBlundr]

The tank is nominally 45l, so you managed to put more in than it should take in theory! I guess the pipes account for some of that...

I'm surprised it didn't go into parallel mode, as it should (in theory) be more efficient if the engine is operating close to it's peak efficiency on the highway, without the losses of (1) powering a generator to (2) fill the battery to (3) power the electric motors, each step of which has losses. Mine certainly goes parallel at speeds below 58mph

25 years ago I managed to set off from London to the Lake District without my wallet, but only realised when I stopped for a coffee near Birmingham. I was driving a Jeep at the time, and you could often see single figure mpg around town :shock: I went to a bank and told them I had no proof of ID, no money, but please could they give me £100. Luckily I was with First Direct, so they were able to confirm my ID over the phone and give me some cash.

 

[user 816]

Its not worth the risk, better to fill up then confess to the petrol station you forgot your wallet and they will usually take your details so you can return to pay or be invoiced.

Police now take a dim view of people who could reasonably have expected to likely run out but still continue. Whilst its not an offence to run out itself. If an accident then happens, well someone was recently jailed in this scenario for 3 years when her passenger was killed. Normally it would have been just an unfortunate accident, but her deliberate running out of fuel made her responsible for the situation.

 

[AndyInOz]

Just in case you haven't thought of this...

Here in Oz, if you forget your wallet, you can still pay for things with your mobile telephone.

It's even possible to request a series of codes which will cause a specified ATM to disgorge cash on command (from your account). This can be done via the internet, or over the telephone with the bank's assistance.

 

[elm70]

Interesting story about parallel/series ... I guess to know which is better between parallel vs series ... it depend of speed and real power need.

When I was trying to optimizing my EV range I did cruise at around 80km/h (50mph) .. and I could see on the watchDog an energy consumption around 7kw

So possibly at 59mpg under a air stream ... you real power consumption must have been similar ... and possibly at that rpm the engine generate too much power for traction the car and not over charge the battery ...

PS: About using the phone ... many banks here have a mobile apps that allows to play using the phone NFC for make payment similar to the wireless credit cards .. and we also have "the dummy codes" from the bank apps too which work in many shops including tank stations..

 

[geoffshep69]

Just in case you haven't thought of this...

Here in Oz, if you forget your wallet, you can still pay for things with your mobile telephone.

It's even possible to request a series of codes which will cause a specified ATM to disgorge cash on command (from your account). This can be done via the internet, or over the telephone with the bank's assistance.

You can do that here too if you bank with Royal Bank of Scotland or NatWest, you just generate a code from within the mobile app and it lets you get cash out of an ATM. Has come in really handy a couple of times when my son has been out and run out of cash – I can just give him the code number and it lets him get cash out.

Re the original post, I generally don’t risk it and always make sure I have enough fuel, but there’s no doubt that the low fuel warnings come extremely early in the process and you usually still have around a gallon left when the dashboard is imploring you to stop and saying that you have nothing at all. I guess that’s a deliberate ploy to try and make sure people full up earlier and don’t risk running out.

 

[Harald]

So far, I emptied my petrol tank on the motorway only once, knowing that I will have sufficient electric range available for reaching the next gas station.

Looking on "Reserve" calculation on other cars:
Years ago, I had a Nissan Primera Diesel which always showed 0 km range keeping approx 10 liters still in reserve. (A nominal 50 liter tank could only be filled up to 40+ when the car showed 0 km range)
That's why i packed extra 5 liters in a canister and drove it once until it was really empty. (No tunnels or motorways...)
The result was 180 km below zero.


Harald