Speak EV - Electric Car Forums banner

1 - 12 of 12 Posts

·
Registered
Joined
·
8,106 Posts
Discussion Starter #1
Has anyone else noticed that if you select HOLD mode you lose a few miles from your EV range estimate?

No idea why that should be.

Are they genuinely lost range or is it a display or estimate issue?

I'd love to know.
 

·
Registered
Joined
·
16 Posts
Yes, I had 4 miles remaining and switched to hold for a long motorway stint - when I came to switch back the battery range was zero.
I am assuming that it is something to do with the hybrid function when in hold mode. ie: battery power is used for acceleration and in stop / start situations and is topped up by kinetic energy recovery in regenerative braking and coasting / downhill situations.
When I owned a Prius the regenerative battery would be in a state of zero to full charge depending on terrain and driving style (ie: if there was more demand from acceleration than power delivered from kinetic engergy recovery then the battery would slowly deplete to it's minimum when the engine would do all the work).
At any time in the journey the battery level would therefore be at some point between full and empty. The same could well be happening here and I do not know how accurately the hold method is supposed to work, what is certain though is that if i look at the power flow display the battery is often assisting the engine.

Regards


David
 

·
Registered
Joined
·
1,777 Posts
Yes I have noticed this too, as above, I saved 4 electric miles for my final cross city drive home but when I came off the motorway and switched I got nothing.

P.
 

·
Registered
Joined
·
16 Posts
Another contributing factor - although it would not explain why four goes to zero, could be the driving style used to calculate the range. Driving style in hold mode is likey to be faster roads and driving on battery is typically more gentile (unless you are addicted to sport mode of course ... not me, honest !??? ...). So it could be that part of the reduction is down to a recalculation of range due to a different driving style.

Regards

David
 

·
Registered
Joined
·
86 Posts
Also had this, and I'm not sure if it was driving style either. A short story of my driving for one day follows...

I decide to drive up to my brothers, to show off the new car :)
Get on the motorway, set the cruise control to 70.
At 5 mile battery range left, switch on hold mode.
Get off motorway, and at 5 miles left to desitination, switch to normal.
Arrive at my brothers with 4 miles range left. :) (It was mostly down hill, and very heavy traffic, so rarely got above 20 mph for those last 5 miles)
All good so far.
Put car on charge for a bit.Go for a 'demo' drive. Put car on charge for a bit longer.
Head home with a battery range of 28 miles.
Same routine as before. Get on motorway, set cruise control to 70, switch on hold mode with 5 miles range left.
Get off motorway, switch to normal, and get 0 battery range :?

I don't see how driving style could cause this, as both the hold mode 'legs' were done using cruise control at 70.
 

·
Premium Member
Joined
·
11,068 Posts
The hold mode was designed for cities that have zero emission requirements and I am still to be convinced of the benefit of using it to 'save EV for later'. To date I have seen no technical explanation of why it is better than using all the EV on the first part of a normal journey.

I am also concerned that if prospective buyers think they have the hassle of switching between modes, selecting L or D messing with tyre pressure, etc, etc, we will just drive them away.... (geek alert?)

It would appear that the motto with regard to your EV range is 'use it or lose it' :D

Paul R
 

·
Registered
Joined
·
8,106 Posts
Discussion Starter #7
There is a benefit for using HOLD mode. If you are driving around town in ER mode it is quite probably at low speed with low acceleration i.e. low power requirements. In that situation the generator does not run constantly. There is no need. It comes on and goes off as and when it needs to to satisfy the power needs. There is an inherent waste when a petrol engine is stopped and then restarted. Also, the generator is required to do more battery charging as the battery is depleated a bit and then recharged. None of that happens if you are in ER mode on the motorway.

When the car is driven at speed there is a much higher and more steady power requirement. The generator can operate at higher RPM (nearer its optimum speed), it doesn't start and stop and can run constantly (or more constantly). All in all it makes more sense from all respects to run the generator when the power requirements are higher and more steady as on a faster road.

As for switching being hassle? Sorry but it isn't any hassle. You switch if you want to or you don't. If people don't want to then they don't have to and they won't. They will probably hardly see much difference anyway as all of this makes a difference, but it is a small one. As is D & L as is any tyre pressure adjustments people might want to make.

I have always said that you should use all your EV range before you next fully charge and I continue to say that but if people want to run their car a bit more efficiently, as I do, then this kind of info is relevant... not to mention fun.

The HOLD mode was designed to HOLD the current state of charge for whatever reason the owner wants to use it for. It may have been put in with Zero Emission cities in mind but it is a feature of the car and so why shouldn't we use it in our own ways if it helps improve the cars performance?

There is another aspect to it for me and that is that if I am going to be burning petrol anywhere then I'd rather do it on the open road instead of in towns and cities where there is the highest population. One of my personal reasons for buying the Ampera is to reduce my impact of burning petrol partly by burning less but also partly by being able to chose where I do it and by using HOLD mode in this way helps me with that objective.

I really don't think that as owners we should concerned ourselves with what prospective buyers will think. If we use the cars in our own ways and it is a success then I am sure that others will see that success. Some of us will be techie and use HOLD mode to meet our needs, others will just drive the car like a normal ICE. Either way, if it works then both ways are valid in my opinion.

Edited: If anyone has reason to believe that I am wrong in saying that there is a benefit to using HOLD in this way then please say so. I have made some assumptions based on my understanding of how the generator works and how petrol engines work... I accept that I could be mistaken and I don't want to mislead anyone... or myself :)
 

·
Registered
Joined
·
387 Posts
Hi Paul,

I did not see this when I went for my one and only long run. There was 34 miles in the battery when I started using hold mode and 34 when I stopped. I will however take closer note of what happens next time.
 

·
Premium Member
Joined
·
11,068 Posts
Paul C

A bit of a mix of opinions and facts in your last post. To correct one fact, the engine does switch off when in ER mode on the motorway at 70 in cruise and there is a decline and on steeper declines there is regeration.

To clarify, my post was to stimulate discussion...

Paul R
 

·
Registered
Joined
·
8,106 Posts
Discussion Starter #10
proddick said:
Paul C

A bit of a mix of opinions and facts in your last post. To correct one fact, the engine does switch off when in ER mode on the motorway at 70 in cruise and there is a decline and on steeper declines there is regeration.

To clarify, my post was to stimulate discussion...

Paul R
Yes, it does turn off but a lot less than when in town (I think I said that).

I love everyone playing devils advocate or stimulating discussion but sometimes it can be difficult to know when someone is doing that or is voicing a heartfelt opinion. Sorry. Either way keep the discussions coming... this is a super way to thrash out the intricacies. :)
 

·
Registered
Joined
·
21 Posts
Since the Volt does not have HOLD in '11 & '12 people just use the Mountain Mode when they want to give demos at a final destination. Hitting MM subtracts about ~14 EV miles (aka ~40% SOC). Do it before it gets down to 14 miles OR the ICE revs hard to get it back up to 14 miles.

I suspect the loss of a few EV miles when switching to HOLD is because it uses some as a buffer and dips into it. The ICE cannot always keep up with the energy demand to propel the car if there are hills/mountains/high-speed-driving as an example.

In the Volt the ICE turns on/switches_over when you get to ~22% SOC but then it will raise it to ~25% for high speed merging/hills/etc (buffer to dip into). That is similar to where I thought your EV miles went as you switch to HOLD mode with 4ish EV miles left.
 

·
Registered
Joined
·
8,106 Posts
Discussion Starter #12
Yes, that sounds possible.

Another thought is that when you switch to HOLD it doesn't transfer immediately to using power from the generator while the generator warms up reducung the load on the ICE while cold and dipping into the buffer Scott talks of and reducing the EV miles while the generator warms up.
 
1 - 12 of 12 Posts
Top