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Discussion Starter · #1 ·
I'm looking at chopping in our second car (ICE) for an i3 REx as we do the vast majority of driving, probably 95%, within EV range and then can rely on REx for the longer trips.

My question is this: At what %SOC can you turn on the REx?

This may not even be possible, can you manually turn it on? What I'm thinking is can I manually turn the REx on at say 90%/80%/70% or whatever it is and try to hold the %SOC as high as possible? I'd like to avoid getting down to a low %SOC and then having it kick in, preferring to rely on it holding a higher %SOC and I can refuel or rapid if needed.

Thanks!
 

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Can manually select voltage hold mode once the battery is at or below 75% altho not for US models.

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Yes, no problem at all doing this. Turn on the REx near 75%, run the fuel down to zero and then back to battery until you find a filling station. If you're confident of getting a charge somewhere then switch back to battery a bit earlier to run it down instead.
 

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I don't manually enable it. I've had the Rex for 2 years, and never seen the need to manually try on the Rex. I've only once noticed a reduction in power from not having any battery left, and all it did was reduce my speed on the motorway from 70 to 60. All other times using the Rex there has been no problem with letting the i3 decide when to turn on the Rex.


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Discussion Starter · #6 ·
Thanks for the responses everyone.

My main thought is that if I rely on the REx at a higher %SOC then it's easier to refill the fuel than it is to refill the battery. Interesting note from Paul, good to know it generally doesn't have problems with the fallback to REx mode.
 

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I believe you will want to run the battery down as much as possible to maximise the charge you get especially when using the EH, when the battery is virtually empty the current will be highest and start to taper down until after around 80% capacity the current will be down to less than 10amps, it usually takes around 10-15mins to reach 80% after which you can decide to terminate the charge early and get on your way or stay for the full 30 mins but you won't gain much for the last 10 minutes or so.
 

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Thanks for the responses everyone.

My main thought is that if I rely on the REx at a higher %SOC then it's easier to refill the fuel than it is to refill the battery. Interesting note from Paul, good to know it generally doesn't have problems with the fallback to REx mode.
I've never had a reduction in power either but I usually turn the rex on early. I have seen the soc drop by as much as ten percent below the point where the rex was turned on which if I'd let it start on its own accord could spell trouble, but so far the lowest it has got when started on its own is 1%.

I have confidence that in most cases it would be safe to let it start itself but not if there are big hills ahead. Much better just to keep some charge in reserve until you are approaching a charger then run it down and arrive just before rex re-engages.

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What is I've seen happen is the Rex kicks n when range drops below 3 miles.

From here there is a fight for balance. The engine charges the battery which powers the motor, sometimes there is excess energy, and the electric range goes up, sometimes the REx can't charge the battery as fast as the motor uses power and the range drops. Eventually the range can hit zero, so you are relying purely on how fast the Rex can charge the battery vs power requirement.

This is where you can be impacted in power requirement, but for the vast majority of your needs, you will not notice any issues. Only at speed on hills, or if you try to accelerate VERY hard, will you notice a difference to the normal power output of the car.

In my case, I tried to accelerate up a hill on the motorway and found the car had insufficient power to do this, and eventually slowed a little to 60mph. It wasn't a big hill, and on the other side I got regen to bring the electric range above 4 miles and give some 'reserve' for the next hill.

In my view, unless you regularly use a motorway with a bloomin' big hill (M6, Shap for example) you don't need to worry about manually activating the Rex. Get the most use out of your (cheaper) battery miles.


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In my case, I tried to accelerate up a hill on the motorway and found the car had insufficient power to do this, and eventually slowed a little to 60mph. It wasn't a big hill, and on the other side I got regen to bring the electric range above 4 million miles and give some 'reserve' for the next hill.
Wow that must have been some hill, if I could get half that I would never need to charge ever again.:D
 

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On ling journeys does it make sense to switch the ICE on when going up hill and off every where else? and in winter a bit of heat as well.?

The ICE generation will then in effect be going directly to the motor and missing out the inefficiency of the batt ?
 

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On ling journeys does it make sense to switch the ICE on when going up hill and off every where else? and in winter a bit of heat as well.?

The ICE generation will then in effect be going directly to the motor and missing out the inefficiency of the batt ?
No it doesn't. The I3 REx doesn't help with cabin heating, except that things in the boot get a bit warmer. Turning it on and off means more of the time it is running inefficiently because it is cold. Either wait until it comes on of its own accord or turn it on early and leave it on until you have just enough battery to get to next next charger or destination.

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Hi Scott,
You will love the car. I just head for a rapid and allow for about 120 miles on battery. I have done less than 1% on the REX but it make planning simple and stress free. The dealer who delivered the car set one of the function buttons on the dash to turn REX on/off (I have only used it once to try it out). If you are manually using the REX then it makes it very simple and no fiddling about with the menu system. I was going to use it to have the REX on out of towns - but have never needed it.

Richard
 

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Thanks for the responses everyone.

My main thought is that if I rely on the REx at a higher %SOC then it's easier to refill the fuel than it is to refill the battery. Interesting note from Paul, good to know it generally doesn't have problems with the fallback to REx mode.
If you enable the Rex at high SoC then you will arrive home with unused battery after having used petrol unnecessarily. It is better for your pocket and the environment to use the battery before the petrol.
Just let the car do its own thing. It works great.
 

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If you enable the Rex at high SoC then you will arrive home with unused battery after having used petrol unnecessarily. It is better for your pocket and the environment to use the battery before the petrol.
Just let the car do its own thing. It works great.
I think you misunderstand: the idea is still to run down all of the battery, just not to run it out until you are nearly at your destination. If you judged it right you used the REx at high speed on the motorway and not polluting the streets near home.

Using the REx only at higher speeds may be slightly more efficient because the ICE runs continuously and all of the power goes straight to driving the wheels whereas pootling along in stop-start traffic means the ICE keeps cycling on and off with some energy going via the battery (with associated losses).
 
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