Coding - REX and SOC - Dumb question

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CSP

Member
Joined
Sep 19, 2016
Messages
15
Hi Guys,

Tried to search the forum, but did not find an answer to a question.

Car : 2016, i3 REX [Bought in Canada]

If on coding to have REX started on demand, need to understand what happens in the scenario mentioned below.

a) Battery charge at 20%
b) Start REX
c) Going down hill on cruise OR slow moving traffic

Assumption : REX runs at constant RPM and does not frequently change that, except when large amount of energy is required.

Question : When in a situation as described by item 'c', would the excess power generated by REX charge the battery ?
If the answer to the above question is 'YES'.
Then what is the maximum level to which the REX will charge the battery ? 75% .....

The reason I ask this question, is that for temporary storage of any kind be it liquid/gas/charge all designers will implement a high and low water marks OR cut-in and cut-out. By extension the i3 should have such configurable options. If these are settable by coding it would help.

i3 REX gurus, your wisdom will help decide if coding is worth it.

Thanx in advance

CSP
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Coding allows the Hold State of Charge screen to be accessed via iDrive (Settings/Range Extender). When you access that screen, you'll see a check box for HSOC. It will be greyed out unless the car is below 75% SOC.

When you activate the checkbox, the REx gas gauge turns a brigher white (from grey) and the REx should start up. The idea is that the REx will run automatically, either at a medium setting (medium RPM) or high setting (high RPM) to keep the SOC at the indicated level. Note that you can easily consume power from the battery faster than the REx engine can generate it, so you will likely see the actual SOC drop below the set point. But if you are driving at or below 56 mph and are not climbing hills, the REx will eventually be able to catch up the SOC to the set point. It will cycle on and off automatically to maintain that point.

If you are going downhill and are in regen mode, the REx will shut off once the set point is reached. Note that on a long downhill, you may actually see your SOC climb above the set point due to Regen. However the REx will never charge above the set point, it turns off once the set point is reached. There is some hysteresis, but it seems to be under 1%.
 
Thanx for the detailed explanation of coding behaviour.

Please elaborate on "However the REx will never charge above the set point, it turns off once the set point is reached."

a) Is the 'set point' the point at which REx was activated ?
b) if YES. Would that mean the cut-in and cut-out points are at the same ?
c) if YES. Is there way to make cut-out greater than cut-in, by coding ? Intention is to prevent short cycling of REx.

CSP
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Once you activate the REx hold function, whatever value the SOC was at that point is your maximum...the only way it will rise above that is if you're in a regen situation, not because the REx is running. Whenever you restart the car to the READY state, the maximum hold value is whatever your SOC is at that moment. The only way to raise the hold point would be if you were in an extended regen situation, rose the SOC above the original set point, then shut the car off. When you restarted the car, that new SOC could be used as your hold point. Same situation if you had say set the hold function on when the SOC was 50%. If it happened to be at 40% because you were charging up a long grade and then shut the car off, your then new maximum would be 40% (not 50% - it does not remember the last hold request).

Unlike the new 7-series hybrid, the car cannot be used to recharge the battery level above the starting SOC level. To do so would require much more coding than what is available to the user...it would be a core functionality, not an option, and thus, not accessible.
 
Why would anyone want to recharge form the gas engine? I can only think about an unlikely scenario of driving towards a last gas station before a 100 miles stretch of the road.
 
gt1 said:
Why would anyone want to recharge form the gas engine? . . .
Fast DC chargers are rare. So it would OK with me to park the car and have the REx put a charge on the battery while my wife and I are having a meal or break. Soon as we're done, top off the tank and suddenly we're looking at ~140-150 miles of highway driving before we repeat. This beats the heck out of 70 miles segments to refuel the REx.

Bob Wilson
 
As currently configured, while stopped, unless the SOC was below when you initially turned it on, the REx would just shut off (assuming it wasn't still in maintenance or warm-up mode).

The new 7-series will allow you to recharge the batteries to any value so that, say, when you got to the city, you could run entirely on electric without running the ICE at all once there. Because the REx's output is quite small verses that hybrid arrangement, that isn't particularly feasible...just sitting, idling, is illegal in many places, and trading electrical charge for fossil fuels and their pollutants without motion just doesn't seem to fit into the concept of the i3.
 
We'll probably have to agree to disagree about this:
jadnashuanh said:
. . . Because the REx's output is quite small verses that hybrid arrangement, that isn't particularly feasible...just sitting, idling, is illegal in many places, and trading electrical charge for fossil fuels and their pollutants without motion just doesn't seem to fit into the concept of the i3.
  • rarity of CCS chargers - I just mapped a trip from Huntsville AL to New York City. There are significant gaps and some of the charges for the 72 mile, nominal EV range are unrealistic (i.e., $10???)
  • truck stops - typically have a steady drone of idling diesel engines.
  • 22-24kW REx output vs. 7.24 kW L2 charging into 18.7 kWhr battery. Even if the cut-off is 80% SOC, ~15 kWh, we're still looking at ~40 minutes.
My rational is strategic:

  • It is better to highway travel in the REx and operate on battery at the destination than to substitute a highway specific vehicle and have little or no BEV at the destination.
Understand I am no fan of the Volt nor the newly announced Prius Prime. The Volt barely does highway driving more efficiently, ~42 MPG, than our REx with fewer fuel stops and the Prius Prime is the highway king at 54 MPG. But neither matches the 72 mile battery range of our REx at the source and destinations.

If we can improve the REx cross-country capability, it soon puts the Volt to shame and becomes peer to the Prius Prime (when it eventually goes on sale.)

Bob Wilson
 
Why not just put a 2 gallon can in the frunk?
Doing AL to NY in an I3 will be uncomfortable one way or another. This car was designed for driving around town.
 
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