Bimmercode hold state of charge.

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TerraRex

Member
Joined
Mar 24, 2018
Messages
6
I cannot seem to get bimmercode to enable "Hold state of charge" on my 2015 Rex.
Help greatly appreciated

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i3 user group on Facebook is so darn quick. The reason it's not available is because it is fully charged. The battery has to be <75% to engage the "Hold Charge"
 
I followed a recommendation and assigned this to my Function Key #8.
So quick and easy to simply turn on the REX by hitting this one button (when below 75%).
 
It also may take a moment. Sometimes it takes a couple minutes for it to actually react. Other times, it's instant. What I don't know though is that if you run out of gas, whether it will switch back to electricity on its own. Would be good to know before needing it on the road.
 
I regularly set hold at 75% and run until I am out of gas and keep driving on electric until I get to a convenient gas station. Totally seamless, and means I am not stopping as often for gas if gas stations are annoyingly spaced. Like "do I stop at this gas station with 30 mi gas range (and 50 mi electric) left because the next one is 35 mi away?" Nope, just use some of the battery.
 
sipabit said:
It also may take a moment. Sometimes it takes a couple minutes for it to actually react. Other times, it's instant. What I don't know though is that if you run out of gas, whether it will switch back to electricity on its own. Would be good to know before needing it on the road.
Just for clarification...there are two ways to make a hybrid and they are called either serial or parallel.

A serial hybrid is like a diesel electric locomotive and the i3 REx. They both have engines, but those engines drive a generator...the ONLY thing that drives the actual wheels is the electric motor...the engine drives a generator whose output can either go directly to the electric motors or, if there's excess power available, into the batteries. A special note, though, the engine-driven generator of the REx is only around a 34Hp motor...the i3's electric motor is a 170Hp device. If you think about it, there's no way the REx can provide 170Hp, so under heavy load, you WILL also be using battery power. The way this works, though, is normal cruising doesn't need 170Hp, but, the faster you go, the bigger the hill you want to climb, the more lights you want to run, or the harder you make the HVAC system work, you'll not be able to maintain battery levels. Lots of things go into this, but on flat ground, if you're traveling faster than somewhere around 70mph...your SOC will decrease, even with the REx pumping out as much power as it can. Start to go uphill, it will decrease faster. Slow down, and you might be able to recharge the battery.

A parallel hybrid is one where either the electric motor, or engine, or both drive the wheels of the vehicle. In this type, you could run on only electricity, only gasoline (through the engine), or with both. They type of hybrid will typically have a much smaller battery than a full EV or a serial hybrid.

There's actually a third type that we'll see more of in the next year or so called mild hybrid. These tend to switch many ancillary devices in the vehicle to electrical operation - steering (fairly common now), compressor, water pump, and probably more. To achieve better optimization, they will switch from 12vdc stuff to 48vdc...you can use smaller wires to get the same power when you raise the voltage (think power = volts * amps...raise volts, you can lower amps and use smaller wires, while providing the same power to a device. Smaller wires, less weight, which can help, too. Taking more of the parasitic loads off of the engine means start/stop becomes more efficient as well while maintaining creature comforts fully.
 
I'm aware of the differences but thanks for clarifying. It helps. I'm still at a loss though as to whether the car will return from gas back to electricity ones the gas is out. This scenario would be the opposite of what the car is "supposed" to do. Normally, it runs out of electricity and goes to gas. I'm wondering if the reverse would happen if there's still loads of electricity left.
 
So, the car is always "running the wheels" on electricity. No matter what (unless you run so far out of battery+gas that it refuses to move at all.)

When the REx is running, it is supplying electricity to the batteries. The motor then draws power from the batteries to run the wheels. Regardless of if REx is running in "stock US limited" mode or in "Charge Hold" mode, the motive force is coming from the batteries. In both modes, the REx will run the gas tank out of gas (literally for non-US or coded to remove the limit; or "artificial software limit displaying 'out of gas'" in stock US limited mode) and the car will continue to operate on whatever battery charge remains.

If in standard US mode, this means you will probably only have 6% battery remaining (or less, if you had been pushing the car hard so that the REx couldn't keep up.). In Charge Hold mode, you will have whatever threshold you had set it to (default 70%,) again possibly a little lower if you had been pushing the car harder than the REx could keep up with.

I drove my car using Charge Hold mode over 100 miles in a single trip last week. Got on the freeway, enabled Charge Hold, drove ~45 miles, exited the freeway and disabled Charge Hold. Drove around town on battery, got back on the freeway, enabled Charge Hold, drove ~45 miles back, REx ran out of gas just as I was exiting the freeway, but I still had ~50% battery to get the last couple miles from the freeway back home.
 
sipabit said:
I'm still at a loss though as to whether the car will return from gas back to electricity ones the gas is out.
As explained by others, an i3 is always propelled by electricity, so there's no returning from gas back to electricity. As long as the battery pack isn't fully discharged, propulsion of an i3 would continue even after the REx engine runs out of gasoline and quits.
 
sipabit said:
whether the car will return from gas back to electricity ones the gas is out. This scenario would be the opposite of what the car is "supposed" to do. Normally, it runs out of electricity and goes to gas. I'm wondering if the reverse would happen if there's still loads of electricity left.

There is no such thing as "back to the electricity", or "back to the battery". Like explained by others, it always takes the power (energy) from the battery. REX running or not. So you don't have to fear to be stuck without power in the scenario you describe. As long you have energy in the battery. The REX will only help to maintained the battery level. So don't fear the i3 to stop when the REX will stop. There is no such thing as switching the power source from the REX to the battery. Or vice versa. Power comes from the battery , REX running or not.

Louis
 
Is it possible to actually "raise" the state of charge? For example, if I am at 50% battery charge, could I somehow make the extender to keep charging the battery, say up to 75%?
 
Mehdi said:
Is it possible to actually "raise" the state of charge? For example, if I am at 50% battery charge, could I somehow make the extender to keep charging the battery, say up to 75%?
I have not read of anyone discovering what needs to be done to make this possible.
 
Mehdi said:
Is it possible to actually "raise" the state of charge? For example, if I am at 50% battery charge, could I somehow make the extender to keep charging the battery, say up to 75%?
Considering the HP output of the REx, which is often not able to keep up with holding the charge if you're climbing a hill or traveling fast, I doubt it would work, or if it did, it wouldn't very often. Vehicles that CAN do it all have a much a larger engine and gas tank. It has about the power of one of the first VW bugs...IOW, not a lot.
 
I find that, except for cold nights in the winter or a long uphill drive, the REX is more than capable of charging the battery to a higher level than it is but it is set to not do that. I did however read someone saying that it is possible to put the car in emission test mode and that would cause the battery to be charged to a higher level. This means the car has to be parked, the lift gate has to be open and this can be done only for 20 minutes at a time. But at least it is an option.
 
It all depends on your driving style, primarily speed, but lights, heating, and grades take more power and stop and go with rapid acceleration is a factor. The motor can draw up to 126Kw (that's approximately the conversion of 170Hp), which is like nearly 4x what the REx can put out not counting the other things drawing power in the car. Certainly, you're not doing that constantly, but in stop and go, the regen is not perfect, and the REx would have a problem at times. Freeway driving with traffic at 70-80mph with the lights, heat, (or a/c) will put it right on the edge or over capacity.

If BMW wanted the car to be a no-nonsense replacement for an ICE, in this hybrid, they would have supplied a larger engine and gas tank. that they didn't should mean something to people if they think about it. It was made as a city car. Drive it to work or shopping, charge if needed, then drive it home and charge it up. The REx was an emergency backup in case you miscalculated. that you can use it for longer trips is sort of a secondary, somewhat limited benefit, but it has compromises.
 
louisgrenier said:
sipabit said:
whether the car will return from gas back to electricity ones the gas is out. This scenario would be the opposite of what the car is "supposed" to do. Normally, it runs out of electricity and goes to gas. I'm wondering if the reverse would happen if there's still loads of electricity left.

There is no such thing as "back to the electricity", or "back to the battery". Like explained by others, it always takes the power (energy) from the battery. REX running or not. So you don't have to fear to be stuck without power in the scenario you describe. As long you have energy in the battery. The REX will only help to maintained the battery level. So don't fear the i3 to stop when the REX will stop. There is no such thing as switching the power source from the REX to the battery. Or vice versa. Power comes from the battery , REX running or not.

Louis

I see what you're saying. There's no gas engine. The gas feeds the generator which converts to electricity which the car runs on. Essentially, it's always running on electricity. I get that. However, if you manually switch the mode to run the REX while you still have battery beyond what the REX is outputting (meaning state of charge is say at 40%), I'm not sure the software will recognize that the car still has juice and will continue running the car since the REX is designed as a backup once SOC is less than 6%.

So you're saying that if I switch the REX on with 30% battery left (or anything over 6%), run out of gas, then the car will definitely continue running? That would be great, but I was just too scared to test it. Have you done it? Or just a theory that it will?
 
The car will continue to run until it runs out of battery power. It doesn't matter if you got that power from plugging it in, or from the REx trying to maintain. Note, the maximum level the REx will charge to is whatever it was when it first was turned on...IOW, if, say you had not tweaked the thing by coding to raise the level (depending on where you live and the model year), if it automatically came on at 6%, that's the max it would try to maintain. If it is coded to the max, and you turned it on at <75%, that would become the new goal. Depending on the load on the car, the REx can turn on/off, and vary it's RPM to produce more or less power, but you're always running on electricity...the car doesn't care where it comes from. Run out of gas, as long as there's battery capacity left, it will just continue.
 
jadnashuanh said:
The car will continue to run until it runs out of battery power.
There have been a few reports of REx propulsion stopping when the engine ran out of gasoline despite having battery charge remaining. Apparently, turning the car off and then on again allowed driving to continue. This behavior is almost certainly due to a software bug that likely exists in only a few system software versions.
 
""""So you're saying that if I switch the REX on with 30% battery left (or anything over 6%), run out of gas, then the car will definitely continue running?

Yes. This is the way i drive it when i know that i have long stretch to do. I hold the the holding point to 75%, and use all the fuel i have. If i was speeding over 90 km/h, or if i am going up a mountain, the battery will slowly go down even if the REX is running. When the fuel is depleted, the REX stops. The car continue without knowing it. The battery will go down faster of course now that the REX is no more there to put some juice in the battery.

Again, there is no connection, software or else, between the REX and the electric engine running the car. The car moves as long there is power left in the battery.

Louis
 
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