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Discussion Starter · #1 ·
Just wanted to share some of my notes and observations on the 4xe in terms of regeneration and battery life. Feel free to comment and ask questions.

I have done the testing with the top in the same manner, same road, using the same landmarks for indicators, and generally the weather has been the same. So the only changing factors are related to mode, style of driving, etc. This is with steel bumpers, and the one touch roof. Will post more after I get the lift kit installed this weekend do more tests and then when I get the bigger wheels after that.

On average when I break from around 50-60mph to full stop with proper distance with max regen off:
I can regen an average of 1% battery life in 2wd.
Interestingly enough I find I regen 2% sometimes 3% when doing the same in 4wd auto.
It seems the actual regen is being done by the electric motor being spun by the force of the wheels engaged with the drivetrain and doesn’t have regen at the actual wheels. Otherwise it wouldn’t change between drive modes. If we can find a way to only engage that 4wd auto during breaking we could recover a lot more energy and get more distance.
An average peak regen of 25kw in 2wd vs 35

Unfortunately running in 4wd auto does eat more battery at those same speeds. Probably 10%-15% more. Haven’t done a lot of testing on that but it’s been less distance everytime it’s been on.

The most efficient regen method seems to be light to moderate breaking pressure to regen for a longer period of time vs over a shorter distance and time. This is where I noticed max regen doesn’t work well for me. The smallest pressure off the gas with max regen and it wants to apply a bit of heavier breaking, takes away from momentum and left over energy and in return less energy into the engine is returned. I also see peaks of regen with it on of around 15kw and some 20kw hereMax regen seems to have 2 possible useful purposes.

1. stop and go traffic at low speeds of 25mph and less. Seems to be I get marginally better battery life in these conditions with max regen on. However it’s within 1-5% that can be up to other factors such as the amount of traffic. Hard to say 100% on this. But it does seem to be a touch more.
2. When doing off-road in 4wd it does seem to work a bit better. But this kinda follows the idea of #1. Your going at lower speeds so the harder break doesn’t make you lose too much over distance.

The electric engine does not like sustained speeds above 65mph. I have noticed the battery life drains FAST at those speeds and above. Cutting down distance by an average of 15% when always at that speed.
it seems that speed requires the electric engine to run at almost 100% output and drains quick. It seems to be the most efficient when it’s running at 15% output. Which brings me to point out more so the aerodynamics are a big factor as well (duh!) as being able to draft off another car I can gain almost 20% more distance with the battery. This keeps me in that 15-20% engine output to sustain those speeds and it just goes further.
Another thing on aerodynamics is there is less distance when the one touch roof is open (duh) because of the increasing drag and wind. This seemed to give an average of 10% less energy by the time I reached the same waypoint near empty on battery.

An interesting thing is when you run at 60mph with cruise control on. This thing balances the use of gas and electric very well when the human element is removed. However, the same trip that I would be getting 23miles electric and 15miles gas. Would consistently end with almost an exact split of 18 miles For each and leave me with still 5% battery left at the end. When I would normally run out about 2/3 of the way on the trip.
I think that is optimized to get the most overall distance. But not for fuel efficiency.
The battery output and engine Output stayed just about even, sharing the load. I did notice more fuel was consumed confirming the numbers reported at shutoff.

Finally… performance… so if you take off. And I mean accelerate to full speed no easing to it. You get the fastest speed the fastest with traction control off, 4wd auto on, hybrid mode, and max regen off. Almost everyone knows that…
But we aren’t going to drive with 4wd auto on all the time we know it’s fuel inefficient already. But the observation made… is that if you accelerate like this and you get up to the speed you want, the battery actually gets used less to get to full speed over distance and the downside is, unless you actually release the pedal, the engine seems to stay in a performance mode. So you will actually use more gas.
So a useful technique has been to punch it to get up to speed, take off the pedal a moment and then ease back on to let the electric maintain the speed.

Anyway that’s all the little things I have noted or at least can think of for now to share. Curious to see how a lift kit will effect distance/regen and more so once the larger wheels get installed.
 

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Wow, I'm surprised 4H auto makes for more regen - I have noticed 0 regen when the wheels slip (IE downhill on a dusty road), so I'm guessing the FCA computers try to limit regen to keep things under control. I need to try this!

And yup, the rest of the post matches my experience. We have a really awesome powertrain overall - but electric power (and thus maximum regen force) are limited compared to BEVs, and the aero of a Wrangler is, well...
 

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Discussion Starter · #5 ·
One thing I didn’t check yet was how regen worked normally with the settings under e-save in the hybrid pages.

i just tested it a bit the last two days. Confusingly in 2wd with the e-save setting on “e-save” instead of “charge” and driving it in hybrid mode:

I actually see higher spikes of energy recooped during breaking according to the hybrid pages.
Seeing readings of 35-45kw that I never even got in 4wd during breaking.
Now I just noticed this so this is going to throw my measurements off potentially since it’s in for a lift kit to be installed.
But when I tested the same setting with 4wd auto on, it did not seem to give as proportional a gain.
In fact it seemed to be just the same as normal.

Why this setting changes regen rates during braking is confusing. It should only be telling the gas engine to run a bit more for more energy.

my theory is that because it runs the gas engine, it is effecting how the electric engine is spinning for regen. Like it slows it down. Now I am curious if I am actually gaining a higher recharge, or if it’s just giving erroneous data during braking. But I doubt the data would be wrong.

I’ll do some testing again with the lift kit and extras installed to set a new baseline and then see if these gains are correct.

But it seems that battery charge mode might be doing more than just killing gas mileage and could be reducing what we get for regen.
 

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Interesting stuff, thanks for posting this.

I am curious if anyone knows the C rating of the lithium ion battery?

I have limited experience with this but knowing the C rating may help determine the maximum charge rate of the battery.

The reason I want to know is what is the max kw regen we could target before either the regen energy exceeds charge rate or the charge efficiency starts to reduce?

How many kw’s from regen can actually be used?Does the electric break generate more than the charge controller will use to charge the battery? If so, what is that number and out of curiosity where does the excess energy go (large resistor?)
 

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Discussion Starter · #7 ·
So this is a very good point I was wondering as well. I think our limitation is on amperage, we know that it can’t take more than 32 amps back. But we don’t know if there is a voltage limit.

Driving it with the e-save setting to “save only” I have seen spikes of 52kw during breaking.
However I am not noticing any increase to what is going back into the battery. Still maintains 1-1.5% return from braking.
 

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If in eSave mode and the ICE is running to charge the HVB, I wonder if the system prioritizes which source the recharging energy is coming from? Meaning, if the ICE is running to recharge the HVB, then maybe the system has nowhere to put the energy captured from regen braking? Or it significantly reduces the regen braking because the HVB is currently being charged from the ICE. I don't know for sure, and I have no way to test since I am still anxiously awaiting the transport truck to show up at my house with my Sahara 4XE. But I am certainly excited to start experimenting with this stuff. I've been driving BEVs and PHEVs for years now, and I always love playing the game of trying to increase EV efficiency. I'm excited because this is the first PHEV I will have that has the ability to specifically recharge the HVB via the ICE.
 

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insert typical amateur disclaimer

I had to go back to some high school physics and a quick google search for this so there is bound to be a bunch of holes in the math but:

I = Amps
P = Watts
V = Voltage

I = P/V

For example

I = 9000 / 400
I = 22.5 A

So that is 9000 watts / 400 volts = 22.5 A

This is assuming that the battery is operating at 400 volts ... I'm not sure about this so if anyone knows better let us know.

By re-arranging the formula to solve for P we get:
P = I * V

Substituting with max current we get:
P = 32 * 400
P = 12 800 Watts or 12.8kW

Can we only regen at 12.8kW?

I know using max regen I see numbers higher than 12.8kW but this might not mean all that energy is being used to recharge the battery.

There may be other components in the regen system that help us use more of this energy, or... it may just be wasted.

Regen is ok but in my experience it doesn't seem very efficient, I think I get significantly more charge by regenning less for longer rather than trying to max regen over a shorter period of time.

I remember reading somewhere that regen would reduce speed up to 0.25g max - this would make sense, regen should not behave differently in different scenario's in order to maximize regenerated electricity, as a user this would be really confusing and we would expect max regen to be applied in a uniform manner other wise us users would find it odd and unreliable to use as a breaking mechanism and not trust it, or result in accidents...

Sorry for the rant but this is an interesting topic.
 
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