A basic Hymotion question

Howdy, I own a Hymotion kit and love it! (though I should say every PHEV owner favours their brand to all others )

The L5 supplies energy directly to the electric motor and recharges the Prius OEM traction battery. The kit also hooks into the on board computers and sends a signal to the hybrid ECU that the traction battery is fully charged, and a second signal to the MFD (centre-stack touchscreen) to display the L5's state of charge. It will also send EV mode requests whenever your speed is under 52Km/h for a few seconds so that you can use even less gas.

Once the L5 is depleted, the Prius resumes normal operation as if the PHEV kit was not present.

 

Snookums - are you sure about that? My impression with my Hymotion kit is that the Hymotion battery supplies power to the Prius battery only and does not provide direct power to the electric motor.

 

Let me throw another question into the queue...

If Hymotion is spoofing the HV SOC at 80% as long as it has power left, then the Prius, of course, is going to be using as much EV as possible to avoid an assumed overcharge of the HV battery.

My question is - what happens to Regen energy during this time? Does the Prius throw it away trying to avoid (rightly or wrongly) an overcharge of the HV battery??? This would seem to be an inefficient use of Hybrid technology.

 

When you step on the brake the SOC drops to 70% and you still get full regen. I'm guessing you can fill the stock battery up to 80% but I have not tried it yet. The only issue is that if the stock SOC is say at 65% the Hymotion will spoof it to 90% when you step back on the accelerator.

 

I can say that for sure yes. I have an XGauge setup to monitor my HV battery draw, and it typically hovers around 2amps when sitting still. With the Hymotion on, the draw can go as high as it needs (remember that I am only monitoring the HV battery current, not the electric motor current) but it typically stays below 40damps. When the Hymotion is discharged, I typically see a draw over 60damps with barely any pressure applied to the gas pedal... then I get kicked out of EV mode!

TheForce is right. Regen braking still works, though I typically see better regen when the Hymotion is off. The Hymotion also stops spoofing entirely when the car is put in reverse.

 

The Hymotion battery only sends energy to the Prius HV battery. It NEVER sends energy directly to the motors. It is set up to maintain a SOC of 62% in the Prius HV battery. That leaves plenty of room for regen, while still staying above the threshold at which the Prius starts conserving battery power by kicking you out of EV mode and/or starting the engine.

Arthur

 

If there is an expert (or someone with a reliable source or article) that would care to correct me please chime in!

@Arthur, I'm pretty sure you're wrong. You've described exactly how the Engineer system works, but based on what I have observed of my Hymotion I'd say you are wrong.

@sub3marathonman, this is how I think it works (and have vague memories from articles from years ago about this stuff)...
The L5 supplements the HEV battery by maintaining the HEV pack's charge at a standard level. The L5 also is also drawn from by the hybrid system directly to propel the car. So depending on what the electric motor is drawing, the electricity will come from either the L5 or the HEV battery.

The reason I think this is because I have watched my HEV battery draw go down into the negative while sitting still. This means the regen braking could not have been engaged, and the engine was not running. I have also never seen the HEV current draw go up as high while the L5 is on; leading me to believe that the L5 is directly feeding (at least part of) the electricity required to run the motor. And again, I have seen myself continue driving along at 40-50Km/h while also seeing the HEV battery draw go into the negative; leading me to believe that either the regen braking had engaged, or that the L5 was charging the HEV battery; since I did not "feel" the car slow at all, I assume it was the work of the L5.

I also vaguely remember watching a video (or seeing a picture) of an early Hymotion L5 prototype, and someone posted a comment about how it must work (or be capable of working)... I would love it if someone could find a source explaining exactly how it works. I'm at work right now and can't spend too much time on PCcom.

 

Apologies to everyone for the misinformation, but I have confirmed Arthur's statement and contradicted my own. The current-draw number I was seeing in my SG2 was the net draw after the L5 automatically started charging the battery while in use.

@sub3marathonman; the Hymotion kit only charges the HV battery, but it does spoof CAN messages to make the Prius behave differently.

 

I'm right royally confused too; my confirmation came from a friend who is familiar with the Hymotion kit. He is by no means an official source, and I figured that if Arthur and my friend both said it was a NiMH hookup, I must've been wrong.

I'm emailing Hymotion right now, I'll try to get an official word.

 

Still no word from Hymotion, I'll send them a poke email tonight.

The XGauge result shows the OEM battery draw, but if it is being charged and discharged at the same time, then the net draw could be zero or negative. It would be like having a glass of water which is 62% charged (OEM pack) and a bigass-bucket (L5 pack); as the glass pours out some water, the bucket refills the glass. The result is that the glass stays at roughly 62% while the bucket drains.

The XGauge doesn't measure the charge level, we use the SOC XGauge for that; the Bta XGauge measures the amount of water being poured electricity used.

I think my original guess was more probable. Still, need confirmation or a source... I still see negative draw when sitting still from time to time.

 

That's exactly what happens! Nobody ever drinks out of the bucket. They only drink out of the glass. As long as the Hymotion system is active, the glass is kept at about 62% full (by drawing from the bucket).

If you use a "passive SOC" xgauge, you can see the spoofing that the Hymotion system is doing.

Here are the parameters for the "pts" (passive traction SOC):

TXD: 03 C3
RXF: 01 03 82 CB 00 00
RXD: 20 10
MTH: 00 0A 00 02 00 00
NAM: pts

When you are braking, you will see the actual SOC of the traction battery. If you do down a long hill, this value can go as high as ~82%.

If your foot is not on the brake (or if you are only braking VERY lightly), you will see the spoofed value of the SOC. If your actual value is up around 80%, the spoofed value will be well over 100%. That doesn't matter. As long as it is above 80%, the car's behavior is the same.

The Hymotion system does not change the operation of the Prius. It's no different from having a normal Prius with an EV-mode switch installed (and a magical bucket that keeps the "glass" at 62%).

The Hymotion Prius runs up against the same limits as a regular Prius: there is a maximum rate at which energy can be drawn from the traction battery.

This becomes very apparent when you are trying to go up a hill without getting kicked out of EV mode. Depending on the grade of the hill, your "EV-mode speed limit" will be somewhere between 5 and 10 mph. As long as you stay in EV mode, you can crawl up Mount Everest if you want. (OK, even with a brand new Hymotion pack, you're probably limited to a mountain of about 3.25 miles.)

I say 3.25 miles, because your "miles per kWh" will be abyssmal when crawling up hills this way. It will be somewhere around 0.67 mi/kWh.

Compare this to an "ideal" rate of about 5 mi/kWh (a warm day, on level ground, with the battery "warmed up" before you start your test, AND staying below 32 mph in EV mode.)

Arthur

 

To be completely accurate, I should have said:

...(and a magical bucket that keeps the "glass" at 62%, AND CAUSES THE GLASS TO PRETEND THAT IT'S AT ~80%, EXCEPT WHILE YOU'RE BRAKING).

Arthur