My Hymotion: What I've Learned So Far

[chogan2]

IMHO the GFCI is not really necessary unless you plan to charge the car barefoot and/or while holding onto a metal pole AND the 120V has shorted to the vehicle chassis AND the connection to the ground (third wire in the extension cord) has been broken. I wouldn't hesitate to charge the car without one. But they are so cheap that there's no reason not to have one.


GFCIs are harmless on circuits that don't have motor-driven appliances on them. I think they are required now in all potentially wet situations (bath, kitchen, outdoor). So if you charge your car outside, yeah, you're supposed to have one in line. If you don't want to rewire a wall socket they make plug-in GFCIs.

Just bear in mind the motor issue. Many (well, some) of them will misinterpret the motor startup as a short to ground and trip, which, if it's your freezer that's just started up, and you don't figure it out for a while, can be a problem. If installed according to the instruction, a GFCI "protects" everything that's farther down the circuit (farther away on that circuit from the electrical panel). Which mean that (e.g.) if you install a GFCI for the Hymotion, then plug in your table saw further down the circuit, in my experience, it'll trip the GFCI on startup.

[boxer93]

Arthur,
Nice to see you getting into EV mode at low temps (below 32 f), A definite bonus. As for the 3 beeps that is the Hymotion trying to get EV mode engaged. I have been hearing beeps more these days that the high temps are now in the 30s F. Especially if the ICE had just started and the speeds are low <20MPH. 33f for ICE temp is very low. I would again reccomend grill block. Also the ICE temp has nothing to do with the battery temp. You can have the ICE at 157f and EV won't work if the battery is still too cold.
Chris

[Arthur]

Originally Posted by boxer93

Arthur,
Nice to see you getting into EV mode at low temps (below 32 f), A definite bonus. As for the 3 beeps that is the Hymotion trying to get EV mode engaged. I have been hearing beeps more these days that the high temps are now in the 30s F. Especially if the ICE had just started and the speeds are low <20MPH. 33f for ICE temp is very low. I would again reccomend grill block. Also the ICE temp has nothing to do with the battery temp. You can have the ICE at 157f and EV won't work if the battery is still too cold.
Chris

Yes, I'm definitely going to try the grill-blocking thing soon.

In the meantime, I'm still trying to fully understand the EV mode and battery temperature thing. In the evening, I start my car in the parking lot at work. At first, it won't go into EV mode (probably low battery temp). By the time I get to the other side of the parking lot, I hear the three beeps. The beeps mean that the car is TRYING to enter EV mode and being denied. However, the beeps ALSO means that the battery is now ready to allow EV mode.

That sounds contradictory, but it's not. There are essentially 2 ways to get into EV mode: EV mode with a cold ICE and EV mode with a warm ICE. If the battery temp is warm enough AND you don't have the defroster on, the Hymotion system will put you into EV mode when you first start the car (even when the ICE is cold). This only works when you first start the car. After the first few seconds, you can't get back into EV mode unless you either restart the car or get the ICE up to the right temp.

So, when I hear the three beeps, it tells me that the car is refusing to go into the "EV mode with a warm ICE" (because I don't have a warm ICE at that point). But, it also tells me that the car is ready to go into the "EV mode with a cold ICE." So, I stop my car, shut it off, turn it back on, and I'm in EV mode.

Yesterday, I was Googling the term "charge current limit" (CCL) and found some interesting info. It seems that the battery temp is not the limiting factor. It's just that low battery temp often causes the Prius to limit the current that is charging the battery. For some reason, EV mode is not allowed when the charging current is being limited. So, when my car lets me into EV mode after crossing the parking lot, it's not that the battery warmed up that quickly. It's just that the software decided to cancel the Charge Current Limit that was in effect when the car first started.

So, those three little beeps are really a "CCL cancellation" message.

I've been trying to figure out the exact relationship between battery temp and EV mode. It turns out that I was asking the wrong question. I should have been asking these two questions:

1) What are the exact criteria that cause the charging current to be limited?

2) Why the hell did Toyota decide that EV mode should not be allowed when there is a CCL in effect?

Anybody have the answers?

[PeakOilGarage]

Arthur, you and I have early software versions of the Hymotion that allows EV without a warmup. Others will have a different experience now with the latest firmware updates.

I would like to get that EV circuit to avoid the 12 volt battery issue, but it would also mean that I get the CARB update that forces the warmup. Since I know how to avoid the LED 12 volt flashing error, I am going to stay with my current software version. I love pure EV in the morning.

I do not use GFCI. I just use a regular outlet.

[hobbit]

EV is denied when cold because you really don't want to be slamming
lots of current into or out of the cold battery. Having the
engine on allows the system to moderate charge/discharge as it
sees fit. I don't get any more than 40 or 50 amps of regen in
that state either, and the CCL/CDL gradually creeps up as the
pack gets warmer from use. Internal resistance goes *substantially*
up at low temperatures; I can probably find some paper references
someone sent me on this if folks are interested.
.
_H*

[Rokeby]

Originally Posted by hobbit

EV is denied when cold because you really
don't want to be slamming lots of current into or out of the cold
battery...

Internal resistance goes *substantially* up at low temperatures;
I can probably find some paper references someone sent me on this
if folks are interested.

Hobbit,

please do post that info. It should also be helpful for anyone mulling
over the idea of possibly maintaining HV battery temps overnight as
discussed here:

http://priuschat.com/forums/prius-te...ody-tried.html

Cross Posting would be alright too.

[ibcs]

Originally Posted by PeakOilGarage

Arthur, you and I have early software versions of the Hymotion that allows EV without a warmup. Others will have a different experience now with the latest firmware updates.

I would like to get that EV circuit to avoid the 12 volt battery issue, but it would also mean that I get the CARB update that forces the warmup. Since I know how to avoid the LED 12 volt flashing error, I am going to stay with my current software version. I love pure EV in the morning.

I do not use GFCI. I just use a regular outlet.

I received the 12V fix from Hymotion. It is a harness that goes between the existing harness. The good news is that it does not require a flash of the firmware, but the problem appears to solved. We have not had really cold weather to know for sure.

[boxer93]

Kent,
Tidy little device. Would you know if it's something we can request of Support or Erin or ?? Looks like you had no difficulty installing it.
Chris

[Arthur]

Originally Posted by hobbit

EV is denied when cold because you really don't want to be slamming
lots of current into or out of the cold battery. Having the
engine on allows the system to moderate charge/discharge as it
sees fit. I don't get any more than 40 or 50 amps of regen in
that state either, and the CCL/CDL gradually creeps up as the
pack gets warmer from use. Internal resistance goes *substantially*
up at low temperatures; I can probably find some paper references
someone sent me on this if folks are interested.
.
_H*

I'm actually starting to think that I want to avoid trying to change the way the system works (trying to heat the battery or trick the system into using EV mode when it doesn't want to).

At this point, I'd just like to have a better understanding of what the car is doing and why. This Prius/Hymotion system is fairly complicated. Having more quantities that I can monitor would be useful.

I bought a ScanGauge a couple months ago. So far, I'm monitoring RPM, SOC, engine coolant temp, and EV mode status. I tried to set up a gauge for battery temp, but it didn't seem to work on my 2008 Prius. Has anyone had any luck monitoring battery temp on a 2008 Prius?

How about other quantities? I'm going to try setting up gauges for battery current and voltage, but it would be nice to monitor the CCL/CDL, too. Does that require more than just a scangauge?

[boxer93]

Arthur,
Not sure if you've checked out scangauge for dummies over at cleanmpg.com That is where I found the EV and MPG for trip and day gauges. The 12V battery voltage is a built in gauge in the SGII, nothing to configure. I currently monitor VLT (for morning startup), MPG for the current trip, EV mode and ICE temperature.
Chris