Battery recharge threshold mod?

If you understand the Prius and think of the battery life , you don't want to do that or Toyota may void the warranty.

Ken@Japan

 

Ken is right on. Taking the battery to a lower DOD will definitely shorten the cycle life. The Prius battery isn't meant to be deep cycled, as you desire. The car knows what to do and how to do it ... just go with it.

Ken - You have some inside info on the working of Prii. I've read on here - from people with CAN view - that the upper limit for SOC is 80% and the lower limit is 40%. If these are accurate, I guess I just don't get it.

Upper limit - Why so low? I realize large power spikes could occur during regen, but it seems like they could have gone to at least 90% SOC for a little more storage capacity. 80% seems a little too conservative. The car's software could attenuate the regen depending on SOC, and I know Toyota and PEVE have developed accurate SOC algorithms (probably in the 1% range).

Lower limit - Again, why so low? Not so much as "why" but "how"? All of the prismatic data I've seen (AABC papers and the like on gen 1 and gen 2 modules) suggest this level of DOD wouldn't provide enough cycles to get the battery life we're seeing. It looks like a 15-20% differential from max to min SOC would be the limit. Can you explain?

 

<div class='quotetop'>QUOTE(Red Trebor @ Jul 3 2006, 11:26 AM) [snapback]280581[/snapback]</div>

when you say recharging the battery I assume your looking at the energy screen and seeing the arrows going back to the battery as well as MG2. Don't assume that there is a lot of charge going into the battery, it's probably under 10 Amps. MG2 can't use all the energy that the ICE is forcing MG1 to produce so the excess is available for charging the battery, but it's a very small amount. As you have a 2k5 your a candidate for a CAN-view so you could see all the charge/discharge rates and temps etc. Even my Classic puts about 7 Amps into the battery on a very steep hill over and above what MG2 uses to climb it.

 

<div class='quotetop'>QUOTE(McShemp @ Jul 3 2006, 10:32 PM) [snapback]280472[/snapback]</div>

Thank you for your comments.
I think you understand Prius very much.

I just have the Toyota Tech Manual, and the internet info is my friend.

I saw 84.5% SOC max. The battery temp was 50C, which means it becomes almost full.
I think the 90% SOC level is dangerous and I believe Toyota did a lot of testing to find the reasonable upper limit for both performance and battery life.

Prius is just a hybrid vehicle which does not require big battery capacity.
Please understand Toyota reduced the battery capacity...
NHW-11 273.6V * 6.5Ah = 1778Wh, NHW-20 201.6V * 6.5Ah = 1310Wh
However, both vehicle performance and mileage number are improving on the NHW-20 Prius. That's the technology innovation.
Also, note that the plug-in hybrid vehicle is completely different animal. Prius is not a good candidate for the plug-in hybrid.

Ken@Japan

 

If you're able to temporarily slow from "highway speed" to under
34 mph for the last bit of your climb, an EV button would allow you
to use up the battery down close to that 40% level if you timed its
invocation right. Also, depending on how hard you push it on the
up side, you may be asking the system to supply more *from* the
battery in the first place to help move the car -- but you have to
be running the ICE up around 3000 rpm before that starts happening,
which may be too aggressive in your setting.
.
If you must maintain highway speed on both the up and the down, why
do you have a need to brake that much on the backside? Air resistance
should be able to hold you back, and if you need to provide any
motive power at all then it should only be at the warp-stealth level
[which very slowly *uses up* battery power, but no fuel] and just
coasting along otherwise.
.
I'm sure that with a little thought and more familiarity with how
the system works, possibly coupled with an EV mod if you're into
that sort of thing, you'll come up with the best way to conquer
the hill.
.
_H*

 

<div class='quotetop'>QUOTE(ken1784 @ Jul 3 2006, 08:00 PM) [snapback]280719[/snapback]</div>

Ken - I was just questioning the SOC swing and the lower SOC level of 40% (I still have a hard time buying that number). No NiMH life cycle info I've seen on PEVE modules supports taking them that low and still getting the number of cycles demonstrated with the Prius. I don't have anything in front of me now, but I'd guess <100,000 cycles when taken down to 40% SOC. I know each cycle on the battery isn't all the way down to 40%, but the car does a ton of discharge cycles in everyday driving.

As for the capacity differences between the NHW-11 and NHW-20 Prii, I think that is just a result of a lower bus voltage (likely due to changes in the electric motor/generators between Prius models). The PEVE modules still have the same capacities (6.5 Ah) and the same nominal voltage (7.2 VDC). However, fewer modules are needed at the lower voltage (28 vs. 38). I think this explains the lower capacity.

BTW - Prii are great candidates for plug-ins as long as it's the "extra" battery approach (like CalCar's).

 

<div class='quotetop'>QUOTE(McShemp @ Jul 4 2006, 11:50 AM) [snapback]280778[/snapback]</div>

I think the zero bar of the battery level on the energy screen is 40% SOC.
I have never down to 45% or less. I know it is not good for battery.
I don't know how PEVE did the cycle test.

The NHW-20 Prius requires higher voltage. Please remember it has step-up circuit up to 500V.

If your commute is short distance, the plug-in vehicle is almost an EV through out a year.
Why we have to carry a heavy 1.5L engine all the time on such EV like vehicle?
Also, Prius consumes a lot of electric power, 250Wh/mile, on the other hand a good EV consumes less than 200Wh/mile.
My ideal plug-in hybrid is an EV based series hybrid with small (less than 1L) engine.

 

Since Red is driving Highway 17, there's always the some good braking on the downhill portion. Trucks and lane-changers force this.

Red, the first thing you must consider is that Toyota is warranting the hybrid components and battery for 10yrs/150k miles in California. If you were able to make any changes in that system, you'd probably make things worse. You'd certainly void your warranty.

As Frank Hudon said, we're not talking about a lot of charge here. The ICE must run to provide the climbing horsepower, as with any car. Much of the ICE horsepower goes directly to the wheels, and some goes to MG1 to generate power. MG2 uses that power to add to the wheels.

Occasionally, MG1 generates a surplus, so the Prius opts to throw that into the battery.

It would be nice to provide "hints" to the system about expected terrain behavior---because the computer can't know you plan to go downhill soon. But what happens if you change your plans? You decide to turn off the road at a scenic overlook or stop for lunch. Now you've shut down the car with the battery in a very low SOC.

Having driver "hints" wold be nice, but it's a double-edged sword. The car would have to obey the hint, and then it can't stop you from double-crossing it!

 

I too drive hwy 17 in CA and have noticed that I fully charge the high voltage battery from the summit about halfway down and have wondered what happens with the extra charge after the battery shows full green and I'm still coasting and going downhill.

A larger batter capacity would be beneficial.