Current flow on highway

actually, its not really switching back and forth that much. its monitoring current flow and flow will hover at about 1-2 amps which means only nominal drain. at freeway speeds, the EV plays very little roles and so the need to charge is greatly reduced since only accessories will be draining the battery.

if you watch CANVIEW, it will hover around 1-2 most of the time but will drop to larger negatives briefly if accelerating or starting up a grade. as soon as it hits a certain demand or charge level, then recharging begins and you will see a larger positive charge usally at least 10 amps give or take.

 

Clearly the native MFD averages a great deal. It also tends to report charging a bit more than discharging. The "glide" mode on the MFD is a fiction. You never get to neutral charge. I no longer try to "dead band" rather I try to accelerate such that I am changing at least the rate that I am discharging,,, 5-9 amps. Peering into the innards of this car is fun.

 

The analog needle reveals much, in fact. Instantaneous feedback
from the current through the wires, no waiting. I could have [and
in fact could swear I *have*, somewhere] detailed the story if
one had asked... anyways, yes, that back-and-forth you see is by and
large very minimal current flow. What this reflects is the hybrid
system always seeking the 60% battery charge level, and while getting
there it bobbles back and forth either drawing little bits of current
out or sending charge back in. This is under *steady-state*, i.e.
a completely unchanging demand.
.
But demand always changes, doesn't it? Either your foot moves or
cruise control makes a change. The first response to this comes
from the battery, because it can be done instantaneously. Some time
later, engine RPM and throttle are controlled to sort of "catch up"
with the new situation. This gives you, among other things, a mild
simulation of fuel enrichment, a la the classic accelerator pump.
But there's no pump, and since the ICE wants to always run at a
stoichiometric mix, fuel enrichment is studiously avoided. The
closed-loop feedback time constant pretty much dictates that throttle
and injector-time adjustments must be done *slowly* to keep the
whole mess under control. I'm not exactly sure what happens after
a *reduction* in demand, except that a big ol' pulse of charging
current is sent to the battery. I theorize that it's additional
load put on MG1 to slow the engine down, with its output sent to
the battery because, well, there's no other place to send it.
.
I'm pretty sure other people have written this up better than my
attempt above. I can try to find some of those things if I haven't
explained it well enough. I don't know if can-view is fast enough
to show it, but if I'm on the highway and I bounce my foot up and
down a little, I see substantial current spikes [~ 40A?] in both
directions, while engine RPM [and thus power output] hardly changes
at all over that very short timeframe.
.
_H*

 

i think Frank mentioned that there is a 95ºC thermostat which would be ummm about...207ºF? so unless you are in that range for extended periods of time, your cooling fans dont even kick on. (they would usually only come on when not moving in any case)

on the MFD, there is a "dead band" range where small changes are not going to be measured because there really is nothing to measure. also the delay in the MFD screen to changes in condition is actually quite long (not quite a second but far far from instaneous) so having it miss short charge cycles completely was not a surprise to me since all one has to do is punch the accelerator on flat ground and watch the arrows change after letting your foot off the gas. i have actually done this and had the mpg reading stay on 99.9 mpg. i dont really think there is a huge need to update the screen quicker. in fact, CANVIEW updates faster than i need it too.


i don t think the Prius attempts to maintain a 60% SOC that tightly. iow, there is not going to be an attempt to charge unless there is a specific level of need. that need will cause a charge of min about 5-10 amps (this seems to be controlled by speed somewhat just as regen levels are).

on the inverter temps, has anyone found out what kind of temps we should be trying to avoid yet??

i havent seen 120º but one time when MOVING, but have had it spike to 130 if stopping for less than an hour and then taking off again. after a few minutes it will drop back down to the 110 range.

 

they are snapshots BUT, the CANVIEW uses a different scale than was is actually transmitted on the bus so you will be getting rounded off values for some. for instance, the RPM's are stated in 25 rpm increments, but the bus transmits them in something weird like 35 rpm increments. norm chose the 25 rpm increments because they are easier on the brain. that is why (i think) you will sometimes get very rapid toggling between values.

 

<div class='quotetop'>QUOTE(efusco @ Apr 1 2006, 09:18 PM) [snapback]233646[/snapback]</div>

if it was only briefly and only 199 don't take it out yet, when you first get your temp to 212F for more than a minute, that's the day I would call it summer and take it out. 199's not even hot yet and with Mobil1 in the cc your not hurting anything.

 

yesterday coming home from the interior there are 3 hills you have to climb first one is 7% grade for 2 miles and I had MG1 inverter to 157F 67C by the time I made the top of the hill, holding 60 miles per hour. By the time I got to the next hill the car was cooler as it was snowing so I didn't get it over 50C and most of the time it was about 43-45C. I had taken the lips out for this trip because of the hills, the first of which is a 9% grade for about 1 1/2 miles. The top of the pass is 4400' and this trip I was in up to 4" of slush with the temp at freezing. I almost stopped and put the lips back in but I had another climb to 3800' after a decent to about 2000' but they are short steep climbs and didn't need to be stopping to pull them again. This summer I'm going to design an adjustable grill blocker and install it. Most likely one I can adjust from the inside of the car as I'm driving if required.

 

Not sure how we diverted off to temperature ... but for whoever
asked about the fans, they just come on when the normal coolant
thermistor indicates somewhere around 100 degC. It's controlled
by the ECM.
.
_H*