Getting a Prius is interesting. It wasn't until I got the Prius that I realized that my commute one way is slightly uphill. So going to work my FE is lower then going home. Going home I get many 5 minutes parts over 75mpg and average above 60, but going to work I'm at least 10mpg lower. I'm driving on suburban 35mpg roads, there is some traffic but limited P&G is possible but not always. I've found several seemingly flat roads that where I can basically glide all the way home but going to work i have to run the ICE all the time. Looking for ideas how to tackle slight inclines the best especially when i can't P&G.
Hi SomervillePrius, My comments are within the context of a reasonably charged HV. A lot of my driving is like yours. I glide down, and deadband (?correct term) up. By that I mean no arrows to or from the battery. I like driving inclines like this, because the incline bleeds off speed when I have to stop for a red light. The rationale is to use the ICE at an efficient output. P&G is not the best in this case because you would be just putting the battery in the middle of your energy flow without benefit. Long inclines that are too steep for deadbanding from the beginning, and would bleed the HV battery down too low if I just relied on it for the extra power then entire distance is something I have not figured out to my satisfaction. Lately I have been pulsing up to 5 mph or so greater than the lower speed I can drive, and then deadbanding until pulsing again. If I fail and the SOC runs down, low FE results. The engineers in the group may have to correct me, but my impression is that ICE deadbanding is not a constant power output level. It seems that a short pulse at high power output allows subsequent deadbanding at a higher power output than would have been possible otherwise. Or maybe I'm just enjoying a shoulder of the rpm/torque topology. Or maybe, I am rambling, and this is nonsense.
Thanks, I think I understand your comment and will test (I think I've been charging the battery to much going to work so far). Your technique might be more efficient then the limted p&g I've been testing (glide part short, pulse too long AND hard to do in traffic). Though when "deadband"ing it it seem to keep the FE meter low. Need to play with this a couple of days to see what happens.
Deadbanding instantaneous MPG depends on speed. At 35 mph I see FE mid 30's, and at 40 mph, low 40's MPG. So a good drive gives glide down and 35 - 40 mpg up, or an average of 70 - 80 mpg.
Thanks, I seem to see the same numbers. It's just hard when you need to keep it at <40 (often 35) mpg for a long time. I guess I need to remember the ride home
The "deadbanding" level of demand [right foot] depends ENTIRELY on battery SOC. When it's at 60% nominal [six bars], most normal acceleration doesn't charge or discharge it -- no need, since it's at the target level already. That's your easy "deadband" with no arrows to or from the battery. When the SOC gets lower, the system tends to charge the battery unless you make a much *heavier* demand, in which case more of the engine's output needs to go to the wheels. So if you're trying to "deadband" with a low SOC you're going to carom into the car ahead of you. Conversely, if the SOC is high then the system is going to give you more out of the battery and you won't see the "charge arrow" at all until it gets lower. . It's not really about SOC. Sure, cranking less energy in and out of the battery results in better engine-to-wheels efficiency, but I believe that this is trumped by having the engine run in *its* own most efficient power-output region. Thus for pure P&G it doesn't really matter where your SOC *is*, what matters is how much delta it goes through in the course of you optimally running the engine. . These days I tend to use a "slightly augmented" glide, letting the car tool along on about 10A of battery current [it turns out that in no-arrows "glide" the system can be drawing up to 5A out of the battery anyways, so helping it just a little more seems fine], and then pulsing to greater than 1500 RPM if traffic allows. Increased following distance gives a much wider window to play in. So at times I can hold that 10A glide for a long time and the SOC drops, but this has a mild advantage that my threshold for the next engine-run is at a lower demand and that makes it easier to "pulse" in heavier traffic without taking off too fast. I don't worry too much about battery current flow during pulse; the system is going to do what it thinks is necessary to get back to 60% target with or without my help. . _H*
If I had to go uphill steady I would try for limiting my fuel flow to x gal per hour. That is assuming no traffic stuck behind. It might be 1.5 gal or 2 etc depending on the grade, and how much I felt like slowing. (readout on the can view.) I would let the battery do some chargeing. When it gets to the set point it will stop. I would never try to run it down, unless I had a long downhill ahead. I would try not to discharge the battery going uphill while the engine was running. I generally use just one can view screen for regular driving showing: Fuel flow, Amperes, SOC, and Engine Temperature.
