driving tips to avoid recals?

Discussion in 'Honda Hybrids' started by pcope, Jul 27, 2012.

  1. pcope

    pcope Well-Known Member

    hi all,

    this has probably been addressed in earlier threads, but it wasn't jumping out at me; any input would be helpful.

    My 2008 HCH II has been behaving reasonably well until recently, and I'm now experiencing an increased number of battery recals. Sigh.

    Admittedly I've got sub-optimal driving conditions: a 5 mile AM commute with hills, so there's no good way to avoid imposing a fair amount of charging and assist (as I travel up and down my commute).

    I've gotten pretty good at recognizing the conditions that are likely to induce a recal, but it's a bit counterintuitive. If I approach my final gnarly hill with relatively low charge left (4 or low 5 bars), I can often coax the engine into charge mode while going up the steepest part. Though a bit counterintuitive, this prevents a subsequent recal, and my net milage for the day is better.

    However, if I go into the final hill with more charge (high 5 or 6 bars), I can't seem to avoid evoking 2-3 bars of assist, more often culminating in a recal; and my net milage for the day drops considerably (again, a short commute doesn't help).

    So my impression is that if I could induce a forced charge when going up the last hill, I'd be avoiding many of the recals, but so far I've not been successful. I tried dropping into 'S' mode, but strangely that did not help; I still seem to evoke the same amount of assist, rather than eliciting a force charge. My car is reasonable well warmed up (typically 80-85o) and I never use the AC in our temperate climate.

    Any suggestions?


  2. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    Try cruise control on the uphill -- that seems to have worked for another member even though it is counter-intuitive.
  3. Bennett

    Bennett Well-Known Member

    Yeah, I found cc or S mode works - what seems to happen in each case is you rev beyond where you need (with assist) then as you drop the rev down (slowly!) you can invoke 1-2 bars of regen on the way up. The effect of cc does seem to depend on the SoC going into the hill. The other thing with S mode is I can at least often lose all assist even if I can't coax it into regen uphill, and then regen all the way down. This way I have climbed even long, steep hills on 5 bars of charge and avoided a recal event (which for me seems to kick in somewhere between 4 and 5 bars)

    Other things I have done - which probably overall cost more gas but do avoid recals (so you have the autostop and assist when you need it) are dawdling around at low speed in S or L rather than D (so invoking 1-2 bars regen if I can), or dropping into L mode when stopped and getting 4 bars of regen. Other forum members have reported this doesn't work for them so it may be software-dependant.

    How steep are the hills? Mine are crazy - 8% jobbies in some places.

    I also found that a long highway run "cleaned out the cobwebs". NO idea why.
  4. Bennett

    Bennett Well-Known Member

    How fast do you have to travel up the hill? I get best results between 35 and 45 mph (hill limits are 35-40mph). Revs 2500-3000 (fairly high for me, since I otherwise never get above 2000) in S mode. If I get assist I back off on the throttle. It takes a feather foot to get it right. When you hit the sweet spot you can feel it - the car is definitely revving more than you think it should for the speed and kind of 'floats' once you get regen going. If you're still getting assist you can feel it pulling/chugging.

    Sometimes you have to start off in D then as it chugs drop into S and the revs jump while the assist drops away, add a smidge more throttle for a second, then back off and the regen kicks in.

    Done right you won't lose speed unless the grade changes significantly, and can even end the climb with a higher SoC than you started with. Once you get the sweet spot you have to hold the throttle position with absolute accuracy. A minor drift either way will mess it up (even a big bump in the road can move your foot enough to upset the balance).
  5. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    Bennett -- thanks for chiming in!

    RE your "clean out the cobwebs" observation -- this is because on the highway (particularly with the headlights on) the car does background charging at very low levels. If you do it long enough it has a bit of a balancing effect on the pack.

    Also note that adding some throttle in S encourags a lower gear ratio selection from the CVT so that you get more torque from a higher RPM -- backing off gently after doing this lets the computer know you don't need as much power to continue at the selected speed so rather than changing the CVT ratio to match it is just shunting the excess off to the battery. This is one of the characteristics of S as compared to D -- more variability in CVT ratios for torque purposes as opposed to adding assist.

    Philip, I highly recommend you try to emulate the S procedure Bennett has described along with giving CC a try to see if there is any difference. Take it out on a 30mi highway trip too so that everything gets up to temp and the battery is conditioned a bit.
  6. pcope

    pcope Well-Known Member

    thanks, all, for the input and suggestions.

    After I read Sean's first suggestion (cruise control), I went out and tested it- and by jove! For some of the longer hills that I've had problems with, it does indeed seem to help-- with the behavior exactly as Bennett described; the loss of speed on my longer steep uphills evokes an 'over the top' response (revving the engine into high RPMs, well above 2000), then backs off once the target speed is reached-- actually, often with an overshoot, followed by a period of regen. And rather disturbingly, this cycle has not caused a significant drop in my MPG (a minor blow to my self-esteem as a hypermiler wannabe).

    The only problem I've still got is that for my short steep uphills in the morning (around some sharp curves), I'd have to pull a Mario Andretti to keep my speed at 25 MPH, which I guess is where the cc will engage. I've been experimenting a bit with dropping into S mode, but initially this didn't seem to affect the assist usage. However, so far, this approach does has seemed to prevent the full charge recal (again as Bennett noted). Because I was bored, I even tried dropping into L mode; fortunately no fireworks. I'll have to try Bennett's suggestion of playing with the timing of when I drop int S mode as I ascend the hill; I definitely have NOT found the sweet spot yet!

    And lastly, I hear you about the need to give the engine an occasional 'airing out' on the freeway; I've noticed the cobwebs phenomenon but don't always have the chance to use it as a preventative measure. Looking over past postings, I guess I should also try resetting the PRP, something that MSantos recommended awhile ago (and I've not done in awhile).

    Thanks all for the suggestions--

  7. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    Great news, Philip! Glad to hear you're seeing some improvements. :)
  8. pcope

    pcope Well-Known Member

    And thanks again Bennett,

    I've been playing a bit with dropping into S mode at different points during my uphill climb; I definitely see what you mean; the higher RPMs were initially disconcerting (accompanied by the transient increase in assist), but then the engine more readily drops out of assist and into charge mode. I can also see how some feathering will help minimize the loss in MPGs; so far I'm avoiding recals-- great suggestion!

  9. Mendel Leisk

    Mendel Leisk 2010 Prius (CAN Touring) Staff Member

    The camshaft has a second, higher lift lobe that engages under heavy load, like accelerating on upgrades. You can feel it come on, might be worth trying to kick that on. I'd concur that shifting to S should help, too.
  10. Bennett

    Bennett Well-Known Member

    Glad it's helping - and that someone else is seeing the same behavior!

    Sadly my little Zephy is currently in the shop from a fender bender, so I'm driving what I consider an awful Dodge Avenger... :(
  11. EdwinTheMagnificent

    EdwinTheMagnificent Legend In His Mind

    Everyone considers the Dodge Avenger to be awful.

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