Highway trip with MIMA and Rostra

[aisbell]

I recently completed my first highway trip (7,000 km or 4,000 mi) using MIMA in PIMA mode with a Rostra cruise control. I traveled the speed limit the entire trip which varied from 70 kph (43 mph) on windy 2-lane secondary highways to 120 kph (75 mph) on freeways. I used the A/C on the warmest days and the defogger which uses the A/C during cool, rainy periods. I used no hypermiling techniques instead letting the Rostra control the car's speed much of the time. My car averaged about 3 l/100 km (~80 mpg) which I consider quite good considering that my car was fully-loaded with 2 adults, 2 backpacks including a tent, sleeping bags, and cooking equipment, and clothing for those days when we weren't backpacking.

I adjusted the PIMA set points so that assist and regen were very aggressive, both commencing with the slightest increase or decrease, respectively, in engine load. My goal was to adjust these set points so that the charge level of the IMA battery never reached 0% or 100%. This resulted in electrons flowing in and out of the IMA battery almost continually. The battery cooling fan was almost always blowing.

Driving my Insight in aggressive PIMA mode made my car feel much more powerful than normal. My car was able to climb hills with less downshifting and was a pleasure to drive. However, driving this way did cause a couple of problems:

- The cruise control tended to overshoot the speed set point in both directions resulting in repeated acceleration-deceleration cycles. Only when I manually intervened by not allowing the accelerator to decelerate too much could these acceleration-deceleration cycles be broken. Have you been able to adjust either your cruise control or PIMA to avoid such cycling? If so, how?

- On 3 occasions, aggressive PIMA assist reduced the battery charge level to 0 bars, yet assist would continue for quite some time despite no charge level bars showing. This was not a result of a negative recal; the charge level dropped at a rate consistent with continued assist being provided. So it was very encouraging that such aggressive IMA battery usage throughout the trip did not result in any negative recals which have been so prevalent with my previous 2 IMA batteries. But I'm concerned that assist continued despite the battery charge level reading 0. This has never occurred before I installed MIMA. Please explain how MIMA is able to continue providing assist at such low charge levels. Can this damage the battery?

[retepsnikrep]

Originally Posted by aisbell

- On 3 occasions, aggressive PIMA assist reduced the battery charge level to 0 bars, yet assist would continue for quite some time despite no charge level bars showing. This was not a result of a negative recal; the charge level dropped at a rate consistent with continued assist being provided. So it was very encouraging that such aggressive IMA battery usage throughout the trip did not result in any negative recals which have been so prevalent with my previous 2 IMA batteries. But I'm concerned that assist continued despite the battery charge level reading 0. This has never occurred before I installed MIMA. Please explain how MIMA is able to continue providing assist at such low charge levels. Can this damage the battery?

This is the sign of a good strong battery, be pleased. MIMA can't overide the safety systems so the battery was better than the soc gauge thought it was. It will keep discharging as long as the overall battery voltage and the battery tap voltages are OK even if the soc is non existent. The soc is only the car's estimate of what if left and we know it is very unreliable.

[faxe]

In my car when the SOC is down to zero, the BCM guage still shows 20 %
so the battery is not empty.

@Art: Might be a stupid question, but are you running your speedo in Miles or Kilometer now you are here on this side of the big pond. ?

[aisbell]

Originally Posted by retepsnikrep

This is the sign of a good strong battery, be pleased.

I am pleased. I am also thankful for your grid charger that has probably helped keep my battery strong despite my parking my Insight for significant periods of time. My battery is likely happier in the Swedish climate which is considerably cooler than the Hawaiian climate where my car had all of its battery problems.

Originally Posted by retepsnikrep

MIMA can't overide the safety systems so the battery was better than the soc gauge thought it was. It will keep discharging as long as the overall battery voltage and the battery tap voltages are OK even if the soc is non existent. The soc is only the car's estimate of what if left and we know it is very unreliable.

I am just surprised that before I installed MIMA and possibly also before I started applying a balancing recharge after every period of parking for more than one week, I had never been able to discharge my battery below about 2 bars before a negative recal and an immediate forced regen occurred. I have never experienced a forced regen since I installed MIMA and began using your grid charger even after I have continued using mild assist for a couple of minutes after the indicated charge level dropped to 0 bars.

[aisbell]

Originally Posted by faxe

Might be a stupid question, but are you running your speedo in Miles or Kilometer now you are here on this side of the big pond. ?

km, kph, l/100 km. I don't want to risk getting a speeding ticket which can be very expensive in Sweden.

I do occasionally temporarily switch to mi, mph, mpg because mpg is displayed in more significant figures than l/100 km making slight changes in the fuel consumption rate easier to detect.

[Mike Dabrowski 2000]

I don't have a cruise control, but understand from talking with people that do, that once you find the best PIMA and cruise control settings that it works very nicely.
The activation slope that the cruise control uses when a speed correction is required and the slope that PIMA activates assist at based on the increased engine load (MAG factor)
must be set so the engine is supplying at least half the power, or you will deplete the battery quickly.
The deadband between the last assist, and first regen in PIMA is another important variable.
Too early with regen will reduce the MPG, too late and you will drain the battery.
Lots of variables, with the cruise control adding another.
Rick Reese had the cruise/PIMA tuned perfectly, and was getting over 90 MPG on long highway trips.
He describes his technique here:
MIMA Honda Insight Modified Integrated Motor Assist - MIMA 001 Hypermiler Rick R
Happy to hear that your battery came back so nicely.
Have Fun