That's an idea. Although I see a couple of problems.

First is that if you "trickle charge" while driving to get 6 bars or the theoretical max charge, you can't put any more in. So, if you fully charge it, then end up going down a hill or slowing down, there is no way to capture that excess energy... you now just have to use your brakes and convert your kinetic energy into heat. I think that's why it seems to "want" to stay at 4 bars. You have plenty of juice if you need it, but also have a buffer ready to accept more re-gen braking.

Second problem is that the battery is not a perfect storage medium. You lose some energy when you charge the battery and lose more when it's discharged. That's why there is a heat vent from the battery compartment into the trunk (and why you should not store ice cream on the right side of the trunk...). Some of the energy is lost to heat. If you needlessly force a trickle of energy into the battery you lose some (10%, 20%???). Again, when you use it. You'd be better to just keep the energy in your driving and only charge when you slow down. I look at the system as a neat way to capture at least some of the energy usually lost to braking and use it for forward propulsion. That's also why you'll get better mileage on the highway by letting the car speed up on the downhills and bleed off speed on the uphills. If you keep in on cruise control, it scrubs off speed on the downhills and powers up the hills with the battery, sometimes also kicking in the other cylinders. Problem is that you lose energy (read: mileage) every time power is put into the battery and taken back out. (can get 42 mpg hwy myself, but only around 35 with cruise) Better to keep the kinetic energy in the car's forward motion.

 

"First is that if you "trickle charge" while driving to get 6 bars or the theoretical max charge, you can't put any more in. So, if you fully charge it, then end up going down a hill or slowing down, there is no way to capture that excess energy..."

There are no hills where I live but I see your point if I lived in an area where there were hills. As far as slowing to a stop I would personally let the system bleed off the 5th and 6th bar a few miles before I had to stop so I could use the regen braking as designed.

I would also probably not actually strive for the 6th bar via a trickle charge. Just the 5th. I've noticed my Accord is much more willing to electrically help forward propulsion when the 5th bar is lit. Some with a 4th bar and virtually none with 3 bars unless I stomp on the accelerator. I just want to achieve the assist characteristics when the battery is showing 5 bars more often. For me if I have 5 bars, the assist will be given for about 7 to 12 seconds before it drops to 4 bars. Sometimes that is just enough to keep it in eco mode on a slight incline without losing too much speed.

I've done lots of testing by force charging the batteries by putting the car in park and revving the engine to 2500 RPM. This gets the battery to 6 bars in usually less than 2 minutes.

Another scenario is accelerating to 55 from a dead stop. If I could trickle to 5 bars (from another power source) and maybe get to 6 bars from regen, then from 0 to 55 it gives lots of assist but it goes back down to 3 or 4 bars in less than 20 seconds. Then for a 20 mile, no traffic drive it gives absolutely nothing for assist that whole time. It won't charge off the engine either so that is good. It just sits there.

Most of the time for a 55 to 0 regen it is doing its job but rarely do the bars move. If at 4 bars I get full regen but it is still at 4 bars at the stoplight. If I force the charge to 5 bars and regen from 55 to 0 then it stays at 5 bars. If I force charge to when the 6th bar first lights then slow down from 55 to 0 I still get full regen. The only time I cannot get the regen to work is when I force charge to what I would call "the top of 6 bars" then slow down from 55 to 0. That is all brake pads.

To those that wonder how I can get up to 55 with a full 6 bars I manually put the transmission in 1st and then manually shifted to 2nd at 35 mph, purposely keeping the RPM high and I never get assist.

My Accord is very predicable. It is like a game driving that thing. The 5th bar is the key. Some day for testing I will throw some heavy but fully charged lead acid batteries in the trunk and 3 or 4 DC to DC isolated switching power supplies with a max current of 5 amps in series to 170 volts or so. Complete with an isolation diode so I don't get back feed from the regen and see if I can keep the hybrid battery at 5 bars more often, therefore triggering the assist more often. Even if it is only for a few seconds. If these test prove fruitful I would gather my data and calculate out how often I could trickle the battery back up to 5 bars if I had a more exotic type of battery that weighed less than lead acid. Charge the axillary battery overnight from the grid.

 

My HAH is predictably unpredictable when it comes to the benefit of the IMA in regards to hypermiling around town. I continue to get what I consider good gas mileage but just feel that if the IMA would do just a bit more it could be much better. Slipping out of ECO with the IMA doing nothing with 4 bars present is to say the least frustrating. When 5 bars are present it participates to a much greater degree. Anyhow it is still a car great as it fits my needs. (34+ mpg mixed drivng since I bought it in Jun 09)

There is a IMA pack charger being used by the Insight I owners to keep the car at a full charge while parked or bring it up to full. Personally I don't need regen braking from a stopping perspective as coasting is the best use of the kenetic energy. Even in my regen equiped BEV it is better to coast to a stop when you can.

I am going to investigate getting a new 12V battery next week. Have been checking it and find the voltage drops after a couple of days so as to be at about a 50% SOC. This could be hindering the IMA as indicated in many posts. I let the car sit alot as the EV does all the local driving.

 

I could not agree more. I have been following Insight I threads and I would love to apply some of what they have developed to my Accord.

We drive our car daily and never let it sit and I think that is good relative to keeping the hybrid battery balanced. We now have dipped down to 28 mpg but that is normal for us this time of year. Tonight it will be 14 below zero F. Even at below zero the IMA motor starts the car great! I have never heard the car start with the old fashioned flywheel starter.

The battery level in our Accord has never done any kind of positive or negative recal and sits at 4 bars 90% of the time. 5 bars 6% of the time and 3 bars 4% of the time. Only once I have seen 6 bars when traveling through Colorado and never 2 or 1 bar.

 

I love the idea that started this thread.

I just got my 'Certified Used' 2006 HAH and have put about 500 miles on it (it now has 51000). I love the car because it is the best of both worlds for me. An economical commuter and a fun car for other times.
I've commuted to and from work 3 times now and I've gotten 37.7, 38.5, and 38.1 mpg over my 55 to 60 mile commute (it varies based on route).

I've been trying to determine how to get the best MPG from this thing during my commutes. I've been able to determine one thing for sure so far -- and that is that trying to get assist is FRUSTRATING. It always assists when their are 5 or 6 bars showing but hardly ever otherwise.

Back to the topic at hand, I agree that if there was a way to keep the battery boosted to higher levels, I think it would get much better gas mileage. The original poster said there's an economical balance to be kept. Spending a lot to get a little more mileage may not seem like the best use of resources. (Wait, didn't we do exactly this when we bought these cars?) BUT...there's a lot of value in figuring it out! Call it hobby expense.

So here are my neophyte thoughts for hacks, presented here just to stir everone's thinking. Maybe there's a solution out there somewhere in someone's head.

1) Topping off from the grid would only work for the first few minutes of a drive.

2) Some kind of increase in capacity would be nice -- charging from Lead Acids is the given example. What about having 2 hybrid packs - charging one to 6 bars, flipping a switch and charging the other to 6 bars.

3) What about a software hack that would let us determine the criteria of when boost kicks in. Oooo. Wish I had the source code. I wish the engine auto stop worked at higher speeds for example.

4) A manual 'boost' switch that drives the motor from some external power source other than the hybrid battery.

 

1. True

2. Some of the more daring folks over at insightcentral.net that have Generation 1 Insights are doing just that. Some have used lithium ion batteries rather than lead acid.

3. Again for Insight folks a hack has been created. It is called MIMA and it allows the manual override of regen and assist. As far as I know no one has hacked a Gen 2 Insight, Civic or Accord.

4. I had thought about that too but I don't personally know enough about the electric motor in our Accords. Even if I did, I'm not so sure I would be ready to disconnect the factory connections and hook up my own controller and battery pack. I think the Honda system does well, it just needs a larger battery pack in my opinion.

 

The Honda dealer agreed with my assessment of my 12V battery and installed a new one yesterday (warranty). Will see if that makes any difference in the IMA assist side of the equation.

I do know it will make a big difference in the not functioning because the voltage is only 8.4V . Definitely dropped a cell or 2 in the end of days.

The nice thing about jump starting a HAH is you only need to get the voltage up and enough current available to make the computer happy and the NiMh pack does the rest. My smart charger set at 10 amps and for about 10 seconds was all it needed.

If this actually makes a difference I will report it.

 

There is a noticeable improvement in the IMA with a new 12V battery. It didn't turn it into a EV or anything but it is definitely in the "blue" more often.

 

What warranty? The OEM one or battery warranty? My 07's battery would no longer be covered would it?

And the jump thing's great to know if you're near a charger and outlet. A floating charger did it for you?

 

The OEM 12V battery in my 07 HAH was covered for 3 yrs and unlimited mileage. This is on page 26 of my warranty book. (This is a CA car but I doubt if that is a factor on this item.)

I don't know if a really low amperage (say 1 or 2 amps) float charger could get the voltage up enough to start the car if the battery failure was resulting in a lot of resistance. Chances are it could given a few minutes of charging, certainly worth a try if it necessary. 10 amps was more than enough and I never tried it with less, but I'm betting it wouldn't take much if you turned off all the accessories and waited for all the interior lighting to turn off.