Does 12V Engine Battery Interact W/ IMA Battery & Affect

webmonk · 11-08-2007, 10:24 PM

I have a 2003 Manual Insight. For the first three years I was getting 60+ MPG. I moved and before I moved I had a regular 60,000 mile service. I moved to an area with a lot of hills where I had to get up to speed (60 MPH) while going up hill. My MPG dropped to like 53. I attributed the drop to the hilly area, but even when I was not dealing with the hills I struggled to get the IMA charge to much more than 50-75% charged. If and when it reached near 100% it would quickly drop back down, often to about 40%.

I moved again and in the new area did not have to deal with the hills and yet the IMA charge was not staying high like it should. There had been a short in the wheel speed sensor wire six months ago, so on a hunch I took the car in and had the 12V engine battery checked out and it reported as bad. I had it replaced. Almost immediately the IMA charge went to 100% and my gas mileage went back up to 62+ MPG. I was thrilled!

Problem is that within a week everything went bad again. MPG was down to 53 again and the IMA charge was between 40-50%.

I had the 12V engine battery checked again and it seemed to be fine.

Why did replacing the battery improve things and bring performance back up to where it should be? Why did it drop back down so quickly?

Any advice on why I might be getting such bad performance would be GREATLY appreciated.

Caryfd227 · 11-09-2007, 05:52 AM

The 12 volt battery is charged by the IMA system. I would check the engine and transmission grounds asap. They are just a short piece of copper wire attached from the engine block to the frame and transmission to the frame. If they are broke it could affect your ability to get high FE and would also cause issues with the battery.

webmonk · 11-09-2007, 11:55 AM

Quote:

Originally Posted by Caryfd227

The 12 volt battery is charged by the IMA system. I would check the engine and transmission grounds asap. They are just a short piece of copper wire attached from the engine block to the frame and transmission to the frame. If they are broke it could affect your ability to get high FE and would also cause issues with the battery.

Thanks for the info. I did a quick check this morning for connections to the frame and found three, 1) one from the battery itself, 2) one just in front of the passenger seat and 3) one in the front right corner (from a support for the air filter). Are there others?

#3 above, the support is connected to the air filter assembly and has a bolt on the other end that mounts the support to something, not sure what it is. The bolt is sheered off and the support is moving freely. If there are not other grounds, AND your suggestion IS the problem this might be the source. I will look for other grounds and a way to reconnect the support so it has a constant ground connection. If someone could let me know if there are any other grounds or possibilities I would appreciate it.[/b]

**uhtrinity** · 11-09-2007, 06:17 PM

He is talking about the fairly heavy gauge grounding wires in the engine compartment. Both are on the drivers side. One runs from the frame to the transmission, the other from the frame to the engine block.

webmonk · 11-25-2007, 10:41 PM

Quote:

Originally Posted by uhtrinity

He is talking about the fairly heavy gauge grounding wires in the engine compartment. Both are on the drivers side. One runs from the frame to the transmission, the other from the frame to the engine block.

I finally found time to look into this more. I found the two ground wires on the drivers side. They both had several inches of exposed wire that was corroded, but they were intact. I went ahead and replaced them since it hardly cost anything, but it did not improve anything. I just got done driving back from the in-laws (about 200 miles) and I only got 52MPG and continued to struggle to keep 1/2 charge on the IMA battery. Any other grounding points to be concerned about? Any other ideas why the details from my original post would be causing reduced MPG and 1/2 charge on the IMA battery?

Caryfd227 · 11-26-2007, 12:19 AM

are you battery terminals clean? Are you seeing regen on your commutes?

webmonk · 11-26-2007, 01:14 PM

Quote:

Originally Posted by Caryfd227

are you battery terminals clean? Are you seeing regen on your commutes?

Terminals are clean since it is a brand new battery. The connectors were cleaned when the new battery was added. I work from home, so no regen on commute.

However, under the ideal circumstances (lots of downhill and breaking) I can get the IMA battry up to 100%, but that is only under IDEAL conditions. It quickly falls to around 50% when things return to normal conditions. The only reason it probably stays at 50% and does not drop to 0% is because of the forced regen at that level.

Just to reiterate, the charge and MPG went back to normal (95-100% and 62+MPG) for a day or two when I put in the new battery. Something seems obviously wrong, just cannot put my finger on it.