2007 hchII 97,000 mi. I was getting about 38 mpg but now its more like 30-32 mpg. The other day I was on the highway (5 bars of batt) and got no IMA assist just a very sluggish attempt at passing when I punched it. Are these signs of the beginning of the end of my battery.

 

That is unusual for a HCH2. They normally are assist happy. Maybe check your 12v for strength. If it is the original 12v it may be week? Not sure if that would cause the problem you had however.Those are very low #'s depending on how you drive it! I normally come home at 50 to 55 mpg US. H

 

Thanks for the reply Harold. I'll have the 12 volt load tested. It's such a small battery. Does anyone no if the standard load test is valid for a batt of this size.

 

On separate occasions both the 12v and IMA batteries in my 2006HCH had to be replaced.

When the 12v became marginal the car operated like it was confused. For example at steady state cruising it would bounce back and forth between IMA charging and IMA assist. The dealer replaced the battery under warranty and the problem cleared. The computer runs off of the 12v so that any issues with the 12v could impact operation.

The IMA was replaced at about four years and 25K. Bottom line was that the SOC would suddenly drop from 5-8 bars down to 1-2 bars and there would be no assist. My position was that the car was unsafe to drive. At the moment assist was needed.... it might not be there. There was some back-and-forth with Honda America but after several discussions and the dealer having his techs drive it for a few day, Honda America covered the IMA battery replacement. Otherwise the car is great and I get about 43MPG calculated manually.

Since the IMA battery was replaced the the software updated, even when I have four bars there is plenty of reserve to pass another car. On the rare occasion that the SOC drops to three bars the regen is activated until the SOC is back to four bars.

 

I haven't had the battery tested yet. The sightglass says its good but I'm sure that is more of a gimmick than a reliable guage. I've noticed that the no assist seems to happen early in my drive. So I'm guessing that the initial current draw is sucking the battery voltage down and then charges (repairs) itself as I drive further so my symptoms go away.

 

What a difference a battery can make ! I changed out my OEM battery last night. (Walmart Everstart brand group 51r $75.00). I have driven 60.1 miles. 12 on country roads with 7 stops the other 48 on highway mostly 65-75 mph cruise control. 42.2 mpg. That is my best ever. I usually hovered around 36 to 38mpg. I obviously make no attempt to maximize my mileage. I just get in and drive. I can tell you one thing for sure. Don't believe the sightglass.

 

That is good,enjoy! H