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Saturday, December 6, 2014

Disabling dual mode charge on a Honda CRV

Sue's 2010 Honda CRV has had problems with the battery not getting a complete charge under some driving conditions. We first had issues when it was 6 months old... battery to low to start it. Took it back to Honda and they said nothing was wrong. It did the same thing a couple other times so we replaced the battery at 3 years old. Now a year later it did it again, It seems some Honda U.S. models have a dual mode charging scheme for economy. Short version is the battery charges to 14.4 - 14.9 volts IF there is a 15 amp load as determined by a load detector. IF there is less than 15 amps load the charging voltage is set to 12.4-12.9, there are some other conditions that override this as set in the ECU.
The car needs to be reliable for how we use it so something needs to change. It has no non-factory electronics except a dash cam that shuts off with the ignition.
Description of Dual Mode
http://opensiuc.lib.siu.edu/cgi/viewcontent.cgi?article=1011&context=auto_pres
or
http://opensiuc.lib.siu.edu/auto_pres/10/
The above are the best information I could find.
It seems the voltage regulator is in the alternator and not the ECU. The voltage regulator has two setpoints controlled by the ECU grounding or letting float the "C" connection to the alternator. The "C" wire is white/green and is supposed to be the same across Honda models. What I did was cut the white/green wire and fold it back in the harness. Now the alternator charges like a normal car at 14.4-14.9 volts. Voltage seems to follow temperature as it should like a normal car.  The battery has not used water from overcharging.No codes have been set either. I think it will work for us now.


3 comments:

  1. it seems to me there is a failure in Honda's R&D to design it this way. That is weird and very unusual.

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  2. Have you had any issues since you have done this "mod" I am having very similar issues on my '13 CRV. I installed LED headlamps, and the DRL low beams flicker, but when the alternator kicks to the "high" mode w/ full blower or rear defrost they are fine. I have had the battery "die" a couple times too since the vehicle generally only drives <10 miles a day. I have been thinking about doing something similar for a while now.

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  3. Steve it's been fine ever since. Just drove it back from Chicago today, about 1,000 miles round trip. No more dead battery or having to replace it.

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