Hi, I had a new battery installed by Honda agency (Mexico) approx 3 years ago and all has been good until now. I had always thought it was maintenance free but it went flat recently after leaving the car unused for several days and I noticed the two filler caps. Of course the plates were dry - I topped the levels up with de-mineralized water and jump started the car. It now starts OK but the voltage at idle is around 19 volts. Is this just because the battery is still pretty flat or is it a regulation problem?

 

19 volts is definitely a problem. Battery charging is usually done at 13.8 to 14.2 volts with a little higher in very cold conditions.

 

Furthermore, that 19V could be why the battery fluid 'boiled' out.

So get it checked out. (probably an alternator problem)


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BTW, FWIW, Honda charging systems normally run at ~ 14 .5 VDC - 14.7 VDC.