@AnthonyW posted a Battery Maintenance SB (89-003) that instructs dealers on proper maintenance of 12V batteries of all Honda vehicles. Attached is the important graphic from this. According to this, a car whose 12V battery has not been charged in any manner for a period of 60 days could have permanent battery damage. "American Honda recommends pulling the backup fuse while the vehicle is in inventory." Not sure where this fuse is, but I'm also pretty confident dealers are not doing this.
Pep Boys report: 12V battery rated at 550 CCA, current charge 451 CCA. Voltage: 12.8. Rest of report: Good Battery. State of Charge 100%.
The Clarity doesn't have an alternator. How would the high-voltage starter motor/generator switch from charging the HV battery and adjust its voltage to charge the 12-volt battery?
You mean the Leaf's main battery is 12 volts? That's difficult to believe. If the main battery isn't 12 volts, there has to be something to convert the DC from the main battery down to the 12-volts DC for the accessory battery. Here's an SAE paper that mentions the Clarity's 12-volt DC-to-DC converter: The Intelligent Power Unit contains 17 kWh high-capacity battery modules and a 12 V DC-DC converter. https://www.sae.org/publications/technical-papers/content/2018-01-0415
I had never noticed until today what the manual says about that little 12-Volt battery indicator: It comes on when the 12-Volt system is NOT charging. Seems odd. geo
I agree the Leaf's main battery is certainly the source of the electricity used to charge the 12-volt battery--there is no other source of electricity in the car. But what's going to happen when you attach the Leaf's 403.2-volt battery to its 12-volt battery? Instant charging or a fried/exploded 12-volt battery? My point is there has to be a voltage converter. Here it's explained for the leaf. The Clarity's starter motor/generator doesn't generate ~12 volts to recharge the Clarity's HV battery. That means it cannot directly recharge the 12-volt battery. Honda has used a DC-to-DC converter to recharge the 12-volt battery in all of its hybrid cars since my 2000 Insight. Unless the SAE paper is wrong, Honda still uses an HV DC-to-12-volt DC converter to recharge the 12-volt battery in the Clarity Plug-In Hybrid.
I was going on history and the SAE paper, but I could be wrong. I'll acknowledge any citation that presents a credible alternative explanation.
Found this about the Chevy Volt. In the Volt, whenever the vehicle is "running" (i.e. powered on), the 12V battery is being charged, although not by an alternator, but rather by a converter that takes power from the high voltage battery. Probably the Clarity works the same way.
Look at the 2019 Insight's Mode buttons. I'm going to order the one on the right and install it in my Clarity to eliminate premature enginulation. Believe me (the phrase I use when I'm delivering fake news).
A friend told me a warning light keeps coming on in his car. I told him to put a piece of black tape to cover it up.
@bobcubsfan - maybe that's the answer for angry bees and premature enginulation! I bet nobody who listens to Black Sabbath, AC/DC or Megadeath in their Clarity would ever hear the ICE no matter how angry. geo
Just wear full coverage noise-canceling headphones. That would also solve the issue of the sirens from those annoying emergency vehicles.
Premature enginulation, Black Sabboth, noice cancelling headphones, black tape for idiot lights... I love this forum!!!!
Quite the thread drift on this one! The paper cited by @insightman is correct. I took my trusty multi-meter out to the car this evening and confirmed the 12V battery is charged when the car is plugged in and being charged and also when the car is on, with or without the ICE running. That's all done through the DC-DC converter mentioned in the paper that converts the high voltage of the hybrid battery to 12V for all the 12V needs of the car. I have not been able to find the voltage of the hybrid battery, but I'm sure it's hundreds of volts so that lighter weight and less expensive wire can be used to push the amps to the traction motor. The 12V battery is used to keep power to the car's "base load" when off and to energize the relay that connects the hybrid battery for driving the car when the "Start" button is pushed. I suspect (but don't know for sure) that the high voltage hybrid battery is completely disconnected when the car is off for safety reasons. The voltages and amperages present in the high voltage circuits are way over lethal values.
Bob, you may not have found out what the problem is yet, but at least you can eliminate your 12v battery being defective. Mine read 13.1v at rest and your more extensive test says yours is fine. Still a puzzler as to why your ICE seems to come on excessively compared to the rest of us.
