My starter battery died. Confused.

[Theoburns]

Were you in Utility Mode? It's my understanding that if you use Utility Mode to run accessories, it uses your drive battery and saves the 12 volt battery. So far, it's worked for me in my 2021 Kona EV.

Clarity does not have a Utility Mode like the Kona. Clarity only has a 12V Battery Killer Mode, also known as ON Mode. There is also Accessory Mode which powers infotainment and the USB and 12V ports, but it only runs for about thirty minutes before shutting off.

Utility Mode on the Kona, I am guessing that just runs 12V items, so no heat or AC right? If so then I'm sure it's a great feature for camping, etc. where the main goal is to provide 12V power to the campsite. However for just sitting in the car parked I wouldn't think that Utility Mode would be as useful, and it seems a little clunky to get into as you have to go into the user menu and enable it, then I think that's just for one time, when you power off the car then Utility Mode is turned off and if you want to use it again another time you have to go into the user menu again, is that right? I'm not saying that's hard to do and I can understand why they don't have a simple button that you can press as someone might accidentally go into Utility Mode, whereas putting it in the user menu ensures that someone is deliberately turning it on.

 

[Theoburns]

Wrong- push it once as though you are about to drive away but keep the car in park mode. You can still take the key with you if you must

In the situation being discussed where someone will be remaining in the car, then yes you can take the fob with you. However if the car will be left unattended, you can't lock the car from the outside while in READY mode, so anyone can get into the car, and even drive off. Although if they turn off the car they won't be able to start it again.

Remote climate works pretty well when the car is unattended, on a hot day if I am going into a store after getting out of the car I start remote climate using the fob, which will run for about thirty minutes. If I will be inside longer than that then I use the HondaLink app to turn on remote climate about fifteen minutes before I will be leaving. It doesn't always work but it usually does. The bigger problem is that I normally forget to turn it on while I am inside the store or wherever, and I think about it only after I step outside into the heat and realize that I forgot to turn on remote climate.

 

[William Gleason]

it’s all very counter-intuitive. Why is the 12V battery even needed to start the car, as there’s nothing to crank? I also don’t understand why I should have needed a jump start from a third party when I already had a massive battery sitting there that (if the engineers had thought about it) would be fully capable of doing the job.

It's counter intuitive, but this is for the safety of firefighters in the event you get in an accident.

Firefighters are already trained to cut battery leads and remove the battery in bad accidents to make sure that vehicles are fully shut down, and the batteries can no longer short out and explode.

In PHEV, there's also the concern of the high-voltage lines hurting/killing the firefighters. The "simple" solution Honda used was to have a 12v-triggered contactor disconnect the 348v drive leads at the battery. This is the same sort of setup that's used in the Prius. When the 12v battery is cut out after an accident, it disconnects the power flowing from the drive battery making sure the firefighters don't get electrocuted by high-voltage DC.

Because of this setup, the 12v battery is needed to activate the drive battery, even if the drive battery is charged.

It's annoying, but I can understand it.

 

[Theoburns]

It's counter intuitive, but this is for the safety of firefighters in the event you get in an accident.

Firefighters are already trained to cut battery leads and remove the battery in bad accidents to make sure that vehicles are fully shut down, and the batteries can no longer short out and explode.

In PHEV, there's also the concern of the high-voltage lines hurting/killing the firefighters. The "simple" solution Honda used was to have a 12v-triggered contactor disconnect the 348v drive leads at the battery. This is the same sort of setup that's used in the Prius. When the 12v battery is cut out after an accident, it disconnects the power flowing from the drive battery making sure the firefighters don't get electrocuted by high-voltage DC.

Because of this setup, the 12v battery is needed to activate the drive battery, even if the drive battery is charged.

It's annoying, but I can understand it.

I agree on the reason why the 12V battery (or a 12V jump start) is required to activate the HV system. However regarding firefighters, just cutting the 12V out won't necessarily kill HV power if the car is still on. That's why there are two cut points under the hood. The first one you can hardly miss as it's marked with a big yellow label on the 12V battery negative cable, with a picture of a firefighters helmet and wire cutters. The second one is not as noticeable, but if you look at the back of the engine compartment on the passenger side you will see another cable with a yellow label, cutting that cable cuts the DC-DC converter. According to the Clarity Emergency Response Guide it requires cutting both cables to deactivate the HV system.

However according to the response guide, cutting cables is only a backup method, the preferred method is to simply press and hold the power button for three seconds. Which is not much different than a normal shutdown, the main difference is that besides shutting down the HV system it also disarms the airbags and seatbelt tensioners, as both of these pyrotechnic devices are on the 12V system. Although when I have tried the 3-second press you don't get any messages on the display or anything confirming what all has been shut off. I can imagine some firefighters may not trust this method and will still cut the two cables.

 

[TotalClarity]

I had a doctor appointment today, and left my wife in the Clarity in the parking lot, with the heater and other electrical stuff going, for about an hour. The engine was not running. There was plenty of charge left in the traction battery, which was showing 20 miles EV.

When I got back the dashboard was dark, and I couldn’t restart the vehicle. AAA came with a jumper box, and it started right away.

This doesn’t make sense to me, as I didn’t think the starter battery would be draining in that situation. Did I do this wrong?

Same thing happened to me in an Accord Hybrid I had before the Clarity. I was waiting to pick up someone and left the car on for about 30 minutes. It wouldn't start.

 

[Tangible]

After discovering that my battery wasn’t holding a charge, I took the Clarity to the dealer today. They confirmed that the battery was bad, and replaced it free under warranty. Lucky me: my three years are up in two weeks.

I imagine the battery was weak before the incident I first posted about, contributing to the rapid loss. For the past year I’ve driven very infrequently [Where was there to go???], and assumed that keeping it plugged in to 240v power was also keeping the 12v battery healthy. Reasonable, and wrong.

Thanks to all who have posted to this thread. It’s been quite an education.