4 Problems at the Drive-in

First to go over some basics that you probably already know, but just in case some of it is not clear, there are three modes that the car can be in:

ACCESSORY
ON
READY

The first two are activated by pressing the power button without pressing the brake pedal. One press for ACCESSORY, another press for ON. Pressing the brake pedal while pressing the power button puts the car into READY mode. The word READY will always appear on the display when you are in that mode, if it doesn't then you are either in ACCESSORY or ON mode.

It's important to note that ACCESSORY and ON modes draw only from the 12V battery and will eventually drain it. Only when in READY mode does it draw from the HV battery. Which of course can be drained also but it takes a whole lot longer, and also when the HV battery does get down to 0 then the gas engine will automatically come on to recharge the battery. Whereas in ACCESSORY or ON modes it will let the 12V keep draining until it is dead. Although in ACCESSORY mode it will turn off after 30-60 minutes which is what you experienced, but it won't stop you from repeatedly turning it back on to ACCESSORY mode and continue to drain the 12V for another 30-60 minutes at a time until you have successfully killed it. ON mode meanwhile will just keep running continuously until the 12V well is dry, which it will do much faster since ON mode activates the entire electrical system except for AC compressor and heater.

Also the HV battery is lithium ion which is designed to be cycled (i.e. drained and recharged). Whereas the 12V is a traditional lead acid which gets worn out when it is drained excessively, and draining it too low can greatly shorten it's life. Meanwhile the HV battery has built in safeguards to keep you from draining it enough to harm it.

So to avoid putting unnecessary strain on the 12V battery it's normally best to avoid ACCESSORY or ON modes except for brief periods. Although just using the radio in ACCESSORY mode might be okay for a couple of hours, it's just not great for the 12V battery. And it also requires you to have to press the power button every 30-60 minutes or so to turn it back on. You could avoid that by putting it in ON mode, however that activates the entire electrical system and will drain the 12V much faster, not to mention also lighting up all of the dash lights, so no real advantage to being in ON mode, you might as well put it into READY mode.

As for the DRL's, there's a trick to turn them off, simply activate the parking brake prior to turning the car on, and voila no DRL's as long as the headlights are not on and as long as the car is not in gear.

The dash can be dimmed using the brightness button behind the left side of the steering wheel. Also the infotainment screen has a separate brightness control, press the brightness button on the lower left side of the infotainment screen to cycle between day and night modes, each of which have separate brightness settings. The third setting is off which makes the infotainment screen go completely dark, although for some inexplicable reason the control buttons on the left side of the infotainment screen then go to maximum brightness. But at least that gives you just a small strip of light that can be more easily covered up.

What I would recommend for movie outings is the following:

- Put the car in READY mode. Another nice thing about READY mode is that you can run climate control for heat or AC. As long as the HV battery has a decent charge you will be fine running climate for two hours. And no real risk as the worst case is you run it down to 0 and the gas engine will come on, although even then it will only cycle on for a few minutes at a time if you are just sitting parked.

- Use the buttons behind the steering wheel to dim the dash to the lowest setting

- Press the infotainment brightness button and cycle the infotainment screen to off

- Make a small cloth or cardboard cover that will cover the infotainment buttons and the power button (the big red glaring one)

- Make another small cover for any of the climate or gear select buttons that are still on, unless you don't find them bothersome

- Make a cover for the main display, unless at it's full dimmed setting you don't find it bothersome.

Since we are on the topic of the 12V battery there is the subject of when it gets charged. There had been some mystery about that, but some Clarity owners have hooked up voltmeters to the 12V battery and done some tests and have come up with the following:

- The 12V battery is not charged by the gas engine, i.e. the gas engine does not have to be running to charge the 12V

- The 12V battery is charged from the HV system anytime the car is in READY mode

- The 12V battery is also charged whenever the car is being charged. Note that just being plugged in will not charge the 12V battery, it's only during the time when the HV battery is being charged that the 12V battery is charged

Some people have experienced a dead 12V battery in their Clarity after letting the car sit for a week or two, leading to theories that there is some parasitic drain going on, but others have gone that long or longer without a problem, so it is suspected that the ones that died from sitting for a week or two were probably weak already. Either way if your car will be sitting idle for more than a week you probably should give the 12V an occasional charge. You can use battery chargers designed for this purpose, Battery Tender for example is a popular brand. But an easy way is to simply turn on the car to READY mode and leave it sitting like that for thirty minutes or so. Just remember to go back out there and turn it off! It would be very rare for the gas engine to start up during this time, but it's not entirely impossible so if the car is in an enclosed garage it's best to do this with the garage door open.

If you do wind up with a dead 12V battery, it can be jump started like any other car. Actually what is safer and easier is to use one of those small portable jump-start batteries, they are about the size of a paperback book and work surprisingly well even for regular gas powered cars in most cases, but they work especially well for Clarity (and most hybrids) because when starting the car the 12V battery is only used to power up the electrical system, and then the HV battery does the actual turning of the engine. So very little power is needed to jump start. They are a little pricey around $40-$50 but it's great peace of mind to keep one in the trunk or glovebox, and also you will likely find you are able to help other people get their car started with it.

Just add a bit of info that might help with the skeeters: I live in southwestern Mississippi where it is usually a tad bit warmer and more humid than Maine. I visit an allergist for weekly injections and, due to Covid-19, they are given outside the office. I am then required to sit in my car for 30 minutes before having the injection sites checked. Sitting in the car in broad, unshaded daylight when the temperature is at 110 degrees is NOT something one does with the windows open - so I run the AC. The AC system in the Clarity is surprisingly quiet when running at normal speed and the drain on battery range is negligible - just a few tenths of a mile for 20 minutes. Yesterday I had cataract surgery and my "surgery buddy" was not allowed inside the building but had to sit in the car - in 112 degree weather. She sat in the Clarity listening to the radio with and with the AC running, surrounded by HUGE pick-ups and SUVS (all running their ICEs, pumping out heat and exhaust) for just over 90 minutes - and the Clarity registered a 2-mile drop in range.

JimO said:

Excellent forum! I was almost stranded last night in my 4 week old 2021 Clarity. I had left my wife in the car when shopping at Home Depot for about 45 minutes. When I got back, the car failed to turn on - getting lots of system failures. Realizing that the 12v battery was discharged, I switched to "OFF". After waiting (and praying) for a minute or two, I was able to push on to "Ready" mode and drive off.

I thought initially that I had left the car in "Accessory" mode but understand now that I mistakenly put it in "ON" mode. If I had left it in Assessory mode, the power would had turned off. - lesson learned.

Click to expand...

READY mode is much better in these situations as there is no drain at all on the 12V battery. Also while in READY mode you can use heat or AC if needed. You might lose a few tenths of a mile of EV range if you sit for an hour, a bit more if you use heat or AC.

If you don't want the DRL's to be on while sitting in the car in READY mode, simply set the parking brake, then turn the car off then back on again and the DRL's will not come on. They will only come back on when you put the car in gear.

If you want to sit in the car with heat or AC but don't have a need to have anything else turned on, you can pull out the key fob and press the remote climate button. Remote climate will run for about 30 minutes at a time. Remote climate has no effect on the 12V battery, although it will use a little bit of your EV range. The only drawback with remote climate is you have to accept what it gives you, you can't control the temperature or fan speed.

JimO said:

QUESTION: When level 1 charging, is the 12v battery also topped-off. Logically, I think yes; otherwise a continuously charged Clarity would fail to start in a few months left unused.

Click to expand...

The 12V will charge while the HV battery is being charged, but if the car is not being driven then the HV battery will need very little charging, so there might not be enough charging time to keep the 12V going. For long term storage you would want to occasionally turn the car on to READY mode for an hour or so which will charge the 12V.