Clarity Won't Start - No Power

[Robert_Alabama]

You could also give charging the existing battery a go. Also most auto parts stores will check it for you at no charge, but to test it, you will probably have to try to charge it first. They might also do that for you.

 

[boniam]

You could also give charging the existing battery a go. Also most auto parts stores will check it for you at no charge.

Thanks. I am going to buy a charger and try to charge overnight. But i will try with my NOCO one more time. What i am confused is ICE seems to start for few seconds with NOCO booster and shuts so i am not sure if there is other issues. MY EV battery is also empty and that is why i put in charger. Any other trick? I saw somewhere steps to start ICE engine by putting in maintenance mode but it seems if EV battery is drained should it not start ICE automatically?

 

[Robert_Alabama]

I don't think the car will run with a near dead battery, in maintenance mode or otherwise. Hopefully you can get it to hold a charge. If so, then the question would be "What discharged it?". Leaving the car on might be the answer, but I'm a little surprised it drained it this low before shutting down.

 

[boniam]

what do you mean by "I don't think the car will run with a near dead battery". Should usually we not be able to jumpstart even with low battery and then run the engine to charge 12V. My car has gas but EV is almost gone. I feel either alternator is bad or system software is getting confused becauase both battery is near dead. When i said "maintenance mode" I meant jump start in that mode. Not sure if there is such thing.

 

[Robert_Alabama]

I meant that I think there is a limit to how dead the battery can be and the car still run. I assume there has to be a reasonable voltage at the battery, even when it is charging. I could be wrong about that, though. I don't know if there is a limit on what the DC/DC converter will do to keep the car running if the 12V battery is completely dead (or removed). I want to believe I used to have a gasoline powered car that once stopped running with a dead battery even though the alternator was healthy.

 

[boniam]

I was finally able to start and solve issue. I will post my finding in case it helps someone in future. I believe my issue was that both EV/main battery and 12V were depleted. I also think it happened because I left car running and plugging in charger. I remember i didn't have any EV range when i plugged in. (Also my other car is Tesla and have gotten used to not turn off car so i have left clarity running few times).

Anyway, as I mentioned I had tried jump starting with my Noco boost plus gb40 and engine started and shut off in 2-3 seconds. I tried few more things.
(1) I tried to start engine and quickly put in reverse or drive and still didn't work.
(2) I put car in maintenance mode (which is supposed to kick in and stay in gas engine) and start but again it shut off in 2-3 s.
(3) THIS IS WHAT WORKED. Next I connected fully charged NOCO boost plus (jump starter) to get 12V circuit power and plugged in level 2 charger. It was charging. (i actually tried this before and last time it shut down quickly because my NOCO was out of juice I think). I left it for 15 minute and I had to leave and didn't want it connected and NOCO was anyway almost discharged. But when i disconnected NOCO, Car kept charging and car lights and accessories mode stayed on. So it seemed plugging in level 2 charged 12V quite quickly. When i tested using multimeter it read 13V and it seemed it all worked. I left it plugged in for couple of hours and it fully charged and started without jump start and I could drive for 12 mile trip. So it seems it is all good. I will see if i have any trouble starting tomorrow but i am hopeful it will be fine.

It all make sense except i feel most gas engine can jump start with very low battery (in fact NOCO has a mode to jump start even if battery is less than 2V) and then if you leave car running it will charge battery. For clarity it seemed it needed some charge in EV battery. I am also surprised honda has designed it so poorly that it let it drain to that level when parked in few hours.

 

[Landshark]

I believe my issue was that both EV/main battery and 12V were depleted.

Nothing works on the Clarity without a healthy 12V battery. The traction battery will not charge when the EVSE is connected, for example.

“Jump starting” the car does not guarantee that the engine will run. It simply powers up the system so that the vehicle can be operated.

The Clarity has no alternator. It uses a DC/DC converter to charge the 12V battery from the traction battery. The engine does not need to run for 12V charging to occur. 12V charging happens when the car is in READY mode or when the traction battery is being charged. Having measured 3.6V on the 12V battery, you’re on borrowed time with that component.

 

[megreyhair]

ICE still needs the 12V battery to run. There are lots of electrical stuff like water pumps, fuel pumps, starter coils, computers, ECM, etc and they all need 12V. The DC/DC high voltage to 12V converter can't run if you are 0% with 12V batt. So without a somewhat charged 12V battery, ICE would stop after running after the 12v batt is drained. This usually won't happen on a regular car with an alternator.

Glad you are up and running again.

 

[Landshark]

ICE still needs the 12V battery to run. There are lots of electrical stuff like water pumps, fuel pumps, starter coils, computers, ECM, etc and they all need 12V. The DC/DC high voltage to 12V converter can't run if you are 0% with 12V batt. So without a somewhat charged 12V battery, ICE would stop after running after the 12v batt is drained. This usually won't happen on a regular car with an alternator.

Glad you are up and running again.

First off, nothing is going to happen with a dead 12V battery. You won’t be able to operate the vehicle in any fashion whatsoever. Not in EV, HV or HV+. The ICE will never run. There won’t even be a single warning light on the dash. A 12V power source is required to begin the funtivities. A jump pack, a jump from another vehicle or a new battery are a few options.

Second, a couple of owners reportedly used the DC/DC converter for input to an inverter. My recollection is that the rated output was sufficient to operate a 2000W inverter. Maximum may have been 2300W. That is certainly adequate output to run some 12V gadgets. Need proof? When the vehicle is operating properly, the DC/DC converter powers all the aforementioned devices in addition to charging the 12V battery.