High Voltage Battery Charge Too Low - Vehicle Cannot Start

[alchemistjazz]

Hi there,

I have a Honda Jazz 2021  - Hybrid.

I have been away for about 6 weeks and left my car, and now I am getting the message: High Voltage Battery Charge Too Low - Vehicle Cannot Start with all warning lights when I attempt to start.

The 12v battery was dead, so have tried to charge it.

The EV battery is showing 0 bars. I have tried to jump start the car but nothing much seems to happen.

Any suggestions would be appreciated.

[Marco1979]

Strange! There should not be a drain on the high voltage battery, so maybe the 12v was so low that it cannot measure the high voltage correctly?

You might be able to reset it somehow when 12v is charged again. Or call Honda assistance.

Good luck; keep us posted.

[Whiteshark]

Likewise, that is a most unusual situation. I think I would call Honda Assist, but would be most interested to know the cause. Good luck

[Kremmen]

What was the car usage before the 6 week break ?

If it was left on say, 3 bars, that may have been low enough.

[Lord Voltermore]

Oh dear, that is unusual.  Even if Honda Assistance or the dealer are able to get the car started fairly easily and send you on your way for now  I'd want to ensure the HV battery etc is thoroughly checked while its still under warranty. 

I notice the car has done 28000 miles, but has it recently had little use in addition to  the 6 weeks you mentioned?   eg has the car been DRIVEN   for at least 30 minutes  in the last 3 months? ( There is a warning about this in the handbook, and on a label under the bonnet.)   I believe the HV battery needs to go through some charge and discharge cycles during this 30 minute drive.   It may not be enough just to start the car and let the engine run on the driveway.   

[Marco1979]

I would be intrigued to know the cause and how to avoid it. Living in a 20 mph zone, the car is always down to 2 bars when I park. The longest I left it unused was probably 2.5 weeks.

[Whiteshark]

From my experience leaving unused for a long period is not necessarily the problem. There is much info on here, plus manuals etc.
We left our hybrid jazz for over 7 weeks unused in April/ May this year, but …….. it was advised on here to insure the 12v battery was fully charged before we left, and that is what I did using a CTek. I do not remember, because I didn’t check what the high voltage battery charge was like before we departed, although the vehicle is used regularly, but weekly, not daily, and does 4K per annum.
What I do know is that on return, everything worked perfectly

[coravel]

Same thing happened to me when I returned from a 3 month holiday.  The car was completely dead so I called out Honda Assist (the AA) and the mechanic charged up the 12v battery for 20 minutes which allowed the car to start and then told me to drive it for half an hour to charge up the high voltage battery.  No problems with it since and the battery was found to be in good condition when tested during the first service.

[alchemistjazz]

I did try and charge the 12v battery, and then start but it didn't work.

[John Ratsey]

Same thing happened to me when I returned from a 3 month holiday.

Did you have a low HV battery problem as well as a dead 12V battery?

Given that in normal operation the vehicle won't let the HV battery drop below 2 bars on the gauge (ie about 20% charge), the HV battery is completely disconnected when the vehicle is switched off and the self-discharge rate of lithium batteries is very low I have to wonder if there's a more fundamental problem with the problem HV battery. One possibility is that after 28k miles and innumerable partial charge/discharge cycles the car no longer knew where zero is on the battery as it never normally goes there (it does reach full charge when going down a long hill). And if the car has lost track of the empty point then the HV battery could have been only slightly above the low battery threshold when parked up.

[Steve_M]

A dealer will need to put the vehicle into maintenance mode, that allows the HV battery to use the reserve power (if there is any) to turn the engine over, the generator can then charge the HV battery. If there is no HV charge it will mean replacement of the HV battery.

Had there been any issues before the lay up period?

[alchemistjazz]

Haven't had any issues before.

Charged the 12v battery until it was fully charged. After a few attempts to start it, a voltmeter in the 12v cigarette lighter reads 8v, does that mean I need to replace the 12v battery?

Also if the HV battery is flat will a tow of the car allow it to re-generate a charge?

[Kremmen]

8v does indicate a dead 12v battery if that's immediately after a full charge

I think when towing, the front wheels must be off the ground

[ahavoja]

Charged the 12v battery until it was fully charged. After a few attempts to start it, a voltmeter in the 12v cigarette lighter reads 8v, does that mean I need to replace the 12v battery?

Also if the HV battery is flat will a tow of the car allow it to re-generate a charge?

For a 12 V lead acid battery, about 13 V indicates fully charged battery, and 11 V would mean completely drained battery. So 8 V sounds like either it wasn't charged, or it's broken. If you have a multimeter, you can try checking the voltage directly from the battery terminals. Also while charging, the battery voltage should be higher, like 13 - 15 V. That way you can verify if the charger is working. It may take 10 or even 20 hours to fully charge a car battery.

Interesting idea, if the HV battery could be charged by towing the Jazz. In theory it would be the same as driving downhill and using regenerative braking in B mode to charge the battery. In the boot, behind the right wall there is a detachable towing hook. I suppose it attaches to the front of the Jazz, so that another car could be used to tow the Jazz with a rope.

Does the car allow you to switch to B gear, or is it stuck in parking gear?

[alchemistjazz]

The gear is stuck, but if I keep rocking the car, I am able to release it from parking.

While charging it went to 14.5V at the battery.