Author Topic: Starting the car in the event of a flat hybrid battery and 12v socket supply  (Read 358 times)

alboy

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If the hybrid battery was ever to go flat would the engine still start if the 12volt battery is okay ?
I cant seem to find out whether the hybrid battery starts the engine or the 12volt battery does
also does the 12volt socket lose supply when the ignition is turned off  I want to fit a dashcam and don't want to risk it running the battery flat, also which battery feeds the 12volt socket for running external devices
many thanks for any replies
« Last Edit: June 02, 2022, 11:02:43 AM by alboy »

shufty

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Re: Starting the car in the event of a flat hybrid battery
« Reply #1 on: June 02, 2022, 10:55:23 AM »
...I would go with the 12v (sorry I meant battery starting the car not the socket for the dashcam)
I was 'playing' with some settings and depleted the battery enough that I had no power to start the car, lock it or close the windows etc.
Using another vehicle I went and bought a cheapish usb car starting battery which I put on to charge.
After a couple of hours by which time the charger was still a bit off fully charge I tried locking the car. This worked as did remote close of the windows. Tried starting the car it was back to normal. Went for a drive and all was OK again. Never got chance to try the battery starter.
Unless the 12v can bring itself back to life after a couple of hours being left alone you would conclude that hybrid battery recharged the 12v?
« Last Edit: June 02, 2022, 03:32:26 PM by shufty »
MY22 Jazz EX - Sunlight W

sportse

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12V batteries can recover a bit if the temperature rises, on the Jazz it only needs enough power to boot the system.

Once the car is in ready mode then the 12V is being recharged- you donít have to actually be driving. The petrol engine will start as needed to charge the HV battery.

Other hybrids Iíve driven the Ďstarter motorí equivalent runs on a few hundred volts direct from the HV battery.

Karoq

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Assuming the JAZZ is the same as the HR-V hybrid, the 12V socket is ignition controlled.
Beware when fitting a dashcam Check what voltage the camera requires. Most run on FIVE volts. 12 into 5 does not go and you will eventually fry the camera. Might take a few months. If it does need 5 volts and you insist on using the 12v socket get a voltage dropping plug from ebay. or even simpler don't use the 12v socket, use the USB power socket which is also ignition controlled and runs at 5 volts (in every car I have had... don't blame me if Jazz is different. Check first!)
Dip Mech Eng (automotive)

Kremmen

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... or better still get the option connector that is designed for accessories.

Having said that, the option connector is very difficult to obtain and needs to be ordered from Japan, once you've found a supplier.
Let's be careful out there !

PWV

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Picked up my new Jazz yesterday, and as we are low milleage long holiday people, it was one of my handover questions.
It will not start if the reduced size 12V battery is flat- it is for activation..
It can started by another car as normal.
It can be charged by a intelligent battery charger without being disconnected from the vehicle.
Although I don't know the exact arrangement for charging it when it's running, but the manual (p72) shows an icon that displays when it isn't charging. If it comes on while driving and you need to stop DONT turn the engine off it might not start.

Now p227 says don't let the high voltage battery get close to zero or it won't start.

I have been told that the high voltage battery can/will charge the 12V one.
But having only just taken the car from the dealer the hybrid battery indicated half charge and the short journey home and then supermarket reduced it to 3/4 bars.
During the second trip I selected the power train to display but on such a short journey was unable to get any meaningful info. 
But the dealer said if it fails to start use the roadside assistance provided by Honda.
.
« Last Edit: June 02, 2022, 02:42:01 PM by PWV »

shufty

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... My 12v battery must've replenished itself then, enough to bring everything back to life, if the high voltage one didn't do it. I'm not sure which one was responsible tbh.
MY22 Jazz EX - Sunlight W

sportse

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Usually there is a big relay that isolates the HV battery from the system.

When the car powers up, if the safety checks are ok then the relay is closed and the system works from then.

Hybrids don't need much power to boot up the system, just enough for the computers.

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