12V battery flat

[Zaier]

Yes Colin, you're right about checking the 12V battery when the car is not in "ready mode".
To do so, you need to press the power button twice without pressing the brake pedal, the cars goes into "accessory mode".
In this condition, all the car is live, except ICE and HV part (Inverter, MG etc.), so the 12V battery will not being charged, indeed, you can see the red indication of the 12V battery not being charged on the dashboard.
Whereas, if you press the brake pedal and then the power button, the car goes into "ready mode", where the HV is connected to the inverter and thus also charges the 12V battery.

[jazzaro]

.

[Kremmen]

Just tested mine, yes, needs ignition on on my Civic.

Car been sitting since Monday morning:

Engine Off:



Engine running:



The unit:

[Pine]

I have been following all the discussions on the Mk4 Jazz with interest as a lot of the issues raised are also applicable to my Toyota Corolla hybrid.  Flat batteries are also an issue on Toyota hybrids when they have not been used for a while.  Battery capacity on my Corolla is only 45AH, but I believe from the start of this year it has gone up to 52AH.  Some owners on the Toyota forum think it may be because the car can detect the key if it is nearby and the car is in some sort of standby mode.  My spare key is in my bedroom but from there it is capable of unlocking / locking the car in the garage so I have now shut down the key with a few presses of the buttons as detailed in the handbook, is there a similar procedure for the Jazz key fob?

With regard to RDMS I don't think it has to be enabled to get 5 stars from NCAP.  Toyotas have the same system but it is operated on/off by a button on the steering wheel.  On starting the car it remembers its last position.

As a long term Jazz owner ( Mk1 & Mk2) I got into the habit of looking at this forum and still do even after transferring my allegiance to Toyota.

[John Ratsey]

My spare key is in my bedroom but from there it is capable of unlocking / locking the car in the garage so I have now shut down the key with a few presses of the buttons as detailed in the handbook, is there a similar procedure for the Jazz key fob?

For the Mk 4 Jazz hold down both buttons for several seconds and a little red LED flashes to confirm that the remote has been disabled and won't transmit any signal until a button is pressed. Even if the primary remote and/or vehicle are stored where there's no risk of a relay attack it's prudent to put the spare remote to sleep to reduce the drain on its battery.

[Hugh R]

Since I have to park in the road, will it be ok if, from time to time, i charge the 12v battery with a solar panel connected to the OBD2 port?  On Mk 4 Jazz will the OBD2 connections be correct/allow for this?

[Kremmen]

Do I, don't I ?

Connect CTEK and give the 12V a charge or just leave it. If it can't do any harm then I'm leaning toward giving it a boost.

Reading above, connect to both terminals works OK.

[Neil Ives]

Reading above, connect to both terminals works OK.

I don't get the issue of not connecting to the negative battery post. Surely the vehicle earth/body and the battery - ve must be at the same potential.

[sportse]

In the owners manual it says when jump starting to use the positive battery terminal and only an earth point near the screen wash filler - it says don’t connect it anywhere else

I think there is a note too about disconnecting the battery before charging, but dealers have chargers connected so it must be ok?

It means I can’t ever use my portable jump pack as the cables won’t reach that far.

[John Ratsey]

I put the 12V battery on charge several times last winter when the vehicle wasn't used for several weeks at a time. I was more concerned to keep the battery healthy than have a completely dead 12V battery immobilising the car because there's no power for the ECU. While my voltmeter reckoned the battery was down to below 12V, the charger would switch from charging to trickle in very few minutes. I connect the charger to the +ve battery terminal and to the earth strap end of the battery sensor fixed to the -ve terminal.

[culzean]

Reading above, connect to both terminals works OK.

I don't get the issue of not connecting to the negative battery post. Surely the vehicle earth/body and the battery - ve must be at the same potential.

There is a current flow sensor between negative post on battery and metal of car body,  by connecting the charging negative clamp directly to post you are bypassing the current flow sesnor, so you are still charging the battery but the cars computer is not registering that battery is being charged.  Judging the state of charger of a battery by terminal voltage is no longer used, instead 'coulomb counting' is used, where all current flowing in and out of battery is monitored, and the computer decides if the battery is charged or not.       

Even something as simple as an electric toothbrush or razor these days uses coulomb counting.  I replaced the Li-ion battery on my razor,  fitted a fully charged new one ( soldered in ) and turned the shaver on, the red light flashed but the razor did not rotate.  I measured the terminal voltage on cell and it was something like 3.75V, so fully charged but the razor said NO...  I had to unsolder the battery, use a 5watt bulb to discharge the battery down to 3.4 volts or something, solder battery back in and then charge the battery again via the proper circuitry in the shaver, and then that shaver worked fine.  By putting a fully charged battery in the shaver the current  sensor had not seen any power flowing into battery, so assumed that battery had no power, and would not allow motor to run even though it was fully charged.

[Jazzdriver]

I'm picking up a new Crosstar from the dealer tomorrow.  All this electrical stuff seems a bit daunting.  The car should get frequent use, so I hope I don't have such problems.

[Steve_M]

The main reason the Owners manual tells you to connect to the engine mount stud bolt and for this to be the last connection made is to prevent any spark being made to be away from the battery itself as a 12 volt battery gives of flammable gas, so sparking on the battery terminals itself could cause a fire/explosion.

[richardfrost]

I'm picking up a new Crosstar from the dealer tomorrow.  All this electrical stuff seems a bit daunting.  The car should get frequent use, so I hope I don't have such problems.

I think these people are overthinking this. There really won’t be a problem. I don’t expect to buy a car costing over £20,000 and then worry about having to charge the 12v battery all the time! I have had my hybrid Toyota for 4 years, it is 5 years old. Never thought about this once.

[culzean]

The main reason the Owners manual tells you to connect to the engine mount stud bolt and for this to be the last connection made is to prevent any spark being made to be away from the battery itself as a 12 volt battery gives of flammable gas, so sparking on the battery terminals itself could cause a fire/explosion.

No its the current flow sensor - there was a Honda tech bulletin copied somewhere on this forum that gave the reason for not connecting to battery post.  Modern sealed batteries are designed not to gas, and in any case if they do gas it will only be when they are charging, not when you first attach the charger.   Pretty much every battery charger made in last 10+ years is sparkless,  it won't pass current until correct polarity battery voltage is sensed.  In fact I have been unable to charge a battery that is in a very low state ( not enough voltage to satisfy charger sensor ) and had to connect a good battery in parallel with bad one for a while until bad battery gained sufficient voltage to convince the charger there was a battery there...

Honda tech bulletin attached ( PDF ) - it covers other things so battery charging is third page continuing on fourth page.