Author Topic: 12V battery flat  (Read 1499 times)

Toptek

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Re: 12V battery flat
« Reply #15 on: June 19, 2021, 12:25:25 PM »
Hi, with the cable you suggest for the battery, do you have to detach both battery cables before fitting it? That is, the battery has nothing connected, or can you just bolt it on to the positive terminal and the negative bolt before the battery monitor connection, battery cables in situ?
Thanks.

Expatman

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Re: 12V battery flat
« Reply #16 on: June 19, 2021, 12:50:12 PM »
Ctek chargers come with extensions which connect permanently to battery/body. Extension has terminal that plugs into the Ctek output cable.
To be honest a new Jazz should not need any attention to it's battery for years. Car driven normally should look after itself. If it doesn't there is something wrong and Honda need to fix it!
« Last Edit: June 19, 2021, 12:52:03 PM by Expatman »

culzean

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Re: 12V battery flat
« Reply #17 on: June 19, 2021, 06:04:43 PM »
Hi, with the cable you suggest for the battery, do you have to detach both battery cables before fitting it? That is, the battery has nothing connected, or can you just bolt it on to the positive terminal and the negative bolt before the battery monitor connection, battery cables in situ?
Thanks.

Just attach the ring terminals to 6mm bolts that hold battery clamps ( do not connect negative straight to battery terminal, but to the terminal next to it or the body metalwork nearby ),  leave everything else connected as usual - most chargers now come with the SAE type connector plugs and will plug straight in.
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

John Ratsey

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Re: 12V battery flat
« Reply #18 on: June 20, 2021, 03:28:15 PM »
I would add that on the Mk 4 Jazz the 12V battery is charged from the HV system and doesn't have it's own alternator. A 25 mile trip should be more than enough to get the battery fully charged. Effectively, the 12V battery is a big capacitor to provide a stable supply of power for the 12V accessories. However, if the ECU uses the 12V supply could there be a scenario where a flat 12V battery stops the ECU from powering up and this might mean that the power button doesn't work for waking the system up to start charging the little battery from the big one.

I've just checked and note that there is no separate switch for the boot light which means that this shouldn't be a potential souce of battery drain unless the boot is not latched, in which case the vehicle won't lock.

Kremmen

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Re: 12V battery flat
« Reply #19 on: June 20, 2021, 04:33:29 PM »
So a trickle charge device like a CTEK is useless on the MK4, interesting.
Let's be careful out there!

John Ratsey

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Re: 12V battery flat
« Reply #20 on: June 20, 2021, 10:18:33 PM »
So a trickle charge device like a CTEK is useless on the MK4, interesting.
No. Trickle charging if the vehicle has been standing for a couple of weeks keeps that puny 12V battery in better condition which is never a bad thing. If the battery loses capacity and the vehicle isn't used very frequently then there will be more occurences of flat battery resulting in the remote locking not working and maybe other undesirable effects. However, if there's enough life in the 12V battery to unlock the doors and power the ECU then the big battery does the engine starting.


Kremmen

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Re: 12V battery flat
« Reply #21 on: June 21, 2021, 04:52:14 AM »
Thanks.

So the HV battery doesn't try to keep the 12v one topped up while standing. Just trying to get my head around it.

Shouldn't be a problem as I frequently do 2 x 30 mile journeys weekly. As opposed to daily before I retired.
Let's be careful out there!

richardfrost

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Re: 12V battery flat
« Reply #22 on: June 21, 2021, 11:32:56 AM »
However, if there's enough life in the 12V battery to unlock the doors and power the ECU then the big battery does the engine starting.

Interesting. On my Toyota hybrid, the 12v battery never starts the engine and you cannot jump start the car in the traditional manner. Also, the charge going into the 12v battery is at such a low current you can't charge another car from it at any kind of meaningful pace. When my Jazz battery packed in a while back there was nothing I could do for it from the RAV4, so I no longer carry jump leads in the Toyota now, pointless. I do, however, have a towing cable.

John Ratsey

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Re: 12V battery flat
« Reply #23 on: June 21, 2021, 11:53:46 AM »
So the HV battery doesn't try to keep the 12v one topped up while standing. Just trying to get my head around it.

Shouldn't be a problem as I frequently do 2 x 30 mile journeys weekly. As opposed to daily before I retired.
I'm sure the big battery is isolated when the car is switched off to avoid any risk of the battery draining completely by topping up the 12V battery. If a lithium battery is left fully discharged for any significant period then it's bad for the chemistry and very expensive to replace this battery. The same also applies to the lead-acid battery but it's much cheaper to replace.

The 12V battery doesn't need to be much more than a big capacitor to serve the various components which want 12V power. There's no longer the starter motor to supply (that work is done by the big motor-generator fixed to the engine), most of the lights are LED (so no longer a pair of 60W headlight bulbs) and there are the various bits of electronics which must also benefit from the relatively stable voltage of the 12V battery compared to the fluctuations that the big battery must experience as the drive system changes modes.

However, as the OP has reported, there seems to be a situation where the 12V battery can be drained when the vehicle has been standing for a few days when it should have the capacity to supply for many weeks the residual power demands from components still alive when the vehicle is off (locking system, telemetry, ...). So far, this is a one-off event for which it would be useful to know the cause. I can't be the only person to have had one of these vehicles parked up for many weeks during the lockdowns either side of Christmas. My topping up of the 12V battery was more through habit than necessity.

booty

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Re: 12V battery flat
« Reply #24 on: June 22, 2021, 02:29:53 PM »
I think its all sorted now.
The CTEK was stuck on level 4 with the error light on, battery voltage 11.65V. The CTEK was not happy with the black lead connected to the chassis, after connecting to the negative battery terminal the Ctek competed its charge (green light on 8 hours later)
I have been monitoring the battery voltage and I think the problem was caused by the dealer supplying the car with only a partially charged battery.
I have ordered a voltmeter which can be left in the cigarette lighter so I can keep an eye on the battery voltage.
Thanks for all your help and advice. I liked the battery extension lead idea.

E27006

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Re: 12V battery flat
« Reply #25 on: June 22, 2021, 05:59:34 PM »
However, if there's enough life in the 12V battery to unlock the doors and power the ECU then the big battery does the engine starting.

Interesting. On my Toyota hybrid, the 12v battery never starts the engine and you cannot jump start the car in the traditional manner. Also, the charge going into the 12v battery is at such a low current you can't charge another car from it at any kind of meaningful pace. When my Jazz battery packed in a while back there was nothing I could do for it from the RAV4, so I no longer carry jump leads in the Toyota now, pointless. I do, however, have a towing cable.
Check your Toyota  handbook for safety information on a Toyota hybrid being towed  "front wheels on the road rotating"   for any significant distance and also the not-to-exceed speed. 
 I believe Toyota hybrids have to be towed front wheels off the road  on a towing dolly)  If towed at normal speeds with the front wheels rotating,  MG2 will spin at very high rpm and be damaged.

culzean

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Re: 12V battery flat
« Reply #26 on: June 22, 2021, 07:07:22 PM »
However, if there's enough life in the 12V battery to unlock the doors and power the ECU then the big battery does the engine starting.

Interesting. On my Toyota hybrid, the 12v battery never starts the engine and you cannot jump start the car in the traditional manner. Also, the charge going into the 12v battery is at such a low current you can't charge another car from it at any kind of meaningful pace. When my Jazz battery packed in a while back there was nothing I could do for it from the RAV4, so I no longer carry jump leads in the Toyota now, pointless. I do, however, have a towing cable.
Check your Toyota  handbook for safety information on a Toyota hybrid being towed  "front wheels on the road rotating"   for any significant distance and also the not-to-exceed speed. 
 I believe Toyota hybrids have to be towed front wheels off the road  on a towing dolly)  If towed at normal speeds with the front wheels rotating,  MG2 will spin at very high rpm and be damaged.

IIRC there is also a problem towing CVT and also EV without lifting the wheels off the road.

https://www.motorbiscuit.com/how-do-you-tow-an-electric-vehicle/

Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

richardfrost

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Re: 12V battery flat
« Reply #27 on: June 22, 2021, 08:56:55 PM »
However, if there's enough life in the 12V battery to unlock the doors and power the ECU then the big battery does the engine starting.

Interesting. On my Toyota hybrid, the 12v battery never starts the engine and you cannot jump start the car in the traditional manner. Also, the charge going into the 12v battery is at such a low current you can't charge another car from it at any kind of meaningful pace. When my Jazz battery packed in a while back there was nothing I could do for it from the RAV4, so I no longer carry jump leads in the Toyota now, pointless. I do, however, have a towing cable.
Check your Toyota  handbook for safety information on a Toyota hybrid being towed  "front wheels on the road rotating"   for any significant distance and also the not-to-exceed speed. 
 I believe Toyota hybrids have to be towed front wheels off the road  on a towing dolly)  If towed at normal speeds with the front wheels rotating,  MG2 will spin at very high rpm and be damaged.

The tow rope is for when I need to tow the Jazz for a jump start. Fully aware about towing issues for mine but thanks for the heads up. I also towed a VW Camper van to safety after the driver broke down and was parked on a bad bend.

John Ratsey

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Re: 12V battery flat
« Reply #28 on: June 22, 2021, 09:52:39 PM »
I think its all sorted now.

I have been monitoring the battery voltage and I think the problem was caused by the dealer supplying the car with only a partially charged battery.
Your trip home from the dealer should have provided sufficient time for the 12V battery to be fully charged.

I would keep checking the battery in case there is a problem causing an unexpected power drain.

ColinB

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Re: 12V battery flat
« Reply #29 on: June 23, 2021, 07:22:06 AM »
I have ordered a voltmeter which can be left in the cigarette lighter so I can keep an eye on the battery voltage.

I think the 12V socket is only live on a conventional car when the ignition is on, and when the engine is running the voltmeter will be showing the output voltage of the generator. If you want to monitor the condition of the 12V battery, you’d want to check the voltage after the ignition is on but before the engine is started. Not sure how that would translate to the hybrid if the 12V battery is charged from the HV system rather than directly from a generator ... is there an equivalent “ignition on” state, ie a condition of “accessory socket live but HV system not connected”?

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