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In the winter my wife flattened the 12v by sitting in the car chatting with the heat on full but the car not turned on.

A few months later and the car won't let her in. Eventually she remembers the hidden key option and gets in and there's an error message on the dash - something about apply the parking brake ?

Anyway she gets a jump start and gets home for a full charge. Car seems fine again.

Is the 12v battery on its way out after just 3 years ? Seems a short life to me compared to the cars I've had over the last 30 years or so ?
 

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LEAF N-TEC 62KW
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If the battery is okay after being charged, no need to change it.
If you still have various issues occurring from time to time, replace it.
 

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Just to add that sometimes a totally flat lead/acid 12v DC battery develops a fatal condition. And will quickly show that soon afterwards. Consider buying a modern 'smart' charger that will have a feature that analyses the condition of the battery before selecting a tailor made charge programme from its internal menu. If it detects a problem at the start it will run a conditioning programme first and when that has ended start the charge itself. These new chargers can rectify faults and maintain a good battery health. It is also a sound plan to connect such a charger once a month whether the battery seems to need it or not and let it run for some hours. This will maintain it for much longer than the usual expectations and also avoid being locked out again.
 

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LEAF N-TEC 62KW
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Just to add that sometimes a totally flat lead/acid 12v DC battery develops a fatal condition. And will quickly show that soon afterwards. Consider buying a modern 'smart' charger that will have a feature that analyses the condition of the battery before selecting a tailor made charge programme from its internal menu. If it detects a problem at the start it will run a conditioning programme first and when that has ended start the charge itself. These new chargers can rectify faults and maintain a good battery health. It is also a sound plan to connect such a charger once a month whether the battery seems to need it or not and let it run for some hours. This will maintain it for much longer than the usual expectations and also avoid being locked out again.
Agree. I have a charger that has pulse mode for recovering LA batteries and would be worth using from time to time.
It can reverse soft sulphation, but hard sulphation caused by leaving a battery flat for a long period (weeks) is not reversible.

 

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In the winter my wife flattened the 12v by sitting in the car chatting with the heat on full but the car not turned on.
To be pedantic, you can't leave the "heat on full" with the car not turned on. If the car is only in accessory mode (two power button presses with no foot brake) you will only get the cabin blower fan blowing ambient air, you won't get any Heat or A/C. It will however run the 12v battery down fairly quickly, as the blower fan uses quite a lot of power by 12v battery standards. One reason I never sit using the radio and/or blower fan without the car turned fully on.

Kind of dumb of Nissan to provide an approved mode of operation (accessory mode) that makes it so incredibly easy to discharge the 12v battery excessively. Probably the cause of a lot of flat 12v batteries in Leaf's...
 

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LEAF N-TEC 62KW
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To be pedantic, you can't leave the "heat on full" with the car not turned on. If the car is only in accessory mode (two power button presses with no foot brake) you will only get the cabin blower fan blowing ambient air, you won't get any Heat or A/C. It will however run the 12v battery down fairly quickly, as the blower fan uses quite a lot of power by 12v battery standards. One reason I never sit using the radio and/or blower fan without the car turned fully on.

Kind of dumb of Nissan to provide an approved mode of operation (accessory mode) that makes it so incredibly easy to discharge the 12v battery excessively. Probably the cause of a lot of flat 12v batteries in Leaf's...
It is a poor design - you try that on many ICE vehicles and you'll get a message as it turns everything off.
This should happen, or the DC-DC converter should switch on, along with the appropriate message re reducing the range.
 

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It is a poor design - you try that on many ICE vehicles and you'll get a message as it turns everything off.
This should happen, or the DC-DC converter should switch on, along with the appropriate message re reducing the range.
My ICE is over 20 years old and even it is smart enough to not let you run the blower fan in accessory mode with the engine not running.

When I bought my Leaf I had assumed that accessory mode (which lets you run the blower fan as well as lighting up the full dashboard) did in fact engage the contactors and DC-DC to keep the 12v battery topped up, whilst disabling actual driving of the car, (a perfect mode to leave the car in if you walk into a shop and leave family behind) but NO, it doesn't, it just runs off the 12v battery until it goes flat.... :rolleyes:

Worse still the only clue you're in accessory mode instead of full drive mode (apart from no hot or chilled air) is the tiny little red battery light on the dashboard. Otherwise it looks like a fully turned on car. So I can easily see how someone sitting parked in their car could inadvertently put it into accessory mode rather than on mode while they wait for someone not realising they're running the 12v battery down. Bad design.
 
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