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I am getting several error messages on my DTC check , and although I have no problems with the car, its a slight concern.

I know the battery causes problem and mine is an early 2017 30KW with its original battery.

Before I buy a new one, I note the reading in leaf spy to be something like 13-14v so it appears its fine, but I was wondering how accurate it is in reading the 12v voltage.

Thanks!
 

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John- Get yourself an intelligent 12v charger with a de-sulphate capability.
Every month overnight charge then another 24 hrs on the de-sulphating cycle.
 
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I suspect Leafspy just uses the ELM327 AT comand to read the voltage powering the OBD-II adaptor. In other words its measuring the voltage at the OBD-II diagnostic socket.

In which case the accuracy depends on your adaptor, but it should be pretty good. Mine reads within 0.1v of a digital meter connected directly to the battery.

And yes, the Leaf unlike many other cars lets the voltage sit at around 13.0 volts when it is on but not actively charging the battery.
 

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John- Get yourself an intelligent 12v charger with a de-sulphate capability.
Every month overnight charge then another 24 hrs on the de-sulphating cycle.
I've read all about the problems with 12v battery maintenance on the Leaf but so far I haven't had any trouble with mine.

After about a month of ownership I put my intelligent 12v charger on it (car turned off and asleep) and within about 30 minutes it went back to trickle mode, essentially saying that the battery was nearly fully charged when it started.

My poor ICE vehicle on the other hand, which sometimes goes for weeks without being charged, charged for a good 8 hours on the same charger before it was satisfied...

However I avoid running the radio or fan in the Leaf without the car fully on, (when the 12v battery is not being topped up) and don't leave it plugged into a charging cable for more than a couple of days straight. (avoiding the bug where it won't top up the 12v battery if the car is plugged in)

So I think if those two precautions are followed and the car is used regularly a top up with an external charge may not be needed.

I've also read that 2015 and later models maintain the 12v battery better than early cars but don't know if this is true.

Now that I own one I suspect most Leaf owners bitten by 12v battery discharge issues are either leaving an unused car plugged in for many days or weeks, or are using the radio/fan/accessories for too long without the car fully on.
 

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I've read all about the problems with 12v battery maintenance on the Leaf but so far I haven't had any trouble with mine.

After about a month of ownership I put my intelligent 12v charger on it (car turned off and asleep) and within about 30 minutes it went back to trickle mode, essentially saying that the battery was nearly fully charged when it started.

My poor ICE vehicle on the other hand, which sometimes goes for weeks without being charged, charged for a good 8 hours on the same charger before it was satisfied...

However I avoid running the radio or fan in the Leaf without the car fully on, (when the 12v battery is not being topped up) and don't leave it plugged into a charging cable for more than a couple of days straight. (avoiding the bug where it won't top up the 12v battery if the car is plugged in)

So I think if those two precautions are followed and the car is used regularly a top up with an external charge may not be needed.

I've also read that 2015 and later models maintain the 12v battery better than early cars but don't know if this is true.

Now that I own one I suspect most Leaf owners bitten by 12v battery discharge issues are either leaving an unused car plugged in for many days or weeks, or are using the radio/fan/accessories for too long without the car fully on.
I've read all about the problems with 12v battery maintenance on the Leaf but so far I haven't had any trouble with mine.

After about a month of ownership I put my intelligent 12v charger on it (car turned off and asleep) and within about 30 minutes it went back to trickle mode, essentially saying that the battery was nearly fully charged when it started.

My poor ICE vehicle on the other hand, which sometimes goes for weeks without being charged, charged for a good 8 hours on the same charger before it was satisfied...

However I avoid running the radio or fan in the Leaf without the car fully on, (when the 12v battery is not being topped up) and don't leave it plugged into a charging cable for more than a couple of days straight. (avoiding the bug where it won't top up the 12v battery if the car is plugged in)

So I think if those two precautions are followed and the car is used regularly a top up with an external charge may not be needed.

I've also read that 2015 and later models maintain the 12v battery better than early cars but don't know if this is true.

Now that I own one I suspect most Leaf owners bitten by 12v battery discharge issues are either leaving an unused car plugged in for many days or weeks, or are using the radio/fan/accessories for too long without the car fully on.
 

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Hi Everyone, my first post.

I checked how the leaf (2017) maintains the 12v battery when not in use - basically it charges the 12v (from the hv bat) once every 24hrs for 4mins (ns blue LED flashes).
The timer start from last switch off. I hope the pics show this.

Not perfect but better than an ICE, which does nothing to maintain 12V bat when car not in use.

134598


134600


134601
 

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Great graph. Can you confirm what has been reported online that if you leave the car plugged into a wall charger not charging that the car does not maintain the 12v battery every 24 hours like this ?

It would be interesting to see whether this is the case if it is just plugged in and fully charged (charging has ended at 100% after cell balancing has finished) or whether it also happens plugged in at a lower charge with the charge timer preventing charging.

I have a special interest in the latter as I have the charge end timer set to 7am Monday to Friday but no timer on Saturday or Sunday.

This means even though I still plug the car in on Friday night it will not charge until early Monday morning unless I manually override the charge timer.

I do this to avoid charging the car back up to 100% unless I need the range on the weeked as a 65% charge after commuting on Friday is enough to easily last the weekend for shopping trips etc and I would only need more than this for a long trip - in which case I just use the app to override the charge timer from inside the house. :)
 

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I am getting several error messages on my DTC check , and although I have no problems with the car, its a slight concern.

I know the battery causes problem and mine is an early 2017 30KW with its original battery.

Before I buy a new one, I note the reading in leaf spy to be something like 13-14v so it appears its fine, but I was wondering how accurate it is in reading the 12v voltage.

Thanks!
Hi John, you need to check the 12V battery with the car switched off, with a multimeter (several hours after being switched off). With the car powered on all you are measuring
is the DC/DC inverter output (approx 13-14V), which would be the same regardless of 12V battery condition. (I think the DC/DC inverter can supply over 100A).

I replace the 12V on mine with this


Mark.
 

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Great graph. Can you confirm what has been reported online that if you leave the car plugged into a wall charger not charging that the car does not maintain the 12v battery every 24 hours like this ?

It would be interesting to see whether this is the case if it is just plugged in and fully charged (charging has ended at 100% after cell balancing has finished) or whether it also happens plugged in at a lower charge with the charge timer preventing charging.

I have a special interest in the latter as I have the charge end timer set to 7am Monday to Friday but no timer on Saturday or Sunday.

This means even though I still plug the car in on Friday night it will not charge until early Monday morning unless I manually override the charge timer.

I do this to avoid charging the car back up to 100% unless I need the range on the weeked as a 65% charge after commuting on Friday is enough to easily last the weekend for shopping trips etc and I would only need more than this for a long trip - in which case I just use the app to override the charge timer from inside the house. :)
Hi Simon, I will try to confirm when I have time. From observations you can tell the 12V is being charge when the n/s blue led flashes. Not sure that is the case when car is plugged in, but not charging.
The 12V charge will happen 24hrs after switch, you may be able to see this?
I think the DC/DC Inverter is turned on during HV charging, so 12V will be charging then?
Mark.
 

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Hi Simon, I will try to confirm when I have time. From observations you can tell the 12V is being charge when the n/s blue led flashes. Not sure that is the case when car is plugged in, but not charging.
The 12V charge will happen 24hrs after switch off, you may be able to see this?
I think the DC/DC Inverter is turned on during HV charging, so 12V will be charging then?
Mark.
 

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Hi Simon, I will try to confirm when I have time. From observations you can tell the 12V is being charge when the n/s blue led flashes. Not sure that is the case when car is plugged in, but not charging.
From what I've read the flashing blue light while the 12v battery is being topped up isn't shown while the traction battery is charging.
The 12V charge will happen 24hrs after switch, you may be able to see this?
If it's exactly 24 hours I'll see if I can catch it.
I think the DC/DC Inverter is turned on during HV charging, so 12V will be charging then?
Mark.
Yes, the DC/DC inverter runs the whole time the traction battery is charging, this is evident because the battery voltage is held between 13.0 volts and 14.4 volts, which is higher than the natural voltage of the battery even open circuit let alone under load.

Some people believe the 12v battery only charges at the end of the traction battery charging cycle but I don't think that's the case - I think the lights just don't indicate it. The traction battery contactors are engaged the whole time the traction battery is charging and this takes a significant amount of power from the 12v system, let alone the various ECU's and cooling system (pump, fans) so there is no way the 12v battery would not be actively maintained during traction battery charging to prevent these from discharging it.

Monitoring the voltage as you have done is the only way to know for sure. Out of interest, what software and hardware did you use for graphing battery voltage ?
 

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From what I've read the flashing blue light while the 12v battery is being topped up isn't shown while the traction battery is charging.

If it's exactly 24 hours I'll see if I can catch it.

Yes, the DC/DC inverter runs the whole time the traction battery is charging, this is evident because the battery voltage is held between 13.0 volts and 14.4 volts, which is higher than the natural voltage of the battery even open circuit let alone under load.

Some people believe the 12v battery only charges at the end of the traction battery charging cycle but I don't think that's the case - I think the lights just don't indicate it. The traction battery contactors are engaged the whole time the traction battery is charging and this takes a significant amount of power from the 12v system, let alone the various ECU's and cooling system (pump, fans) so there is no way the 12v battery would not be actively maintained during traction battery charging to prevent these from discharging it.

Monitoring the voltage as you have done is the only way to know for sure. Out of interest, what software and hardware did you use for graphing battery voltage ?
Charge times on graph are: 11:00:15, 11:04:15, 11:08:15, so its every 24hrs and 4mins!!!!
 

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just thought that makes sense, 24hr timer, charge for 4min, start 24hr timer and repeat, so next charge starts 4mins later
Yep, if I wrote the software I'd probably start a 24h countdown whenever the 12v battery stopped being charged, then charge for 4 minutes if the countdown expired
 

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The only thing I find odd is why does it only charge for 4 mins ? logically thinking at the start of the charge you would say ok what is the 12v battery state if its above a certain level leave it, if its below that same level top it up, which could obviously take longer than 4 mins if its really depleted.
As a matter of interest mines a 2015 24kW still on original 12v battery, now thats put the mockers on it its bound to die now.
I do a maintenance charge approx once a month with a smart charger.
 

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At the end of a traction battery charge cycle the 12v battery should also be fully charged. So 24 hours after that if the car has just sat it only needs a slight top up to replenish losses from running ECU's in standby for 24 hours, which will be quite small, as standby current will be a few tens of milliamps.

Lead Acid batteries are quite inefficient and will keep drawing current at their maximum charge voltage even when fully charged, and will just convert that power into heat or if the voltage is too high, start acting like an electrolyser and generate hydrogen. So there is no point trying to over charge it as you'll just waste traction battery energy having the high voltage system active longer than it needs to be.

What would be interesting to know is whether something like leaving the interior light on by mistake would cause those 4 minute charging bursts to be increased to maintain the battery or whether it would stick to 4 minutes and let the battery gradually run down due to the light being left on and not increasing charging to compensate.
 

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At the end of a traction battery charge cycle the 12v battery should also be fully charged. So 24 hours after that if the car has just sat it only needs a slight top up to replenish losses from running ECU's in standby for 24 hours, which will be quite small, as standby current will be a few tens of milliamps.

Lead Acid batteries are quite inefficient and will keep drawing current at their maximum charge voltage even when fully charged, and will just convert that power into heat or if the voltage is too high, start acting like an electrolyser and generate hydrogen. So there is no point trying to over charge it as you'll just waste traction battery energy having the high voltage system active longer than it needs to be.

What would be interesting to know is whether something like leaving the interior light on by mistake would cause those 4 minute charging bursts to be increased to maintain the battery or whether it would stick to 4 minutes and let the battery gradually run down due to the light being left on and not increasing charging to compensate.
I think its sticks to 4mins charge period regardless of battery state.
The old battery was around 12.2V and still only charged for 4 mins (see below charge time 10:29 to 10:33).
134629
 
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