## Removing 12v battery to charge Leaf

markrshort
Posts: 7
Joined: Sat Jun 20, 2020 12:56 am
Delivery Date: 20 Nov 2018

### Re: Removing 12v battery to charge Leaf

Just been doing a bit more reading. Running the wiper blades on their slowest delay apparently sets the voltage to around 14 and puts charge into the 12v. Any idea how long I would have to do this for? e.g how many minutes for 1% of battery capacity (roughly!). Could this approach damage the battery if the battery got to 100% and I kept putting 14 volts in? If I used a resting voltmeter reading before to see if I am under 13 volts. If so I could then run the blades for X number of minutes to maintain the battery charge without going through the hassle of hauling my battery into my top floor flat. Good theory or not?
This would just be a temporary measure while i'm hardly driving the vehicle. I also had no idea that I had to unplug the vehicle from a charger once finished so this was probably the cause of the chronic drain! I was leaving my vehicle plugged in all day at work

Please note, I have had the well known 'no braking power upon start-up' fault so i'm feeling a bit nervous about driving it at the moment.

markrshort
Posts: 7
Joined: Sat Jun 20, 2020 12:56 am
Delivery Date: 20 Nov 2018

### Re: Removing 12v battery to charge Leaf

Further research shows from watching this video (https://youtu.be/ipEzK1yzxHY?t=6760) that the DC-DC converter puts about 4 amps into the 12 battery when running at 14volts. Looking at this 'determining charge time table' (http://batteriesbyfisher.com/determining-charge-time) and its shows the following: with 5 amps, my 500 amp battery with a current reading of 12.35v will take about 2.5 hours to charge fully. This shows the initial bulk charge upon startup for a few minutes isnt going to be at all adequate to recharge the battery fully once it gets low from the parasitic drain (e.g you've left it parked for a long time or you're leaving the car plugged into a charger overnight). When charging the traction on a fast charger do you get 14volts through the system for the FULL duration? if so that would keep it topped up.
It seems the answer is I need to get some miles into the car, which is a waste of time when working from home, and charge the car regularly or sit there with the wipers on for 20 mins every so often. The algorithm must assume(wrongly, in some cases) that the aux battery charge level is never that low and just needs tiny top up each time. I may be wrong on some or all or these theories. Any thoughts anyone?
Thanks again for the info.

GomerK
Posts: 2
Joined: Sat Apr 14, 2018 7:14 pm
Delivery Date: 27 Apr 2018
Leaf Number: 401945

### Re: Removing 12v battery to charge Leaf

I bought my 2013 Leaf two years ago and ended up replacing the 12v battery with an AGM deep cycle 90 days later. Since then, I have often left the car plugged in to the 120v charger for days without driving it and never had a problem (I monitor the 12v charge level w Leaf Spy). If you're not experiencing an actual problem, I wouldn't make yourself crazy trying to anticipate one. As someone else mentioned, knowing the year, SOH of the main battery and if you're experiencing issues would be helpful.

LeftieBiker
Moderator
Posts: 16165
Joined: Wed May 22, 2013 3:17 am
Delivery Date: 30 Apr 2018
Location: Upstate New York, US

### Re: Removing 12v battery to charge Leaf

The float voltage of the 12 volt system will normally read fine, even when the 12 volt battery is undercharged. Are you leaving the car plugged in for long periods after the car finishes charging?
Scarlet Ember 2018 Leaf SL W/ Pro Pilot
2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
BAFX OBDII Dongle
PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

LeftieBiker
Moderator
Posts: 16165
Joined: Wed May 22, 2013 3:17 am
Delivery Date: 30 Apr 2018
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### Re: Removing 12v battery to charge Leaf

markrshort wrote:
Mon Jun 22, 2020 2:22 pm
Further research shows from watching this video (https://youtu.be/ipEzK1yzxHY?t=6760) that the DC-DC converter puts about 4 amps into the 12 battery when running at 14volts. Looking at this 'determining charge time table' (http://batteriesbyfisher.com/determining-charge-time) and its shows the following: with 5 amps, my 500 amp battery with a current reading of 12.35v will take about 2.5 hours to charge fully. This shows the initial bulk charge upon startup for a few minutes isnt going to be at all adequate to recharge the battery fully once it gets low from the parasitic drain (e.g you've left it parked for a long time or you're leaving the car plugged into a charger overnight). When charging the traction on a fast charger do you get 14volts through the system for the FULL duration? if so that would keep it topped up.
It seems the answer is I need to get some miles into the car, which is a waste of time when working from home, and charge the car regularly or sit there with the wipers on for 20 mins every so often. The algorithm must assume(wrongly, in some cases) that the aux battery charge level is never that low and just needs tiny top up each time. I may be wrong on some or all or these theories. Any thoughts anyone?
Thanks again for the info.
If you can't use a plug in battery maintainer with the car, then a solar charger hardwired in may help, although they are often of poor quality. A 51R AGM battery may also work, although if more charge is being drained than is going in, the issue will remain.
Scarlet Ember 2018 Leaf SL W/ Pro Pilot
2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
BAFX OBDII Dongle
PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

arnis
Posts: 1027
Joined: Sat Jan 23, 2016 3:21 pm
Delivery Date: 23 Jul 2014
Leaf Number: 015896
Location: Estonia, Europe

### Re: Removing 12v battery to charge Leaf

If anybody want to "fully charge 12V battery" - just disconnect current sensor plug right on the negative battery connection clamp.
Computer will default back to 14.4V. After that just plug it back. Error code will be stored but who cares.
Short range EVs <30kWh -- Medium range: 30-60kWh -- Long range: >60kWh
Charging: Trickle <3kW -- Normal 3-22kW -- Fast 50-100kW -- Supercharging >100kW

LeftieBiker
Moderator
Posts: 16165
Joined: Wed May 22, 2013 3:17 am
Delivery Date: 30 Apr 2018
Location: Upstate New York, US

### Re: Removing 12v battery to charge Leaf

arnis wrote:
Tue Jun 23, 2020 1:27 pm
If anybody want to "fully charge 12V battery" - just disconnect current sensor plug right on the negative battery connection clamp.
Computer will default back to 14.4V. After that just plug it back. Error code will be stored but who cares.
Thanks - I'd forgotten about that trick. The car would still have to be driven enough to charge the battery at the bulk rate, but it's worth a try.
Scarlet Ember 2018 Leaf SL W/ Pro Pilot
2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
BAFX OBDII Dongle
PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

arnis
Posts: 1027
Joined: Sat Jan 23, 2016 3:21 pm
Delivery Date: 23 Jul 2014
Leaf Number: 015896
Location: Estonia, Europe

### Re: Removing 12v battery to charge Leaf

No need to drive Leaf. It will charge at 14.4V even when stationary and just "READY" mode or "CHARGING"
Short range EVs <30kWh -- Medium range: 30-60kWh -- Long range: >60kWh
Charging: Trickle <3kW -- Normal 3-22kW -- Fast 50-100kW -- Supercharging >100kW

markrshort
Posts: 7
Joined: Sat Jun 20, 2020 12:56 am
Delivery Date: 20 Nov 2018

### Re: Removing 12v battery to charge Leaf

Thanks everyone. The car is a 2016 Leaf tekna with 55900 miles on the clock.

In the last 5 months I've had about 6 breakdowns - all to do with the startup braking problem whereby when you start the car the dashboard lights up like a christmas tree (yellow abs light, yellow brake warning light, red main warning light). If you put your foot on the brake, it goes virtually to the floor and you get abs pulsing sounds plus a horrible grinding noise. If you were to pull away and tried to stop the car it would take A LOT longer to stop and would require a lot more force applied to the brake. When the RAC man came to have a look he checked the voltage on the 12v and it was at only 12.27 volts. After leaving the car on for a bit and then resetting the car it seemed to rectify the problem. So I assumed the battery was not taking enough charge from the DC-DC convertor anymore and I needed a new battery.
I got a new battery(Varta lead acid) fitted but two days later I had the same braking problem. This time the problem occurred about 30 seconds to a 1 minute into the journey(scary! lucky i was on a quiet lane and not going fast) the dash lit up and I lost braking power. This time I had my pregnant partner in the car with me and shes lost all confidence in the car and rightly wont go in it anymore. The fact that the brakes failed after startup makes me wonder if this has got anything to do with the 12v at all and maybe its another design problem with the car. Possibly the firmware on the intelligent braking unit? I asked about this at the dealership and they said it didn't apply to my car despite this link (https://flipthefleet.org/2018/leaf-brakes-failures/) suggesting that it affects models manufactured between March 2012 and Feb 2016 (mine was manufactured in Feb 2016).

So without any other options i'm considering upgrading to an optima yellowtop. Can i ask why would an AGM perform better than a lead acid in a Leaf in particular?. Do they retain a steady voltage despite a descreasing SOC % or is the benefit more to do with their low internal resistance and its ability to take charge better.
My other question would is .. does the leaf warn you when the 12v battery charge is low? The software that manages the charge of the 12v seems totally inadequate and can lead to this dangerous problem(?).

I'm currently working with someone from flipthefleet who is going to provide me a report on his findings about other leaf owners with the same problem. I'm hoping this report alongside my video of the issue will support my case to get a refund on the vehicle from the original dealership. Failing that then i'm taking it to the ombudsman.

Any help more help would be very welcome!
All the best, Mark

LeftieBiker
Moderator
Posts: 16165
Joined: Wed May 22, 2013 3:17 am
Delivery Date: 30 Apr 2018
Location: Upstate New York, US

### Re: Removing 12v battery to charge Leaf

AGM - real AGM, not Chinese "AGM" - batteries can be drained lower, and are usually higher capacity for the size compared to starting batteries. They also seem to accept more charge in a short time with the Leaf; it's speculated that the car was designed for a higher capacity battery, and the charging system 'stops short' and switches to float mode as the voltage on the little starting battery rises quickly during bulk charge.

No, no low voltage warning I'm afraid. Maybe there is a vampire drain in the electric brake booster as you speculate...
Scarlet Ember 2018 Leaf SL W/ Pro Pilot
2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
BAFX OBDII Dongle
PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

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