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elmobob
Posts: 95
Joined: Wed May 23, 2012 7:18 pm
Delivery Date: 26 May 2012
Leaf Number: 020011
Location: Yonkers, NY

Dead 12V battery question

Fri Oct 17, 2014 12:21 pm

Hi All,

Ok so I have a 2012, went on vacation 3 weeks ago and left the car unplugged in a garage with the HV at 4 bars, I return this morning to start it up and I'm greeted with this

http://youtu.be/j_jWlKz5fFY

After giving it a 12V boost/jump for 30 seconds it was all was back to normal and I was able to go on with my day.

I don't know what could have been drawing power from the 12v battery except for maybe the ELM327 Bluetooth OBD-II can-bus adapter I left plugged in. I was under the assumption that once the car is in the off position no power is supplied to it.
Also isn't the leaf supposed have some fuzzy logic waking up every so often to charge up the 12v battery from the HV battery if it senses that it might be low? Has anyone experienced this?
Last edited by elmobob on Fri Oct 17, 2014 1:06 pm, edited 1 time in total.

User avatar
RegGuheert
Posts: 6419
Joined: Mon Mar 19, 2012 4:12 am
Delivery Date: 16 Mar 2012
Leaf Number: 5926
Location: Northern VA

Re: Dead 12V battery question

Fri Oct 17, 2014 12:52 pm

I made some measurements of the 12V battery voltage a couple of years ago. You can see the effect of the automatic charging that occurs every five days at day 19 in the chart. Unfortunately, it is as ineffective as the charging that normally occurs when you drive your LEAF.

And, no, the ELM327 does not get powered off with the car. I have gotten into the habit of unplugging it when I get out of the car. Unfortunately, this makes getting it to reconnect to the Android phone to take a reading a bit more challenging.

I recommend that you put your LEAF 12V battery on a good-quality trickle charger for about 24 hours to ensure it is fully charged so that you don't get stranded in the near future.
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

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Nubo
Posts: 5687
Joined: Fri May 28, 2010 11:01 am
Delivery Date: 31 Oct 2014
Location: Vallejo, CA

Re: Dead 12V battery question

Fri Oct 17, 2014 2:31 pm

- yes the adapter could have contributed. They go into low power mode (stop transmitting) when the car is inactive but they still draw power because they're still monitoring (waiting for the car to turn on). Unplug it if you're going to be parked for more than a couple of days. Or get one with a switch.
I noticed you're still working with polymers.

derkraut
Posts: 1519
Joined: Fri Jul 16, 2010 7:39 pm
Delivery Date: 14 Jun 2011
Leaf Number: 004248
Location: San Diego vicinity

Re: Dead 12V battery question

Fri Oct 17, 2014 3:57 pm

Looking @ your video, it appears that your HV battery was also completely drained? Something was definitely using quite a bit of power. I've left my car parked (unplugged, of course) for up to 5 weeks (with 4 or 5 bars on the HV, and still had 4-5 bars upon my return. I don't think there's anything wrong with either battery in your car.
Derkraut
Color: Cayenne SLE, ETEC trim
reserved: 5/15/2010
Leaf del. 6/14/2011
New Traction battery installed on 7/28/2017:

User avatar
elmobob
Posts: 95
Joined: Wed May 23, 2012 7:18 pm
Delivery Date: 26 May 2012
Leaf Number: 020011
Location: Yonkers, NY

Re: Dead 12V battery question

Sun Oct 19, 2014 7:07 am

derkraut wrote:Looking @ your video, it appears that your HV battery was also completely drained? Something was definitely using quite a bit of power. I've left my car parked (unplugged, of course) for up to 5 weeks (with 4 or 5 bars on the HV, and still had 4-5 bars upon my return. I don't think there's anything wrong with either battery in your car.
Once I gave it the 12v boost the car turned on fine and the HV battery had the same 4 bars I left it with. Looks like the OBD reader left plugged in was definitely the culprit.

User avatar
elmobob
Posts: 95
Joined: Wed May 23, 2012 7:18 pm
Delivery Date: 26 May 2012
Leaf Number: 020011
Location: Yonkers, NY

Re: Dead 12V battery question

Sun Oct 19, 2014 7:20 am

RegGuheert wrote:I recommend that you put your LEAF 12V battery on a good-quality trickle charger for about 24 hours to ensure it is fully charged so that you don't get stranded in the near future.
Thanks, I have a Xantrex marine 10 amp battery charger when I got home I hooked it up and looks like the battery was in bad shape since the charger was in the bulk charging stage for over an hour before settling into the float charge mode. I might take it to the dealer since i'm under 36k to see if they diagnose the 12v battery to be deficient.

woodgeek
Posts: 94
Joined: Sat Aug 23, 2014 3:16 pm
Delivery Date: 08 May 2014
Leaf Number: 425493
Location: Philadelphia Metro

Re: Dead 12V battery question

Sun Oct 19, 2014 7:43 am

I did a 4 week unplugged period this past summer, and from my loss of SOC on the traction battery worked out the the 'off/standby' draw for my 2013S was ~ 4 watts. Your 3 weeks is 21*24*4 = 2016 Wh, less than 10% of traction batt capacity, <<4 bars.

As for the 12V: 5 days = 120 hours * 4 W = 480 Wh, which is a lot to ask from the little 12V battery. IOW, the LEAF design is doing deep discharge expts on the 12V with the 5 day cycling. 2-3 day cycling would be a lot more gentle on the 12V batt, and still drain the traction batt the same amount.

Adding a watt or two from an OBD would make this precarious situation a little worse.

Still doesn't add up.

User avatar
RegGuheert
Posts: 6419
Joined: Mon Mar 19, 2012 4:12 am
Delivery Date: 16 Mar 2012
Leaf Number: 5926
Location: Northern VA

Re: Dead 12V battery question

Sun Oct 19, 2014 8:41 am

woodgeek wrote:Still doesn't add up.
Except I think it is reasonable to assume the following about OP's 12V battery:

- It is significantly sulfated, so the capacity is significantly reduced.
- It was not fully charged when OP left on the trip.

As a result, I expect that OP's battery likely was only storing about 25% to 50% of the nameplate capacity at the time he left, maybe less.

Note that I have directly measured the current draw of the LEAF when off and unplugged:
RegGuheert wrote:This morning, I measured the tare current for the LEAF 12V battery with the EVSE unplugged. Here is what I found:

- For the first ten minutes or so the car drew 330mA.
- After about 10 minutes, the tare current dropped to a lower value. It normally sat at 15mA, but pulsed up to 24mA every two seconds or so.
- Occasionally it would rise up to 115mA for a few seconds. I do not know how often this occurs.

According to this post, the published capacity of the factory 55B24L(S) battery is 45Ah at a 20-hr rate. Let's suppose it has about 50Ah at very low rates. If we suppose the tare current is a constant 15mA, then that equates to a discharge rate of C/4000. But since it pulses above that level, sometimes significantly so, the average current must be higher than that.
Perhaps the real average current is more like 25 mA, but that only equates to about 300mW draw, which is significantly lower than your 4W estimate. I think the difference is explained because there is certainly a MUCH higher energy draw when the 12V battery is charged every five days (until it is dead).

Unfortunately, when I later measured the LEAF current draw with the ELM327 installed, it was MUCH higher:
RegGuheert wrote:So this morning I measured the current draw of the LEAF with it plugged in: 175 mA.
It seems the ELM327 draws about 6X what the entire LEAF draws when off, making the total draw about 7X as much!
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

TimLee
Posts: 2811
Joined: Thu Jan 20, 2011 9:40 am
Delivery Date: 17 May 2011
Leaf Number: 2026
Location: Chattanooga, TN

Re: Dead 12V battery question

Sun Oct 19, 2014 11:14 am

RegGuheert wrote:... It seems the ELM327 draws about 6X what the entire LEAF draws when off, making the total draw about 7X as much!
Interesting.
First quantified report on this I have read.
7X would make leaving it plugged in for four weeks without using the LEAF a real bad idea.

I have been leaving a mini ELM plugged in continually for past nine months, and I haven't yet started doing the right thing and charging the 12V with external charger once a week.
But longest I have went without driving the car for at least ten miles / 30 minutes has been four days.
Four weeks is a bad idea, especially with ELM plugged in.
Best to always hook up external 12V charger for four weeks.

Tim Lee
Chattanooga, TN

Man. Date: 03/10/11, VIN # 2026
Delivered 05-17-2011
Blue Ocean, 2011 SL-eTec

GerryAZ
Gold Member
Posts: 2487
Joined: Mon Nov 22, 2010 6:47 pm
Delivery Date: 12 Jun 2011
Location: Phoenix, AZ

Re: Dead 12V battery question

Sun Oct 19, 2014 11:49 am

Just make sure to unplug the ELM when parking for extended time. I have parked my 2011 at the office or airport numerous times with durations ranging from a few days to 3 weeks. The only time I had an issue was the one time I forgot to unplug the ELM and also left the Kyocera running LEAF Spy laying on the passenger seat. That combination caused me to find a completely dead 12-volt battery when I returned after 6 days.

Gerry
Gerry
Silver LEAF 2011 SL rear ended (totaled) by in-attentive driver 1/4/2015 at 50,422 miles
Silver LEAF 2015 SL purchased 2/7/2015; traded 8/10/2019 at 82,436 miles
White LEAF 2019 SL Plus purchased 8/10/2019

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