Dead 12V battery question

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elmobob

Well-known member
Joined
May 23, 2012
Messages
95
Location
Yonkers, NY
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?
 
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.
 
- 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.
 
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 said:
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.
 
RegGuheert said:
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.
 
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.
 
woodgeek said:
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 said:
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 said:
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 said:
... 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.
 
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
 
Just to be clear, you were looking at loads on the 12V line?

My figure, looking at SOC decrease of a parked car would include your loads, the self-discharge of the 12V (as you noted, made up every 5 days) AND loads associated with traction battery self-discharge (presumably small) and the HV BMS system.

4W versus 24 kWh = 6,000 hours = 8 months to discharge a full traction battery. Too fast for Li-ion self-discharge (?) so we blame the BMS? Might suppose the BMS would be relay'ed open with the car 'off'.

Hmmm.
 
woodgeek said:
Just to be clear, you were looking at loads on the 12V line?
Yes. I measured all of the current flowing from the 12V battery.
woodgeek said:
My figure, looking at SOC decrease of a parked car would include your loads, the self-discharge of the 12V (as you noted, made up every 5 days) AND loads associated with traction battery self-discharge (presumably small) and the HV BMS system.

4W versus 24 kWh = 6,000 hours = 8 months to discharge a full traction battery. Too fast for Li-ion self-discharge (?) so we blame the BMS? Might suppose the BMS would be relay'ed open with the car 'off'.

Hmmm.
I'm thinking that a lot of stuff needs to power up to charge the 12V battery every 5 days. I don't know the total power draw, but perhaps it is several hundred watts. Also, if there are charging timers set, there may be not-insignificant loads that need to be turned on to determine the status of the charging port, etc.
 
I found this topic looking for why my leaf was dead after just a week left in the airport parking lot. I have a wifi ELM327 OBD2 scanner plugged in as well but I can't believe it would draw my 12v down in 7 days. My leaf is not even a year old yet. I'm going to take the battery in to get tested.
 
Twofieros said:
I found this topic looking for why my leaf was dead after just a week left in the airport parking lot. I have a wifi ELM327 OBD2 scanner plugged in as well but I can't believe it would draw my 12v down in 7 days. My leaf is not even a year old yet. I'm going to take the battery in to get tested.
Did you read the fifteen page topic on 12V battery problems?
See http://www.mynissanleaf.com/viewtopic.php?f=30&t=12448&hilit=12V&start=120#p374537" onclick="window.open(this.href);return false;.
Several people have had battery problems on 2013.
Phantom loads that fail to clear, possibly relay bad, speculated by some.
But not many final answers.
Some still struggling with it a year and a half later.
 
GerryAZ said:
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

hoping this is all because of updated programming but my 2013 sat for 5, 6 and 8 days this year and I only remembered to unplug the ELM one time but one time I left it in but only lost about 8 GIDs (or could be 10. not sure due to sloppy handwriting... mine :oops: ) in 6 days.

Another time, I left it plugged in 5 days and lost ZERO GIDs. Big thing which is easy for me since i use a separate phone for it is to log out of LEAF Spy from your phone. the 8 day stint with ELM left in, I lost 5 GIDs

so if you are looking at something to blame, I would look elsewhere.

key thing is make sure you close the app on the phone
 
In a few threads I've seen regarding a 12 volt battery under the hood, am I assuming correctly that it is routinely charged during normal plug in charging of the vehicle? Non owner - yet! But taking my first test drive (extended) tomorrow evening... Dealer is allowing me take it home for the night, drive to work the next day, and return on way home.
 
Twofieros said:
I found this topic looking for why my leaf was dead after just a week left in the airport parking lot. I have a wifi ELM327 OBD2 scanner plugged in as well but I can't believe it would draw my 12v down in 7 days. My leaf is not even a year old yet. I'm going to take the battery in to get tested.

It's a significant load to draw for 168 straight hours.
 
Yesterday we had a dead leaf again, this is getting annoying.

Friday night I topped up the 12v battery, took less than an hour to hit the green. The car ran fine Saturday, was at 65% so we didn't charge it Sunday morning. Sunday afternoon we went to run one of the kids and got the dreaded dash blinking and all kinds of warnings. Turned it off and went to another car. I threw the 1.25 amp deltran charger on it right away and checked the 12v battery, not surprisingly it was at 10.1v An hour later I check the voltage to find it still low at 10.2v. I put a clamp on meter on the leads and sure enough there was a about a 1.1 amp load leaving he battery with 1.2 going in to the battery from the charger. I disconnected the car and then put a larger 4 stage 5 amp charger on the 12v battery overnight. The 12v battery was full this morning, I reconnected the car, checked and the 1.1 amp load was gone, just the usual, .1 amp load, started the car and all is fine with the traction battery at 64%.

So there is something significant staying on, maybe a pump? I don't know what it is, but once in a while something stays on. Its not the headlights (they shut them selves off), not leaving in acc mode (again it shuts itself off), but something that fails to switch off when the car shuts off.

My only thought is to check the load on the battery every time to see what if it is staying on. I believe it is a random thing that sometimes it stays on and sometimes not and power cycling the car to drive mode would likely fix it. Its not a bad 12v battery, it wouldn't have taken more than 4 hours at 5 amps to top it back up if that were the case. I used to think it was the car undercharging the 12v battery, but 95% of the time when I put the chargers on it is "full" in 20 minutes and the fact it took over 30 amps to "fill" the battery back up. I am familiar with dying and dead 12v lead acid batterys and this isn't behaving like them.
 
I would recommend getting a logger to properly measure the usage and chart how the battery is being charged and discharged: http://amzn.com/B003DS0BS2" onclick="window.open(this.href);return false;
 
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