Current draw when off?

[stevempotter]

My accessory battery recently went dead after not driving the leaf for a couple weeks. It is a 2012, so it is probably time for a new battery. But it got me wondering:

WHAT DRAWS CURRENT WHILE THE CAR IS COMPLETELY OFF?
HOW MUCH CURRENT SHOULD I EXPECT TO BE DRAWN FROM THE ACCESSORY BATTERY WHILE IT IS OFF AND PARKED?

I measured it at about 0.5A which seems like WAY too much to me to run the various computer stuff, key sensors, alarm system, etc. in the background. What do you think? 500 mA is a fairly big load, about 7 Watts. No cabin lights are on, nothing on on the dash indicators. Do you think there is something wrong, or is a continual 500mA draw from the accessory (12V) battery perfectly normal? I read here how some of you routinely hook up battery top-up chargers to their 12V battery to overcome the Leaf's poor ACC charging routines, or an aging ACC battery's small capacity. But is this a bandaid for neglecting to fix something that is wrongly drawing the ACC battery down when the Leaf is completely off?

:?:
Thanks,
Steve

 

[Reddy]

The Leaf keeps in contact with the Nissan mothership via cellular for at least a week, so that's probably most of the draw. If you unhook the 12V battery, the main traction battery will stay pretty good for months, maybe losing 1-2%/mo. There are several threads on it. Here's just one:
http://mynissanleaf.com/viewtopic.php?f=30&t=14747&p=333143&hilit=vacation#p333143

 

[LeftieBiker]

If the car is plugged in but not charging, it will keep re-verifying the EVSE connection at regular, frequent intervals, and that is what usually kills the accessory battery in that scenario.

 

[cliff]

You did not say how long after turning the car off that the current was
measured. While the service manual gives some wait times, it might be
interesting to see how long it takes before some of the controllers shut off.

 

[keydiver]

The drain on the 12 volt battery is much less than 500 ma. It wouldn't last too long at that rate. If you were seeing 500ma, either a light was on somewhere, like the trunk, or one of the computers was still awake. If I recall, there is probably at least one of the body control computers that stays active for a few minutes after power off.

 

[stevempotter]

I measured the current for about a minute after the battery was reconnected through the multimeter, and the 500mA draw persisted after an initial couple amps that lasted a couple seconds. So perhaps I need to keep it connected for a while longer to see if the car goes into some sleep mode. Have any of you done that, and if so, how long does it take? I got a new battery today but am leaving it not hooked up while parked, until I learn that the car-off draw will not kill it, too.

 

[LeftieBiker]

Get a battery maintainer, like a 2 amp Diehard, or a Battery Tender or battery tender JR, and make an extension for the hardwire lead so you can run it through a small drilled hole inside the charge port compartment. With the quick connector inside the charge port compartment, it's easy to connect the maintainer when you charge that car. Once or twice a week is enough if you don't leave the car plugged in but not charging. If you do leave it plugged in, just leave the maintainer on the battery and the battery won't suffer. And no, it shouldn't have to be this way.

 

[cliff]

So perhaps I need to keep it connected for a while longer to see if the car goes into some sleep mode. Have any of you done that, and if so, how long does it take?

I have not done that, however the service manual says not to disconnect the
battery for the first 5 minutes after off, or multiple DTC's will occur, and should
wait at least a hour, suggesting that things are happening for at least the first
hour after off.

 

[BrockWI]

I used to see the same thing before I replaced my battery, every once in a while I would check the car and it would be pulling about 1/2 amp or more, WAY after the 30 minute mark. I never did figure out what the drain was or why, it was very inconsistent. I can say once I replaced the 12v battery the phantom drain and other 12v problems have gone away and the 12v is always fully charged now when I check.

 

[dhanson865]

Get a battery maintainer, like a 2 amp Diehard, or a Battery Tender or battery tender JR, and make an extension for the hardwire lead so you can run it through a small drilled hole inside the charge port compartment. With the quick connector inside the charge port compartment, it's easy to connect the maintainer when you charge that car. Once or twice a week is enough if you don't leave the car plugged in but not charging. If you do leave it plugged in, just leave the maintainer on the battery and the battery won't suffer. And no, it shouldn't have to be this way.

If you get a weaker 2 amp unit you won't be ready for the massive vampire drain on a Tesla Model S.

Better to get a CTEK 4.3 amp that will desulphate and have enough amps to keep up with any car you might get down the road that has higher vampire load.

I'm using a CTEK 3.3 amp on my Leaf and Prius 12v batteries but for the price difference going for a new one I'd grab the 4.3 amp now.

 

[Levenkay]

This is one of those "easy for ME to say.." kinds of issues where I hypocritically urge behavior that I'd be too lazy or risk-averse to do myself, but I'll go ahead anyway.

If the LEAF's 12V battery design is so inadequate that the batteries fail like popcorn, then (assuming they fail within their "free replacement" warranty period) the afflicted owners should be showing up for warranty replacement each and every time, rather than propping up the bad design with add-on equipment and depriving Nissan of much-needed and richly deserved feedback.

 

[BrockWI]

I agree. The problem is I took mine in twice and both times they said the battery checked fine and they said there are no known Nissan issues with the 12v battery. So I did give up trying and just got a new battery.

 

[keydiver]

I measured the current for about a minute after the battery was reconnected through the multimeter, and the 500mA draw persisted after an initial couple amps that lasted a couple seconds.

At that point, I would probably start pulling fuses to see which circuit is drawing too much.

 

[stevempotter]

Pull fuses to locate the amp hungry circuit: good idea. Thanks!

 

[GerryAZ]

It takes at least 15 minutes for the residual load to drop off after closing the doors. If the residual load does not drop down to 50 milliamperes or lower after an hour, you definitely have a problem. If the car is not plugged in and everything is working correctly, the DC-DC converter will turn on periodically to charge the 12-volt battery (every 5 days on 2011 and 2012 Leafs, not sure how frequently on newer cars). I have left both 2011 and 2015 Leafs parked at airport or office as long as 3 weeks with no issues except the one time I forgot to unplug the ELM unit from the OBDII port.

Gerry

 

[LeftieBiker]

If you get a weaker 2 amp unit you won't be ready for the massive vampire drain on a Tesla Model S.

I'll just have to take that risk. Two amps is plenty for the Leaf, and even my 0.75 amp Battery Tender Jr. is adequate almost all the time.

 

[stevempotter]

Thanks, Gerry, that was very helpful. I have now let the car sit all off, locked and unplugged, for 20 minutes with the ammeter in place and observed only 20-30mA draw so all is good now that I have a new 12V battery.

I too have left it at the airport for nearly a month over the years, and came back to a working Acc battery and only a few miles down on the traction battery, so it must have been periodically recharging as you said. And I guess every 5 days was not often enough for my aging 12V battery, especially since I probably had the OBDII BT dongle plugged in.

-Steve

 

[Aussie]

especially since I probably had the OBDII BT dongle plugged in.

-Steve

Can anyone quantify how much power the OBDII Wifi dongle consumes while the car is off. I know that I lose wifi connection to leafspy at this time so I had (maybe wrongly) assumed it no longer was consuming any power.

 

[arnis]

Very little. Less than 100mA. Touch it when it is running for an hour. If it is hot then maybe more than that.
Anyway few days does nothing to 12V battery.

Gen1 Leafs had problems with 12V charging - it was overcharging. Especially in hot weather.
One way to prolong life is to add distilled water. But that is temporary fix.
New Leaf has lower peak voltage when Leaf is on (or charging).

 

[GerryAZ]

Very little. Less than 100mA. Touch it when it is running for an hour. If it is hot then maybe more than that.
Anyway few days does nothing to 12V battery.

Gen1 Leafs had problems with 12V charging - it was overcharging. Especially in hot weather.
One way to prolong life is to add distilled water. But that is temporary fix.
New Leaf has lower peak voltage when Leaf is on (or charging).

I never measured the current draw of my Bluetooth OBDII interface, but I know from experience that 6 days is enough to completely drain the 12-volt battery. After topping-off the 12-volt battery a month after purchasing the 2011, I never needed to add water to it again. For my climate, charging and float voltage of 2011 was ideal. I am concerned that the 2015 float voltage is slightly lower, but the charging voltage stays at 14 volts longer after starting the car so the battery is still OK after one year.

Gerry