Flashers for 2 Hrs Kills 12V Battery

[PianoAl]

Today I had the emergency flashers on for two hours on my 2016 Leaf. That apparently drained the 12V battery, since I couldn't open the car with the button. I got in with the physical key and used jumper cables to get things up and running.

Here are my questions:

1. Does this indicate that I should get a new 12V battery?

2. If this happens again, can I assume that I can just disconnect the jumper cables and drive away, confident that the 12V will be charged from the drive battery (or should I wait awhile)?

3. Please tell me under what conditions the drive battery will charge the 12V (while charging from the wall? While waiting to charge (timed)? In ready-to-drive mode? Accesories on mode?).

Thanks!

[DaveinOlyWA]

Why have flashers on with car off? This habit kills any 12 volt battery. But your "if it happens again" question has me confused. Why are you doing this?

[PianoAl]

Why have flashers on with car off? This habit kills any 12 volt battery. But your "if it happens again" question has me confused. Why are you doing this?

Thanks, Dave.

I had to park it on the street while my driveway was blocked. It's a narrow road, and I wanted the car to be visible in the fog.

[DaveinOlyWA]

Why have flashers on with car off? This habit kills any 12 volt battery. But your "if it happens again" question has me confused. Why are you doing this?

Thanks, Dave.

I had to park it on the street while my driveway was blocked. It's a narrow road, and I wanted the car to be visible in the fog.

Leave it running then. FYI; went to Katy Perry concert Tues night in Seattle. Didn't want to deal with traffic so parked at Tacoma Dome transit center and took train up and back. We had floor seats in row 10 but left Tacoma at 2:25 PM. (gates opened at 5:30) So anyway, we get back to car later its after midnight and realized I had left car on.

Not the recommended option but at least the door was locked.

[cwerdna]

3. Please tell me under what conditions the drive battery will charge the 12V ... In ready-to-drive mode?

If in READY (green car with arrows light) mode, yes.

[LeftieBiker]

As already mentioned, leave the car in Ready mode when using any accessories. If you want to keep doing it your way, you'll need a new AGM type battery with more capacity. The size is 51R.

[Nubo]

Today I had the emergency flashers on for two hours on my 2016 Leaf. That apparently drained the 12V battery, since I couldn't open the car with the button. I got in with the physical key and used jumper cables to get things up and running.

Here are my questions:

1. Does this indicate that I should get a new 12V battery?

Hard to say. The battery should be able to blink the lamps for 2 hours no problem, but the LEAF has the added complexity that the flashers are controlled by the brake control module, which is also consuming power, keeping the emergency braking capacitor bank charged, etc... I don't know what the actual consumption is, but I'd probably try to leave the car in READY mode if needing to flashers for an extended period (more than 30 min), to keep the 12V charging.

That being said, a conventional auto battery will suffer if it's run down to very low voltage. I'd say a load test is in order to determine its health. Places like Autozone can do this for you free of charge. Ideally get a load tester or battery analyzer to check the health periodically. You can then be proactive with replacement without guessing and wasting money by replacing on a hunch. ICE cars have built-in battery testers (starter becomes sluggish with weak battery) LEAF doesn't complain until battery drops below a threshold and then all manner of errors and weird behaviors can arise.

2. If this happens again, can I assume that I can just disconnect the jumper cables and drive away, confident that the 12V will be charged from the drive battery (or should I wait awhile)?

The DC-DC converter (what charges the 12V) can put out a lot of power (125+ amps). As long as the battery is not severely degraded, it should get a decent bulk charge in a fairly short period of time. So yes I'd say drive away as long as you can keep the car in READY mode for 20 minutes or more and get to a secure destination before turning off. Top-off should happen when you next charge the car. Of course the best way to make sure is to put the battery on a dedicated 12V charger and take it to full charge. Once charged, do the load test.

3. Please tell me under what conditions the drive battery will charge the 12V (while charging from the wall? While waiting to charge (timed)? In ready-to-drive mode? Accesories on mode?).

Whenever the main (400V) battery contactors are closed. Basically that's when charging and when the car is in Ready mode. Not when waiting for timer. Also the vehicle will top off the 12V periodically if the car is idle for an extended period (once very 5 days or so iirc). On earlier models this feature was inexplicably disabled if plugged-in. Not sure if that applies to later models.

[PianoAl]

Thanks, guys. I think I'll have the batter load tested, and if it's not up to snuff, I'll replace it.

Please recommend the best battery under $200 (exact model).

[LeftieBiker]

Please recommend the best battery under $200 (exact model).

Any AGM type battery you find on sale should work. Some are better than others, and some are not really true AGM, but anything labeled AGM in the 51R size should be adequate for a 2 hour accessory drain. The OEM battery is small and hasn't got a lot of capacity, plus it doesn't take well to repeated deep drains. Optima Yellow Top is recommended by many, although I don't know the current price. That one is, IIRC, a "hybrid" type battery with thicker plates, not a real AGM.

[Nubo]

Thanks, guys. I think I'll have the batter load tested, and if it's not up to snuff, I'll replace it.

Please recommend the best battery under $200 (exact model).

Don't know if it's "the best", but it's a pretty good AGM battery, it fits without any modification, and it's got a great warranty (4 years full free replacement). $146 at Pep Boys
https://www.pepboys.com/bosch-platinum- ... quantity=1