12V battery drained; car won't start!

[salyavin]

Do you have a trickle charger, you could charge the 12vol to full. Charging the car the normal way does not directly charge the 12v it does that in a somewhat wonkey way that usually works. Are you sure your 12v is still good?

[cje]

"Earlier I had seen a message saying external drain was occurring to battery but I ignored it"
Can you monitor the 12v battery current when car shut off?

[LeftieBiker]

Earlier I had seen a message saying external drain was occurring to battery but I ignored it

I'm not familiar with this message. Do you remember the exact wording?

[lebikerboy]

For some strange reason, lead acid batteries don't seem to do well when used in an E/V environment.
I've seen examples of premature failure(s) when used in Leafs, Teslas, smart cars etc. The best option
appears to be a lifepo4 battery and is what I plan on to replace the lead acid version on our 2019 Leaf in the next six months.

[LeftieBiker]

The best affordable option is an AGM 51R SLA battery.

[goldbrick]

There have certainly been 12V battery issues on some early Leaf years but that appears to be due to poor charging algorithms or maybe unanticipated use cases (lots of short trips, no highway driving). There is nothing technologically challenging about keeping a 12V lead acid battery healthy in an EV and while there have been problems, I'd say the majority of users never give it a thought and have no issues.

Probably the biggest difference between an ICE and an EV in this regard is that in an ICE, it's usually pretty obvious when the 12V battery is failing (trouble starting) while in an EV the first symptom is usually a total failure of the entire car with no remedy except a tow and a new battery. Some sort of early warning of 12V battery weakness would not be hard to implement in firmware and could solve this problem easily. We'll see who does it first.

[LeftieBiker]

It seems that Nissan has improved the 2018+ Leaf's ability to keep the 12 volt battery charged, but not by any means perfected it. I've mentioned before that I've seen my 2018's accessory battery at about 12.45 volts; well, we had my housemate's 2020 SV+ under a car cover for roughly three weeks, while the leaves fell. I fully charged the accessory battery before we covered it, but after uncovering it, said battery was at, IIRC, 12.17 volts. I was only able to have it on the maintainer for about 10 hours before she had to use it yesterday, so it will be interesting to see where it's at now, voltage-wise...

[LeftieBiker]

If you are wondering where the first post went, the OP came back and inserted a spam message into it. It and he are now history.

[Nubo]

If you are wondering where the first post went, the OP came back and inserted a spam message into it. It and he are now history.

That's why I'm often leery of responding to the one-post wonders.

[SageBrush]

There have certainly been 12V battery issues on some early Leaf years but that appears to be due to poor charging algorithms or maybe unanticipated use cases (lots of short trips, no highway driving). There is nothing technologically challenging about keeping a 12V lead acid battery healthy in an EV and while there have been problems, I'd say the majority of users never give it a thought and have no issues.

Probably the biggest difference between an ICE and an EV in this regard is that in an ICE, it's usually pretty obvious when the 12V battery is failing (trouble starting) while in an EV the first symptom is usually a total failure of the entire car with no remedy except a tow and a new battery. Some sort of early warning of 12V battery weakness would not be hard to implement in firmware and could solve this problem easily. We'll see who does it first.

My impression is that *EVs tend to pull more amps between charging episodes. The industry has responded by selling 'deep cycle' PbA 12 batteries for our market. 12v batteries for ICE cars are much more sensitive to loss of high load current (marketed as CCA, needed to turn over the ICE during a start.)

This is a trade-off: high CCA batteries degrade quickly when deep discharged.