*every* car drains the 12v battery when in ACCESSORY mode, the first click on turning the key in a car was invented for ICE cars to use a small accessory like radio while sitting in the car and not needing to run the big noisy engine, assuming you take car not to run the aux battery dry or get stuck with a dead car. There are a few EVs that can be smart about monitoring the aux battery and recharging from the pack. AFAIK the Leaf is designed to not be smart, it has a fixed timer that was reduced in later versions when drivers complained that the 12v battery could die before the next time the car woke up. The infuriating thing is that the Leaf does have all the sensors to be smart, it was simply not implemented. Also the 12v charge algorithm pretty much guarantees that with an older 12v battery you will always have problems. To compare: Prius C my wife loves, I just replaced its 2/2019 battery. Almost 7 years. My Leaf of the same year, I have already gone through 2 of the same batteries that I had in the Prius and after struggling to keep the last one alive a little longer, even installing a cut off switch to reduce idle current to just the few milliAmps that the switch receiver draws, I finally broke down, ordered a Lithium battery with BMS and disconnected the Leaf current sensor on the ground terminal. With it not connected, the Leaf always reports a large current and keeps the voltage at 14V. The problem with old Lead Acid is that they charge slow due to hogh knternal impedance. The Leaf monitors Aux battery current, when it drops under 10A it incorrectly assumes the battery is full and drops voltage to 13V, preventing any further charging, so you are always driving around with an almost depleted Aux battery due to tge Leaf algorithm, as soon as your battery ages a little Confession: I am frugal, I prefer to not spend $250 on a 800 Amp cranking battery when I only need 5 Amps, so I have a $45 Garden tractor size U1 battery in all my EVs, and in the Prius C. Due to its smaller size, the Leaf never charges that battery correctly as I found out after 2 dying early. The Prius C does it right and it keeps it running for 7 years... YMMV Cor.
On Thu, Nov 13, 2025, 1:59 PM (-Phil-) via EV <[email protected]> wrote: > It definitely will. Some EVs will detect a low 12v battery (such as > Tesla) and close the contactors to recharge it, but most EVs only close the > HV system online when you are in "ready" mode. You can simply listen for > the "Clunk CLUNK" sound the contactors make when they turn on. Until that > happens, the HV battery is offline. > > On Thu, Nov 13, 2025 at 12:49 PM <[email protected]> wrote: > > > On 2025-11-13 9:50 am, (-Phil-) wrote: > > > The Leaf has to be "Ready to drive" (Contactors closed) before it > > > will begin supporting the 12v battery. The Leaf also senses the 12v > > > battery current on the negative terminal, so do not hook an inverter > > > ground directly to the 12v battery, only hook to the nearest chassis > > > point. This is needed to keep the 12v charge algorithm working > > > correctly. > > > > I see the sensor now and the chassis ground below the battery. > > > > so in assc mode like when radio playing it could draining the 12 volt > > dead if left on tolong? > > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20251113/b08609fe/attachment.htm > > > _______________________________________________ > Address messages to [email protected] > No other addresses in TO and CC fields > HELP: http://www.evdl.org/help/ > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20251113/c82105bc/attachment.htm> _______________________________________________ Address messages to [email protected] No other addresses in TO and CC fields HELP: http://www.evdl.org/help/
