Hi all - I’m looking to buy my first ever EV soon (probably a Model Y, Polestar 2, or BMW i4) and have quick question. I’m often gone from home for a few weeks (sometimes months) at a time, and I currently keep a trickle charger on my 12V battery the whole time (it’s a “smart” CTEK charger that doesn’t overcharge the battery). That charger recently broke after many years of use, so I’m wondering whether there’s any need to replace it.
I know the answer may differ across EV models, but in general: if I leave the car in a garage for a few weeks it’s plugged into the main EV charger whole time, is there any need for a trickle charger?
Any quick thoughts would be greatly appreciated.
You must log in or register to comment.
Certain models (e.g. the ID.4 let you switch on an option that maintains the 12v from the main battery. You might even be abke to keep the car plugged in and start and stop charging sessions with your app. But at 80% charge, without any connections from the app, I’m sure the ID.4 can supply the main battery for months.
probably a Model Y, Polestar 2, or BMW i4
The Model Y has a Lithium 12V battery that is pretty integrated into the car and doesn’t need replacing. The car deals with it so you don’t have to do anything special. I would 100% plug any EV in that you are leaving that long and set the charge level to 50% or something like that.
16V actually.
Thanks to all for the helpful comments!
Unfortunate the top comment right now has a bunch of misinformation. The bottom line is that you don’t need a new trickle charger.
I had a CTEK MXS 5.0 and a Noco Genius 10. The CTEK got too warm when charging 12v batteries so i eventualy took it back. IMO it’s always good to have one of these handy just in case. 12v lead acid batteries don’t like to be discharged for long (even a few days) before damage occurs.
I know the Tesla and probably the Polestar will maintain the 12v automatically. Leave the car plugged in anyway.
Some of the legacy carmakers like Nissan and Chevy (on the bolt, etc) don’t have this and you might want to trickle the 12v. THey only charge the 12v when the key is turned to ACC, which is pretty lame.
I don’t know about the i4.
The Bolt does maintain the 12 V battery even without the car on. The exact criteria for how often it does it depends on the SoC of the propulsion batter and whether a charger is connected, but with SoC above 40%, and/or a charger connected (for the propulsion battery) you are all set.
And the bit about ACC is completely wrong for the Bolt. That setting on the Bolt is specifically to power the 12 V systems while locking the HV systems off. That means it will NOT maintain the battery.
Watch the shitty cable connector on those otherwise good CTEK chargers. You can cut them out and replace them with the ‘2 pin version of the trailer connector’. Make sure the hot pin is the female.
You should not need to worry about this. But, note that some EVs are less happy when doors are left ajar for longer than it takes to get in or out of the car. The best thing to do for EVs with conventional 12V batteries (not 2021+ Teslas) is to add a BM2 battery monitor (voltage logger) so you can check the behaviour and not do stuff that aggravates it.
Tesla: no there’s no need for a 12V trickle charger.
Feeding the 12V from the high voltage pack is well integrated
As many have said, you’re probably OK, but check your specific model to be sure.
My specific model, the 500e, is reportedly susceptible to 12V battery degradation; some model years really want the voltage to be close to 12V and as the battery ages and the voltage drops to 11.8 or 11.7 or lower, it can cause the car to stop working unexpectedly. Some owners report 12V batteries needing replacement every two years. So I bought a bluetooth battery monitor and attached it to the 12V, and now whenever I walk near my car or past the garage I get a notification on my phone that the voltage is still a-ok.