car went dead without warning. apparently the 9v battery was bad but didn’t get any warning light. had to be towed. bmw service mgr said that car needs to be driven on gas engine more often. I use the car mostly on electric for local errands and bought a plug in hybrid for that reason. Has anyone else had this problem? and be told they need to use the gas engine more often?
Your alternator charges your battery while the engine is running. your regenerative braking technology, which allows the vehicle to recoup part of its energy during deceleration and braking will not be enough to keep the battery fully charged.
Regen braking won’t recharge the starter battery at all, only the hybrid batteries. They are different.
If you want the 12 volt (not 9v, this isn’t a transistor radio!) to recharge you do need to drive it on the gas engine more. In my personal opinion, this is a flaw in the BMW design. Either live with it or trade it for another brand of hybrid.
Seems odd for the charging circuitry function to not charge the 12 volt battery at the same time the hybrid battery is being charged in a plug-in-charge mode. Or at least for the car’s circuitry to monitor the 12 volt battery charge and fire up the gasoline engine as needed; but maybe not that big of a deal. OP, how cumbersome is it for you to diddle w/the controls to cause the gasoline engine to run?
That’s why I said it was a flaw.
Stories like this make me reluctant to buy any hybrid except for Toyota/Lexus. And I’m in the market, there are several I’d consider otherwise.
If you’d prefer the BMW otherwise, worse case you could just charge the 12 volt battery with a shop battery charger once in a while.
That is pretty weird lol.
All your accessories should be running on the 9v battery, not the hybrid battery. So it should be charging while driving.
The Prius charges the 12V battery from the traction motor battery. It always stays topped off. If that goes bad I assume it charges it while the engine is running like any normal car.
If the BMW won’t charge the 12V battery off of the traction motor battery and it never gets charged when driving in EV mode or when plugged in without the engine running that’s rather insane. Better get a roof mounted solar panel or add some kind of Voltage converter to charge it off of the traction motor power then. I have a hard time believing that this is really the case. More likely your battery is just old or defective.
Driving in EV mode does not discharge the auxiliary battery. The headlights and radiator fan operate on 12 volts, the auxiliary battery charge is maintained by the inverter/converter assembly via power from the high voltage battery.
Service writers tell everyone to drive more, two dozen batteries are replaced at the dealer every day and the office staff doesn’t know why each one failed.
It is likely the 12 volt battery failed, if it was simply discharged the dealer is required to recharge the battery. The manufacture does not pay dealers to replace good, rechargeable batteries.
That is why Toyota/Lexus plug-in hybrids do charge the 12V battery at the same time as the traction battery is charged.
Take your BMW out for a minimum 20 minute drive once a week. That should keep your 12V battery charged. You can switch stores to one that is about a half hour away for that one longer drive. It’s worth it considering the expense to replace a BMW 12V battery.
A long term option is to buy a full EV and then you won’t have to worry about longer drives. I have a 2023 Tesla Model 3 standard range and I like it a lot. If you want a BMW they sell several models, the iX SUV and the i4, i5, and i7 sedans.
Because of the way that a new battery has to be electronically “registered” to a BMW, it’s unlikely that places like Autozone or Advance Auto would be up to the task.
Or, if he prefers a plug-in hybrid–as I do–he could trade-in his BMW on a Toyota or Lexus PHEV, which recharge the 12V battery along with the traction battery when they are plugged-in for recharging.
But, to return to the issue of “driving more” via the gas engine, that’s not completely invalid advice. Even though I do most of my driving in EV mode, I do occasionally use the gas engine in order to use-up some of the gas. I could probably go a bit longer, but I try to refill my tank once every 2 months or so, in order for the gas to not “go bad”.
IIRC some hybrids monitor ICE use and switch to gasoline power to avoid overaged gas.
I think I recall reading that. I don’t know whether it applies to my vehicle, but if it does, I suspect that my usage would preclude that type of algorithm from automatically switching it to the gas engine.
My Tesla Model 3 Long Range warned me after about 3 years that the 12 volt battery was going to need replacing and to set up a service appointment. I sent in a request for service and said I was worried about getting stuck and they replied not to worry, I had plenty of time. The “ranger” came to my house about 10 days later, with me using the car up to then, and put in a new battery under warranty.
My Subaru Ascent, which I liked, just died while at home in the winter, leaving us stuck. It did this twice. I prefer the Tesla way with a very adequate warning.
Car manufactures (gasoline, diesel, or otherwise) could include that same function without much difficulty, but for some reason choose not to. It’s always been a puzzle to me why they don’t, given that owners are very annoyed when the engine won’t crank in the middle of a supermarket parking lot. Every time the engine is cranked they could do a battery load test for example to track the battery’s condition.
Alternator? Why would this car have an alternator?
Sounds like a good idea!