12V surprise

I too have a 2018 Prime albeit an Advanced trim. Early on I let the 12v drain due to not driving it for 10 days. After searching the threads here I found this is a common issue with cars these days that have Telematics systems. I invested in a battery tender and a BM2 Bluetooth battery monitor. This eventually told me the deep discharge that one time did damage the battery and it never held a charge for more than 7 days before I needed to recharge it via the tender. I replaced the battery 10 weeks ago and the BM2 stats show how much better the new battery holds a charge. I did not loose any settings/presets during the battery install as far as I can tell which was done at my dealership.

 

Yes, if you want to listen to the radio, put the car in ready

 

The batteries in these cars don't last that many years it seems. I used a 9v powered battery memory retainer to keep all the car settings when I replaced my battery. Worked great.


iPhone ? Pro

 

there's a pretty big drain on them when they are off, and charging while in ready does not seem adequate

 

For how long? Best to leave the car fully on (aka Ready) when doing this.

Batteries age. How regular is your use of the vehicle? Infrequent short trips are worst for batteries. Do you frequently sit and listen to radio?

Look up memory savers: you connect before disconnecting the 12 volt for the swap, they supply sufficient juice to avoid memories getting lost.

 

So if I want to swap out my wife's 12-volt in her Prius I can use the memory saver and don't need to visit the dealer for any reprogramming stuff??

 

Yeah they should have something like that.

I’ve found when intentionally disconnecting (say for brake work), it’s no big deal: the clock, trip meters, radio presets. Window auto up/down “may” get screwed up; in my experience it was ok.

I use a jump pack with a special memory saver cord: has cig lighter plug at jump pack end, and OBD plug with just the 12 volt pin at other end. And indicator light to confirm connection.

 

It takes some getting used to with hybrids to realize that there is no point in turning off the car for a short time if someone is still going to be in the car, and they could be using things like the radio or A/C. When we have have a quick grocery trip, I will often run into the store leaving the car "ready" with my wife in the car, mainly for the A/C. Old habits from gasoline engine days die hard.

 

There may be a short circuit or a factory defect! I usually changed the 12 volt battery and that's it! Unforeseen circumstances can always be!