I have too recently fitted a 12V Bluetooth monitor, probably the same as BatteryLife, since the app looks the same.
Rather than play with the 12 battery terminals, I found a more convenient and easily accessible place to fit it.
Under the +12V cover, mine had a spare terminal which I used for +12. For the –ve, I used the nearby headlight mounting point.
Yes, I tested it before fitting, both seemed like a reliable source for the 12V and less risk of disconnecting the battery inadvertently.
Why is there a plastic bag stuffed in here? (Red Arrow)
Now the interesting bits…
During a home charge, the 12V is charged as well, monitor showing approx. 14.9V. Nothing new here. We all know both batteries get charged.
When HV finished charging, monitor shows 12.7V. I was hoping it would be higher, but that is what it is for mine.
I left the granny charger plugged in overnight to see if there was any ill effects. I can only say there was no significant 12V battery drain. Next day 12.69V.
The key fob proximity does affect the car! As I approach the car, the fob starts to blink, I guess forever (well at least 5 minutes). At this time the battery voltage drops to 12.1V. My take is that the car awakes and obviously draining the 12V somewhat. Unfortunately I don’t have a clamp meter to see how much current was being drawn. But I suspect it is not a trivial amount.
I hung around for another 5 mins and key fob still flashing and battery monitor still at 12.1V. Could this be the infamous battery drain? The key fob being too near the car???
I moved away until the fob led stopped flashing. About 3 minutes later the 12V started to creep back to 12.6V. Car must have gone back to sleep.
I repeated this, but put the fob into a metal biscuit tin, but near the car. Same effect; well, we know a metal tin cuts off the signal.
As already stated, the mains was still plugged in, but finished charging, so the charge port light was off.
I used the App to initiate preheating. The charge port light came on (green) and I could hear some fans coming on. The house meter was showing a draw of 3KW. Good, it was preheating from the mains and not the HV battery. The battery monitor showed it was charging at a measly 12.9V, if one could call it charging.
I gave it 5 mins and unlocked the car. BTW, mine is setup to unlock when I touch the door handle, not as I approach.
When it unlocked, the 12V battery was still charging at 12.9V. However when I sat down, the charging voltage jumped to 14.9V. Yay, it was charging properly. The fans were still belting out due to preheat. So I turned them off.
I sat in the car for 15 mins playing with the menus to see if I could fathom the headlight setting (to set it so we drive on the left)… For another episode.
To summarise:
Having the key fob too near the car, keeps the car awake and probably drains the key fob as well.
I suspect my battery is on the verge of dying. 12.6V locked and key fob far away is not high enough in my books.
A 15 minute charge/drive per day is not really enough to keep the 12V battery from dying since I lost 0.1V in this one off experiment and the 15min charge was not enough to replenish the 12V drain.
