I’ve never seen my phone drop and come back up. Are you sure you’re observing that 1% drop because power is being pulled from the battery or is it because a lithium ion battery at 100% discharges itself and a trickle charge is applied by the charger to bring it back to full? Or because modern battery gauges aren’t displaying accurate numbers to account for human behavior and expectations.
I get really mixed opinions about phones when I try to research this and exactly what they’re doing. What I will say is I know there are some devices that operate this way such as my old dell laptop since I could take the battery out while it’s charging without interrupting a YouTube video. (Or put it back in for that matter).
I can’t say I’ve ever seen a charger in any electronic device ever fail nor personally heard of anyone I know having one that failed.
definitely have had lithium ion batteries wear down to a useless max SoC or completely fail altogether.
I’m not convinced this should be that difficult.
I mean, they clearly aren't displaying accurate numbers. I had a phone that displayed "Fully Charged" with no percent until you unplugged, and sometimes it would be 98% right after unplugging. This could be inaccuracy or intentionally hiding the fact the charge behaviour actually does let it drop.
I've also seen videos with USB voltage/ammeter devices monitoring the charge, though on Android phones. By all measurements, these devices
effectively disconnected from USB power after being fully charged (implying that it neither was subsisting off USB power nor keeping the charger active on the battery). Therefore, these absolutely are using the top-up cycles after letting the SoC drop a small amount (which may be small enough to evade perception via the coarse percentage numbers we see).
Laptops are a bit different as you noted. Some (not all) can work off of the charger connection without the battery. Further, some more powerful laptops
need to use both battery power and adapter power because neither is sufficient to cover the power draw at maximum load. The Tesla is unlike a laptop in both regards here. The HV battery can provide way more power than the wall ever could, and it's not designed to function normally without the HV battery.
It's not that it's necessarily difficult to do the way you're thinking, it just has implications that aren't desirable. Keeping voltage applied to Li-ion batteries isn't good (mostly for 100% charge), which is why chargers don't do this and instead do top-up cycles. If you find a charger that keeps voltage applied after a full charge, this 1) is dangerous and 2) basically doesn't exist, even in cheap/sketchy devices (the chips to manage this are dirt cheap and produced in high volumes).
I leave my car parked for days at a time in a parking deck at the airport. Always with Sentry on. My car never loses more than 1-3% of charge per day*. Doing some table napkin math, that would be less than 100W per hour (Prob somewhere between 70-95W on average).
Where is this 300W number coming from? If it was really 300W I’d be losing ~10% per day.
*This measurement, of course, includes all draw on the battery (not just sentry mode).
300W comes from multiple ways to calculate it that agree with each other. It seems to range between 250W-350W. Measuring changes in SoC is certainly one way, and is pretty accurate when compared with a known kWh value for the pack (which can be easily determined by the reported range, if nothing else). Data off the CAN bus, e.g. via ScanMyTesla, is another way to determine this.
If I assume you have an LR, 2%/day (24h period) is closer to 60W. 60W is about the average it uses when
not in Sentry mode. Either something is being calculated wrong or you don't actually have Sentry on somehow (or yours is magically more efficient than pretty much everyone else on this forum).
Not sure where you get your "facts" from but many of the things you're saying are completely untrue.
If the car is plugged in, it pulls from the outlet. Only if electrical needs exceed what the outlet provides then it uses the battery.
They come from many ways that corroborate each other. Here's a simple way to tell without any other hardware or software:
- Plug in your car with the UMC. Wait until charge is done. The screen should indicate it's not internally connected and charging by displaying something like "0/32A" and 1-3V. The low voltage is especially indicative that the onboard charger is not active, and is our first evidence that being plugged in does not necessarily mean it is charging or having power provided from the wall.
- Stand by the UMC and turn on Sentry Mode. If this causes it to start charging, you'll hear a click from the UMC. Sometimes it will, sometimes it won't. In my experience, most times it won't. If you stay there for a while, it will eventually click and start charging (and at this point, you should be able to see that on the app as well probably) because the SoC has dropped enough that it will top up the charge. It will eventually click off again as well.
- Turn on the climate control to a setting that will draw a lot of power (very cold or very hot). You should definitely hear it click now, because it will activate the charger in this case.
Other ways you can monitor this (and far more accurately):
- Power monitoring device like a Kill A Watt. When it's only drawing a few watts, the car isn't actually using it (this is just the "sleep" power of the UMC itself).
- Monitoring powers via CAN bus, with apps like ScanMyTesla.
I have done all of the above, and they all paint the same picture I previously posted.
That is where I get my
facts from. My car could behave different from all others, but this is unlikely (and many on these forums have confirmed the same behaviours).
Tesla literally says to keep your car plugged in 24/7 if being stored for an extended period of time and that "A plugged in Tesla is a happy Tesla."
There is an important difference between being
plugged in and the car
charging. The car can be plugged in without charging, and this is actually the most common state if you keep it plugged in 24/7.
