Model 3 Battery charging every hour for about 2 mins at a time - has anyone figured out why?

[swamibob]

I did some searches and I see that in March a lot of people reported seeing their Tesla charge approx every hour for about 2 mins also.

Did anyone figure out for sure why it was going on? I see some people think it has to do with sentry mode. I never saw this until the latest firmware update, but until now I haven't been using sentry mode either. Or did they decide to do this with sentry mode just to keep the battery from taking any vampire drain when sentry mode is turned on and the car is plugged in?

 

[Terraplane]

I’m getting that as well. I also didn’t notice it until most recent update.

 

[El0n]

I have this exact same thing happening to me. I was under the assumption that when the car is plugged in, all electrons that the car would require come from the wall unit and not the battery itself. This perhaps does not seem to be the case anymore?

 

[srs5694]

I'm not 100% positive, but I think that the car will begin a charge if the car is awake and it notices that the current SoC is below its set level by more than some fixed amount. This is likely to happen on a regular basis if there's something that keeps the car awake; being awake drains the battery at a rate of about 1 mile of charge per hour of wakefulness. Sentry Mode will do the trick, but so will other things. If it's only begun to happen recently, check your Smart Summon settings (if you have that feature). There's a new option for this to keep the car awake to speed up responsiveness to Smart Summon requests. If this setting is active, it'll drain a lot of battery power and, if I'm not mistaken, keep the car awake, so I'd expect it to have a similar effect to Sentry Mode. There are other things that could have this effect, too, like if you frequently check the car's status via the Tesla app. I've noticed recently that my car will tend to charge completely, then do one more brief burst of charging a couple of hours later, then go to sleep. I suspect, but am not certain, that this is because temperatures are dropping here in New England, so the car is drawing some power to keep the battery warm shortly before it goes to sleep. (Whether this is deliberate before sleep or it's just a coincidence that it happens just before the car goes to sleep I can't say; in fact, my whole story on this is speculative.)

 

[SSedan]

Is it topping up the 12volt or actually charging the main pack?

 

[Tam]

...charge approx every hour for about 2 mins also...

I noticed that since when I first brought home my Model 3 over 1.5 years ago so this is not new nor this is due to Sentry Mode because Sentry Mode feature was not introduced until this year, 2019.

Your car does drain power even when it's parked and it's called "vampire drain".

My guess is instead of waiting for a deeper discharge such as 3% or more, it would prefer to keep the discharge shallower like 90% and recharge back to 90% rather than wait until 89% or lower and recharge back to 90%.

That's because there's no battery longevity benefit in waiting for a deeper discharge before recharging.

Here's the same scenario in 2018 prior to Sentry Mode in 2019. I set at 60% and it kept recharging from the level of 60% to 60%:

Is it topping up the 12volt or actually charging the main pack?

Vampire drain drains the 12V battery and not directly the main battery itself.

But when the main battery recharges the 12V, that in turn would drain the main battery itself.

The principle is still the same, should the main battery wait for the 12V to discharge deeper before recharging it?

In Model 3, the answer is if it can prevent a deeper discharge from both 12V and the main battery, then it would do it!

You can force a deeper discharge by:

1) set a schedule mode: the trickle charging seems to stop after approximately 6 hours (I don't have an exact time) and wait for the next schedule time which allows the batteries to discharge deeper without a trickle charge.

2) unplug your car.