Groups: Battery Management

When should I charge my Tesla?

Tesla recommends in the User’s Guide that you should plug your car in whenever you can, so its Battery Management System can keep the battery happy. This is the formal answer to the question, even if you don’t drive much. Put another way, A, B, C, Always Be Charging.

If you can’t plug in all the time (either due to no charging capability where you live or where you’re visiting), then charge when you can. It’s a good idea to charge if you’re approaching 20% state of charge, as that is when other features like Sentry Mode stop working.

There is no need to drain the battery and then charge it up to maintain health. Some have recommended draining the battery to below 10% and then charging to 100% to recalibrate Battery Management System so that the remaining charge percentage gets more accurately reset once every quarter or so, but there is no known direct evidence to support this. Doesn’t hurt to do it infrequently, though.

What should I set my charge limit to?

The official guidance from Tesla is to set your maximum charge somewhere in the ‘Daily’ range on the app and car (50-80%) unless you are going on a trip, where you can then go from 80-100%. Note that it is definitely bad for the (lithium ion) battery to let it sit at 100% for extended periods of time (or to frequently charge up to 100%), so if you are going on a trip, try to time the charging so that it finishes right before you leave. This helps with pre-heating the battery to make it more efficient and can also handily coincide with warming (or cooling) the cabin too.

Any Tesla that comes with an LFP (lithium ion phosphate) battery can actually be charged to 100% as that type of battery chemistry does not suffer from 100% charges. As of December 2021, these are pretty rare in this neck of the woods though.

Note that during peak times, select Superchargers will actually not let you charge above 80%, and the “idle time” charges will kick in once you reach 80%.

How come my range isn’t what it should be?

The key thing to remember about the displayed range remaining in your Tesla is, it is simply taking your battery charge and multiplying by the EPA estimate. Because other things affect how efficient your car is, the actual range left is most likely never going to be the same as the displayed range left. Cold weather, driving style, tire pressure, wind, elevation, extra weight in the car.. all of these affect how efficient your car is, thus causing deviations from EPA estimated range left vs. actual range left. Sometimes you can be more efficient too.

There will also be times, especially on Model 3 and Model Y vehicles, where the Battery Management System will become a bit out of sync. You can read a detailed technical explanation of why, and what to do to help resolve this, by clicking on this article or this one or this one.

As of the Tesla iOS and Android app version 4.11.2, you can actually get some diagnostics run to see if your battery needs service (per this link). Go to Service, Request Service, select Battery, then Range, then enter “loss of range” in the description. That prompts a self diagnostic.

Many people change their display to be percent battery left, not range (miles or kilometers) left, for precisely this reason. Note that the percent battery left is what’s probably not accurate, but this does hide the miles.