Is charging at very low power risky?

[FredDes]

Hello,

I have a Tesla (M3LR boosted) in France. I mainly charge it at home on a standard reinforced plug (230V AC, 13A max). In France, the Tesla app allows you to start charging from 5A, which is the minimum from the app.
By playing with Tesla's unofficial API, I can go below 5A (the 1-5A range is possible). I wonder if there's any risk for the batteries to charge below 5A? (I did note that the efficiency wasn't great, but that's not the point).

For context: I have solar panels that produce 2Kw Pmax and I try to charge my vehicle mainly with my photovoltaic surplus. This installation allows me to charge at 8A in optimal conditions, but most of the time it's lower than that and I'd still like to use this available energy to charge the battery (even if it's slow).

Thanks for your advice!
Fred

 

[ATPMSD]

Not sure you will get a definitive answer, especially as you are looking at doing something that will utilize an unofficial API. BTW, if the car is still under warranty I would not use an unofficial API to do what you suggest.

Tesla are very good at monitoring incoming power and in not allow bad things to happen. But what you propose is very inefficient, which you mentioned, but you should consider that everything wears out. When the car is charging the AC to DC converter is running, and so too will the battery heating / cooling system on an as needed basis. I seem to recall the car consumes about 230 wH when charging, so that is 1-amp (at 230v) lost just to run the car’s charging system.

 

[beatle]

I can't see it causing a problem.. I don't know what the lowest amperage you can set to charge at 120v in the US, but if it also allows 5A @ 120v, you should be able to do 2 or 3A @ 240v.

 

[FredDes]

Hello,
ATPMSD: Thanks for your feedback. I'm currently extracting some data about the efficiency at very low amperage (below 5A at 230V), based on the first data I got in the last few days it's between 100 to 200W lost. It seems the biggest part of this consumption is almost static (probably to keep the vehicle online), the rest is due to the AC/DC conversion.

beatle: thanks for your help. Can someone here confirm the minimum of 5A@120V in US (using the UMC) so that I can feel more confortable to start charging at 2 or 3A at 230V?

 

[bruce4000]

Hello,
ATPMSD: Thanks for your feedback. I'm currently extracting some data about the efficiency at very low amperage (below 5A at 230V), based on the first data I got in the last few days it's between 100 to 200W lost. It seems the biggest part of this consumption is almost static (probably to keep the vehicle online), the rest is due to the AC/DC conversion.

beatle: thanks for your help. Can someone here confirm the minimum of 5A@120V in US (using the UMC) so that I can feel more confortable to start charging at 2 or 3A at 230V?

The lowest the ap in the us is 5A.

 

[AAKEE]

Its not a risk and it will not caues any damage.
As the car is awake when charging it uses about 200-250W just being awake.
Using very low power means a high portion of the energy is not ending up in the battery.
1A /230V would probably just keep the car awake but there is nitinh left to charge the car.
Also I think about 1 kW is the lovest power battery heating I’ve seen. Below 1kW, the battery probably can not be heated so a too cood battery can not be charged.

The 5A minimum setting is probably not a coincidence.