Effect of Frequent Stop/Start Charging

[Nikki's Dad]

I'm working on a software program to optimize the use of my solar array to charge my MS. In a nutshell, the software will only permit charging of the car if it is sunny outside. On party cloudy days, the charging might turn on and off several times over the course of the charging cycle. Any idea if frequent switching on and off of charging is detrimental to the battery?

 

[TexasEV]

There’s more than the battery to think about, there’s the whole charging circuitry and battery management system. It’s not designed to work that way.

 

[Blue Sensation]

I'm working on a software program to optimize the use of my solar array to charge my MS. In a nutshell, the software will only permit charging of the car if it is sunny outside. On party cloudy days, the charging might turn on and off several times over the course of the charging cycle. Any idea if frequent switching on and off of charging is detrimental to the battery?

I would say the very least your screwing up your onboard charger basically shorting it's life as well as other components.

 

[Nikki's Dad]

I checked with Tesla Service and they didn't think there would be a problem.

In my original post I failed to mention that the car charges via a Tesla wall charger and that the stopping and starting of the charging is handled through API calls. Also, the program has a hysteresis built into it so that stop/start commands are not given more frequently than 10 minutes apart.

 

[Blue Sensation]

I checked with Tesla Service and they didn't think there would be a problem.

In my original post I failed to mention that the car charges via a Tesla wall charger and that the stopping and starting of the charging is handled through API calls. Also, the program has a hysteresis built into it so that stop/start commands are not given more frequently than 10 minutes apart.

Great

 

[eschummer]

You're lucky you can charge during daylight hours. Many of us are away from home during the day (remember "work"?), and can only charge at night. I've been thinking about batteries to allow me to time shift the solar contribution so it's usable at night, but at current prices this doesn't seem like a cost effective solution yet.

 

[ucmndd]

I've been thinking about batteries to allow me to time shift the solar contribution so it's usable at night, but at current prices this doesn't seem like a cost effective solution yet.

Net metering and a time of use plan is quite effective at this even without batteries. With PGE and the EV-A rate plan I sell overproduction during the day to the grid at $0.52/kWh and buy it back at night to charge the car at $0.13/kWh.

 

[sorka]

I checked with Tesla Service and they didn't think there would be a problem.

In my original post I failed to mention that the car charges via a Tesla wall charger and that the stopping and starting of the charging is handled through API calls. Also, the program has a hysteresis built into it so that stop/start commands are not given more frequently than 10 minutes apart.

Oh and that's because Tesla the service centers are known for passing on accurate information

I don't think anyone is really going to know. In theory you could be shortening the life of the onboard charger. They already don't have the greatest track record. They do have some physical relays that energize that you can hear clicking away as it starts up. Those will at least wear faster.

But who's to say that having the power pulled externally and frequently while the connector is still plugged in doesn't.

1) Result in excess logging that shortens your MCU life due to emmc(2) wear?
2) Result in algorithmic changes in supercharger charging speed since the charge controller onboard still controls the rate of supercharging.

Not saying either of those are going to happen but I'm just throwing them out as possibilities among many others that haven't been considered.

Is your software going to control the physical power to the wall charger or are you talking about using the REST api to tell the car to charge or stop charging?

Also, isn't this more expensive and possibly even less socially responsible. The best use of your energy produced during the day is to put it on the grid so it can be used to offset demand and prevent power plants from suddenly coming online to support sudden demand which is very expensive and far more inefficient than the power factor loss your generated electricity will experience being transported long distances on the grid vs keeping it local to your property.

It will also cost you more for this reason because you're robbing yourself of the opportunity to sell high during peak and then buy back low during offpeak.

The more solar that comes online during the day and feeds the grid not only reduces the need to bring additional generating capacity online suddenly but also means less plants that have to sit idle at night generating energy from minimum idling costs.

 

[ucmndd]

Also, isn't this more expensive and possibly even less socially responsible. The best use of your energy produced during the day is to put it on the grid so it can be used to offset demand and prevent power plants from suddenly coming online to support sudden demand which is very expensive and far more inefficient than the power factor loss your generated electricity will experience being transported long distances on the grid vs keeping it local to your property.

It will also cost you more for this reason because you're robbing yourself of the opportunity to sell high during peak and then buy back low during offpeak.

While I completely agree with your points, it appears OP is in Georgia, where energy policies that we take for granted like net metering don’t exist. So it’s probably a matter of use it or lose it, or close to that.

I don’t think we’re talking massive wear and tear on the car, but it’s certainly non-zero between keeping the car awake all the time, cycling the charging circuitry, HV relays, etc. If I was considering something like this I’d probably design for like 20 or 30 minutes of hysteresis, not 10 or less. Particularly during winter months when it’s cold out.