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TexasTeslaRacing
Member
Most on this site will recommend daily charging between 80%-90%. I personally always charge to 90%. Using a 72A won’t hurt your battery.
Canuck
Well-Known Member
Charging level and charging amps are two completely different things.
72 amp charging won't harm the batteries at all. If anything, it could harm the onboard charger but I wouldn't be too concerned about that. The old 40 amps ones are known to sometimes fail, so some people like me with dual 40 amp chargers and a HPWC charge at 42 amps so each charger only only uses 21 amps, and then dial it up when faster charging is needed. The chargers are liquid cooled so the theory is lower temps will lead to less chance of a failure. You can dial back the 72 amps if that's a concern too, and if you don't need any faster of a charge.
When it comes to the battery charging level, science tells us that the higher the charge, the faster the degradation so I would not recommend charging to 90% daily unless you need that much for range each day, which seems unlikely for most people. There's a reason for a daily driving "range slider" and that 90% is at the very top end of that range. That's because the science tells us it's best to cycle the battery around 50% for longevity. If you don't care about degradation, then there's no concern, since it likely won't be that much of a loss in the long run anyway but I like to strive for longevity myself.
It's not for battery wear... it's about keeping them open for travelers which is the purpose of superchargers. Never be concerned about supercharging harming the battery. You will hear the compressor rev up to keep the batteries cool and that takes care of the worst degradation part of fast charging -- heat. I supercharge a lot going to and from my cabin many weekends. My car has lost very little range over nearly 4 years now but I rarely keep it at a high state of charge (I use the mid daily driving range) and when I do charge higher I drive it right away. Here's my latest readings, which show most degradation right after new, as normal, then it really slowed down...
431 km new
424 km at 4,700km
412 km Aug 2017 approx 76k km
But I think we need a lot longer to see how lower charging will play out vs. charging higher.
There are lots of variables involved with battery degradation and @Canuck touched upon the big ones.
In current Lithium Ion batteries, degradation occurs when Lithium ions are converted into a metallic form (Lithium Plating) around the anode instead of being transferring as current into the anode. Lots of things can cause this, like temperature, SOC, time, etc. If you can keep the temperature within a narrow band during charging/discharging, avoid charging with a high SOC and minimize the charging/discharging time, you can minimize the Lithium Plating.
Tesla's BMS (Battery Management System) takes care of all that for you, so you really don't need to do much (eg. slows charging when battery is cold, cools battery when it's hot, limits regen when battery is cold, etc.). Of course, you can try to change your usage patterns to make it easier for the BMS, which probably helps.
Since 72A is significantly less than 300+A at a supercharger, don't worry about charging at 72A. If the temperature is hot in your garage, the cooling system will kick-in and/or the BMS will reduce the charging amps as necessary. Some have suggested that since supercharging is so quick, it may actually be better for the battery (reducing the time that Lithium Plating can occur), but I have never seen any scientific study to back this up.
In current Lithium Ion batteries, degradation occurs when Lithium ions are converted into a metallic form (Lithium Plating) around the anode instead of being transferring as current into the anode. Lots of things can cause this, like temperature, SOC, time, etc. If you can keep the temperature within a narrow band during charging/discharging, avoid charging with a high SOC and minimize the charging/discharging time, you can minimize the Lithium Plating.
Tesla's BMS (Battery Management System) takes care of all that for you, so you really don't need to do much (eg. slows charging when battery is cold, cools battery when it's hot, limits regen when battery is cold, etc.). Of course, you can try to change your usage patterns to make it easier for the BMS, which probably helps.
Since 72A is significantly less than 300+A at a supercharger, don't worry about charging at 72A. If the temperature is hot in your garage, the cooling system will kick-in and/or the BMS will reduce the charging amps as necessary. Some have suggested that since supercharging is so quick, it may actually be better for the battery (reducing the time that Lithium Plating can occur), but I have never seen any scientific study to back this up.
From the battery's perspective, that is already very very low rate charging, so it will not care. 240V times 72A is only 17kW. Remember that at a Supercharger, it can be up to about 100kW, so 17 is hardly anything to it.
The other thing which might matter a little is what @Canuck mentioned. I don't like to run my charging equipment like a UMC or wall connector at its maximum amp rating all the time for daily use, because that does get a little hot, and heat is a bit hard on electronics and can shorten its life a bit. I use the UMC at home, and I have it set for about 31 or 32A instead of 40 to keep it a little cooler.
Canuck
Well-Known Member
I was actually referring to the onboard charger(s) inside the vehicle and not the UMC or HPWC, which are not technically "chargers" but EVSEs (Electric Vehicle Supply Equipment). But I agree that dialling down the amps is good for them too.
pers1
Member
I only charge to 70% to preserve the health of my battery pack.
Here is a chart from Jeff Dahn
Jeff Dahn - Wikipedia
Jeff Dahn - Wikipedia
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Yeah, I did see that's what you were talking about, but I was referring to the broader principle of not running something at its maximum rating every day.
