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SeaGeo

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Was chatting with CS and suggested some more advanced A/C charging scheduling logic than is what's in my ID.4 and I received an interesting piece of info I don't think I had seen before. CS said the following:

"It's worth mentioning that on the Rivian, you won't have to worry about not charging up the vehicle all the way in order to preserve battery health. Our Battery Management System is going to be one of the best on the market, and will be able to learn how/when you drive in order to optimize performance and longevity so you don't have to worry about it at all!"

Which creates a whole host of questions that I now have. None of which I felt were appropriate to ask general CS ahead of official communication from Rivian on the topic. Just thought people would find this interesting here.
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skyote

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I'm sure the BMS will be great, but I don't plan on fully charging or discharging unless J absolutely have to!
 
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SeaGeo

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I'm sure the BMS will be great, but I don't plan on fully charging or discharging unless J absolutely have to!
Same. For some added background, my suggestion was prompted by me charging my ID.4 to 70% routinely, and then charging to 100% overnight this weekend and reducing the charging speed so it wasn't sitting at 100% for very long. The response makes me wonder if we'll even have the option to charge to <100% through software routinely, or if they want to entirely rely on the BMS for that. Which is what results in a whole bunch of questions on my end.
 

electruck

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Will be interesting to see how well the BMS "figures out" my charging needs as we don't have a "routine" per se. I've generally not obtained good results from thermostats and other "smart" devices trying to auto-schedule based on observed behavior.
 

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This aligns with guidance from Ford that advertises its 15-100% AC charge times and makes no mention of limiting the charge to prevent damage or wear to the battery pack. I think that as EVs go mainstream, manufacturers will be seeking to make the transition as easy as possible by eliminating the nuances and "gotchas" that EV owners have become accustomed to. Whether it's never charging to 100% or avoiding DC charging when possible, I think it's only a matter of time before we see manufacturers seeking flat DC charging curves to 100% above higher peak outputs.
 

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SeaGeo

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This aligns with guidance from Ford that advertises its 15-100% AC charge times and makes no mention of limiting the charge to prevent damage or wear to the battery pack. I think that as EVs go mainstream, manufacturers will be seeking to make the transition as easy as possible by eliminating the nuances and "gotchas" that EV owners have become accustomed to. Whether it's never charging to 100% or avoiding DC charging when possible, I think it's only a matter of time before we see manufacturers seeking flat DC charging curves to 100% above higher peak outputs.
I think that's because Ford stuck a fat buffer in the Mach E. VW has a smaller buffer, and recommends only charging to 80%, but then allows the user to go up to "100%" (which really still has a buffer) at their discretion.

Ford also completely borked DC charging above 80% to try and protect the battery. Which makes the Mach e really difficult to road trip with when you do need to access that upper 20%.
 

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I think that's because Ford stuck a fat buffer in the Mach E. VW has a smaller buffer, and recommends only charging to 80%, but then allows the user to go up to "100%" (which really still has a buffer) at their discretion.

Ford also completely borked DC charging above 80% to try and protect the battery. Which makes the Mach e really difficult to road trip with when you do need to access that upper 20%.
I was actually only looking at the F150 Lightning guidance for now. And yeah, there are no cars that really push the limit above 80% charge, but I think with the move to higher voltage packs and better BMS and cooling systems onboard, that may become a competitive advantage soon.
 

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Will be interesting to see how well the BMS "figures out" my charging needs as we don't have a "routine" per se. I've generally not obtained good results from thermostats and other "smart" devices trying to auto-schedule based on observed behavior.
100% the same with me. Throw in a hybrid/changing work schedule and different ideals of comfort from the missus, and our smart thermostat is just confused af.

Ford also completely borked DC charging above 80% to try and protect the battery. Which makes the Mach e really difficult to road trip with when you do need to access that upper 20%.
I wonder if this is because their assumption was that most people start road trips from a home base, where Level 2 (or under) will get you to 100% anyway. And, when you're on the road, from what I understand most vehicles suggest unplugging when you hit 80% because DC charging slows down drastically after that so you're better off driving to the next charger to save time.
 

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No more than 10 min ago I posed several questions to CS.

  • Using my Rivian home charger that I pre-ordered, can you set the charge to shut off at 80%, 90% and not go to the full 100%. I am looking to get the maximum battery life and only expect to charge to 100% the night before an extended trip. That is what I do with my two Alta electric dirt bikes.
  • Will the BMS balance the charge between cells before or after reaching 100% SOC?
I will relate their response when I get it.
 
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SeaGeo

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I was actually only looking at the F150 Lightning guidance for now. And yeah, there are no cars that really push the limit above 80% charge, but I think with the move to higher voltage packs and better BMS and cooling systems onboard, that may become a competitive advantage soon.
Will be interesting to see how well the BMS "figures out" my charging needs as we don't have a "routine" per se. I've generally not obtained good results from thermostats and other "smart" devices trying to auto-schedule based on observed behavior.


Another part of this that has me curious is that it sounds like the BMS will give and take usable capacity based on our behavior. I would love to know what that "good" behavior is that the BMS takes into account so that I can take care of the battery and have the AI BMS gods give me more usable capacity when it's needed (ie, the 2 times a year I want to drive a long distance in one shot without easy access to a charger).

It will be interesting to see how Rivian communicates this to us as I'm sure they will want to balance protecting their IP, while I hope they also want to provide us the tools to understand what the hell the thing is doing. The latter has me a bit concerned if they decide to go down the path of not sharing technical details with their users. Whenever I have a device "take care" of things for me without transparency, I always get annoyed by it, like @electruck's example
 

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They have got to let you set a charging limit and it would be nice if they let you set a charging speed too. Beyond that? Knows you leave the house at 0730 and sets start of charging so its at your desired SoC at that time each week day morning but allows different levels, rates and completion times for Sat and Sun?
 

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No more than 10 min ago I posed several questions to CS.

  • Using my Rivian home charger that I pre-ordered, can you set the charge to shut off at 80%, 90% and not go to the full 100%. I am looking to get the maximum battery life and only expect to charge to 100% the night before an extended trip. That is what I do with my two Alta electric dirt bikes.
  • Will the BMS balance the charge between cells before or after reaching 100% SOC?
I will relate their response when I get it.
Rivian could do something non-standard, but the J1772 spec doesn't actually have a way for the EVSE to know how much of a charge the vehicle has. It's up to the vehicle to stop at a specified level of charge.
 
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SeaGeo

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They have got to let you set a charging limit and it would be nice if they let you set a charging speed too. Beyond that? Knows you leave the house at 0730 and sets start of charging so its at your desired SoC at that time each week day morning but allows different levels, rates and completion times for Sat and Sun?
That's actually what my question was. I suggested a software feature to allow us to set a target charge % at a target time (ie 100% at 11 am tomorrow) so that the car can slow down or schedule charging as appropriate so it sits at 100% for the least amount of anticipated time as possible.
 

ajdelange

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Rivian could do something non-standard, but the J1772 spec doesn't actually have a way for the EVSE to know how much of a charge the vehicle has. It's up to the vehicle to stop at a specified level of charge.
The car is in control throughout. The charger tells it how much it can have and the car tells it how much to give or, rather, it tells the charger to increase or decrease voltage to deliver the current it wants.

[Edit]The crossed out bit is a lovely description of how DC charging works but we are talking A.C. charging here and so it isn't applicable at all.. AC EVSE is some safety, communications, status reporting circuitry and a contactor. It checks for proximity (that a car is there), that protective ground is present and that there is no earth leakage, tells the car how much power it can have and closes the contactor. The car then takes as much as it wants up to the limit.
 
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Another part of this that has me curious is that it sounds like the BMS will give and take usable capacity based on our behavior. I would love to know what that "good" behavior is that the BMS takes into account so that I can take care of the battery and have the AI BMS gods give me more usable capacity when it's needed (ie, the 2 times a year I want to drive a long distance in one shot without easy access to a charger).

It will be interesting to see how Rivian communicates this to us as I'm sure they will want to balance protecting their IP, while I hope they also want to provide us the tools to understand what the hell the thing is doing. The latter has me a bit concerned if they decide to go down the path of not sharing technical details with their users. Whenever I have a device "take care" of things for me without transparency, I always get annoyed by it, like @electruck's example
SeaGeo,

When we got back to the Engagement Center at the end of the first night's ride along with RJ, I asked him about the range results and whether the All-Terrain tires impacted it much. In discussing that topic, he stated very clearly that they will be able to monitor everyone's charging and battery use patterns. He said, when warranted, they can and will perform OTA updates to release a small percentage of extra range for those who deserve it. He also made it sound as though that may be done without notification.

Since the cost of replacing or repairing a battery is going to be a significant warranty expense for the company, I can appreciate that they will be very judicious in how and when they extend a vehicle's range. They certainly won't want to grant extra range to someone if they feel they're on the path to degrading their battery beyond the 70% of the original range, as stated in the warranty.

It's that same interest in limiting battery degradation and warranty expense that I expect will result in a Battery Management System that will do a pretty good job of protecting us from damaging the battery when charging at home. If that means an automatic 80 or 90% cut-off built into the system, with the ability to override it to a 100% occasionally, that would be great. I would assume those who might choose to charge to 100% every night night (if possible) would likely never see their range ever being extended, or "opened up".

I'm looking forward to finding out what you and AltaTruck get in the way of responses from Customer Service. I know with my plug-in hybrid, GM advises to just leave it plugged in 24 hours a day, and doing so over the last five years has not resulted in any noticeable degradation of range.
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