Charging Habits

[lefkonj]

I have read all sorts of things about charging, what is good and bad about doing this or that but have a few questions:

1. I understand DC charging all the time isn't great for the battery, ok cool. But what about AC charging. Is it bad to AC charge it every couple of days?
2. When AC charging Rivian recommended 70% but sometimes we just need more than that, I assume it is fine to charge to 90 or 100% when necessary?
3. is it recommended to let the battery hit the 20-30% before charging or is it fine when using AC to just 'Top it off' when necessary?

This is our first EV so just wanted some clarity.

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[CommodoreAmiga]

I understand DC charging all the time isn't great for the battery, ok cool. But what about AC charging. Is it bad to AC charge it every couple of days?

No, it's not bad to Level 2 AC charge, as needed.

When AC charging Rivian recommended 70% but sometimes we just need more than that, I assume it is fine to charge to 90 or 100% when necessary?

I would avoid charging to 100% unless absolutely necessary. I haven't found a scenario where I need to do that, yet. I have charged to 85% a couple times, when it meant giving me a comfortable buffer to get to a charger or make my trip without a charging stop.

is it recommended to let the battery hit the 20-30% before charging or is it fine when using AC to just 'Top it off' when necessary?

I plug in every night.

 

[zipzag]

"Toping off" is only an issue with a cold battery in winter. Energy is used to heat, so there is overhead with each charging session. Fewer session means less overhead.

Of course charge what you need for the trip. If going > 90% its best to finish charging before you leave.

 

[EVnewb]

A Tesla tech told us to leave it our MY plugged in whenever it’s not being driven if possible. It will utilize the house power for BMS, cabin preconditioning, and such. The Rivian doesn’t do that though so not sure if it’s the same recommendation from Rivian. I imagine it won’t hurt it so we keep it plugged in all the time. And like CommodoreAmiga said, charging it to 70% unless you need the extra range is better for the batterys long term health. Not sure about draining it to 20-30% regularly before charging it though.

 

[TucsonST]

Whenever it's in my garage, it's plugged in and set to 70%. If I'm taking a trip, I'll set it to 100% the night before. I think the main thing to avoid is letting it sit on 100% for extended periods. If you charge it up to 100%, then burn it off as soon as possible.

 

[Aardvark]

"Toping off" is only an issue with a cold battery in winter. Energy is used to heat, so there is overhead with each charging session. Fewer session means less overhead.

Of course charge what you need for the trip. If going > 90% its best to finish charging before you leave.

A technique I've used on our EVs since 2012: in the winter, I plug in when needed upon arriving home from driving. The battery is warm.
In the summer, I let the car sit, and the battery cool down after driving before plugging in.
I don't have measurements to quantify the savings, but I know I'm spending less on energy which would otherwise go to battery conditioning.

 

[Taco]

In the winter our cars are plugged in (R1T / Model X) when at home but I tend to check at night before going to bed to ensure they are plugged in, also checking to make sure the kids didn't leave the damn garage door open.
During the summer we're a little more relaxed on the plugged in when at home. Sadly the Rivian currently does NOT use house power when plugged in to warm / cool etc, however the Tesla does. Hopefully this will change soon with the Rivian.

 

[Thedude]

Sadly the Rivian currently does NOT use house power when plugged in to warm / cool etc, however the Tesla does. Hopefully this will change soon with the Rivian.

If you’re plugged in this is kind of irrelevant. You tell the Rivian to precondition the cabin, it draws from the battery to do it and automatically starts charging again at the same time.

 

[lefkonj]

Great feedback folks. This is what I was looking for.

 

[Taco]

If you’re plugged in this is kind of irrelevant. You tell the Rivian to precondition the cabin, it draws from the battery to do it and automatically starts charging again at the same time.

Is this a change with the newest firmware? Under the '2022' code it did not unless you're in a time of day that you allowed charging.

 

[Thedude]

Is this a change with the newest firmware? Under the '2022' code it did not unless you're in a time of day that you allowed charging.

Mine has always done it but I’ve never setup a time of day or charge schedule. Might be the difference.

 

[zipzag]

A technique I've used on our EVs since 2012: in the winter, I plug in when needed upon arriving home from driving. The battery is warm.
In the summer, I let the car sit, and the battery cool down after driving before plugging in.
I don't have measurements to quantify the savings, but I know I'm spending less on energy which would otherwise go to battery conditioning.

Eventually pricing will need to encourage you to charge at the lowest cost of electricity time. I have variable pricing and pay half or less by charging midnight to 5am. But as you point out I don't have a warm battery in winter. So I do bigger, less frequent charges in winter.

On Tesla warming before charging in winter seems to use 3-4 kw. Since I control charging from Home Assistant to the Tesla API I have the data to know exactly, but I haven't done the analysis. I hoping my charging logic can be moved easily to Rivian. The bigger R1T battery may take more warming power.

 

[EarlyAdptr]

Question: Does the rate of charge matter?

I don't drive much each day. I've scheduled my nightly charging to go up to 70% AND I've lowered the amps to 30. It is scheduled to start at 10p and finishes well before I wake up.

Does reducing the rate of charge help in anyway? Or is that just foolish / non-consequential?

 

[lefkonj]

Reducing the charge should have zero impact on battery health. It will just take you longer.

 

[zer0t]

I level 2 charge unless I'm roadtripping or I'm out and about and run low. I only charge to around 70% because I can plug in at any time.

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