Beginners' guide to EV charging?

[CommodoreAmiga]

I am curious. How do you jump start a EV?

the manual has a section on jump starting.

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[ajdelange]

I am curious. How do you jump start a EV?

I'm not sure you do but it may be possible in some cases. What people are talking about here is getting enough charge into the 12 v batteries (and I note with great interest the use of the plural in the manual) that it can operate the computers and contactor(s) which connect the high voltage battery to the car. If there is enough juice left in the high voltage battery to operate the car you should be able to go at least a few miles. While Tesla has always warned against it and Rivian has recently reversed it position on this to agree with Tesla, the vehicles can be charged by towing. Rolling down a long enough hill would also get you a couple of miles without incurring the displeasure of the manufacturers.

 

[MoreTrout]

I am curious. How do you jump start a EV?

If it's me, I'm using my first year of free membership to call Rivian to the rescue. And unless it is a ridiculous monthly price I'll probably continue it.

 

[Trandall]

I'm not sure you do but it may be possible in some cases. What people are talking about here is getting enough charge into the 12 v batteries (and I note with great interest the use of the plural in the manual) that it can operate the computers and contactor(s) which connect the high voltage battery to the car. If there is enough juice left in the high voltage battery to operate the car you should be able to go at least a few miles.

I recall reading somewhere that the R1's would have two 12V batteries, I too am curious as to why they went that way, if true. Is it worth it to replace the lead acid battery with a 12v lithium or is this just add more cost and complexity than it is worth? I have a small boat with a inboard V4 and had the same question about that battery.

 

[ajdelange]

Is it worth it to replace the lead acid battery with a 12v lithium or is this just add more cost and complexity than it is worth?

Good question. I have had a lead acid battery (in a small generator) last 10 years but 3 or 4 is more likely (if it's a premium battery) which is certainly less than the expected service life of the traction battery. Many a Tesla driver has experienced failure of the 12V battery. Getting it replaced (or replacing it yourself) isn't really that big a deal but a PITA none the less. There is an after market Li battery (Ohmu) available for Tesla cars but it is expensive (over $300 IIRC). It's a drop in replacement (has its own BMS). Tesla is now shipping some models with Li 12V batteries.

I'll bet that Ohmu will offer something for Rivian eventually for those who want to go that route.

 

[Max]

TBH, I'd recommend watching a few of their road….

Great tips. As a newbie watching this brought up a bunch of questions:

• Do 12V batteries on EVs die like ICE batteries due to phantom drain or main pack will keep it juiced up during extended unplugged times until pack itself is out of juice?
• Does 21“ road tires mean trouble in winter given weight and aggressive regen? The problem seem to be if I want to reduce regen, I will have to go two wheel drive on R1S and that would mean less traction. He was saying pump the tire pressure back up to normal in winter. Do you lower it a bit during icy conditions to increase contact area?

If it's cold it's especially important to stay plugged in, when you can, so the battery can be kept at a reasonable temp without consuming its own power (and putting additional wear)

Why does battery needs to stay warm? My understanding is that it can receive and give power more efficiently at Warner temps but if it is sitting there for two weeks, Why would I waste energy keeping it warm? It does not sound that green and makes EVs only sensible for those that have a garage.

If I drive my 300 mile range R1S 2 days/20 miles a week, do I really need to have that charging cable hooked up in rain and snow all the time?

Are you saying even without use, cold will reduce battery life or capacity?

Any EV owners in the house that don’t have a garage, leave it plugged in, in winter and can tell how much energy is used just for maintenance?

Is it worth it to replace the lead acid battery with a 12v lithium or is this just add more cost and complexity than it is worth? I

I replaced my motorcycle and my wife’s scooter batter with Lithium Ion and could not be happier. Of course it was much cheaper when I did it but I do plan to replace my R1S’s when it is time with one. Kinda disappointed that it does not come with one (instead of the flashlight in the door).

 

[CommodoreAmiga]

Do 12V batteries on EVs die like ICE batteries due to phantom drain or main pack will keep it juiced up during extended unplugged times until pack itself is out of juice?

Yes, the 12V batteries will still fail, eventually. EVs charge the 12V system when the vehicle is "on" but the high voltage pack is disconnected when the vehicle is not on, for safety. Some EV owners (especially earlier Teslas) have complained about 12V battery life not meeting expectations.

Why does battery needs to stay warm? My understanding is that it can receive and give power more efficiently at Warner temps but if it is sitting there for two weeks, Why would I waste energy keeping it warm? It does not sound that green and makes EVs only sensible for those that have a garage.

Extreme cold can damage batteries. The batteries must stay above a certain threshold simply to remain viable in storage. Another (higher) threshold must be maintained for optimal performance if the battery may be "used". It would be even less green to allow the battery pack to sustain damage.

If I drive my 300 mile range R1S 2 days/20 miles a week, do I really need to have that charging cable hooked up in rain and snow all the time?

For rain, it depends on the temperature. For snow, you're going to be <32 degrees F -- maybe much less.

The vehicle will use its own power to keep temps in the serviceable range. You may find that your remaining range reduces, over time, as the vehicle sits, since it consumes some power to keep itself healthy. If the vehicle runs out of energy to keep itself healthy, then you risk damaging the battery.

Plugging in would let the vehicle use "shore" power to maintain itself -- extending the length of time the vehicle may safely sit and preserving your range.

Are you saying even without use, cold will reduce battery life or capacity?

Yes, that is certainly possible.

Cold temperatures may directly damage batteries that are not being properly conditioned.

The BMS will keep the battery conditioned as long as it has power to do so. If the vehicle sits too long and runs out of power, then the BMS cannot keep the battery conditioned, and it may sustain damage.

I replaced my motorcycle and my wife’s scooter batter with Lithium Ion and could not be happier. Of course it was much cheaper when I did it but I do plan to replace my R1S’s when it is time with one. Kinda disappointed that it does not come with one (instead of the flashlight in the door).

I haven't tried Li-Ion, but I've been satisfied with AGM batteries in my motorcycles and trucks for 10+ years.

 

[SeaGeo]

@Max I think @CommodoreAmiga addressed all your questions. If something is still unclear, let us know.

 

[Max]

Thanks for taking the time to respond.

Extreme cold can damage batteries. The batteries must stay above a certain threshold simply to remain viable in storage.

So do you think, left unplugged, BMS uses a lot more of 12V juice to maintain safe temperatures and kill the 12V battery a lot faster than an unplugged EV in summer time?

The vehicle will use its own power to keep temps in the serviceable range. You may find that your remaining range reduces, over time, as the vehicle sits, since it consumes some power to keep itself healthy. If the vehicle runs out of energy to keep itself healthy, then you risk damaging the battery.

Do you know where the cut off usually is where it needs to be plugged in? Under 20% or 10%?

I can see multiple situations in which keeping it plugged in may be impossible, inconvinient or uncomfortable (staying at friends or relatives place). It would be nice to have some idea how long my R1 can take care of itself before needing CPR.

 

[CommodoreAmiga]

So do you think, left unplugged, BMS uses a lot more of 12V juice to maintain safe temperatures and kill the 12V battery a lot faster than an unplugged EV in summer time?

I would expect the battery heating/cooling functions to be run primarily off of the high voltage pack. However, the controllers are almost certainly run off the 12V system, so there is some load/drain on the 12V batteries, as well.

Do you know where the cut off usually is where it needs to be plugged in? Under 20% or 10%?

I don't believe there is a hard threshold. Every discharge cycle wears the battery pack, so there is probably some cost to longevity for consistently running the pack down due to BMS conditioning. I can't speculate on what that cost will be, specifically, however.

If you are able to keep the vehicle plugged in, then that is ideal. If you can't -- such as staying at a friend's house for a couple days -- then you "can't". I wouldn't worry too much about what you can't control. But for wherever you plan to regularly keep the vehicle, I would suggest planning how you can have an EVSE available to keep the vehicle connected when it will sit for many hours.

I can see multiple situations in which keeping it plugged in may be impossible, inconvinient or uncomfortable (staying at friends or relatives place). It would be nice to have some idea how long my R1 can take care of itself before needing CPR.

Rivian could answer that question, but I wouldn't be surprised if they choose not to. They haven't been particularly forthcoming with the "nitty gritty" details, imo. As more owners take delivery of their R1T/R1S then we'll see more real-world reports and you'll get a better idea of what you might expect.

 

[SeaGeo]

Do you know where the cut off usually is where it needs to be plugged in? Under 20% or 10%?

I can see multiple situations in which keeping it plugged in may be impossible, inconvinient or uncomfortable (staying at friends or relatives place). It would be nice to have some idea how long my R1 can take care of itself before needing CPR.

When @CommodoreAmiga is referring to keeping it plugged in, that's generally for instances where you would be leaving it for a long period of time (several days). In general you don't want to let lithium ion batteries sit for a long period of time (multiple days) at a low state of charge. Somewhere in the 10 to 20% range is probably a good estimate for that. If you're at a friends house overnight, I wouldn't worry about it. If it's *very* cold, you probably want to at least plug it in to a 110v overnight or charge it up a bit ahead of time because it may need to proactively heat the battery. For example, if you visit Minnesota and it's -15F, starting a night at a SOC of 15% may leave you with functionally no range in the morning.

 

[Max]

Rivian could answer that question, but I wouldn't be surprised if they choose not to. They haven't been particularly forthcoming with the "nitty gritty" details, imo. As more owners take delivery of their R1T/R1S then we'll see more real-world reports and you'll get a better idea of what you might expect.

Just chatted with CS. As usual a lot of copy and paste answers that were answers to someone else's question. I doubt they are trying to hide it. I think they just don't have access to people that know the answer. They can only ask their teammates that are just as knowledgeable about the product as they are.

 

[Rivianmd]

@Max I think @CommodoreAmiga addressed all your questions. If something is still unclear, let us know.

I think the responses here are accurate, but to be more specific I don’t think ultra cold storage of a charged battery is harmful, in fact, it may preserve it more than hot conditions. I think battery damage (dendrites) form when trying to draw current when the battery is super cold. If they gave users the ability to conserve energy for long storage periods by reducing the BMS pack min, they would then need to limit quick startup usage. Just my two cents and could be wrong

 

[CommodoreAmiga]

I think the responses here are accurate, but to be more specific I don’t think ultra cold storage of a charged battery is harmful, in fact, it may preserve it more than hot conditions. I think battery damage (dendrites) form when trying to draw current when the battery is super cold. If they gave users the ability to conserve energy for long storage periods by reducing the BMS pack min, they would then need to limit quick startup usage. Just my two cents and could be wrong

Agreed and maybe a “storage mode” could be offered via software, in the future. But it would need a caveat that you wouldn’t be be able to drive the vehicle on a whim…. You’d have to exit “storage mode” and the BMS would have to bring the battery up to a reasonable temp — which may take anywhere from minutes to hours.

might be useful if you won’t drive for weeks — but at that point, easier to just leave it plugged in, imo.

 

[aw113sgte]

Is no one planning on leaving one at the airport for several weeks? Maybe a month? Plugging in isn't an option. I would really want a way to go to a low energy use state.

What about going camping, a cabin, etc. There may not be an option for external power.

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