Charging Best Practices

[teslarati97]

Generally there is more heat (energy loss) charging Level 1 12A @ 120V vs Level 2 6A @ 240V as well as extended standby losses (cooling fans, electronics) over time. I don't know of anyone who regrets upgrading to Level 2 EVSE!

As for the battery health of Level 1 vs Level 2 charging for heat, there is a probably a nominal difference. There might be extra wear and tear on the power electronics if you daily Level 1 charge due to longer charge times compared to Level 2.

Has anyone looked into the AC->DC rectification efficiency of the onboard charger for Level 1 vs Level 2?

 

[Puppethead]

As for the battery health of Level 1 vs Level 2 charging for heat, there is a probably a nominal difference.

Because of the (relatively) low charge rate of the SE (7.4 kW AC [or 11 kW in 3-phase countries], 50 kW DC), I don't think we need to worry about heat damage to the batteries due to charging. That's something other cars that charge at much higher kilowattage (triple digits) can worry about.

 

[Giosan]

This video from the Ioniq Guy talks about the losses with 120v compared to 240v charging his Ioniq5. He used Car Scanner and an OBDII adapter to measure power going into the battery during the different charging scenarios. I didn't catch how far he drives a month, but he says he figures he was wasting $18.54 a month when he was using 120v. He figured the loss was 31.5%, which pretty much agrees with the results @Giosan saw.

 

[Giosan]

 

[Giosan]

Sorry, I couldn't see my thumbnail screenshots. This is how I compared. Temperature was about the same because I'm in Honolulu. Luckily, I don't have to worry about losing range to cold weather.

 

[AndysComputer]

I tested L1 vs L2 efficiency and cost and it’s not that big of an issue:

 

[MiniCoopr71]

Apologies if this is a hijack of the thread but had a related question about charging practices - specifically whether to charge to the maximum 100%. Not for battery life preservation, but for reduced brake wear.
My understanding is that at 100% charge the Mini doesn't perform brake regen charging, but simulates that same regen feel by using the brakes. I know its probably inconsequential, but I'm tempted to charge to a slightly lower level (95%, 98%, when does regen kick in?) and have regen braking for the entire charging cycle to maximize brake life.
Am I being ridiculous in trying to further reduce the overall running costs of a car that already has a low TCO relative to a standard ICE vehicle? Its just that brakes and tires seem to be the only bigger costs to deal with, so if I can extend the brakes I'd like to.
There is a counter-argument that you should probably make sure to use the brakes every once in a while to keep everything rust free and functional.

 

[chrunck]

Apologies if this is a hijack of the thread but had a related question about charging practices - specifically whether to charge to the maximum 100%. Not for battery life preservation, but for reduced brake wear.
My understanding is that at 100% charge the Mini doesn't perform brake regen charging, but simulates that same regen feel by using the brakes. I know its probably inconsequential, but I'm tempted to charge to a slightly lower level (95%, 98%, when does regen kick in?) and have regen braking for the entire charging cycle to maximize brake life.
Am I being ridiculous in trying to further reduce the overall running costs of a car that already has a low TCO relative to a standard ICE vehicle? Its just that brakes and tires seem to be the only bigger costs to deal with, so if I can extend the brakes I'd like to.
There is a counter-argument that you should probably make sure to use the brakes every once in a while to keep everything rust free and functional.

Unless you live at the top of a hill, as soon as you pull away from your house, there will be battery space available for regen braking since you're not getting back more energy than you used in the first place. I wouldn't worry about it.

 

[Puppethead]

Am I being ridiculous in trying to further reduce the overall running costs of a car that already has a low TCO relative to a standard ICE vehicle? Its just that brakes and tires seem to be the only bigger costs to deal with, so if I can extend the brakes I'd like to.

Don't sweat the brakes. When I took my SE in for its 2-year service I had already gone 36,000 miles and my original brake pads were still at 10mm (12mm or 14mm is new, I think).

 

[Giosan]

I tested L1 vs L2 efficiency and cost and it’s not that big of an issue:

It depends what you pay per kwh and what it costs you for a 240 volt charger. On Oahu, the current cost per kwh is about 44 cents now! My screenshots were from a few months ago when it was only 33 cents a kwh. I only spent about $600 on my 240 volt charger and accessories. Bought a manual 2 way splitter that's plugged into the dryer, a 25 ft ev charging rated extension chord, and a 24 amp charger. The circuit for my dryer is 30 amps so 24 amps is the most you should draw. No installation cost.

 

[Carsten Haase]

Because of the (relatively) low charge rate of the SE (7.4 kW AC [or 11 kW in 3-phase countries], 50 kW DC), I don't think we need to worry about heat damage to the batteries due to charging. That's something other cars that charge at much higher kilowattage (triple digits) can worry about.

That's not necessary true (clearly there's some heat because MINI felt it was necessary to run the fans when charging even on L2). What matters is the charge rate for each cell. Faster charging cars can do so because they have larger batteries and the power is divided among more cells. For example, if you charged one cell at 50kW it would surely explode

 

[Puppethead]

That's not necessary true (clearly there's some heat because MINI felt it was necessary to run the fans when charging even on L2).

I should have mentioned the battery cooling management. Since I'm approaching 44,000 miles with daily L2 charging and no perceptible range loss, I think MINI engineered the SE extremely well.

 

[Rexsio]

That's not necessary true (clearly there's some heat because MINI felt it was necessary to run the fans when charging even on L2). What matters is the charge rate for each cell. Faster charging cars can do so because they have larger batteries and the power is divided among more cells. For example, if you charged one cell at 50kW it would surely explode

What is a temperature when fans start on SE as I’m charging in 60- 75’ in my garage they never start as I charge to 100% but in my I 3 a fan start right away with 90’ when I charged outdoor .

 

[SameGuy]

I’m sure I saw this discussed in an earlier thread sometime before I took delivery in early August, but there’s no way I’ll be able to find that now…

For the life of me, I can’t figure out timed charging. This is the first time I’ve tried it. Parking this afternoon with 59% SOC and needing 100% and a warm cabin when I leave at 9:00 am, I turned off “immediate” in the car and in the app, I set my planned departure time, and I set the preferred charging slot, then I plugged in and locked up and went inside. Two hours later the app told me my car was charged. My departure time is 9 AM tomorrow, so… what did I forget from that previous discussion?

 

[Puppethead]

Two hours later the app told me my car was charged. My departure time is 9 AM tomorrow, so… what did I forget from that previous discussion?

See my post on the 30-minute boundary that determines if the time slot charging starts at the beginning or the end.

 

[SameGuy]

Thank you! That was the thread (that my inadequate search fu failed to locate).

 

[vader]

I personally always go to 100%. My car is 2 years old with no degradation. I managed a total range of 270km (125km from 47%) the other day going up the coast. There were several road works which limited the speed to 80kph (which helped). Ideal temp of around 23C. Anyway, I digress - one thing people don't realise is that charging to 100% floats the cells (ie makes them all the same voltage). This has quite a good effect on the cells themselves. When power is drawn, a cell at a lower voltage will still contribute the same current (in series), so it is in fact working harder than the other cells. This increases the "wear" on the lower voltage cell, and will drop the voltage quicker. This in turn means it doesn't get up as high as the other cells if you keep going to 80%. Rinse and repeat, and that is why people generally need to replace one or two cells only. Floating will even the wear out over all cells, meaning you don't need to replace any cells until much later - however you will probably need to replace all the cells. With the buffer built in to the MINI, it actually is better to go to "100%" and float the battery rather than go to 80% all the time. If you really think that 80% is better, at least go to 100% every now and then to float the cells.

EDIT: I charge with a level 1 240V (10A) granny charger, so I am only doing around 1/16C, which won't hurt the battery at all. Most cars can charge at around 2C - hence 1/2 hour to charge (if there was no slow down). Higher than 2C generates a lot of heat. Just in case, the 'C' term is the capacity of the battery. A 10kWh battery will take an hour at 1C (10kW). It takes 1/2 hour at 2C, and 2 hours at 1/2C (again ignoring the slow down at the end of charging).

 

[Marc Wilcox]

My 2023 BRG SE is scheduled for production - who knows at what point I may take possession. The more I read about smart charging practices the more confusing it gets. For a future new owner I will have to rely initially on a level 1 charger and public charging stations. Installing a level 2 charger at this time is financially undoable - main panel needs to be replaced and upgraded and garage is 30 feet from the house. I guess doing will be learning.

 

[Hatch]

I personally always go to 100%. My car is 2 years old with no degradation. I managed a total range of 270km (125km from 47%) the other day going up the coast. There were several road works which limited the speed to 80kph (which helped). Ideal temp of around 23C. Anyway, I digress - one thing people don't realise is that charging to 100% floats the cells (ie makes them all the same voltage). This has quite a good effect on the cells themselves. When power is drawn, a cell at a lower voltage will still contribute the same current (in series), so it is in fact working harder than the other cells. This increases the "wear" on the lower voltage cell, and will drop the voltage quicker. This in turn means it doesn't get up as high as the other cells if you keep going to 80%. Rinse and repeat, and that is why people generally need to replace one or two cells only. Floating will even the wear out over all cells, meaning you don't need to replace any cells until much later - however you will probably need to replace all the cells. With the buffer built in to the MINI, it actually is better to go to "100%" and float the battery rather than go to 80% all the time. If you really think that 80% is better, at least go to 100% every now and then to float the cells.

EDIT: I charge with a level 1 240V (10A) granny charger, so I am only doing around 1/16C, which won't hurt the battery at all. Most cars can charge at around 2C - hence 1/2 hour to charge (if there was no slow down). Higher than 2C generates a lot of heat. Just in case, the 'C' term is the capacity of the battery. A 10kWh battery will take an hour at 1C (10kW). It takes 1/2 hour at 2C, and 2 hours at 1/2C (again ignoring the slow down at the end of charging).

I won't be driving (or charging) as much as most people here. Our car is my wife's and she hardly drives. I'd love to use it daily, but afraid to death of hitting a deer on my way to work. I see them EVERY day. I've had quite a few close calls.

I charged the SE to 100% yesterday. Watching my energy monitor, i see it starts ramping down the power intake at 94% SOC. I'm toying with the notion of unplugging at 92-93. I agree that charging to 100 is necessary at certain intervals (aside from the times you need 100).

I'm thinking that the ramp after 94% is just the basic nature of battery charging in general, rather than some programmed routine. Like my cell phone probably does the same thing. Might this be the clue to a sweet spot that does everything possible to protect the battery?

 

[pictsidhe]

I picked my SE up in July, so early days, yet.

I can set a charging window on my EVSE and I use this to charge to approx 85%. Once a week, a 100% charge to balance cells.
A couple of commutes uses around 55% charge.
This is apparently about optimum discharge for range life.
Last weekend, I checked the SOH and capacity with the electrified app and found it has been dropping.
On a forum, somewhere, I read that i3s need to be charged for 5+ hours at 100% to balance cells. A couple of long floats has restored 0.8Ah

I'll be doing weekly float charges and see how that goes.
Keeping a battery at 100% for long periods is not great for life, hence I was previously doing a charge-n-go.