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Worried or Not? First battery/charge issue and 1st logs

gregd

Active Member
Dec 31, 2014
2,585
1,802
CM98
Another possibility for charging, though probably a long shot.. If your garage happens to have two outlets on separate phases, you can create a 240v / 15 amp circuit with just plugs and wires. Search for "Quick 220". QCP used to sell them (out of stock), but there are ways to build your own with common home hardware store parts. Charge at 240v /12 amps and you should be fine.

Or, it might be possible to squeeze a new pair of 120v / 20 amp circuits to your existing panel by doubling up on some of the existing breakers, then do the Quick 220 thing from that. That would take an electrician and some wiring, but you might avoid an entire panel swap.

I was looking at adding a 14-50 outlet to my garage, to let the dryer have its own exclusive plug, and asked an electrician what it would take. Good thing I asked. Turns out that I had a Zinsco-brand panel from when the house was built (early 1980's). They had stopped making them some years ago because they tended to "fail", as in "catch fire". The electrician was surprised that it hadn't been replaced yet. So, we did that! And while were were at it (and with his guidance) I crawled under the house and strung the wires for the 14-50 and a pair of 15-20's for just the parts cost. Both I and my car sleep much better at night as a result.

Both higher temps and higher current shorten battery life, but there was one study where they found that faster charging means the battery spends less time at an elevated temperature, and that shorter elevated time offset the negative effects of the higher current. I try to keep my battery at 30c or below, both for health of the battery and to let the car (and the little pump) go to sleep at night. I charge mine on 240v at 24 amps, and it seems to work out fine. I could go to 40 amps, but there's no hurry, and the lower current is nicer to the big relay in the wall charger, and to the overall heat equation. I think the efficiency sweet spot is around the 24-30 amp range..
 

slcasner

Active Member
Supporting Member
Feb 20, 2011
1,348
909
Sunnyvale, CA
Another possibility for charging, though probably a long shot.. If your garage happens to have two outlets on separate phases, you can create a 240v / 15 amp circuit with just plugs and wires.
I built such a Y cable some years ago at work when we got a big router on loan that unexpectedly required 208/240V.

But this won't work if the circuits have GFCI outlets or circuit breakers because no current flows back through the neutral. And code requires garage circuits to be protected by GFCI.
 
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Matteni

Member
Dec 8, 2019
128
139
St. Louis
Last night I replaced the three-prong plug on the 110 volt Tesla charger. I removed the ground fault interrupt.

The temperatures were in the 50s and I charged it to see if I really lost 20 or 30 miles of range or if it was somehow related to the GFI

After pulling an analyzing the logs I was hopeful that just swapping out the plug would recover all the lost mileage I was seeing

Temperatures run seasonally cool in the 50s so heat was not a factor

I woke up and went out to the garage fingers crossed and luckily it seems my hypothesis may have been correct. Charged to 182 ideal range which is 1 or 2 miles off highs but in the normal range for me.

I did learn a lot on this thread and I think everyone for helping out I'm sure I'll need plenty of advice during my hopefully long ownership!
 

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Matteni

Member
Dec 8, 2019
128
139
St. Louis
I built such a Y cable some years ago at work when we got a big router on loan that unexpectedly required 208/240V.

But this won't work if the circuits have GFCI outlets or circuit breakers because no current flows back through the neutral. And code requires garage circuits to be protected by GFCI.

I looked into this as well. I do have 2 circuits but would have had to remove the GFI in the wall which is not to code so I decided to hack the dryer plug in the basement under the garage and use dryer buddy, heavy duty RV extension cord rated for 100A and a Y connector to have a 240v charger on both sides of the garage for both electric cars. Not as ideal as a dedicated high amp circuit on each side but a lot less expensive and meets our charging needs easily and was budget friendly as we would have had to buy another subpanel and go to a higher service to add another 40+ amps or more.
 

hcsharp

Active Member
Jun 7, 2011
3,417
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It has been documented here on this forum high charging rates wear the battery out more quickly over time and I am trying to avoid that.
Where has that been documented specifically for the Roadster? I question whether it's accurate. It might be true for DC fast charging but you're not doing that. Even charging at 70A, the max for a Roadster, is fairly gentle on the cells. Let me know if I'm missing some important information.

There's also a good argument that there's more wear on the charging system at lower amps due to having to run for longer periods. That may be offset by other factors so I hesitate to make this argument without more data.

Jeff Dahn (battery pioneer and ongoing leader in Li Ion tech) has made a case for faster AC charging being better for longevity in an EV. One of his reasons is that higher charge rates result in less time at maximum cell voltage. I don't know if this was ever proven but if true it undermines the lower-rates-are-better theory. At the very least it questions whether slower is in fact better.
 
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hcsharp

Active Member
Jun 7, 2011
3,417
1,465
Vermont
also make sure you lock the car when charging; this will signal the car to go to sleep as I read this in another post from @markwj

Are you sure this puts the car to sleep any more than not locking it? I always thought that locking it only makes the charge port lights go out, but does not put the car to sleep.
 

Matteni

Member
Dec 8, 2019
128
139
St. Louis
Where has that been documented specifically for the Roadster? I question whether it's accurate. It might be true for DC fast charging but you're not doing that. Even charging at 70A, the max for a Roadster, is fairly gentle on the cells. Let me know if I'm missing some important information.

There's also a good argument that there's more wear on the charging system at lower amps due to having to run for longer periods. That may be offset by other factors so I hesitate to make this argument without more data.

Jeff Dahn (battery pioneer and ongoing leader in Li Ion tech) has made a case for faster AC charging being better for longevity in an EV. One of his reasons is that higher charge rates result in less time at maximum cell voltage. I don't know if this was ever proven but if true it undermines the lower-rates-are-better theory. At the very least it questions whether slower is in fact better.
GeoTab found that the the two biggest factors affecting the life of EV batteries are battery cooling and frequent high power DC charging. Age and number of miles driven are far less important to how long a battery lasts.

Chart and data collected

What can 6,000 electric vehicles tell us about EV battery health? | Geotab

Article

New Data Shows Heat & Fast-Charging Responsible For More Battery Degradation Than Age Or Mileage | CleanTechnica
 

hcsharp

Active Member
Jun 7, 2011
3,417
1,465
Vermont
GeoTab found that the the two biggest factors affecting the life of EV batteries are battery cooling and frequent high power DC charging. Age and number of miles driven are far less important to how long a battery lasts.

Chart and data collected

What can 6,000 electric vehicles tell us about EV battery health? | Geotab

Article

New Data Shows Heat & Fast-Charging Responsible For More Battery Degradation Than Age Or Mileage | CleanTechnica
It has been documented here on this forum high charging rates wear the battery out more quickly over time and I am trying to avoid that.

OK, sorry for knit picking, those 2 articles don't support the notion that high AC charging rates wear the battery more quickly, instead they appear to suggest little or no correlation, and even if they did, they weren't documented in this forum.

I'm not trying to give you a hard time so please don't take offense. I just wanted to interrupt a rumor before it got started. I think you might have misinterpreted something you read to believe low AC charging rates are better than high for a Roadster. That's why I asked where you saw it documented here on this forum.

Our battery packs are large enough that slow vs fast AC charging is very unlikely to make a measurable difference to battery wear. It has been documented that 115v charging prevents cooling in some cases, accelerating wear, and charging at much less than 30A is less efficient (generates more heat in the PEM per mile of charge). As I mentioned earlier, there are arguments in other forums (Model S) that faster AC charging is actually better for cell longevity and possibly the PEM as well.

Again, sorry for knit picking but I wanted to stop a rumor before it grew legs.
 

Matteni

Member
Dec 8, 2019
128
139
St. Louis
OK, sorry for knit picking, those 2 articles don't support the notion that high AC charging rates wear the battery more quickly, instead they appear to suggest little or no correlation, and even if they did, they weren't documented in this forum.

I'm not trying to give you a hard time so please don't take offense. I just wanted to interrupt a rumor before it got started. I think you might have misinterpreted something you read to believe low AC charging rates are better than high for a Roadster. That's why I asked where you saw it documented here on this forum.

Our battery packs are large enough that slow vs fast AC charging is very unlikely to make a measurable difference to battery wear. It has been documented that 115v charging prevents cooling in some cases, accelerating wear, and charging at much less than 30A is less efficient (generates more heat in the PEM per mile of charge). As I mentioned earlier, there are arguments in other forums (Model S) that faster AC charging is actually better for cell longevity and possibly the PEM as well.

Again, sorry for knit picking but I wanted to stop a rumor before it grew legs.

No hard feelings at all. I respect and admire your work.

I believe "the best data wins". I always try to listen like I am wrong.

That said this is a very large battery study and there isn't any Roadster specific battery data that relates charge rates to battery health.

The authors were pretty clear and the data shows that rapid charging and high charge rates (especially in hot environments is detrimental).

Much less so between Level 1 and Level 2 charging - to your point.

Do you have any data supporting that higher charging rates do not impact the life of Li ion batteries? I know you referenced it but I can't find it.

My car charged to 184 today and was never once range charged and never once charged over 16a (actually for the first 11 years only ever charged on 110V). I do use 240V most of the time when ambient is hot or a fun drive. Not more than 16A however. Not as worried about my PEM as I just had Carl go through it and insulate and replace many of the common weak points. The battery is the most important thing IMO.

Antidotal but not interested in experimenting at this point since my car seems to be holding up better than most of the 1.5's on the road - unless there is data that says otherwise.

I want to drive this car with this battery for 10 years if I can and am very interested in data that would modify my personal advice and approach.
 

markwj

Moderator, Asia Pacific
Apr 10, 2011
4,620
1,254
Hong Kong
CHAdeMO
Do you have any data supporting that higher charging rates do not impact the life of Li ion batteries? I know you referenced it but I can't find it.

To put this in perspective:
  • AC 32A @240V is 7.68kW
  • AC 70A @240V is 16.8kW
  • CHAdeMO (DC) is typically 50kW
  • Tesla Supercharging (DC) is 120kW up to around 250kW
When talking about high charging rates affecting Lithium Ion cells, those rates are normally achieved using DC fast charging (as mentioned in the article referenced).

I don't see the limits anywhere close to being reached when using big batteries and AC charging. A roadster battery is about 53kWh, so even at the maximum AC charging rate of 16.8kW it is nowhere near a C rate that would negatively impact the cells. Have a look at the kW meter on the dashboard next time you hit the accelerator for a real life comparison.

I would worry more about stress on the AC-DC electronics and cables, when charging at high amperages, than the cells in the battery.

For historical reading, here's a very early article by Martin Eberhard (from back in 2006) talking about the Roadster ESS and what they worry about:

A Bit About Batteries
 

hcsharp

Active Member
Jun 7, 2011
3,417
1,465
Vermont
Excellent post by @markwj said everything I was going to say in response to Matteni. Puts it all in perspective.

The best data we have is the Tesla Roadster battery study which is ongoing. Thank you Tom Saxon. (Reminder: submit your data again.) I don't have time to check now but I vaguely remember somebody looking at charge rates at some point in that study. I know he analyzed some data on range charging, and also Roadsters in hot climates. Sample size is still small.

Like most everyone has said, heat is your worst enemy with the ESS and probably with the PEM, too.
 
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im4uttx

Supporting Member
Supporting Member
May 28, 2019
375
247
Spicewood, TX
No hard feelings at all. I respect and admire your work.

I believe "the best data wins". I always try to listen like I am wrong.

That said this is a very large battery study and there isn't any Roadster specific battery data that relates charge rates to battery health.

The authors were pretty clear and the data shows that rapid charging and high charge rates (especially in hot environments is detrimental).

Much less so between Level 1 and Level 2 charging - to your point.

Do you have any data supporting that higher charging rates do not impact the life of Li ion batteries? I know you referenced it but I can't find it.

My car charged to 184 today and was never once range charged and never once charged over 16a (actually for the first 11 years only ever charged on 110V). I do use 240V most of the time when ambient is hot or a fun drive. Not more than 16A however. Not as worried about my PEM as I just had Carl go through it and insulate and replace many of the common weak points. The battery is the most important thing IMO.

Antidotal but not interested in experimenting at this point since my car seems to be holding up better than most of the 1.5's on the road - unless there is data that says otherwise.

I want to drive this car with this battery for 10 years if I can and am very interested in data that would modify my personal advice and approach.
Not specifically to you, but, I think there are SO many variables with regard to battery health in these roadsters, we have to be realistic in our expectations and the actual parameters we can control.

As @markwj mentions, the perspective of power and regen (thx @gregd ) show that the 30-70A charge rate for the roadsters isn't really putting a burden on the battery.

Personally, I think other variables are far more damaging to the battery health. Some things we just can't control, i.e. environmental heat, while others we can, perhaps, i.e. keeping it plugged in. I looked at the CAC for my roadster after purchase last year and it showed (and shows) loss when left to drop to low charge levels and extended periods of no charging. Once before my purchase the logs show, while it was being transported and/or sold/transferred, and once again when it was in for repair, it lost 1-2 off the top of CAC each time.

I think the mid-range current, in the 24-32A range, is a decent range that doesn't put too much strain on the system, and allows enough power to allow the battery to be cooled properly during charge. I am not saying you should change your current protocol...just that I think there are far too many variables to be able to trace longevity of your battery to the 16A/110V/240V charging regiment.
 

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