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how to test for battery health during a test drive.

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Hello everyone,

I've been lurking on this forum for quite a while, as i am interested in buying a used Tesla model S, probably a 2013-2014 85kwh model as a replacement for my 1996 BMW 540I.
The cost for newer models is unfortunatly too high to consider, and the model 3 is still relaltively new here and out of my price range.
I should add that, while i did drive electric cars before for short periods of time, i've never had the chance to try a Tesla before.

Main reasons for choosing a Tesla model S are :
* I wanted to switch to an electric car.
* I love the look of the model S, it does not scream "I aM aN eLeCtRiC cAr, LoOk At Me!" like other cars in this pricerange, the look of the car is frankly a major point for me.
* in this price range it is the only car on the used market here in the Netherlands that does not have despicably low range, optional DC fast chargers or rented battery packs.
* It would be a lot more future proof then my current car.
* It would cut my car expenses down to around 1/4th until 2025 (when road tax for ev's will be fully introduced here)

I care nothing for self driving other then perhaps showing it off once or twice if i had it, and though the free supercharging is a boon, its not a must for me.

Though this won't be happening until around the end of this year, I wanted to educate myself a bit on things to look out for during a test drive.
I know of the common quirks of these model S cars, and i am not that scared of the battery dying on me as battery repair is a viable option for these cars.
I am also under the impression that total battery failure is somewhat rare, but when it happens it obviously gets a lot of attention.

That being said however, I DO obviously NOT want to be the guy that buys a used tesla only to have his battery fail within half a year if that can be prevented, so is there a way for me to check for general battery health during a test drive, or perhaps a way i can be 100% sure about it?
Would the data from the CANbus be a good source or are there better ways to test this?
does it register the amount of times the battery has been charged to 100% or discharged to near 0? (or just cycles?).
Can parasitic cells / modules be identified using canbus?
forgive me if something simular has already been posted anywhere, i've not managed to find a thread about this in the enormous amount of posts about test driving various cars on this forum yet.

also, do I need to have an account on the tesla app in order to test drive the car, or can it be driven without logging in?


Thanks in advance!
 
Battery health is unfortunately going to be tough to test -- some things I would check are the battery pack part numbers (check against the "bad" or "problematic" ones that have been in market), compared original miles vs today (then you back into a curve of degradation although its best guess at most) and sadly but truly, you're going to have to ask the seller his charging regimen and even more believe it.

Some 85 packs did have issues so as above thats first for me.

It didn't exist back then, but you could always ask the seller if they've kept a tracker on the car (like TeslaFi) which could show charge cycles, SC vs home, etc. The MCU doesn't keep track of charging activity beyond scheduled charging rules and the sorts, so it has to be managed elsewhere.

I think others may have some better advice for you, but in the end to me, it's going to come down to finding a genuine seller sharing the true story of the car.
 
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Hello everyone,

I've been lurking on this forum for quite a while, as i am interested in buying a used Tesla model S, probably a 2013-2014 85kwh model as a replacement for my 1996 BMW 540I.
The cost for newer models is unfortunatly too high to consider, and the model 3 is still relaltively new here and out of my price range.
I should add that, while i did drive electric cars before for short periods of time, i've never had the chance to try a Tesla before.

Main reasons for choosing a Tesla model S are :
* I wanted to switch to an electric car.
* I love the look of the model S, it does not scream "I aM aN eLeCtRiC cAr, LoOk At Me!" like other cars in this pricerange, the look of the car is frankly a major point for me.
* in this price range it is the only car on the used market here in the Netherlands that does not have despicably low range, optional DC fast chargers or rented battery packs.
* It would be a lot more future proof then my current car.
* It would cut my car expenses down to around 1/4th until 2025 (when road tax for ev's will be fully introduced here)

I care nothing for self driving other then perhaps showing it off once or twice if i had it, and though the free supercharging is a boon, its not a must for me.

Though this won't be happening until around the end of this year, I wanted to educate myself a bit on things to look out for during a test drive.
I know of the common quirks of these model S cars, and i am not that scared of the battery dying on me as battery repair is a viable option for these cars.
I am also under the impression that total battery failure is somewhat rare, but when it happens it obviously gets a lot of attention.

That being said however, I DO obviously NOT want to be the guy that buys a used tesla only to have his battery fail within half a year if that can be prevented, so is there a way for me to check for general battery health during a test drive, or perhaps a way i can be 100% sure about it?
Would the data from the CANbus be a good source or are there better ways to test this?
does it register the amount of times the battery has been charged to 100% or discharged to near 0? (or just cycles?).
Can parasitic cells / modules be identified using canbus?
forgive me if something simular has already been posted anywhere, i've not managed to find a thread about this in the enormous amount of posts about test driving various cars on this forum yet.

also, do I need to have an account on the tesla app in order to test drive the car, or can it be driven without logging in?


Thanks in advance!
Hi there, welcome to the Tesla. There’s a Dutch forum as well where you can introduce yourself. That being said, this is what I would pay attention to:
Can it supercharge? Some cars are blocked by Tesla because they were totaled
How fast can it supercharge? If it doesn’t exceed 50 kw then it is limited by Tesla due to excessive charging
Has the motor or pack been changed? If not, you might hear grinding noises which can indicate a failing engine
You can get a setup ready to read the canbus data from the battery but without an understanding of what you see it’s difficult to make sense of it
Hope this helps!
 
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Hi there, welcome to the Tesla. There’s a Dutch forum as well where you can introduce yourself. That being said, this is what I would pay attention to:
Can it supercharge? Some cars are blocked by Tesla because they were totaled
How fast can it supercharge? If it doesn’t exceed 50 kw then it is limited by Tesla due to excessive charging
Has the motor or pack been changed? If not, you might hear grinding noises which can indicate a failing engine
You can get a setup ready to read the canbus data from the battery but without an understanding of what you see it’s difficult to make sense of it
Hope this helps!
Thanks for the welcome!

I am aware of the dutch forum, but figured i got more answers in this general sub.

I was not aware however that tesla limited supercharging down to 50kw after "excessive charging", does this happen for all cars, or only cars that basically exclusively supercharge?

I was aware of the update that lowered charging speed to the battery, but it would still charge fast enough for me to take it on roadtrips without it beign a major inconvenience.

For day to day use its not such a big deal in my case, but for longer trips, having to wait 1,5 to 2 hours for a 90% charge is atrocious.
 
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Thanks for the welcome!

I am aware of the dutch forum, but figured i got more answers in this general sub.

I was not aware however that tesla limited supercharging down to 50kw after "excessive charging", does this happen for all cars, or only cars that basically exclusively supercharge?

I was aware of the update that lowered charging speed to the battery, but it would still charge fast enough for me to take it on roadtrips without it beign a major inconvenience.

For day to day use its not such a big deal in my case, but for longer trips, having to wait 1,5 to 2 hours for a 90% charge is atrocious.
It’s car specific so I’d test it. Do make sure the battery is warm (either pre-heat or a long drive) otherwise the results will be skewed.
 
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Would the data from the CANbus be a good source or are there better ways to test this?
There is more in-depth data on the battery that can be accessed via the CANbus. I know of one product, Scan My Tesla, which is an Android app. I believe their is now a beta version of an iOS app, Scan My T3SLA.

Full disclaimer - I have not used either, just aware that they exist and have seen many others reference using it to look at how well the pack is balanced, etc.

It will require a special cable which you plug into the diagnostic port that you can access by pulling out the small storage shelf immediately under the main central MCU screen. You also then will need an OBDLink adapter to communicate with your phone/tablet where you have the Scan My Tesla|T3SLA app installed.

Just an option if you want to investigate it.
 
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There is more in-depth data on the battery that can be accessed via the CANbus. I know of one product, Scan My Tesla, which is an Android app. I believe their is now a beta version of an iOS app, Scan My T3SLA.

Full disclaimer - I have not used either, just aware that they exist and have seen many others reference using it to look at how well the pack is balanced, etc.

It will require a special cable which you plug into the diagnostic port that you can access by pulling out the small storage shelf immediately under the main central MCU screen. You also then will need an OBDLink adapter to communicate with your phone/tablet where you have the Scan My Tesla|T3SLA app installed.

Just an option if you want to investigate it.
Thanks, and you got it spot on about reading out the canbus!
i've been looking into scan my tesla for a bit today after your comment and what parameters it can give, and i think i can get a pretty good sense now of how to predict battery health, though it is by no means set in stone, it gives me enough indications

i'll be sure to have one ready before a test drive!
 
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I have just recently sold my beloved BMW E39 530d (I am guessing yours is a E39 as well - wonderful car!) - completely rebuild, lots of retrofits; nice and shiny - and I got a Model S.

I researched into how to test battery condition but had to give up doing a "real" battery condition test.
It is just not practically possible when buying a car.

I tried to look at the general power usage in the cars I tested before purchase and the history - they all looked about the same, but it was kind of a gamble and a gut feeling.

No regrets so far.
Wonderful car and I can recommend purchasing the MCU2 computer upgrade and the CSS as well - I did just as soon as I got the car. The MCU2 is MUCH better and also solved some Summon instability in my car.

From what I can test the car has only lost 1-2% of range - so nothing to worry about.
My is a P90D Ludicrous 2015/11 and had 47000 miles (76000km) on the odometer when I bought i two months ago.
 
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Yeah tesla battery is hit or miss. The only way is to see if the car was replaced with a new pack recently. Old packs will have problems down the road and you can check the CAN bus to see if there are problems, but it won't protect you fully. This is not just a tesla problem, but more of an EV problem, though others manufactures algorithm might be more forgiving.

Anyways the only way to test for some battery reliability is to let the pack run low, i.e. less than 10% SOC and then while you are connected via the CAN bus, log the all battery cell voltages while you are driving it hard both in acceleration and braking to test regen. Then review the data to see if any battery cell line is drastically different from the others. If they are closely matched, then there is less likely you will have problems down the road. If not, I'm pretty sure the outlier cell pack line will fail eventually and cost you $15-$20K replacement down the road.

Personally it is really you pay now or pay later. You can get a cheap model s right now, but there is a reason why they are cheap. Think Jaguars. I would recommend looking at other EVs because tesla might be cheap now, but are notoriously expensive to operate once out of warranty. Best of luck on your decision.
 
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You can get a cheap model s right now, but there is a reason why they are cheap. Think Jaguars.

Hey N2D, can you elaborate? One of the few EVs on my list that I am considering other than a Tesla is the Jaguar I-PACE. I haven't done any research on them yet, still early days yet and i'm learning about Teslas. I have had 3 other Jags so far, from various time periods, and the key there was always not being afraid to work on them, and knowing which parts cross-reference to other common parts off other makes. Not sure how that plays out with an EV.

Is the I-PACE a bad option? Unfortunately things like Taycans etc are probably forever out of my price range, so the pool is shallower at this end...
 
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Hey N2D, can you elaborate? One of the few EVs on my list that I am considering other than a Tesla is the Jaguar I-PACE. I haven't done any research on them yet, still early days yet and i'm learning about Teslas. I have had 3 other Jags so far, from various time periods, and the key there was always not being afraid to work on them, and knowing which parts cross-reference to other common parts off other makes. Not sure how that plays out with an EV.

Is the I-PACE a bad option? Unfortunately things like Taycans etc are probably forever out of my price range, so the pool is shallower at this end...
Yeah jaguars are notorious for depreciation mainly due to cost of maintenance after warranty. They just constantly break. For the early tesla model s, it is the same. Heck a lot of them have issues even before warranty is over. Tesla just fixes them so the owners don't complain too much. Later model s are better, but still have bad build quality. As for the ipace, I have not research them so I can't say if they are any good. If cost is you main concern, I would wait out the inflated car cost. It is not a good time to buy cars. And also a lot more EVs are coming out 2022 that will give tesla a lot of competition. Hopefully vehicle cost will go down because of the increase in competition.
 
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