Tesla Model 3 battery degradation tuning

[bwilson4web]

Hi,

I wanted to share my experimental tuning of a 2019 Std Rng Plus Model 3 to compensate for battery degradation. Widely reported, the first year is ~5% followed by a 1% loss every year. My battery is about 3-4% (not an easy metric) so I wanted to start a tuning effort to compensate for the initial loss.

My first effort is to replace the OEM rims and tires with lower weight rims and lower rolling drag tires. My particular car has a single, rear drive motor and ~50 kWh battery, 2/3ds the size of the other models. This means I can 'lighten up' on the tire loads because it is ~600 lbs (273 kg) lighter. Furthermore, I drive in "chill" mode, about 75% of the maximum, "standard" mode.

Using Consumer Reports claims:

• Bridgestone EP422 Plus - low rolling resistance series
• 235/45R18 -> 225/55R18 - narrow tread and lighter weight
• lighter weight rims

Compared to the OEM rims and tires, each saves ~5 lbs (2.8 kg) times four tires. Unfortunately, the front has an overhanding, king pin support that forced the first two tires to be on the rear only. Regardless, the high wear rating means these tires should last at least 2-3x longer than the OEM.

An on-going experiment, the front tires have a low wear rating and a recent screw event meant the local tire shop would not repair it. The "Stop and Go" kit using a mushroom shaped plug failed so I reverted to 'sticky string' which so far, is doing OK.

I have three candidate, front tires and am leaning to lowest rolling resistance tire with modest wear rating. Since the front wheels are not powered, they should have an 'easy life'. We typically saw ~2x difference between the powered versus unpowered tires in our past Prius.

Source: https://teslaownersonline.com/thread...-2#post-290660

Enjoy!

Bob Wilson

[jjackstone]

Originally Posted by bwilson4web

Hi,

This means I can 'lighten up' on the tire loads because it is ~600 lbs (1,320 kg) lighter. Furthermore, I drive in "chill" mode, about 75% of the maximum, "standard" mode...

Bob Wilson

Bob,
1320 kg=2900 pounds.
600 lbs=272 kg
I know it's just a typo.

JJ

[jakobnev]

How evenly does the battery wear? (Are some modules worse or better than others?)

[bwilson4web]

Originally Posted by jjackstone

Bob,
1320 kg=2900 pounds.
600 lbs=272 kg
I know it's just a typo.

THANKS! I know the ratio is 1-to-2.2 but more than once got it wrong.

Bob Wilson

[bwilson4web]

Originally Posted by jakobnev

How evenly does the battery wear? (Are some modules worse or better than others?)

I've not studied that but others, Sandy Munro and Jack Rickard, have reported very small differences. My interest is in temperature differences and they have been within a fraction of degrees C.

Bob Wilson

[bwilson4web]

Here are the first results:

• Red line diamonds - a baseline recorded in March 2019 from our Std Rng Plus Model 3. It had the stock rims and tires with the aero covers.
• Green line triangles - recorded August 11, 2020 with 18x8 Enkei trims and 225/55R18 Bridgestone ECOPIA EP422 Plus on the rear. The front tires are the Tire Rack recommended 235/45R18 Michelin Pilot Sport 4.

At lower speeds, the lower rolling resistance tires on the rear are working great. So now I need to look at aerodynamic tricks.

My first thought is rear wheel well pants. I can test it using heavy paper/cardboard and blue sticky tape. I'll only need to replicate the 63 mph benchmark. This approach doesn't add a rotating mass to the wheels.

There are rear spoilers sold but at $700, they are pricy and I'm seeing credible data showing a significant drag reduction. But I can hack-test with heavy paper/cardboard and blue sticky tape.

Bob Wilson

[bwilson4web]

Something I shared at Fred's TDI:

Just sharing some data points:
$37,990 - current price for Standard Range Plus Model 3 which includes basic AutoPilot

March 26, 2019 bought mine $41,000 with Autopilot and Blue paint
Got $18,300 trade-in on Prius Prime, net $22,700
Odometer 28,154 miles running version: 2020.36 updated two days ago

Local electricity $0.11/kWh

$2.70/100 miles ($0.027/mile) from house power
1/3 local electricity from free chargers while shopping

SuperChargers ~120-180 miles apart along Interstates

$3.50/100 miles using SuperCharger point-to-point
$3.00/100 miles staying overnight at a motel with free breakfast and charging

Other electricity

Can use RV and recreational area, NEMA 14-30 and 14-50 charging
Can use ordinary 110-120 VAC outlets (best to ask)

Typical cross country trips:

714 miles straight through to Detroit, ~14 hours, $25 charging
750 miles to Dallas, Coffeyville, and home

~90-95% of driving is using AutoPilot anywhere

Handles lane changes with 360 degree cameras
Unexpected medical issue handled by keeping car out of ditch and at speed

Full Self Driving (FSD), $6,000 last October

Stop sign, stop light, yield sign logic works with "green light" PING
Summon with dogs in car is amusing ... it looks like they are driving

Self-repairs

Banged into curb on passenger side, stripped part of rims yet tires held air
Replaced passenger side bearings using jack, jack stand, and ordinary hand tools

Battery degradation

Measured 3-4% in first year, miles: (240 - 234) / 240 and (240 -232) / 240
Subsequent years expecting 1% per year
Replaced OEM rims and tires compensates for initial degradation
Up to 45 mph, new rims and tires, 5 lbs lighter each, are better than OEM
Above 45 mph, I am working on aerodynamic hubcaps

Maintenance

Window washing fluid
Add air in Fall, monitor otherwise
One machine screw fixed by 'sticky string' plug
One sidewall puncture from road junk, road hazard warranty replaced

Driving

"Chill" mode so it won't 'speed frantic' in traffic
First across intersections at stop lights
Reach speed limit 200 yards ahead of everyone else

Cross country

1st leg with 100%, overnight charge to go as far as practical, ~210 mi, ~3 hours
next legs
Fast food for biology break, snacks and beverages
Drive to SuperCharger for 15-20 minutes to eat snacks and stretch

SUMMARY

Half the cost per mile of our former Prius Prime and fun to drive. The driver assistance of AutoPilot and FSD, makes long distance and even city driving safer, easier and relaxing.

Bob Wilson

[Hersbird]

Not to be picky but your Prius Prime would have made a 714 mile trip in 11 hours and cost the same $25 in "charging". Not sure how you get 1/2 the cost per mile. How long did those Model 3 tires last and how much were they to replace? That alone would buy years worth of Prius Prime gas, and a Prius is super easy on tires.

[bwilson4web]

Originally Posted by Hersbird

Not to be picky but your Prius Prime would have made a 714 mile trip in 11 hours and cost the same $25 in "charging". Not sure how you get 1/2 the cost per mile. How long did those Model 3 tires last and how much were they to replace? That alone would buy years worth of Prius Prime gas, and a Prius is super easy on tires.

“714 mile trip” is inaccurate. I drove that Prius Prime 1,200 miles from Rhode Island in just under 23 hours. It would have required a full tank at the start and a fuel stop on the way as my trip from Rhode Island did. But the real Prius Prime failure is the 25 mi EV range.

In Huntsville, the Prime became a ‘3 stop’ EV car while our BMW i3-REx was a ‘10 stop’ car. The BMW was used and the Prius Prime became driveway art. The majority of our miles are urban and that is where the Prime failed.

I was looking at a significant capital expense, $29,400, that was not returning value. So I traded it in, $18,300, for a Std Rng Plus a Model 3 that is cheaper both City and Highway. My capital expense must carry its weight.

Bob Wilson

[Hersbird]

So you are counting the maximum possible depreciation cost by trading in after one year as a cost against the Prius? Are you only allowing the Prius to be used in EV mode? That seems like an unfair use, the whole purpose is to use that 40 mile range 80% or the time but then let the gas kick in when you need longer trips. Otherwise you are hauling around that big engine for no reason.

I just think in a fair comparison, normal usage, taking in all factors, no way the cost per mile on a model 3 is 1/2 a Prius Prime. Maybe pick something less efficient or more expensive car and you would get there, but a Prius Prime is not a high cost per mile car.

Your Tesla is a $47,000 car, you don't get to reduce it's cost by counting the Prius trade value as some kind of offset. If the Prius was a mistake for you, if anything that cost goes onto the Tesla's cost, not reducing the Tesla cost. If you look at your overall cost per mile over the last 3 years you are basically doing terrible. My $3500 3/4 ton Suburban does better getting 12 mpg.