Toyota Rav4 EV Forum

It is currently Tue Jun 25, 2019 1:30 pm

All times are UTC [ DST ]




Post new topic Reply to topic  [ 53 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6  Next
Author Message
 Post subject: Re: How to Calculate Rated Range / Battery Degradation with
PostPosted: Thu Aug 25, 2016 6:31 am 
Offline

Joined: Mon May 13, 2013 6:15 am
Posts: 343
Location: Volcano, CA
i just got 140 @ 55K miles. 4.2% degredation.
Thats way better than i thought it would be.

_________________
--
2013 Shoreline Blue Pearl Rav4 EV #1634
2018 Tesla Model 3 Dual Motor, ER, EAP


Top
 Profile  
 
 Post subject: Re: How to Calculate Rated Range / Battery Degradation with
PostPosted: Thu Aug 25, 2016 5:13 pm 
Offline

Joined: Sun May 12, 2013 6:00 am
Posts: 62
Location: San Diego, CA
This test by no means provide any value for degredation. It's based on voltage, and it absolutely useless to determine the AH capacity of the batteries.
I have 40,000 k miles on my car, and if I connect via techstream, the kw capacity is still at 34+ KW, exactly what it was the day that I bought it on a regular charge.

I reuse the 18650's from dead laptops batteries all of the time, and unless they are bad/defective, even the ones that are 90% degraded will charge to 4.2 volts.

The real test is when I load test them @ 1amp, 2amp, and 3 amp, that's when the 90% degraded battery will only last for about 15 minutes vs 1 to 2 hours for a good one @ 1amp.

Even then, it really is not a true indicator, because the 90% degraded battery will go one hour if I drop the load to .25 amps .. So, I can put 4 of them in parallel, and get over an hour @ 1amp

I seriously doubt, Tesla is allowing these batteries to charge to 100% @ 4.2 volts, so depending on how many cells are in parallel, even if your battery was degraded 20% percent, the voltage woudl still be the same, and your test would not provide any value ...

In order to provide good data for this test is to have had a baseline that you can compare to ..
Since I have bought the car, I have done 4 extended charges, specifically to top/bottom balance them with a drive from El Cajon to Julian . In 40K miles, with the extended charge, and exact same speed, and passenger load, I have used 8 bars to get to Julian, and 4 to get back for a total of 4 bars left .......This kind of test is a lot more reliable for your capacity..

Does this mean that I have no battery degradation? Maybe, because I have also never let my pack get below 40% state of charge, and based on the 18650 cycles at that discharge level, I should see my real 5% to 15% degradation at
about 80k miles (everything staying the same)

So, I would recommend doing Tony's test, and then picking a long drive for your baseline ... And then do the same after 10K miles, and then compare, and that will give you the real % degradation ......


Top
 Profile  
 
 Post subject: Re: How to Calculate Rated Range / Battery Degradation with
PostPosted: Thu Aug 25, 2016 5:31 pm 
Offline

Joined: Thu Jan 17, 2013 11:13 pm
Posts: 1756
Location: Los Altos, CA
Tony's test is based on what the Tesla BMS is saying about the battery. Your presumption that the test is purely based on top voltage is a little naive. I expect that the Tesla BMS is much more advanced than that. In order to have an even half-decent estimate of SOC, the BMS has to watch the accumulated watt-hours vs. voltage over time. I think your measurement method of driving the same route would have much more measurement error than the BMS. I'm not saying that evaluating the actual driving distance you can get over time is worthless, just that if you don't collect any other data at the same time, you're not accounting for environmental variables. At the very least you should record the trip figures that the car reports like miles traveled and mi/kWh so you know how many kWh the car thinks it's used.

_________________
2012 Shoreline Blue #1462 w/JdeMO | 2018 Tesla Model 3 LR | 4.32kW Motech/Enphase PV Solar + 2x Powerwall 2 AC| Leviton EVB40 40A & Jesla Home Charging | 2015 e-Golf LE (returned)


Top
 Profile  
 
 Post subject: Re: How to Calculate Rated Range / Battery Degradation with
PostPosted: Thu Aug 25, 2016 6:59 pm 
Offline

Joined: Wed Nov 14, 2012 9:50 pm
Posts: 4047
Location: San Diego
Let's start with the very basics.

1) When the battery is fully charged on the 92 series battery pack at 4.2 V per cell, the pack voltage is 92 * 4.2 = 386 V

2) When the battery is in new condition at 386 V, it supplies 41.8 kWh usable. That is the documentation from Tesla and Toyota.

3) When the battery is degraded by any amount, whether 5% or 50%, the maximum voltage is still 386 V.

4) The test that I have outlined has absolutely nothing to do with battery maximum voltage. The only variable is the internal resistance of the cells and how many amp hours the combined total of the cells can produce.

_________________
Tony Williams
QC Charge
1780-104 La Costa Meadows Drive
San Marcos, California 92078 USA
tony@QCcharge.com
www.QCcharge.com
Twitter: QCPower
1-844-EV-PARTS
1-844-387-2787
1-760-798-0342 Office
Hours M-F, 9-5 Pacific Time


Top
 Profile  
 
 Post subject: Re: How to Calculate Rated Range / Battery Degradation with
PostPosted: Thu Aug 25, 2016 7:02 pm 
Offline

Joined: Wed Nov 14, 2012 9:50 pm
Posts: 4047
Location: San Diego
My personal RAV4 EV has 75,000 miles with about 15% degradation.

The task that I have outlined supports that amount.

_________________
Tony Williams
QC Charge
1780-104 La Costa Meadows Drive
San Marcos, California 92078 USA
tony@QCcharge.com
www.QCcharge.com
Twitter: QCPower
1-844-EV-PARTS
1-844-387-2787
1-760-798-0342 Office
Hours M-F, 9-5 Pacific Time


Top
 Profile  
 
 Post subject: Re: How to Calculate Rated Range / Battery Degradation with
PostPosted: Thu Aug 25, 2016 9:21 pm 
Offline

Joined: Wed Nov 14, 2012 9:50 pm
Posts: 4047
Location: San Diego
rayray wrote:
I seriously doubt, Tesla is allowing these batteries to charge to 100% @ 4.2 volts, so depending on how many cells are in parallel, even if your battery was degraded 20% percent, the voltage woudl still be the same, and your test would not provide any value ...


You'd be seriously wrong! Yes, the regen / charge max cell voltage is EXACTLY (to three decimal places) 4.2 volts. There are 92 cells in series. 48 in parallel. 4416 total. Panasonic 18650 cells, 2600mah.


Quote:
So, I would recommend doing Tony's test, and then picking a long drive for your baseline ... And then do the same after 10K miles, and then compare, and that will give you the real % degradation ......


I suspect that I've done more EV range tests that just about anybody. This forum is full of data like that. Here's a good place to start:

viewtopic.php?f=2&t=67

_________________
Tony Williams
QC Charge
1780-104 La Costa Meadows Drive
San Marcos, California 92078 USA
tony@QCcharge.com
www.QCcharge.com
Twitter: QCPower
1-844-EV-PARTS
1-844-387-2787
1-760-798-0342 Office
Hours M-F, 9-5 Pacific Time


Top
 Profile  
 
 Post subject: Re: How to Calculate Rated Range / Battery Degradation with
PostPosted: Thu Aug 25, 2016 10:30 pm 
Offline

Joined: Sun May 12, 2013 6:00 am
Posts: 62
Location: San Diego, CA
TonyWilliams wrote:
rayray wrote:
I seriously doubt, Tesla is allowing these batteries to charge to 100% @ 4.2 volts, so depending on how many cells are in parallel, even if your battery was degraded 20% percent, the voltage woudl still be the same, and your test would not provide any value ...


You'd be seriously wrong! Yes, the regen / charge max cell voltage is EXACTLY (to three decimal places) 4.2 volts. There are 92 cells in series. 48 in parallel. 4416 total. Panasonic 18650 cells, 2600mah.


Quote:
So, I would recommend doing Tony's test, and then picking a long drive for your baseline ... And then do the same after 10K miles, and then compare, and that will give you the real % degradation ......


I suspect that I've done more EV range tests that just about anybody. This forum is full of data like that. Here's a good place to start:

viewtopic.php?f=2&t=67


I was hoping they did not, .... But then that proves the point that Voltage does not equal capacity, and that's what this test is...
I would also take range charts as a basic guidance, as on my car I have a hitch, roof rack, running boards, child seat that I always carry around including towing a Yamaha wave runner, so my range chart is completely different, and accounting for the added extra weight that I'm carrying around, if I went by those charts I would have a very wrong picture of my battery pack capacity/health .


Top
 Profile  
 
 Post subject: Re: How to Calculate Rated Range / Battery Degradation with
PostPosted: Thu Aug 25, 2016 11:16 pm 
Offline

Joined: Thu Jan 17, 2013 11:13 pm
Posts: 1756
Location: Los Altos, CA
rayray wrote:
I was hoping they did not, .... But then that proves the point that Voltage does not equal capacity, and that's what this test is...
No. That is not what this test is. This test is showing you the the "rated range" of the car. It is calculated from the Tesla BMS report of the SOC times a fixed efficiency value. The fixed value is why this is "rated range" and not the "estimated range" that the car gives you as it accumulates your driving history. Tesla knows how much energy is in the battery at every single moment. If you have CANbus tools, you can extract that value - even when the car is off.

_________________
2012 Shoreline Blue #1462 w/JdeMO | 2018 Tesla Model 3 LR | 4.32kW Motech/Enphase PV Solar + 2x Powerwall 2 AC| Leviton EVB40 40A & Jesla Home Charging | 2015 e-Golf LE (returned)


Top
 Profile  
 
 Post subject: Re: How to Calculate Rated Range / Battery Degradation with
PostPosted: Fri Aug 26, 2016 5:23 am 
Offline

Joined: Wed Nov 14, 2012 9:50 pm
Posts: 4047
Location: San Diego
rayray wrote:
I was hoping they did not, .... But then that proves the point that Voltage does not equal capacity, and that's what this test is...
I would also take range charts as a basic guidance, as on my car I have a hitch, roof rack, running boards, child seat that I always carry around including towing a Yamaha wave runner, so my range chart is completely different, and accounting for the added extra weight that I'm carrying around, if I went by those charts I would have a very wrong picture of my battery pack capacity/health .


I don't know what to tell you. There's no "voltage measurement". I'm not sure why you're stuck on something that doesn't exist in my procedure. Heck, it's obvious that you didn't even know what the pack or cell voltage even is on the RAV4 EV.

As to any specific configuration forecast (which is what a range chart is), if you have something DIFFERENT than the specific configuration, you will get a different result. Obviously.

If your range chart is "completely different" than mine with just a child seat and the relatively low impact drag / weight item you list, I think you have a bit more work to do on you chart!

Pulling a trailer is so obviously something significantly different, as a trailer could be any weight or aero drag confirmation. I pulled a 1500 pound load on a flatbed trailer from San Diego to Washington state in May 2016, and took a 30% loss of autonomous range. If that was a box trailer, the range loss would have far worse.

Issues that affect range

1) Drag - Wind resistance - The RAV4 EV has a fixed amount of aerodynamic drag in its original configuration. Obviously, anything you do to change aero drag, like a dog strapped on the roof, will change the drag calculation. High elevation and hot ambient temperatures thins the air, making it easier for any object to pass through the air. In the airplane business, we call this calculation "density altitude". Here's an easy to use online version: http://wahiduddin.net/calc/calc_da.htm. The most "aerodynamic" vehicle will cut through the air with the least resistance.

2) Drag - Rolling resistance - drag from everything that rotates to move the car; tires, wheel bearings, u-joints or cv-joints, gears and bearings, gear lubricant. Generally, the hotter the lubricant, the lower its resistance; the higher the tire air pressure, the lower the tire resistance.

3) Gravity and Mass equals Weight - It will takes energy to accelerate mass. Obviously, it also takes significantly more power to lift the mass away from the gravitational pull of gravity while driving uphill. Quite simply, lighter is better.

4) Ideal speed - every vehicle has a speed where the intersection of the power required to overcome drag and weight is the least. Heavy cars with high drag tires (but extremely aerodynamic) like a Tesla tend to be most ideal in the 20-25mph range and small, lower mass cars like LEAF and Spark EV are probably in the 10-15mph range. Obviously, anything that uses power that isn't being used to overcome drag and weight is a waste; the heater, a/c, etc.

5) Hot batteries store more energy - the hotter the better, however, this same heat tends to significantly shorten their life (Nissan LEAF in Phoenix) and in some cases (Boeing 787), make the battery fail.

***********

Here's some links to some LEAF range testing I've done:

LEAF Range Test links and battery issues:

http://www.mynissanleaf.com/viewtopic.php?t=9694

http://www.mynissanleaf.com/viewtopic.p ... 81#p225481
Planning for September 15, 2012 range test in Phoenix

http://www.mynissanleaf.com/viewtopic.p ... 26#p228326
Phoenix Range Test, Sept 15, 2012

http://www.mynissanleaf.com/viewtopic.p ... 45#p269645
LEAF-S San Diego Range Test on Feb 22, 2013

http://www.mynissanleaf.com/viewtopic.p ... 48#p273048
Nissan LEAF Side by Side Range Comparison, 2012 vs 2013, March 8, 2013

_________________
Tony Williams
QC Charge
1780-104 La Costa Meadows Drive
San Marcos, California 92078 USA
tony@QCcharge.com
www.QCcharge.com
Twitter: QCPower
1-844-EV-PARTS
1-844-387-2787
1-760-798-0342 Office
Hours M-F, 9-5 Pacific Time


Top
 Profile  
 
 Post subject: Re: How to Calculate Rated Range / Battery Degradation with
PostPosted: Fri Aug 26, 2016 6:01 am 
Offline

Joined: Sun May 12, 2013 6:00 am
Posts: 62
Location: San Diego, CA
I actually know what the pack voltage is .. It's 386.4 volts - Per Toyota (check the dismantling guide)
I also know, per Toyota a fully charged pack will go 152 miles at 60 MPH, so that is 3.6-3.7 miles per KW which would equal about 42 KW

Now according to your own numbers of 92 cells in series (92 x 4.2 volts), that number matches ....386.4 volts
But the 48 in parallel, would equate the pack to to 48KW ( 2.6ah x 48 x 386.4) = 48.2KW

Also to address the other post, yes I have connected to the car via techstream, and when I posted on this site that it showed 34.1 KW with regular charge which meant no degradation, it was you, yourself that dismissed it and said, it's not realistic.
You are also giving the BMS too much credit ... The capacity it calculates is based on how much it puts into the battery before it hits 4.2 volts ... I can send you many batteries that have a very high resistance, and will take more change than good 18650's with 2 AH capacity, yet not be able to provide more than .25 AH capacity.

You are also saying these are 2.6 AH Panasonic batteries, and they are charged to 4.2 volts, and if that is the case, then that means on the numbers that you provided, the pack is 48KW. and not 41.8, which means it's software limited ?, and if so, then how can you truly measure degradation correctly ? Seems to me, you would not see any for 100K miles, unless you abused them to 5% SOC on every use.

Anyways, this has gone down enough rat roles .... For me it's a not a valid test of capacity, but for everyone that wants to do it, by ole means, it's definitely educational ...
I'll leave it be ...

Thanks ....


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 53 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6  Next

All times are UTC [ DST ]


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
cron
© Toyota Rav4 EV Forum - part of the MyElectricCarForums.com Group