Toyota Rav4 EV Forum
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Battery Degradation / Extended Charge
http://www.myrav4ev.com/forum/viewtopic.php?f=8&t=2474
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Author:  miimura [ Mon Aug 31, 2020 10:44 pm ]
Post subject:  Re: Battery Degradation / Extended Charge

Using the GOM to estimate anything is meaningless unless you have the computer reset the mi/kWh used for display. Then you can use it to compare the usable capacity from one time to another. The simplest way to reset the mi/kWh is to disconnect the 12V battery. However, the usable energy reported by the BMS also varies with temperature and time since charging if it is balancing the battery.

As the battery degrades, the Extended Charge energy will gradually reduce until it doesn't add any energy to the battery beyond the Standard Charge. This is because Toyota wanted the Standard charge to represent a constant amount of energy. As the battery ages and degrades, the Standard Charge will charge up to a gradually increasing percentage of usable energy in the battery pack. Once the Standard Charge reaches 100% of the usable energy, the Extended Charge setting won't do anything.

Long story short, it's very unlikely that the battery would degrade 20% in the first three years and then not at all in the following three years. It's more likely that your understanding of the actual battery degradation over time was inaccurate.

Author:  smkettner [ Tue Sep 01, 2020 5:13 am ]
Post subject:  Re: Battery Degradation / Extended Charge

atzmark wrote:
One of the frustrating things about this board is that you can ask a specific question, and you get lots of answers that don't address or answer the question.

My original post ask this question: "It seems odd that the battery would degrade 20% in the first three years, and not at all the following three years. I was expecting the loss to be somewhat linear, rather than gaining 5 miles of range."

No one has answered the question. I thought that the the degradation stopping for three years might indicate a charging problem.

Any answers to the above question would be appreciated.

Thanks, Mark
Yes lithium degrades on a curve. Fast at first and then it slows down. This includes several factors including usage, time, heat, average charge level and probably more. The fact that the curve has flattened is actually expected. This is a battery, not brake shoes.

I really expect the 5 miles gained is based on your current driving style, general driving conditions and temperature as the primary factors. The 5 miles gained does not reflect actual battery capacity change. DTE meter changes based on conditions and is an estimate of range only not a battery capacity meter as then it would read energy units not miles.

Author:  atzmark [ Tue Sep 01, 2020 6:15 am ]
Post subject:  Re: Battery Degradation / Extended Charge

Thanks all for the info on battery degradation. This my understanding of the several responses:

I shouldn't complain that my 7 year old 60K mile EV still gets 65-75 GOM (& actual) range. I rarely drive more than 25 miles a day, so who cares what the GOM says.

Like taking my blood pressure, I can "feel" when I using a lot of juice (85mph+ freeway, love the Sport button!) and my internal GOM adjusts the range pretty accurately.

I don't know how the first 35k miles were charged/driven; I drive hard, short runs.

While a declining capacity curve is the norm, the 3 year curve & followed 3 year flat line is uncommon, regardless of prior & current use & driving style.

Most likely my charging system is fine.

As the motor whine gets louder, I'll bring the car in for replacement (under warranty) and hopefully get a Techstream or Tesla diagnostic readout having some battery capacity info.

Thanks again to all. I think we can put this thread "to bed". Really appreciate all the responses & info.

Mark

Author:  alflash [ Tue Sep 01, 2020 10:59 pm ]
Post subject:  Re: Battery Degradation / Extended Charge

atzmark wrote:
... As the motor whine gets louder, I'll bring the car in for replacement (under warranty) and hopefully get a Techstream or Tesla diagnostic readout having some battery capacity info.
...
You can know, for example,
Image

Do you have a record of sound of motor whine?

Author:  atzmark [ Thu Sep 03, 2020 3:56 am ]
Post subject:  Re: Battery Degradation / Extended Charge

No recording.

Seems I would have to put the car on a lift and get some recording equipment.
Or I would hang out the door and hold the cell phone under while moving (sounds scary).

Any info on how to get a recording of the motor noise would be appreciated.

Mark

Author:  alflash [ Thu Sep 03, 2020 5:54 pm ]
Post subject:  Re: Battery Degradation / Extended Charge

atzmark wrote:
No recording.
Seems I would have to put the car on a lift and get some recording equipment.
Or I would hang out the door and hold the cell phone under while moving (sounds scary).
Any info on how to get a recording of the motor noise would be appreciated.
Mark
For example (without a sound finders),
https://youtu.be/dEYsYZo8Oz8

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