Range on RAV

[waidy]

I'm worried. After perhaps five charges that topped out at around 103 the next two were 120. I then needed to drive from south of Santa Cruz to Palo Alto and so put in an extended charge for some breathing room in my range. My RAV4 EV charged to 150 mile range. The balance left after my trip north and back was a few miles more than there should have been, which is okay with me. I didn't know that when extended charge is selected it STAYS in that mode and so when I charged that night the next morning's range was again 150 miles. I turned off the extended range charge mode and it's now charging sometimes 113 and sometimes 120. Please don't congratulate me as I'm worried that this is overcharging the battery and shortening its service life. Any thoughts or advice?

Don't worry. It is OK to charge to 100% as long as you don't let the battery sits at 100% (i.e. use it within half to one hour). The first couple hours (especially the first hour) after the battery top off, it self-discharges in high rate. Self-discharge has effects on SOH (state of health). Therefore, if you charge your EV to 100%, it's best to drive it and not let it sits.

 

[waidy]

I've read previously that, "The best thing you can do to prolong battery life, other than to do extended charges sparingly, is to stay "plugged in" as much as possible when the car is parked and it is convenient to do so."




Question... I noticed that in the Panasonic literature for the 18650 Lithium Ion Cobalt cells that are likely close to the ones in our Rav4 EV's, Panasonic suggests to store the cells at room temperature charged to between 30% and 50%. If we are using our cars for just short trips each day is it better to leave them plugged in between trips, which would keep them at 80% (standard) charge. Or is it better to not plug in the car until the battery guage shows 50% (8 bars) or so, and then plug the car in overnight to give the car time to charge and do a charge balance?

This assumes a moderate climate. If it is very hot maybe it is best to always leave the car plugged in so that the battery Temperature Management System can run?

My 2002 Rav4EV has close to 130K miles on its original battery pack. My charging habits has already been (whether it's the 2002 Rav4EV or the 2011 LEAF): only plug in when it's below 50% and only charge to 80% (unless I am have to drive long distance). Once in a while (~1000 miles), I charged to 100% for it to do cell balancing. And I always make sure I have somewhere to go after the 100% cell balance event.

 

[Richard C.]

I drive only 15-20 miles per day, on average ... and I only charge every third day. I believe the fewer charge/discharge cycles, the better.

 

[TonyWilliams]

I'm worried.... Please don't congratulate me as I'm worried that this is overcharging the battery and shortening its service life. Any thoughts or advice?

My advice is spend less time looking at and worrying about the GOM.

There's nothing wrong with your car.

I have left my house with 88 on the GOM and promptly DROVE (not estimated) 140 miles. If you must have a GOM value to make you feel good, always leave the heater / air conditioner off, and then disconnect and reconnect the 12 volt battery to get:

Extended charge: 146 miles default GOM (41.8kWh * 3.5 default miles/kWh economy)


But, if you want to chat about the GOM, here ya go:

 

[TonyWilliams]

I drive only 15-20 miles per day, on average ... and I only charge every third day. I believe the fewer charge/discharge cycles, the better.

The other component [edit: to long lithium battery life] would be keeping the SOC % as close to 50% as possible. With your extremely low miles, I would only charge to about 60% regularly.

You concept of "cycles" is a bit skewed. A cycle is from dead to 100% charged. There's no advantage in terms of battery life to charge less often, and actually a disadvantage by having a larger range of charge SOC % to discharge SOC %.

 

[Ampster]

.........
The other component would be keeping the SOC % as close to 50% as possible. With your extremely low miles, I would only charge to about 60% regularly.

You concept of "cycles" is a bit skewed. A cycle is from dead to 100% charged. There's no advantage in terms of battery life to charge less often, and actually a disadvantage by having a larger range of charge SOC % to discharge SOC %.

I agree with Tony. Isn't that what Toyota is implying when they say that using extended mode will shorten battery life. Because the charge/discharge curve is flat with very steep knees at either end, it is important with this battery technology to stay away from those over charge or over discharge ends of the curve. That is what the Battery Management System is supposed to do for us. This is different from other battery chemistries.

 

[Richard C.]

The other component [edit: to long lithium battery life] would be keeping the SOC % as close to 50% as possible. With your extremely low miles, I would only charge to about 60% regularly.

You concept of "cycles" is a bit skewed. A cycle is from dead to 100% charged. There's no advantage in terms of battery life to charge less often, and actually a disadvantage by having a larger range of charge SOC % to discharge SOC %.

Good advice ... thanks Tony. So, just to make sure I'm understanding correctly (I have the flu right now, so not up to full strength), I should charge most every day, but stop charging around 60%, and charge again when drops to around 30-40%? If so, I think I'll default back to the 110 charger that came with the Rav. I'll use the 220 in the rare time I need a quick charge for an extended trip.

 

[TonyWilliams]

The other component [edit: to long lithium battery life] would be keeping the SOC % as close to 50% as possible. With your extremely low miles, I would only charge to about 60% regularly.

You concept of "cycles" is a bit skewed. A cycle is from dead to 100% charged. There's no advantage in terms of battery life to charge less often, and actually a disadvantage by having a larger range of charge SOC % to discharge SOC %.

Good advice ... thanks Tony. So, just to make sure I'm understanding correctly (I have the flu right now, so not up to full strength), I should charge most every day, but stop charging around 60%, and charge again when drops to around 30-40%? If so, I think I'll default back to the 110 charger that came with the Rav. I'll use the 220 in the rare time I need a quick charge for an extended trip.

Exactly!

Also, never let the batteries get hot (which really doesn't apply in your neighborhood) and those batteries will last a good, long time.

Even Phoenix Tesla Roadster drivers are doing great after many summers there, thanks to the temperature control of the battery. The Nissan LEAF... Not doing so well (no battery temperature control).

 

[FreshAndClean]

I read Tony's statement about keeping the SOC around 50% to increase battery life. I'm wondering where that percentage came from. I came across this old Tesla roadster forum post about battery longevity. I saw this statement from a Tesla rep:

"Just remember that the car does benefit from being allowed to sit fully charged in Standard mode, and should be allowed to do so frequently, especially if being used on a daily basis. Leaving the car plugged in in Standard mode after it is done charging will initiate this balancing program automatically. This doesn’t take much time, 30 minutes or so should do. It may take several of these balancing cycles to bring the car back to a balanced state if it has become imbalanced, which is something that a lack of regular Standard mode top ups and subsequent balancing cycles can induce."

Is this "balancing program" specific to the Tesla roadster? Or is this balancing cycle inherent in the chemistry/technology of the battery pack itself?

Here is the post in full....
http://www.teslamotorsclub.com/showthread.php/3848-Tesla-Roadster-Battery-Care

So is cutting your charging short of the normal full charge really going to make that much of a difference in the long run especially if Tesla recommends fully charging your battery frequently?

 

[FreshAndClean]

On another note, is it possible that my battery pack is already unbalanced? I

I have 399 miles on it and have been driving very efficiently (about 3.5miles/KW). However I've only gotten to full charge maybe 4 times. My driving range on full charges went from 118 to 108 to 99 to 98. Most of the time the SOC is probably hanging out around 60%.

Last week I drove a total of 300 miles (this was the period between the 108 and 99 driving range on full charges). I have a round trip of 60 miles to work and never quite got to full charge because I've been charging on 110V until Friday when I got access to a level 2 charger. I also have driven with AC off since I got the car.

My GOM read 98 on a full charge (off 110V) today. I know this is not an accurate representation of driving range and a 12V battery disconnect would reset this to around 118 However, I thought the GOM calculates the driving range based on prior driving history. If that is so, then shouldn't my GOM read higher since I am driving efficiently (again 3.5miles/kW)?

 

[Dsinned]

FreshAndClean, "balancing" does in fact occur in our RAV4 EV battery pack, but not until after a full (either std or ext'd) charge has completed, and then usually only several hours later on. Balancing all the cells (4500?) in the pack typically takes <30 minutes. It sounds like the Tesla Roadster battery pack does the same thing, which is no surprise since both cars have essentially the same battery packs designed by Tesla.

Here's a view of my home energy monitor which can be used to graphically understand how charging the RAV4 EV battery "looks" from beginning to end, allowing extra time for balancing to occur.

https://www.enerati.com/Electricity/ConfigDashboard.aspx?param1=NzM0&param2=NTU0&param3=ODAwMDAxMDAxMDAwNDAwMjkwMDAwMDAyMDAwMjAwMDA=

 

[waidy]

FreshAndClean, "balancing" does in fact occur in our RAV4 EV battery pack, but not until after a full (either std or ext'd) charge has completed, and then usually only several hours later on. Balancing all the cells (4500?) in the pack typically takes <30 minutes. It sounds like the Tesla Roadster battery pack does the same thing, which is no surprise since both cars have essentially the same battery packs designed by Tesla.

I do not understand why cell balancing happens few hours after the vehicle completed its charge (whether it is completed in normal mode or extended mode). The first few hours after it's fully charged, discharge rate is much much higher. The 2002 Rav4EV does the cell balancing RIGHT after it's fully (100%) charged. I don't mind leaving my EVs several hours after 80% charge complete, but I don't like leaving it at 100% charged for several hours to wait for the cell balancing.

This is one of the many items I will bring up at the Toyota dealer meeting on March 19.

 

[Kohler Controller]

Dsinned,
Was that power capture of a standard or extended charge profile? If it was of a standard charge, could you also capture and share the extended profile?

I'm wondering if standard charging simply charges the pack until a certain voltage setting, then shuts off, where the extended profile should show the power be at max and then gradually back down as the charging profile switches from Constant Current to Constant Voltage setting.

 

[Dsinned]

Here's another one for an "Extended" charge:

https://www.enerati.com/Electricity/ConfigDashboard.aspx?param1=NzM0&param2=NTU0&param3=ODAwMDAxMDAxMDAwNDAwMjkwMDAwMDAyMDAwMjAwMDA=

This one also had a similar deferred "balancing" event about 3 hours after extended charge completion, although the balancing charge had a lot more variations initially before it stabilzed at a constant level, but still had a duration of ~30 minutes. The end result was a range reading of 129 miles on my GoM.

 

[occ]

Here's another one for an "Extended" charge:

https://www.enerati.com/Electricity/ConfigDashboard.aspx?param1=NzM0&param2=NTU0&param3=ODAwMDAxMDAxMDAwNDAwMjkwMDAwMDAyMDAwMjAwMDA=

This one also had a similar deferred "balancing" event about 3 hours after extended charge completion, although the balancing charge had a lot more variations initially before it stabilzed at a constant level, but still had a duration of ~30 minutes. The end result was a range reading of 129 miles on my GoM.

Dsinned, this looks the same as the previous graph you linked to.

 

[Dsinned]

Yes, I know. Good catch! The link provided (which is still the same as before) only allows a public view going back 48 hours of "events" captured by my home energy monitoring system, so the standard charge (over 24 hours ago) is no longer viewable.

 

[Kohler Controller]

Dsinned,

So the standard charge (first graph you posted) charged at full power and then just turned off, presumably when the pack hit a preset voltage.

This extended charge graph looks that it reached a voltage limit, then backed off to 3kW gradually, then turned off. 6 hours later it is charging again, but this time limited to 3kW.

Is this a different charge session or vehicle, or is this a continuation of the same initial Extended charge (picking up where it left off) putting in the "extended" part of the charge (final 10%)?

 

[Dsinned]

Same vehicle and two different charges on my RAV4 with the one in the middle done to my Chevy VOLT. Kinda confusion but the RAV4 charges clearly show how scheduled charges do not work as expected.

Both charging modes are almost identical, but I do not know what "controls" the duration of charging, nor the interval between full charging power followed by a "rest period" before restarting to balance the cells. It probably does have something to do with the measured voltage level (internally) of the cells, which ultimately controls the duration, whether it be a standard vs. extended charge. The duration of the subsequent "balancing" operation is the same either way, just short of 30 minutes. However, the charging current initially is much higher, leveling off to a constant (reduced) current before it ends.

Of note in the following graph (which is merely a continuation of the last two, including a charge to my Chevy VOLT in between the last two for my RAV4), is that although the "scheduled" extended charge worked, it initiated too early at around 11:35pm and the balancing did not end until about 7:10am this morning. The start and stop times are outside the desired "window" for off-peak electric rates on a TOU (Time of Use) billing plan such as E-9A, PG&E's special rate for EV homeowners. If not for the 3 hour gap in between completion of the extended (or standard) charge and the resumption and completion of the balancing charge, staying within this window would be quite easy. This makes is very difficult to "schedule" during the period of time when off-peak rates are generally available to the consumer on a weekday!

https://www.enerati.com/Electricity/ConfigDashboard.aspx?param1=NzM0&param2=NTU0&param3=ODAwMDAxMDAxMDAwNDAwMjkwMDAwMDAyMDAwMjAwMDA=

 

[Stan]

<snip> ...although the "scheduled" extended charge worked, it initiated too early at around 11:35pm and the balancing did not end until about 7:10am this morning. The start and stop times are outside the desired "window" for off-peak electric rates on a TOU (Time of Use) billing plan such as E-9A, PG&E's special rate for EV homeowners. If not for the 3 hour gap in between completion of the extended (or standard) charge and the resumption and completion of the balancing charge, staying within this window would be quite easy. This makes is very difficult to "schedule" during the period of time when off-peak rates are generally available to the consumer on a weekday!=

Another approach is to give up on the timer in the car altogether and connect a timer controlled relay to the EVSE that just enables charging between midnight and 7am every day. Put the relay in series with the "Pilot" wire in the J1772 cable. When the "Pilot" wire is disconnected by the relay, charging is disabled. Timer controlled relays are cheap. Here is one that can be powered by the same 240vac circuit as the EVSE itself:

http://www.amazon.com/Amico-Digital...8&qid=1363309113&sr=1-2&keywords=amico+cn101a

 

[TonyWilliams]

... Put the relay in series with the "Pilot" wire in the J1772 cable. When the "Pilot" wire is disconnected by the relay, charging is disabled. Timer controlled relays are cheap.

I'd recommend it interrupting the proximity signal instead, or more appropriately switching to 480 ohms to stop the EVSE.