50kWh???

http://www.windingroad.com/articles/reviews/driven-2012-toyota-rav4-ev/

According to the above link, the 2012 RAV4 EV's "actual" maximum storage capacity is 50kWh. I think this may be true.

Here's why . . .

In all of TOYOTA's literature, the Tesla battery spec is always said to be "41.8kWh". But, this number is always also said to be the "USABLE" amount of the battery's total capacity, not necessarily the "actual" total capacity. The consumer's perception of the RAV4 EV is that the usable and actual battery capacities are the same, but I don't think so.

It would be prudent for the longevity of the battery to hold some amount of the battery's SOC in reserve. I am more familiar with the Chevrolet VOLT and this is the case for that car's battery. GM rates the total and the usable differently. The latter on my 2012 VOLT is 10.4kWh, but the actual total is 16kWh. GM only "allows" the VOLT to use between ~20% and ~90%, or ~70% of total stored energy. Unlike the RAV4 EV, there is only ONE charging mode in the VOLT. Of course, a recharge can be interrupted before completion if the owner so chooses, but most VOLTs are typically "FULLY" recharged to the so-called maximum "useable" capacity of the battery, i.e. no more than 10.4kWh. Of the 5.6kWh extra UNUSEABLE capacity, some is kept in reserve at the bottom and some potential capacity at the top that is never actually used.

In CS (charge sustaining) mode, the VOLT switches on a 55kW electrical generator via a 1.4L gasoline engine. This provides the means to maintain a sufficient charge on the battery so the driver can literally "extend" a VOLT's range several hundred miles on a full tank of gasoline. Except for rare situations, the gas generator is not used to directly power the drivetrain. The drivetrain is ALWAYS directly powered by the traction motor via energy drawn from the battery. The function of the generator is really just to keep the battery from dropping below its minimum allowable 20% SOC.

TOYOTA probably does somewhat the same thing, especially on the bottom end, except it "allows" the RAV4 EV owner to have more "selectable" control of the high end SOC.

Of course, I am not certain of how Toyota (Tesla) manages the RAV4's battery's SOC, but I suspect the "usable" amount of its total capacity is about 65 to 70% based on "normal" charging, and maybe as much as 85 to 90% based on "extended" charging.

So, when TOYOTA states that a normal charge restores the electrical energy in the battery to ~80%, I think that really means no more than its actual TOTAL storage capacity of 70%. And when they say an extended charge restores the battery to 100%, I think that really means no more than its actual TOTAL capacity of 90%.

Comments?

Dsinned said:

Comments?

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My comment is we went through all this same guessing and pulling needles out of the haystack.

I prefer to just measure it.

Dsinned said:

So, when TOYOTA states that a normal charge restores the electrical energy in the battery to ~80%, I think that really means no more than its actual TOTAL storage capacity of 70%. And when they say an extended charge restores the battery to 100%, I think that really means no more than its actual TOTAL capacity of 90%.

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Like I said previously, any of the pure BEV manufacturers will not use GM and Toyota's model that they successfully use on their hybrid cars.

SOC will be 100% at whatever that maximum of the battery actually is, and regardless of its ACTUAL capapcity (when 50% degraded, it will still have "100% SOC", for instance).

I think I already posted this, but it will look like this for a NEW non-degraded battery:

100% SOC = 41.8 kWh (or whatever the real capacity... I hate guessing)

100% stored energy = 93% SOC = 38.9kWh

100% useable energy = 90% SOC = 38.436kWh = "Extended" charge

100% useable energy (what we use in the range chart) MINUS unusable of 0.836kWh at the bottom of the pack's charge = 37.6kWh (still 90% SOC)

80% useable energy = 30kWh = 71.8% SOC = "normal" charge

0% useable = 2% SOC = 0.836kWh

Edit: the batteries are 2200mAh Panasonic 18650's (18mm diameter, 65mm length... about the size of a AA battery), and assuming 3.6v each, I get 107 in series = 385.2 pack voltage. I estimate 5363 cells, so 50 would have to be in parallel for each of the 107 in series.

This is an interesting conversation to me as I compare the data from my VW conversion and my RAV.

For my VW conversion I charge to 80% of capacity and never go below 20% capacity at the bottom, So I have a usable 60% of my total pack capacity. I constantly have to be aware of AHrs consumed so I don't push my batteries too far. In the case of the RAV a lot of that calculation is done and translated into miles so I can relax a lot more about range and getting home with AHrs in the pack.

Ampster said:

For my VW conversion I charge to 80% of capacity and never go below 20% capacity at the bottom, So I have a usable 60% of my total pack capacity.

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What battery chemistry?

Ok, here's some real data:

This is a Turtle to 100% "extended range" charge:

2012-Nov-18

Average Power:
7.202 kW (Blink 30amp EVSE)


00:57:03 until 08:10:32 - 49.909 kWh (7 hours 13.5 minutes)


Looks like a little cell balancing followed by a top off charge two hours thirty minutes later:

10:40:58 until 11:07:04 0.509 kWh (26 minutes)


So, what can we learn from this?

1) I'm quickly warming up to the idea that the battery is really bigger than I originally thought, which means it's a REAL PIG in efficiency !!!

2) 49.909 + 0.509 = about 50.4, but some of that was discharged during the cell balancing. I'll say 50.2kWh. Then, we have to estimate the charger efficiency, which I'll just say 85% = 42.67kWh in the battery
Then, we have to add about 2.39% at the bottom of the battery of the battery = 1kWh (0.0239 * 41.8kWh)

42.67 + 1 = 43.67kWh stored energy (about 87.3% of estimated 50kWh advertised / rated size)

Then, I'll take 94.75% of that (0.9475 * 43.67) = 41.4kWh calculated useable capacity

Ok, I will believe that there is 41.8kWh "officially" useable in that 860 pound battery. Don't ya just love numbers?

NOTE: All of this is assuming no power was used for battery temperature control (or more accurately, the 85% charger efficiency reflects all power losses).

Tony, thanks for the data. Are you certain all of your data is accurate, and not based on assumptions. Here are my thoughts on this discussion:

1. How do you know the source voltage was exactly 240Vac at your Blink charging station? What about load current? Were you measuring and/or recording these parameters for the entire charging duration? Your Blink's 7.2kW charging rate is its "rating" and not necessarily the actual output power while charging. Thus, it can only be used as an approximation in computing the actual power required in terms of killowatt-hours to charge the battery. Also, what was your AC "power factor" while charging? If PF is not at unity as seen by the load (battery), then it must also be measured to accurately calculate actual power consumed in killowatt-hours by the battery while charging. (As an aside, most battery's appear as a purely resistive load, so a unity PF assumption is generally warranted in such power calculations.)

2. Where are you getting the percentages for the RAV4 EV's battery reserve at the bottom end SOC threshold to "turtle mode" as well as the top end's margin to being actually fully 100% charged? As you know there threshold's have not been published by Tesla and are held as "intelligent property" by most big manufacturers. Your #s are very precise, so you must have a very knowledgeable/reliable source for this kind of information at Tesla, correct?

3. How do you know the efficiency and therefore the internal losses of your Blink charger and same for the onboard charger in the RAV4 EV? 85% is probably a good "guess" but you may be off by as much as -15%, or +5%. To some degree the length of the charger's output cord (typically 25') also contributes to the overall losses, which is especially noticeable if the surface temperature of the cord feels warm while charging.

4. The way most EV onboard chargers work, is they slowly ramp the applied voltage down as the battery reaches a full charge. So, you cannot assume a constant or steady state rate of charge to the battery, especially during the last 30 minutes.

5. The post-charge "topping charge" may have actually been the battery's thermal management system operating to cool or warm the battery, or precondition the interior of the vehicle (which should only last for ~15 minutes).

I know you don't put much stock in this sort of information, but just out of curiousity what was the fully extended charged reading that resulted on your i/p range gauge, or what you call the "GoM"? And also, I would be interested to know what was your cummulative "average" miles/kWh leading up that extended charge?

Also, based on your collected real world data so far, are you of the same opinion that the RAV4 EV (Tesla) battery pack "as designed" has a maximum storage capacity of 50kWh, not 41.8kWh as most people probably think? That is USABLE capacity only, and this is what I was saying at the start of this tread. If your assumptions are fairly accurate, it sure looks like "50kWh" is the actual capacity doesn't it! :mrgreen:

Dsinned said:

Tony, thanks for the data. Are you certain all of your data is accurate, and not based on assumptions. :

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Mostly assumptions, until such time as we prove them.

1. How do you know the source voltage was exactly 240Vac at your Blink charging station? What about load current? Were you measuring and/or recording these parameters for the entire charging duration? Your Blink's 7.2kW charging rate is its "rating" and not necessarily the actual output power while charging. :

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The Blink measurements are just that; measurements acquired by the Blink EVSE. They are recorded continuously. I reported them verbatim. I have measured my supply voltage many times over the years, and it's rock steady at 240v.

2. Where are you getting the percentages for the RAV4 EV's battery reserve at the bottom end SOC threshold to "turtle mode" as well as the top end's margin to being actually fully 100% charged? As you know there threshold's have not been published by Tesla and are held as "intelligent property" by most big manufacturers. Your #s are very precise, so you must have a very knowledgeable/reliable source for this kind of information at Tesla, correct?

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Well, I think I have pretty good insight on this, but I already was surprise at 41.8kWh useable being actually useable. Facts are rare in EV land, and BS rules the day (until it's regulated).

3. How do you know the efficiency and therefore the internal losses of your Blink charger and same for the onboard charger in the RAV4 EV? 85% is probably a good "guess" but you may be off by as much as -15%, or +5%. To some degree the length of the charger's output cord (typically 25') also contributes to the overall losses, which is especially noticeable if the surface temperature of the cord feels warm while charging.:

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My charger efficiency guess is not off by the numbers you suggest. At 120v, I would guess 75%. Longer charge times equal lower overall efficiency.

4. The way most EV onboard chargers work, is they slowly ramp the applied voltage down as the battery reaches a full charge. So, you cannot assume a constant or steady state rate of charge to the battery, especially during the last 30 minutes.

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You are correct. I don't have to assume that... It's measured and documented. Fast DC chargers at 120 amps start ramping down at 50% SOC.

5. The post-charge "topping charge" may have actually been the battery's thermal management system operating to cool or warm the battery, or precondition the interior of the vehicle (which should only last for ~15 minutes).

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Eh, maybe. The garage is about a perfect 70F degrees. But, it does have to balance and top off cells. Especially after running it to such low SOC.

I know you don't put much stock in this sort of information, but just out of curiousity what was the fully extended charged reading that resulted on your i/p range gauge, or what you call the "GoM"? And also, I would be interested to know what was your cummulative "average" miles/kWh leading up that extended charge?:

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Don't know, don't care. I won't ever document a fluid number like the GOM. If I drive up a hill before I charge it, I get one value. If I drive down the hill, I get another. No thanks.

maximum storage capacity of 50kWh, not 41.8kWh as most people probably think? That is USABLE capacity only, and this is what I was saying at the start of this tread. If your assumptions are fairly accurate, it sure looks like "50kWh" is the actual capacity doesn't it! :mrgreen:

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I'd say it's between 46kWh and 50kWh, but that really doesn't affect me directly. If it ain't useable, it ain't useable :mrgreen:

TonyWilliams said:

Dsinned said:

So, when TOYOTA states that a normal charge restores the electrical energy in the battery to ~80%, I think that really means no more than its actual TOTAL storage capacity of 70%. And when they say an extended charge restores the battery to 100%, I think that really means no more than its actual TOTAL capacity of 90%.

Click to expand...

Like I said previously, any of the pure BEV manufacturers will not use GM and Toyota's model that they successfully use on their hybrid cars.

SOC will be 100% at whatever that maximum of the battery actually is, and regardless of its ACTUAL capapcity (when 50% degraded, it will still have "100% SOC", for instance).

I think I already posted this, but it will look like this for a NEW non-degraded battery:

100% SOC = 41.8 kWh (or whatever the real capacity... I hate guessing)

100% stored energy = 93% SOC = 38.9kWh

100% useable energy = 90% SOC = 38.436kWh = "Extended" charge

100% useable energy (what we use in the range chart) MINUS unusable of 0.836kWh at the bottom of the pack's charge = 37.6kWh (still 90% SOC)

80% useable energy = 30kWh = 71.8% SOC = "normal" charge

0% useable = 2% SOC = 0.836kWh

Edit: the batteries are 2200mAh Panasonic 18650's (18mm diameter, 65mm length... about the size of a AA battery), and assuming 3.6v each, I get 107 in series = 385.2 pack voltage. I estimate 5363 cells, so 50 would have to be in parallel for each of the 107 in series.

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From the statement given under this forum's home page description for "specs", "The 2012 Rav4 electric’s battery pack is a 386 volt lithium ion battery comprised of 4500 cells and rated at 41.8 kWh. Maximum output is 129 kW." I have seen the same reference to the number of cells in a couple of places, so let's assume it's true, although "4500" is likely a rounded off number, but close enough.

Can we then not deduce what the total or actual maximum "as designed" battery capacity should be as well?

From Tony's post above, he says the capacity of each Li-ion cell (made by Panasonic) is 2200mA-hrs. Therefore, the total amp-hour capacity would be 9.9kA-hrs. Thus, if, for the sake of argument, the actual nominal terminal (no load) output voltage of each cell is say 3.7Vdc (which of course, may not be accurate), then the maximum battery capacity would only be 36.63KW-hrs. But, as we all know, this is untrue, as the actual "rated" (usable) battery capacity is 41.8kW-hrs.

What am I missing here??? Tony??? Anyone???

Dsinned said:

From Tony's post above, he says the capacity of each Li-ion cell (made by Panasonic) is 2200mA-hrs. Therefore, the total amp-hour capacity would be 9.9kA-hrs. Thus, if, for the sake of argument, the actual nominal terminal (no load) output voltage of each cell is say 3.7Vdc (which of course, may not be accurate), then the maximum battery capacity would only be 36.63KW-hrs. But, as we all know, this is untrue, as the actual "rated" (usable) battery capacity is 41.8kW-hrs.

What am I missing here??? Tony??? Anyone???

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Panasonic makes several different capapcity cells.
http://industrial.panasonic.com/www-cgi/jvcr21pz.cgi?E+BA+4+ACA4001+4++WW

2900mAh - NCR18650
3100mAh - NCR18650A
3400mAh - NCR18650B

My understanding is that Tesla is currently using the 3100mAh and the 3400mAh cells in the Model S (depending on which version of the car you buy). My guess is that the Rav4ev is using the 3100mAh cells. (51.615kWh)

palmer_md said:

Dsinned said:

From Tony's post above, he says the capacity of each Li-ion cell (made by Panasonic) is 2200mA-hrs. Therefore, the total amp-hour capacity would be 9.9kA-hrs. Thus, if, for the sake of argument, the actual nominal terminal (no load) output voltage of each cell is say 3.7Vdc (which of course, may not be accurate), then the maximum battery capacity would only be 36.63KW-hrs. But, as we all know, this is untrue, as the actual "rated" (usable) battery capacity is 41.8kW-hrs.

What am I missing here??? Tony??? Anyone???

Click to expand...

Panasonic makes several different capapcity cells.
http://industrial.panasonic.com/www-cgi/jvcr21pz.cgi?E+BA+4+ACA4001+4++WW

2900mAh - NCR18650
3100mAh - NCR18650A
3400mAh - NCR18650B

My understanding is that Tesla is currently using the 3100mAh and the 3400mAh cells in the Model S (depending on which version of the car you buy). My guess is that the Rav4ev is using the 3100mAh cells. (51.615kWh)

Click to expand...

I don't think that's right. The skuttlebut is 3100 for both Tesla S-85 and the physically lighter S-60 (it just uses less cells).

It is believed that the 40kWh Model S will not use the 3100s, but obviously, that car hasn't been built yet.

Toyota was offered either battery choice, but 3400 wasn't one of the choices. In my above quote, there are tons of guessing and mistakes. We know a little bit more now.

I've not seen anything difinitive either way. But it does look like the rav is using the "a" cells if the count is truly 4500. 4500x3.070aH = 13815ah * 3.7v = 51,125.5kWh.

You may be right that all cars are currently using the 3100 cells. But there was/is a rumor that the 85kWh Performance cars are using the 3400's.

Actually, nominal cell voltage for the NCR-18650A, per Panasonic's specs, is 3.6V. Therefore, assuming 4500 cells is accurate information, each typically rated at 3070mAh, (as stated on Panasonic's lookup table specs per the above link given by Tony), the 2012 RAV4 EV's total Li-ion battery capacity is 49.734kWh (@25C).

Rounding off to 3100mAh (which is what Panasonic did in the 16850A's actual datasheet spec), the number would be 50.220kWh (@25C). Worse case, using the "minimum" spec of 2950mAh, the number becomes 47.790kWh (@25C).

By George, I think we've got it!!! :mrgreen:

Dsinned said:

Actually, nominal cell voltage for the NCR-18650A, per Panasonic's specs, is 3.6V. Therefore, assuming 4500 cells is accurate information, each typically rated at 3070mAh, (as stated on Panasonic's lookup table specs per the above link given by Tony), the 2012 RAV4 EV's total Li-ion battery capacity is 49.734kWh (@25C).

Rounding off to 3100mAh (which is what Panasonic did in the 16850A's actual datasheet spec), the number would be 50.220kWh (@25C). Worse case, using the "minimum" spec of 2950mAh, the number becomes 47.790kWh (@25C).

By George, I think we've got it!!! :mrgreen:

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I have a hard time believing it is some perfectly round number like 4500 cells, but I don't have an alternate number.

Now, we can start guessing on the cell arrangement (parallel and series).

110 in series and 41 in parallel (110s41p)would give you 4510 total and a pack voltage of 396 assuming a nominal cell voltage of 3.6.

These cells charge to a higher number (4.2v) than other LifePO's that I am familiar with. They also hold there nominal voltage much farther into the discharge curve. Here is one of the discharge tests I found.

Pack voltage is 386. The LEAF uses 4.05 volts per cell at 80% charge, and 4.1 at 100%.

The cells are rated up to 4.3, and Nissan had originally had used 4.2.

I'm resurrecting this old thread just to see if we have learned anything new that can shed more light on this mysterious "number". :mrgreen: