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Jime are you saying 540:00 bucks for the 2 blocks ,how did you come up with that number,,plus what other fees or expenses you think,,sounds very good,,
 

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Jime are you saying 540:00 bucks for the 2 blocks ,how did you come up with that number,,plus what other fees or expenses you think,,sounds very good,,
The price of $270/block is the special Greentec discount price, only at InsightFest 2020. It is mentioned in the InsightFest planning thread in the socials section, but obviously I need to get information on the discount program much more visible. Farther discussion of the discount program in this thread would be off topic.

Later: If you study this thread carefully, there will be at least one PC board from Peter required, and the aluminum mounting rails - which I hope someone will produce for sale. I personally think the total would be somewhat below a 3 yr. NiMH purchase, but it is VERY early in the game. It is entirely in Peter's hands to make the electronics work, the rest will be pretty easy.
 

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I have been lurking on this thread and have a couple of questions:

1. Do 48 cells have more or less capacity than the original NiMH pack? (let's us watt-hours for comparison sake?)

2. Is the same amount of assist/regen as the NiMH pack the goal? If so, will the motor handle the additional current? My in-my-head calculations suggest 50% more current (or more) might be required to get the same motor output at lower voltages.

3. Are there temp sensors in the motor (hopefully in the windings) that could be used to determine this?

4. If the total capacity is less than the NiMH pack, will this demand a more aggressive background charging regimen?

5. How much more current than a NiMH cell can one of these cell conduct? If a lot more, then what about going with smaller cells that handle the same amount as the NiMH cells, but are cheaper, but then would permit more in series and permit higher voltages (lower current to the motor)?
 

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1) More = approx 3 times.
2) Yes the motor will handle the current.
3) There is no temp sensing in the motor, it has been over driven many times before without incident or failure.
4) The LTO capacity is more so this question isn't relevant.
5) Probably the LTO can discharge at twice the current of the Nimh. so 200A v 100A

Smaller cells aren't available in such an easy to use package.
 

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Long answer follows, then I think we should get this type discussion over into another thread. This 2 block idea is experimental and somewhat speculative at this point, IMO. Folks who want to do a conversion at this time are probably best with the 3 block approach, using plate and sideways mounting of BCM/MCM. Peter seems to like to think these kinds of questions linearly without taking every tributary in the river.

I understand your questions. I'll give it a shot, subject to comment/correction by the more qualified.
1. The stock pack NEW has about 3.9 Ahr usable capacity at the nominal voltage of 144V. My testing of the 24 cell packs shows about 16.4 Ahr in a "safety" range of 2.5V-2.0V/cell, or 16.4 Ahr for a 48 cell pack at a nominal voltage of 2.3V/cell or 110.4V total nominal. Short answer - a lot more capacity, but Peter's electronic wizardry is required to extract this much capacity at the reduced voltage.

According to my calculation the stock pack usable energy is about: 3.9Ahr x 144V(avg)= 936 watt-hr.

The 48 cell configuration would be 16.4Ahr x 110.4V(avg)=1810.6 watt-hr., assuming Peter's wizardry can extract it all.

2. I think that Peter addressed the assist level in his post #12 above. Since he is powering the electric motor at lower than stock nominal voltage, the current hack may be required to get back to stock levels of assist. I take it from his post that he doesn't actually know this answer yet, but he may speak again. As I recall from his other posts short current boosts of 50% have not produced damage. I guess that data comes from the rally car.

3. There are no temperature sensors in the motor. I suspect folks would like to see some for this experimental work. Just my guess, but if one started cranking continuous assist levels, then heat might become an issue. Even if we had sensors, would we know where the limits were? If one were going to contemplate damage thresholds, I guess one would look at deterioration with temperature of rare earth magnets, and maybe varnish on the stater windings???

4. There is much more capacity, not less, but don't exactly know what will work out for background charging. Since Peter's efforts seem devoted to fooling the BCM/MCM into "seeing" a stock battery, I assume background charging would look about the same.

5. As I recall from my dash gauge, the stock setup NiMH delivers about 80A for short bursts. Some of the Toshiba data talks about charging and discharging(?) rates as high as 200A. At a 48 cell pack price of $540 for LTO, with all its inherent advantages, what do you see as effectively cheaper? Folks who have made the conversions with LTO like the packaging, stability, and long cycle life of these packs. Since the two block pack is an easy physical fit, what's not to like? As for smaller cells, certainly available, but I don't see the advantage. eq1 experimented with the 2.9 AHr SCiB but he hasn't pushed that as an alternative. I think he bought them new so maybe he can comment on their cost. I really don't know about cost currently, I just know I can, in practice, get things done with the Greentec packs at a price which seems reasonably attractive. I did a little poking around on the internet at available cells. I didn't see anything as cost effective in terms of watts/$. I just don't know of an ACHIEVABLE alternatives which deliver the same bang for the buck. This has been widely discussed for almost 4 years now, since mudder introduced the Leaf cell idea, and nothing usable has been mentioned.
 

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Thanks for the detailed answers, @jime.

The post title "48 cells - can it be done" made the engineer in me ask the corollary, "what might be a show-stopper". It sounds like most things are not a concern. But long term operation at elevated current may be a concern if the only testing done to date is short bursts or regular driving at low altitudes.

The use case I'm thinking of is an August day on Interstate 70 in Colorado and Utah, and also in portions of Arizona or New Mexico, on one of those long grades at 6000+ feet, or crossing the Sierra Nevada or the Rockies through one of the scenic passes.

There you have to worry about heat buildup because there are fewer air molecules at altitude to remove heat energy. Add that the double whammy of a hot day, because it increases the energy of each molecule. Not only is there does each molecule have less capacity to accept heat from the engine, but there are fewer of them, because the more energetic molecules push themselves further away from each other. (aka "density altitude").
 

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There are no temperature sensors in the motor. I suspect folks would like to see some for this experimental work. Just my guess, but if one started cranking continuous assist levels, then heat might become an issue. Even if we had sensors, would we know where the limits were? If one were going to contemplate damage thresholds, I guess one would look at deterioration with temperature of rare earth magnets, and maybe varnish on the stater windings???
With enough Googling and perhaps conversations with people identified in those searches, one might find enough literature to determine where to place sensors and what the limits might be. That data might include the temperature at which the permanent magnets start to lost magnetism, the temperature rating for the motor enamel, etc. As for experimenting, one might start by instrumenting some cars in western states. To make data collection prompt and seamless, one might use Bluetooth so that the driver's phone can be used to send the data directly back to a server for analysis. Ideally, coming up with a regime that could be performed on a dyno would complement real drive data nicely.
 

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That's all been discussed before and for another thread really, so let's keep on track with fooling the voltages to get it working for now.
 

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But long term operation at elevated current may be a concern if the only testing done to date is short bursts or regular driving at low altitudes.

The use case I'm thinking of is an August day on Interstate 70 in Colorado and Utah, on one of those long grades at 6000+ feet, or crossing the Sierra Nevada

There you have to worry about heat buildup because there are fewer air molecules to remove heat energy.
This discussion definitely does belong somewhere else,
(mod feel free to split/delete these and above comments into an appropriate thread)
my 2 cents having owned an antique EV many years is that it’s not just current but also voltage that makes heat. (AKA overall power dissipation)

As hard as it may be to believe all things remaining the same
higher voltages have always lead to my older EV running higher motor/brush temperatures despite actually using a lower peak amperage at the higher voltage .

This same phenomenon would apply to BLDC in the case you run a lower voltage but higher amperage, in a hybrid this would be even more applicable,

I will leave it to you to puzzle out why actual dissappation goes down with voltage (even at higher current)
in this application on your own.
There are other angles to this discussion on this same forum

Feel free to pm me, I will not respond further in thread.
 

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Thanks for the detailed answers, @jime
The use case I'm thinking of is an August day on Interstate 70 in Colorado and Utah, and also in portions of Arizona or New Mexico, on one of those long grades at 6000+ feet, or crossing the Sierra Nevada or the Rockies through one of the scenic passes.
I think the quick answer to such situations is that affected owners should first thing install Calpod/clutch switches so that they can disable assist in these situations. A more sophisticated solution may come along.

BTW, the reason that higher current gets dangerous is that power loss to heat, goes up with the square of a current increase:

P=(I^2)R ,

Though the R here isn't purely resistive iirc

Also, as mentioned above, as voltage increases, current and heat can drop:

P=VI

All very interesting to contemplate.
 

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P=(I^2)R ,

Though the R here isn't purely resistive iirc

Also, as mentioned above, as voltage increases, current and heat can drop:

P=VI

All very interesting to contemplate.
in a car like an insight the motor/controller does not support field weakening, so your ability (opportunity) to use the extra current is in a more narrow window at lower voltages meaning (most likely) in the case you are climbing a mountain you will be much less able to access the power in the battery even on a full charge.

this would also be true in regular driving as assist would fad much more quickly.

min my old EV despite thinking I was driving the “same” and higher voltage would reduce current my efficiency at lower speeds was reduced due to switching losses and obviously I was once again able to access more power during acceleration meaning more heat.
In my case the heat didn’t much matter since most motors have a pretty generous 1 hour rating.

I guess what I’m saying is use common sense but more than likely even having a big battery can’t likely exceed the limits any more than the original design would in rolling hills.
 

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I guess what I’m saying is use common sense but more than likely even having a big battery can’t likely exceed the limits any more than the original design would in rolling hills.
There are some things which can be done through control electronics changes. The retepsnikep current hack circuit is apparently quite successful in producing higher currents and more power from the electric motor. I haven't driven one. At my age the stock acceleration levels from an untinkered 72 cell LTO are adequate.

I'm not so sure about the 48 cell approach. I think for folks who are converting soon, the well proven 72 cell approach is probably best. It may take a year to get the 48 cell configuration well sorted.
 
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