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Discussion Starter #41
OK, it's running. No fires and no explosions yet;)

I had precharged the battery to 2.6V/cell, so didn't see much charging at idel. Voltage seemed to pretty much be 13.92V +/- a couple of mV. I drove it in the neighborhood a bit and noticed that when one uses a lot of assist, the voltage drops about half a volt - all read with my Fluke taped to the dash. Didn't have time to set OBDII C&C parameters, but certainly will.

I did notice when I auostopped that the Bam started reading about .8A and the 12V battery rose to 14V pretty quickly, so things are right at the edge of the LTO and may need 6 cells. Anyway, just some quick observations. Will drive more this afternoon if weather doesn't storm like crazy.

Picture below.
 

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How about turning off the IMA battery and see what happens with engine starting on the 12v LTO system.
 

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I thought cutting the red/yellow wire would "peg" the dc-dc output at 13.85V, but apparently it just eliminates the "cold start" 14.8V phase.
I've only seen 13.85V, like the target is 13.85V, but I'm sure there can be fluctuation under different loads and conditions... But yeah, detaching DVCT just gets rid of the DCDC's ability to change voltage based on engine temperature.
 

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Discussion Starter #45
How about turning off the IMA battery and see what happens with engine starting on the 12v LTO system.
Yeah, 12V start works fine. Can't remember the surge current limit for the LTO, but it is quite high. 105A sticks in my mind, but not sure of that.
 

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Yeah, 12V start works fine. Can't remember the surge current limit for the LTO, but it is quite high. 105A sticks in my mind, but not sure of that.
I believe it's 10C so for a 20ah battery it would be 200 amps. That being said I believe that's the SCIB cells and haven't done the math on the busbars used so the fit packs might be less than the battery themselves. Doing the math on the Fit EV itself with the motor all out and other accesories running it definitely could do over 100A though.
 

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Discussion Starter #47
Drove some more. Saw just a couple of instances of voltages above 13.92, but even that is on the steep part of the charge curve. At that point on the charge curve, it would only take a small amount of charging current to push the battery voltage up rapidly, but I'm not seeing it so far on the Fluke.

It is little hard to discern the roll of counter voltage of the battery in limiting the current from the dc-dc converter. Everything seems to be in rough equilibrium at 13.8-14.0V, but that is right at the ragged edge for 5 cells. I'll drive it for a while, but I'm already looking at 6 cells.

@eq1. I assume that your 13.85V is read at the OBDII C&C. Initial testing shows some voltage drop between the battery and the gauge. I think this has been noted before. The measurements at with a Fluke directly at the battery, for what its worth.
 

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Can't remember the surge current limit for the LTO, but it is quite high. 105A sticks in my mind, but not sure of that.
I believe it's 10C so for a 20ah battery it would be 200 amps.... it definitely could do over 100A though.
These sounded low to me (105A and 100A), so I perused my SCiB lit and it's weird - none of it actually shows a figure for the high energy cells, unlike for the high power cells... The 10 second max discharge current for the 10Ah high power cells is 750 amps. In a pack brochure, they show a large pack made up of 40Ah cells, what I presume to be the high energy type, and give a max discharge current of 300A. In this same brochure they don't show a max discharge current for the 20Ah pack, and it's right next to the 40Ah one.

In any event, we know they do something like 120 to 150 amps seemingly easily based on Peter's work with the 48 cell pack... The 12V starter load is about 1000W; with a 12V lead acid it's something like 140 amp discharge current, but of course with massive voltage sag... My guess is it'd be something like 80-90 amps with the 20Ah Fit LTOs...

I start my car with 10 OEM NiMH cells - it'd be a walk in the park for the Fit cells...

I assume that your 13.85V is read at the OBDII C&C. Initial testing shows some voltage drop between the battery and the gauge. I think this has been noted before. The measurements at with a Fluke directly at the battery, for what its worth.
My figures, including the 13.85V one, are based on measurements at the battery with a DMM checked against a 10V voltage reference. As I mentioned in my previous post, the OBDIIC&C values will be higher and fluctuate.
 

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Yeah, 12V start works fine. Can't remember the surge current limit for the LTO, but it is quite high. 105A sticks in my mind, but not sure of that.
Honda
~20kwh for ~92kw peak motor:
Used less than 5C peak in the Fit.

Toshiba
Seems to
Reccomend ~3C if you want ~20,000 cycles to ~75% capacity.

With fewer total cycles .. Burst up to 10C (6min rate)
If you are more than 20% away from the end
.. ie 20% from top on charge .. and 20% away from bottom on discharge.
 

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Burst up to 10C (6min rate) if you are more than 20% away from the end, i.e. 20% from top on charge and 20% away from bottom on discharge.
Technically, that's a charge rate (that graph), not a discharge rate. I know the high power cells can actually do better on charge than discharge. But the high energy cells?
 

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Technically, that's a charge rate (that graph), not a discharge rate.
Agree .. however .. myself , I'd apply it both ways .. the ion diffusion rate through the electrolyte is the same in either direction .. there is a small direction difference on the anode/cathode .. but (myself) I don't think it's enough to worry about in this context.

I know the high power cells can actually do better on charge than discharge. But the high energy cells?
Both of those graphs I linked to were for the 20Ah version .. ie .. the version being used by jim here.

 

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I know the high power cells can actually do better on charge than discharge.
depends on which high power cell
on the 2.9Ah high power cell 420w out .. vs .. 480win
on the 10Ah high power cell 1800w out .. vs .. 1500w in
 

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^ My point was that the graph shows the charge rate, we're talking about discharge rate when it comes to starting the car. Most conventional lithium ion cells have a paltry charge capability compared to their discharge capability. The high power SCiBs have a much more even charge vs. discharge capability, with the small ones having a better charge capability. But the main point there is that charge vs. discharge is much more even than conventional cells.

So, How do we assume that the discharge capability of the high energy cells is even like the high power cells? I find it real odd that Toshiba doesn't post any discharge power figures...

Ion diffusion through the electrolyte isn't the only or even the main factor determining discharge/charge power capability. You've also got to pull stuff out of the neg electrode and push it into the positive, and vice versa... The fact that one cell is 'high power' and the other is 'high energy' means there's a difference in the electrodes, probably the NMC ratios on the positive... Do we know that that doesn't effect the charge/discharge balance? Does anybody actually have a max discharge spec from Toshiba for the 20Ah cells??
 

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^ My point was that the graph shows the charge rate, we're talking about discharge rate
repeat of already agreed in post #51 above.

IamIan said:
But the main point there is that charge vs. discharge is much more even than conventional cells.
again .. repeat .. already agreed in post #51 above.
IamIan said:
.. however .. myself , I'd apply it both ways
Ion diffusion through the electrolyte isn't the only
who said it was the only .. not me .. I specifically said it wasn't the only.

or even the main factor determining discharge/charge power capability.
disagree.

You've also got to pull stuff out of the neg electrode and push it into the positive, and vice versa... The fact that one cell is 'high power' and the other is 'high energy' means there's a difference in the electrodes, probably the NMC ratios on the positive.
no it doesn't have to mean that .. it could .. but it doesn't have to.

It is very common to change the ratio of the thickness of the conductor .. copper .. aluminum .. to the thickness of the chemically active material.

Does anybody actually have a max discharge spec from Toshiba for the 20Ah cells??
sense you've rejected what has been provided (because of your personal opinion) .. what would you accept ?

batteries are not a black and white thing .. higher rates do damage faster .. but damage / degredation still happens at slower rates too .. it is not .. at __amps there is zero and __+1 there is suddenly all the damage.
 

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Discussion Starter #55
Sorry I brought up the surge current.

I was probably wrong anyway. I "think" the 105A was the maximum sustained charging current, iirc.

Anyway, it looks to me like much of the discussion is about long term charge and discharge. Starting the Insight is probably well within the definition of "surge." The starting pulse only goes on for a few seconds. I checked the manual which says the starter current is 80A or less. That is well within 5C, so Insight starting with the LTO wouldn't seem a problem even though we have the high energy cells, not the high power. Starting on the 12V is so infrequent, there are virtually no cycles unless someone is running in bypass mode. JMO

I think the paucity of good data from Toshiba does cause confusion, but we are all friends here so lets keep it down to a faint roar;)

I think the longer period use of current hacks is a better question than the starting question. How much current can we draw for longer time frames without degrading the life cycles? Ian's spec for the Fit said 5C which would be about 100A, about a 25-30A increase over stock I suppose, but even here the relationship to life cycles comes up. I don't have a clue how to make a decent judgement. (Maybe this is good subject for a new thread.)

Maybe the best course, for those deeply committed to this technology is to have a full set of spares on the shelf. They are cheap enough to do that. What is the storage life anyway?
 

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Discussion Starter #57
Just separated a 6 cell set, but did damage the seventh cell. I think I learned something about the separation tool. I also just realized that on these "separation" exercises, the risk of shorting two adjoining cells cases is eliminated by first drilling off one end of the bus bar at the split line and keeping it isolated.
 

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Just separated a 6 cell set, but did damage the seventh cell. I think I learned something about the separation tool. I also just realized that on these "separation" exercises, the risk of shorting two adjoining cells cases is eliminated by first drilling off one end of the bus bar at the split line and keeping it isolated.
Nice! Did the now solo damaged cell get punctured? If not I wouldn't mind paying for it to experiment on tapping depth.
 

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Discussion Starter #59
^ Sorry, it's punctured. Just realized that the sharpened bevel on the pain scraper needs to be flawless. Otherwise it can penetrate the "off" cell wall with any irregularity on the cutting edge. I'll just drill out the tapping hole and give you the data:)

BTW, the odor of the electrolyte is kinda strong and distinct, but not hurtful near as I can tell.
 

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^ Sorry, it's punctured. Just realized that the sharpened bevel on the pain scraper needs to be flawless. Otherwise it can penetrate the "off" cell wall with any irregularity on the cutting edge. I'll just drill out the tapping hole and give you the data:)

BTW, the odor of the electrolyte is kinda strong and distinct, but not hurtful near as I can tell.
Wow that's mighty kind of you! I can certainly paypal you a few dollars for doing that if you want since I know for your application in the car it's not going to be deep enough for the vibration.
 
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