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I understand the LTO conversion is an excellent choice for many reasons including safety, wider temperature range, specifically low temp performance, long life and very high cycle durability; that’s the reason I’m in the middle of one myself. What I have a hard time understanding is how does this conversion increase mpg; I’ve read some posts that say this, maybe from the same person?? From what I can find the specific energy in Wh/kg and energy density in Wh/L are very similar between LTO and NiMH. Is there another pertinent spec I’m missing? Can someone please explain what specification, i.e. specific energy / energy density / power / other specification makes LTO superior to NiMH. Can this conversion possibly increase mpg? Can some ‘battery brains’ chime in please.
 

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Guess it means you can use the IMA battery for assist "LONGER" than with a nimh type.
 

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I think most people who claim the LTO mod increases mpg are probably focusing on the specific Fit LTO swap where you have larger cells and thus have more electric to use, especially if you're judicious in your use -- restrict charging to regen that wouldn't sap momentum or do plug-in stuff.

Other than that, the LTOs are probably slightly more energy efficient than the OEM NiMH. OEM NiMH might be around 87% energy efficient (I did a little test the other day with some old cells and that's one value I came up with). The Fit LTOs?? Maybe in the 90s? 93%? 94% Depends how you use them... The resistance of your LTO cells/pack will be lower (half the number of cells, and each cell has a lower internal resistance than the OEM NiMH). So, voltage will increase less on charge (i.e. lower power to charge), and sag less on discharge (i.e. more power on discharge). That should produce an overall efficiency delivering power to the wheels, where ICE usage is less. But I doubt this would be a very sizeable difference, probably hardly noticeable impact on mpg... It would make a big difference if you were moving from a crudded-up old NiMH pack, especially if it were so bad that it imposed a lot of background charging. But that'd be the same if you were moving from a cruddy NiMH pack to a good NiMH...

Anyway, not sure what spec captures this latter efficiency idea. Seems like it'd probably be specific energy in some form, like if you compared the specific energy value of 1 LTO cell vs. 2 NiMH ones and scaled-up to the pack level...

edit: Actually, I don't think you can do the comparison from 'specs'. I just tried to wade into a calculation of a sort and I don't see how it would work...

What you would or could do, though, I think, is calculate the energy efficiency from a charge and discharge of a NiMH cell and an LTO cell, and then scale-up to the pack level. Here's a link to some similar calculations, for the NiMH cell, I did the other day. You'd need to have similar values for an LTO cell. I actually have some data for small SCiB LTOs, so maybe I'll look into those later...
 

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EDITED

It all depends on how you look at things. If you have a battery that is 3X to 4X the total capacity of the OEM, then you can make battery energy a larger percentage of the total energy required to move the car at hypermiling speeds, for longer periods - perhaps for your entire commute round trip. You would do this by setting in a constant moderate level of "assist" with a MIMA or an IMA C&C, and lighten up on the throttle. The FCD will zoom up to 150mpg.

Now what does it really mean???? It is probably mostly eye wash, but if you are a serious environmentalist, you are using more electricity and less carbon based fuel. Then, you have to ask yourself how clean is your electricity. At one extreme is coal fired electricity, at the other end would be wind or hydroelectric.
 

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edit: Actually, I don't think you can do the comparison from 'specs'. I just tried to wade into a calculation of a sort and I don't see how it would work... What you would or could do, though, I think, is calculate the energy efficiency from a charge and discharge of a NiMH cell and an LTO cell, and then scale-up to the pack level.... I actually have some data for small SCiB LTOs, so maybe I'll look into those later...
Here's what I calculate for energy efficiency for a 5 cell SCiB LTO 12V battery. I think we need to do this sort of thing with multiple cells rather than just single cells, so here I'm using a 5 cell LTO and for an NiMH you'd probably have to do this for at least a stick, that way we capture the impact of cell-to-cell interconnections, though we don't capture the 'stick-to-stick' interconnections...

Charge/discharge stats for 12V LTO module:
Charge: Duration 31:48, avg. power 69.336, energy= 2205W
Discharge: 29:24, avg power 73.115, energy= 2150W

Overall energy efficiency: 2150W/2205W= 97.5%

Pretty impressive. Not sure how kludge-y my calculations might be. For example, normally you'd have to use calculus, I think, to 'integrate the area under the curves'. Just using average power is a short cut... Plus, these values are for a full charge and discharge, whereas normal usage you wouldn't be using full range...

But, here we see a 10 point increase in efficiency over the NiMH figures I posted before. Although we'd still need to scale-up to the pack level, this can at least give us some idea of the efficiency difference. I think you'd then have to factor this efficiency difference into a normal drive cycle for each pack.

In general, I think this value means that, with the LTO pack you might expect a 10% decrease in the energy you'd be consuming during those segments of your trip when the IMA is in play.

So, for example, in a given trip you might normally have an IMA-based round trip energy usage/throughput of say 864 watt-hours, where you lose 864Wh - (0.87 X 864Wh), or 112.3Wh -- with a NiMH pack.

With an LTO pack it'd be 10% less, like 0.1 X 112Wh= 11.2Wh. That's what the LTO 'pack' saves you in energy, in 'gas', per this fictitious trip... Something like that.

edit:
Those data above are for a 2C charge and discharge. Here's data for a 3C charge and 7C discharge. Also, keep in mind that these are Toshiba's 'high power' cells; the Fit cells are 'high energy', slightly different formulation...

3C charge: 21:14, avg power 101.634, energy= 2158W
7C Discharge: 8:50,avg. power 234.749, energy= 2074W
efficiency: 2074W/2158W =96.1%

Now, just for the sake of sussing-out the 'savings' of roughly a 'NiMH vs. LTO' scenario, in the strictly battery-efficiency related sense (not by having more battery to use), I think we'd need to do something like this:

I said above we'd save 11.2Wh.
A gallon of gas has 33.7 kilowatt hours of electricity.
Insight ICE efficiency is 30%?? So we get 10,110 Wh out 1 gallon of gas.
We'd save: 11.2Wh/10,110Wh/gal gas = 0.0011 gallon of gas per 865Wh fictitious trip.
 

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I said above we'd save 11.2Wh.
A gallon of gas has 33.7 kilowatt hours of electricity.
Insight ICE efficiency is 30%?? So we get 10,110 Wh out 1 gallon of gas.
We'd save: 11.2Wh/10,110Wh/gal gas = 0.0011 gallon of gas per 865Wh fictitious trip.
So, though there is a small MPG improvement due to the small improvement in efficiency of LTO over NiMH, it looks insignificant on a constant comparison(i.e. all things being equal). The huge MPG numbers that folks are going to turn in, come hot weather, will primarily be due to their skill at closely setting their assist augmentation to match their battery capacity and their trip length. (Or, someone may simpley set a high assist level and call it a skill - it is just a game.) Given a 20 mile round trip and exhaustion of the operational capacity of a 72 cell LTO pack, the booby prize is going to the best hypermiler. See my signature. I know how to play this game and the primary variable will be skill and planning. I think someone will get so far beyond 150MPG, that they will be using the metric scale (km/l) to read out their results ;)

I think you recognized this back in post #3 when you said, "I think most people who claim the LTO mod increases mpg are probably focusing on the specific Fit LTO swap where you have larger cells and thus have more electric to use," That is really about the only thing to focus on, and it isn't a bad thing environmentally.
 

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Battery capacity, type, efficiency etc is barely going to make a difference in terms of MPG, as you've calculated.

The biggest contribution of the battery to MPG in a stock Insight is that it helps you accelerate, which is where the most fuel is used. When you're cruising on the freeway, the battery makes 0 difference (unless you're accelerating). The biggest "problem" with the battery contributing to MPG is that in the Insight, the battery is recharged by the engine, so whatever energy you use in electricity essentially converts directly into fuel usage, plus the inefficiency of the electrical system. The only energy input into the Insight is gasoline, so no matter what you do with your battery, you're still burning gas in the end.

The best way to improve your MPG with a battery is to use a grid charger. Then the higher-capacity LTO really shines, because you can charge it up every night, then use it to offset your fuel usage (make sure you disable background charging, of course).

However, depending on your electricity cost, this might still be a wash in terms of monetary savings... let's say you got 60 mpg before, and now you get 75 mpg by using assist all the time (a 25% reduction in fuel use), and that you drain (and recharge at night) 2kWh from the battery every day. If a tank of fuel is $35, you'll save $8.75 per tank in gas. But if your electricity costs $0.13 per kWh (average in the US), you'd spend almost the same amount just on electricity in a month. If you can make your tank of gas last 45 days (that's driving 16 miles a day, at 75mpg), you'll save... $1.56 per tank of gas. :) If you spent $2500 on your LTO conversion, it'd take you about 200 years to pay it off.

When you actually do the math, you will essentially never make back any money you spend on Insight mods. But, an LTO conversion is worthwhile in my opinion because it should last far, far longer than a NiMH pack, which could save you money depending on how many times you would have had to replace the pack otherwise. When there's a good LTO solution (I'm waiting for Linsight), I'm definitely going to convert my car and have fun with more power and capacity. But I'm certainly not expecting to ever make it back.
 

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Battery capacity, type, efficiency etc is barely going to make a difference in terms of MPG, as you've calculated. The biggest contribution of the battery to MPG in a stock Insight is that it helps you accelerate, which is where the most fuel is used. When you're cruising on the freeway, the battery makes 0 difference (unless you're accelerating)....
Good points. Thinking about these things, doing those calculations, has really helped me conceptualize the crux of the issue: The IMA probably helps fuel consumption only a little bit and/or how much depends a lot on how you drive. And then, a seemingly sizable efficiency difference in batteries - say the 10% I mention above - is still only going to be a fraction of a small fraction of the overall energy used to make things go.
 

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EDITED

Good discussion guys.

The advantage of the large LTO packs will not result in much monetary savings, as we all agree, but there are other substantial advantages. Maybe this is the list listed in priority order, at least my priorities:
1. It gets rid of the damnably unreliable and expensive NiMH disaster. In the long run, this factor may result in significant monetary savings.
2. Same as 1. but again ;)
3. If one does their own work, the 72 cell configuration is probably slightly cheaper initially with the used Fit packs. Though there are lots of bells and whistles which one may have to use and monitor more effective, nothing more than the fooler and the interceptor are really required - maybe not even the interceptor.
4. The PHEV move(using grid charginG off cycle) is clearly environmentally cleaner- IF one's source of home electricity is clean.
5. It increases pack capacity by 3X to maybe 5X, allowing the car to function in a pseudo PHEV mode.
6. The large capacity allows magical games with fuel economy to be played, though the results are probably illusory. MIMA and IMA C&C facilitate these games.

Incidentally, the small efficiency increase becomes slightly more significant as the user begins to use the pack more fully in a PHEV mode.
 

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^ The "larger" part has been mentioned a couple times; the "efficient" part we're saying doesn't amount to much in the scheme of things... And the 'capture kinetic energy' part I think Mario was suggesting that in the end analysis all the energy comes from gas. For example, if one were to hypermile and conserve momentum, instead of regen-ing you'd be moving farther forward, it's at best a wash (because if you regen, then use that energy for motion, you've lost energy in the conversion process -- better to just conserve momentum in the first place)... Personally I don't really fall in line behind that idea, because it takes a special kind of driving, there's just a lot of energy that's wasted that can be recaptured with normal driving - if you have an IMA, particularly with a large, good battery. Maybe I misinterpret what Mario was suggesting though...
 

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Basically, I think the biggest advantage would be braking to a stop or going downhill. You're definitely right about conserving momentum being best case, but anytime the brake pads touch the rotors you're turning energy into heat and dust. A more efficient or larger battery would be able to capture some of that that a lesser battery wouldn't be able to handle.

I can't imagine it'd be a /huge/ amount, but probably not negligible.
 

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Please include your Location in your Profile, as ALL g1 Insighters have done.
Thank You.
 

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....but anytime the brake pads touch the rotors you're turning energy into heat and dust. A more efficient or larger battery would be able to capture some of that that a lesser battery wouldn't be able to handle. I can't imagine it'd be a /huge/ amount, but probably not negligible.
I think this is actually a pretty complicated problem. I've always had a hard time putting into words the impact of driving style on questions of 'efficiency', or making sure that driving style is held constant. If you want to accelerate fast and slow down fast - call it 'normal' or 'spirited' driving - then I think there's a lot to be gained from an IMA system, especially one with good management and a great battery. But if you drive gingerly and adjust to system limitations, to maximize energy usage efficiency, then there really isn't much to gain. I think here we're assuming the normal/spirited driving scenario...

In the context of the thread topic, the comparison is between the stock NiMH pack and the Fit LTO conversion. I did some rough calculations and came up with about a 10% efficiency increase at the ~sub-pack level. It'd be slightly more at the pack level, since an LTO-based pack usually has about half the number of cells, so about half the resistance. The difference is about the energy equivalent of being able to run a typical household LED light bulb with the LTO pack any time you're using the IMA. Like I said earlier, it's only a small fraction of a small fraction of the overall energy used to make you go, i.e. electric is only a small portion of the energy that makes you go, gas being the bulk of it, and then the efficiency increase going from NiMH to LTO is only a small fraction of that. So, at this level, it is negligible...

Now, the functionally limiting factor isn't the battery, it's the management. If the NiMH can meet the system's max demands - which a good NiMH pack does - then no better battery will be an improvement (in terms of overall energy efficiency 'at the wheels'). In stock form the IMA system can't capture all kinetic energy available on your typical (normal/spirited) urban drive. I'm not sure how much that limitation is due to management being designed around NiMH limitations or other things. I think it is the battery. If so then underneath it all the battery is the limiting factor.

But, in order to see overall gains you have to hack the management, such as by installing a 'current hack' that will allow the system to put out and take in more power... I don't think stock NiMH cells are pushed as hard as they could be, or rather, I don't think management maximizes and optimizes their usage. But certainly the Fit LTO cells can handle more...

I'm getting bogged down... Basically, the LTO cells/packs don't offer much more than the NiMH packs in terms of efficiency. But they can handle more power, so if you hack the system to put out and take in more power, you can get overall energy efficiency gains from that -- in normal/spirited driving scenarios.

So far none of this really has anything to do with having a larger pack, such as 6.5Ah vs. 20Ah or 144V vs. 166V. When it comes to the Fit LTO cells, size might matter a bit, in the sense that they can handle more power probably at least in part because they're larger cells. A lot of Toshiba's testing on those cells for instance was at a 3C rate; 3C on 20Ah cells is 60 amps, but it'd only be 19.5 amps if they were 6.5Ah cells like the stock NiMH cells. If we had a larger NiMH pack it too could handle more power - so we kind of have to hold stuff constant and make sure we're comparing apples to apples. I think OP's original question was trying to focus-in on the distinctions between the two, mainly trying to understand if there were any electro-chemical performance differences between the two cell types, the two chemistry types. On the flip side, I have ~3Ah SCiB cells that are smaller than OEM NiMH cells but handle more power. Those handle more power due to the chemistry and construction, not due to their size...

Anyway, I've pretty much lost the thread at this point. Lots of details to consider. A larger capacity pack, such as the stock ~1kWh NiMH vs. Fit LTO conversions of about 3.3kWh only becomes a factor in terms of energy efficiency at the wheels if the type of driving you do actually needs that extra capacity, or if you do plug-in stuff. For example, if all you do is stop and go, accelerate and decelerate, one event after the other, you can use the energy to accelerate and then recoup it when you decelerate. The next acceleration event uses the energy recouped from the last deceleration event, and on and on. The total energy used for each of these cycles is very very small -- maybe 24 watt-hours, only 2.4% of the stock NiMH pack. Maybe you can't recoup after every acceleration event, driving circumstances don't allow it. But maybe during an entire trip you can eventually even-out discharge with charge. So, how big a pack do you really need for this? a 10 cycle buffer? 20 cycle buffer? (cycle being that 2.4% acceleration amount)...

Bigger packs only make sense in the Insight if you do plug-in or the size of the pack enables more power and you've hacked the system for more power. Otherwise, small packs are more than enough.
 

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I have a Lean Burn CVT with ObdIIc&c and IMAC&C. Here a my observations and rational for converting to LTO.

I’ve only owned my Insight for half a year or so but I love it. Perfect car for my 25,000 mile yearly commute. I plan to keep this car for 20+ years. Already bought a spare CVT Transmission for it.

IMO if you plan to keep an insight for a long period like this the only options are LTO or bypass. NIMH would be to expensive to replace over a 20 year period if its even available in another 10 years.

As is my LB CVT gives me 75 mpg to work at 55mph. What makes the Insight special IMO is the efficient ICE when combined Lean Burn. In ideal road conditions I’ve managed 90 mpg at 50mph for a 40 mile stretch of road.

The only problem with LB is it requires a light touch to the gas peddle to maintain it. Especially if climbing a hill. There is a small window for optimum LB performance. With 15 amps of IMAC&C assist the window for LB operation increases greatly. This allows for MPG to shoot over 100 on the FCD. Allows you to maintain speed and LB on hills or maintain high speed near 70 mph while cruising in LB.

I have seen first hand what IMA assist is capable of when combined with LB. due to capacity and efficiency of NIMH I only use IMAC&C when climbing hills.

As mentioned LTO with 84cells at 210 volts and 4kw of capacity driven in PEHV mode can give substantial assist with no ICE charging for up to an hour of drive time. MPG of 100-150 easily attainable during that time.

This compared to NIMH that I might use judiciously for 20 minutes, but would require 20 minutes of background charging making LB more difficult to hold during that time.

This all combines for an even greater package when you add Peters current hack, which NIMH can’t handle. IMO an LTO Insight would be more efficient than any PEHV on th market today.

My commute to work is 45 miles one way. A Honda Clarity would get me to work on a 17Kw battery but only gets 55 mpg so I would use .8 gallons of gas and 17Kw electricity. LTO Insight is 4Kw battery and I’m guessing my commute will use .8 to 1 gallon for my 90 mile commute.

Big selling points for LTO

• Economical choice over 10+ years vs NIMH replacements.
• More fun to drive with increased capacity, voltage, and current hack.
• Substantial MPG gains.
 

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That is the same thing I said in post #2 ...................only longer and more details Thanks.
 

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As mentioned LTO with 84cells at 210 volts and 4kw of capacity driven in PEHV mode can give substantial assist with no ICE charging for up to an hour of drive time. MPG of 100-150 easily attainable during that time.
Does this mean you are gonna build one??
 
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