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Old 07-19-2018, 04:11 AM   #1 (permalink)
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Hi Everyone,

I'm new to the world of Honda Insights, and I was just informed by the local Honda dealer that my IMA needs to be replaced ($4K). I bought this 2000 Insight for less than $4K a couple of years ago. I work with Li-ion batteries (all 6 chemistries), and LTO is one of my favorites, especially for EVs. Putting a power pack together is easy, but it's the implementation or interfacing with the Insight's electronics that's got me confused.

How do I get the documentation and schematics for the Insight's IMA system to better understand the system architecture? Thanks.
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Old 07-19-2018, 04:22 PM   #2 (permalink)
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Thank you, gentlemen. I have 30 more pages to go (and a manual). My LTO suppliers in China will be providing me with some prices (including BMS), and I'll compare that against LFP prices. LFP is usually 30-40% less expensive, but also less than 3,000 life-cycles as compared to > 10,000 for LTO. If interested, I'll be glad to share that with you. Karl
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Old 07-20-2018, 04:09 AM   #3 (permalink)
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To get a more accurate price quote from my suppliers in China, I'd like to have the following for a basic power pack:
- Max pack voltage
- Max continuous discharge (amps)
- Max regen charging voltage and current
- Capacity of existing NMH power pack
- Max dimensions of power pack

While LTO can easily handle all of the Insight's requirements, but I need to select the right recipe for LFP (20-40% less expensive than LTO) for best performance and service life.

Thanks.
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Old 07-20-2018, 04:58 AM   #4 (permalink)
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OK, after going through some of the generously provided tech data, I see the power pack nom. voltage is 144V and the motor is 10kW. So, max current output is going to be less than 70A, the same with max inbound regen current to the pack.

The current NMH pack is 750Wh? Once I know the pack dimensions, then I'll be able to estimate the kWh that I can build with LFP or LTO. Even a rough estimate will help. I just got my Insight back from the Honda dealer shop today, so haven't had time to pull the pack out myself yet. Thanks for any numbers.
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Old 07-20-2018, 07:11 AM   #5 (permalink)
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Quote:
Originally Posted by Olympia-WA View Post
OK, after going through some of the generously provided tech data, I see the power pack nom. voltage is 144V and the motor is 10kW. So, max current output is going to be less than 70A, the same with max inbound regen current to the pack.

The current NMH pack is 750Wh? Once I know the pack dimensions, then I'll be able to estimate the kWh that I can build with LFP or LTO. Even a rough estimate will help. I just got my Insight back from the Honda dealer shop today, so haven't had time to pull the pack out myself yet. Thanks for any numbers.
I think the pack is closer to 1 kWh.

Here's what I have in my notes. This was gleaned from other's postings. I haven't measured it myself, so I can't swear to it.

100 amp discharge 50 amp charge rate

Pack dimensions: 17 1/4 L x 11W x 5H

Battery bay dimensions:
Including the space of the side Junction Board all the way to the DC/DC wall , you have about:
W ~571 mm side to side (~22.48") or 16.5" with junction board left in place
L ~333 mm front to back (before the little bump ups and space for OEM air intake and exhaust) (~13.11")
T ~235 mm top to bottom (without computer modules and such on top). (~9.25")
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Old 07-20-2018, 12:34 PM   #6 (permalink)
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bump to top of list.
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Old 07-20-2018, 01:44 PM   #7 (permalink)
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Keep us posted on how things go.
Very interested.
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Old 07-20-2018, 08:06 PM   #8 (permalink)
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Yes ,,we all been waiting to see who can make this a for the masses. Am sure China is a good start.
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Old 07-22-2018, 03:57 AM   #9 (permalink)
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Quote:
Originally Posted by Olympia-WA View Post
To get a more accurate price quote from my suppliers in China, I'd like to have the following for a basic power pack....
A lot of the answers to these questions can depend on your implementation...

- Max pack voltage

The absolute max is 192V - that's the MCM's high cutoff voltage, i.e. if it sees a tap (12 monitored NiMH cells per tap) at 19.2V it will throttle regen current...

- Max continuous discharge (amps)

The system max discharge current is a little below 100 amps. But, in practice, the car only commands max assist for about 4 seconds at full throttle in 3rd and 4th gears, so except for that 4 seconds, it's ... about 6.4kW. Basically, designing a pack you'd want to be able to do close to 100 amps continuously, I'd think, and do a current hack and some such mods to increase the stock power output... If you didn't want to do that you could get by with a pack that can do a solid 5-10 seconds at 100 amps and a continuous discharge of about 50 amps...

- Max regen charging voltage and current

192V, ~50 amps... Since you're asking this here, your first question about max voltage makes me think you're looking for something different for 'max voltage'... The car charges the pack and 'recals' to a nominal 75% state of charge at about 17.4V per tap, so 1.45V per cell. Not super sure about this, as it might be 17V at rest rather than say 17.4V at a modest charge rate (like 6-10 amps)... In any event, this is about the voltage that the car considers the pack 'usable-full'...

Basically, the usable voltage range per tap, at open circuit, is about 14.4V to 17V (144 to 170 pack voltage); the absolute low voltage is about 12V, the absolute high is 19.2V. I think the MCM throttles current if a tap can't hold a voltage of at least 13.2V...

- Capacity of existing NMH power pack

Nominal is 6.5Ah. In general, the car only uses the 25 to 80% state of charge range at max; in practice it uses a lot less than that, like 50-75%... And given the exigencies of the NiMH cells, it ends up being pushed higher and higher over time, so instead of say 50-75, it's more like 65-90...

edit: One more thing... I've looked quite a bit at using LTO cells as near direct replacements for the stock NiMH. I looked mostly at Toshiba's SCiB 'power' cells (opposed to their 'energy' cells), with a nominal voltage of 2.4V. Given the NiMH nominal of 1.2V and the way the car's 'system' is designed around that, I'm pretty convinced you could use 60 LTOs, 6 cells per tap, and it'd work under most circumstances without much fuss... At some point I'll have time to actually build a pack out of a bunch of cells I bought a while ago... I think the only thing I'd add to the system would be Peter's BCM Interceptor, so I could control the high voltage cutoff; as I mentioned, the stock system routinely charges to about 17V per tap (and allows 19.2V), which would be too high for cells with a nominal max voltage of only 2.7V (so 16.2V per 'tap')...
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Old 07-22-2018, 06:55 AM   #10 (permalink)
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Thanks so much for the info everyone. I will design my pack to a max of 192V and 100A continuous. Using LFP, that's 60S25Ah or 4.8kWh, if I can fit all the cells in the space. If using LTO cells, then it'd be 80S6p or 1.5kWh (using 1.3Ah cells). I'll find out the cost of these two packs with BMS from my Chinese suppliers. Might reduce the LFP cell capacity to reduce cost (maybe to 2kWh pack). If using 25Ah LFP cells, the max is 4C, so should not be a problem. Some LFP formulations go up to 50C (reduced cycle-life) for race cars and motorcycles.
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