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Discussion Starter #1
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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Discussion Starter #2
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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Discussion Starter #3
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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Discussion Starter #4
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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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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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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Discussion Starter #10
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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LTO > 10,000 cycles is interesting..

If the cells can repeatedly take 100A assist & 50A regen then a small cheap micro (light) pack with a usable (~1ah) is worth considering.

I had 0.8ah approx in my supercap conversion that was fine for 85% of the time.
1ah would put that nearer 90-95% of the time in flatish terrain.

You would use them like supercaps and cycle them hard.
Cycle as we know doesn't mean they suddenly die at 10,001 cycles it means the capacity falls away....
There may be some graphs for life after 20,000 cycles for instance..
Perhaps down to 80% etc etc. That's still useable..

So how much real world driving (miles) does 10,000 1ah cycles get you...
Anyone care to have a go at that?
 

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Discussion Starter #12
1Ah x 2.4V = 2.4Wh
10kW x 15-sec = 42Wh (assuming 15-sec of full power to accelerate to 60mph)
80 cells x 2.4Wh = 192Wh
192/42 = 4.6 or 22% of pack
If you go 25-miles for each 0-60 cycle, then 10,000 cycle can get you get up to 1-million miles (roughly).
 

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Discussion Starter #13
1-million miles

Has any 1st gen Insight achieved 1-million miles yet? The new Li-ion battery pack that I'm working on should get you there.
 

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Discussion Starter #14
My IMA is dead, so I've been driving around the past month on the ICE only. Last week, I left the car at the airport for about 3-days, and forgot turn off the dome light. When I got back the battery was dead. Good thing I had a battery jump starter in the car. As I drove out of the parking lot, I noticed that the engine light was off and the NMH power pack was charging again. After about 30-60 minutes on the highway, the NMH pack was fully charged, and then the engine light back on again. Now the IMA is disconnected again.

This seems to suggest the NMH power pack is still able to store energy and the charger is working. I still see a 95% charge in the pack after a week. So, does this mean the problem is really a sensor and/or a switch? It seemed to have reset itself when all the power is drained. Once the power pack is fully charged, it stops working.

Any thoughts, anyone? Thanks.
 

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What's the code? Sounds like you're getting a P1449-78 - the car tries to charge the pack but it can't charge more than about 10-20% before one of the taps hits the upper voltage threshold, which causes an error and the system to disable... The car needs to be able to charge at least 10% of total capacity (that's the rated amount, I've seen about 20%) within the usable voltage range in order to be usable...
 

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When the 12V went dead, the BCM lost track of all battery data. Upon start, it conducted a forced charge to see how the battery responded. It ended in a positive recalibration that took SoC to full and the conclusion, "this battery is not good. Can I get a CEL/IMA light please?"

Of course, I'm just guessing based on your input, which has not included DTC information.
 

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Discussion Starter #17
According to the OBDII device that my friend used, it showed these problem codes: P1163, P1444, P1449. According to the local Honda dealership, they said the entire IMA needs replaced.

Currently, the NMH pack meter still shows fully charged (minus 1-bar). Any way to check to see if the cells are all or mostly still in good shape?
 

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According to the OBDII device that my friend used, it showed these problem codes: P1163, P1444, P1449. According to the local Honda dealership, they said the entire IMA needs replaced.

Currently, the NMH pack meter still shows fully charged (minus 1-bar). Any way to check to see if the cells are all or mostly still in good shape?
P1444 indicates HV leak. One of your cells has likely vented leaking electrolyte such that it's shorted to the PTC circuit.

P1449 is usually a full cell failure, but it could have several other causes. You need to blink the codes to confirm (link in sig).

To address (not answer) your last question, you realize you're asking about 120 individual NiMH cells? As someone who has battery cell experience, I'm a little surprised at this question. It's fundamentally no different than what you would do with the cells of the 6 different Lithium chemistries with which you work.
 

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Discussion Starter #20
In the Li-ion world, the more sophisticated packs have BMSs that can tell you which string or even which cell has a problem (e.g. voltage level). Since I've not worked with NMH packs before or even removed my Gen-1's pack yet to see how it's configured, I thought someone can tell me if the Gen-1 might have some built-in diagnostics to let you know which cells are in trouble, since the number of cells are not that much.
 
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