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Converting my Nimh CRZ to Lithium (Cells & Supercaps) and boosting IMA performance...

57433 Views 399 Replies 33 Participants Last post by  PeterPerkins
I'm a long time member/admin on the Insight Central forum and have worked on lots of the Honda IMA cars developing gadgets and doing Lithium conversions.
I've just bought a nice CRZ for myself and intend converting it to Lithium, upping the IMA power output and developing manual IMA control and info display devices.

I'll be documenting it in detail on here.

However for background reading visit
That's were millions of posts and most of my daily work is as I still have two G1 Insights and support owners worldwide.

The IC link below gives you a heads up and a few details on my ideas.

Honda CRZ Nimh to Lithium Conversion.

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Just got a second battery assembly on the bench ready to do the necessary mods.

Nimh sticks removed and will be making the BCM Fooler and high current wires later today.
Should be very simple to reassemble it and swap it over for the unit in my new car.
The LTO lithium packs will just be sitting in some sort of tray in the boot for now.

Couple of disassembly videos and pics. All looks fairly straightforward.

CRZ 125A Fuse versus G1 Insight 100A fuse.


Inside the BCM/MCM Combo unit.
Note the HV isolated section on the right.


Vacant space after batteries removed.


You might be able to get the 2 LTO blocks in here but I need to look at the actual space/height in the car.

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Sounds awesome. Looking forwards to seeing all the hackery
Following!! Willnit be possible to convert to lithium pack with normal operation do you think?

What is the weight difference.
Modifying the CRZ switchboard for Lithium and adding a BCM Fooler.
Note this fooler is made from 7 x 10k 0.1% tolerance resistors.
I have also allowed for potential higher voltage hacking with a pre-resistor.



Tomorrow i will be looking at the temperature sensors, IPU serial comms and battery current sensor.

TanZf1 not quite sure what you mean?

Weight a bit heavier but not measured yet.
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Sorry i meant if it isn't currently possible to swap out the nimh for the lithium pack, will what your doing make it possible to do so?
Sorry i meant if it isn't currently possible to swap out the nimh for the lithium pack, will what your doing make it possible to do so?
No, maybe, possibly. The OEM Lithium pack is much more complicated, rarer and expensive. :unsure:
I won't be looking at that unless someone gives me a free OEM Lithium pack to examine or funds my purchase of a second hand one here in the UK. .

But my present work if successful will make it possible to shoehorn any suitable homemade Lithium pack into an NIMH car.
The associated voltage and current hacking work may also significantly improve on the OEM 10kw maximum assist level. :devilish:

The standard G1 Insight IMA motor can do 30kw with voltage and current mods. The CRZ should be very similar.
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Sorry i meant if it isn't currently possible to swap out the nimh for the lithium pack, will what your doing make it possible to do so?
probably not, but perhaps if there's a way he can make a stand-alone BCM fooler.

This looks like the car is just going to think the NiMH pack is still there.
Okay i think i get it, I'm useless at this kinda stuff tbh.
I'm liking the sounds of increasing the assist level!!
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Thanks for the link. I have a 1st Gen Insight, but I haven't been over to insightcentral in quite a while--I recognize your forum name, though. :)
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I might investigate upping the current to the motor on my 2013 CRZ.
I have electronic and printed circuit design skills but its the wrong time of year to work outside so will spend the winter researching what can be done.
It sounds like modifying the current sensor signals will be relatively straightforward.
Food for thought..
Todays tweaking and research..

Reattached modified switchboard to pack.
Installed 3 x 9.1k battery temperature fooling resistors.
Measured voltages of current sensors etc and input circuitry on BCM/MCM pcb.
Checked removal of battery and voltage tap board etc would not adversely affect airflow.
Fan draws air through the IPU section before venting it so all seems good.

Powered up some modules on the bench to gather data for analysis.

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I expect theLi Ion battery electronics will be different.
I expect theLi Ion battery electronics will be different.
Indeed. But worth researching for useful info and comparisons. Good luck.
I suggest start a thread to document your ideas and progress.
Testing the IPU (Intelligent power unit) with my HV supply whilst gathering data and I took it up to 200V without issue.
(I wasn't expecting any to be fair as the IMA motor will stress it far beyond that if the main fuse blows at any time and the engine is at high rpm.)
Over 250V output is not uncommon for the unloaded IMA motor at high rpm.

Early research is indicating that simply substituting a higher voltage pack 3 LTO blocks (172V Nominal) instead of 2 (115V Nominal) will be worth attempting later.
Initially if the 48 cell works ok I will add another half block (12 cells) for 144V Nominal.
Obviously some mods are required for the car to accept this configuration, you will see these as we go along.

A few pics of some bits today.

9.1k Temperature sensor resistors. (Should get us around 25C)

Underside of MCM pcb.

Battery current sensor inputs. 82k resistor to ground then 15k resistor into nether regions of board.

Phase Currents sensor inputs. 10k resistor to ground, then 2k resistor into nether regions of pcb and beyond!
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So if I can locate the current sensing resistors on my 2013 MCM and parallel the resistors to reduce the signal, this should cause the MCM to increase the max current.
Or are the signals pwm and the ecu is monitoring the duty cycles?
Presumably the motor current is varied by pwm of mosfets, so it would be interesting to know how close the pwm gets to 100% on full assistance.
It's not pwm asfaik.

All the current sensors are 5V devices and rest at 2.5V when no current is flowing.
So above 2.5V = assist (discharge), below = regen(charge), or vice versa. I don't know which way round it is at the moment.

So you can't just double up or parallel the resistors shown as any % change has to be the same in each direction.

You will of course also need a higher rated main fuse if you up the current.
If you fake the current then your systems SOC counting will also be out.

(Upping the voltage for me may well be a much easier way to gain power and won't impact the fuse in amp terms or affect OEM SOC calculations.
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So needs a bit more circuitry to detect the direction and then switch in a resistor. I'd use an Atmega or AT Tiny processor and 4066 cmos switch + resistor.
If the current control pwm is already close to 100% for full assistance, then higher battery voltage would be needed.
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