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Old 09-24-2017, 10:20 AM   #1 (permalink)
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Default LTO "Lithium" battery conversion thread

I am starting a LIthium titanate (LTO) battery conversion on my 2000 Insight.
I will try and give details and pictures about the whole process.

The conversion will be a 3.3KWH, 72S, ~185 volt 90lbs pack.

UPDATE: Upgraded it to a 3.86KWH 84S, ~210 volt pack by adding 12 extra cells.

I will be using the BCM fooler + BCM interceptor, as they are simple to install and should make the whole conversion integrate nicely.

The battery packs are from a Honda Fit EV, which was produced in the USA from 2013 through 2015 and available by lease only.

Packs come in 24 20AH cells, 1.1KWH (they actually test at 22AH but rated sticker is 20AH)
2.3 volt nominal,
voltage range : 1.5 - 2.7 *most 95% of capacity is between 2.0 - 2.5 volts
Weight of pack: 30.2 LBS
Deminsions: ~10.5" x ~9.5" x ~5.5" *Each 24 pack can be divided easily in half.
Continuous charge: 160 amps
Continuous discharge: 160 amps
Temperature Performance -30C to 55C


Voltage DROP across 3 cells at resting 7.17 volts was .16 volts at 61.8 amps. Compare that to a 2 volt drop on one of my NIMH sticks which was fully charged.

From my testing of the 3 packs 72s, there was only 1 bad cell. The other cells tested fine and moved in perfect balance with each other.

The active BMS located on the packs is not usable and seems it needs to be plugged into a honda fit car so that it can communicate. So far there are really not many options for a BMS.

The reason I decided to use these cells is they are very robust, extremely long life, work in freezing temperature, Very safe from fires. They simply make a perfect NIMH hybrid battery replacement. The drawback is they are heavy, weighing in at almost NIMH weight. A 72S 3.3 KWH pack will weigh 90 LBS.

Thorough testing at 20 amp charge/discharge of all the cells.


Each pack has removable black covers that go over the top.


30.2 LBS per pack, which is heavy considering you need 3 of them.


Voltage and capacity out at 20 amps discharge rate, test starts at middle of paper below or 50 MAH.
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File Type: jpg 20171109_170633.jpg (184.8 KB, 54 views)

Last edited by insightbuyer; 03-13-2018 at 12:54 AM.
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Old 09-24-2017, 10:27 AM   #2 (permalink)
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Advice needed on my conversion:

What wire gauge should I use connecting these individual packs in series? Is 10 AWG Gauge stranded enough or should I use a thicker gauge wire?

The wire runs are so short so I am not sure if I need to use thicker than 10 gauge.

Thanks.
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Old 09-24-2017, 11:49 PM   #3 (permalink)
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I recommend 4 gauge ultaflex if you're going to be running OEM current.
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Old 09-25-2017, 01:12 AM   #4 (permalink)
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Quote:
Originally Posted by mudder View Post
I recommend 4 gauge ultaflex if you're going to be running OEM current.
Thanks, I was thinking about using 4 gauge but thought it was overkill. But I may do a hack down the road to use even more current if possible.

Maybe I'll buy some of this cable I bought it for my spot welder probes. It is like the 10 gauge silicone wire I buy from hobbyking, but just 4 gauge.


1 ft 4AWG COPPER HEAVY DUTY super flexible Silicone Wire white (aka SUPERFLEX) | eBay
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Old 09-25-2017, 04:43 PM   #5 (permalink)
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Quote:
Originally Posted by insightbuyer View Post
Thanks, I was thinking about using 4 gauge but thought it was overkill. But I may do a hack down the road to use even more current if possible.
If you end up buying stuff from Peter, like the BCM interceptor and fooler, then you should buy a current hack board at the same time. Your LTO pack should have way more power than what the OEM system demands of it... The current hack board does +30% and I think there's an option/method to increase that higher, or maybe you combine that with a voltage hack as well, etc. However you do it, your pack should have way more power than stock demands, so you should be trying to take advantage of that from the get go...
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Old 09-25-2017, 05:22 PM   #6 (permalink)
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Luckily in support of his project I included a free current hack and obdiic&c pcb..
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Old 09-25-2017, 05:32 PM   #7 (permalink)
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Can't beat that deal...
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Old 09-26-2017, 01:48 PM   #8 (permalink)
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Really, I would be so happy to get a current mod. The LTO cells can easily handle, I believe, 160 Amps continuous, and Toshiba says it can handle around double that for short bursts. However, I'm not 100% sure about these specs as it was listed someplace for 20 AMP hour cells, and another for 40 AMP hour cells or 2P. Can't confirm for sure the current handling.

Either way I should easily be able to handle 160 amps for 10 second bursts of assist.

Here is where a current spec is listed if anyone is interested.
https://www.toshiba.com/tic/datafile...e2014Final.pdf

The good thing is you can beat these cells all day at high amps and they will take it. I also believe you can beat the electric motors all day with no issues. I push 7500KW on my ebike all day and that is considered low power compared to what many other people are pushing on these small motors with not very good cooling. I could imagine a bigger motor, like what would be in the insight could handle much more power without any problems, especially considering you are not using continuous power at high levels.

Last edited by insightbuyer; 09-26-2017 at 01:53 PM.
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Old 09-26-2017, 09:54 PM   #9 (permalink)
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retepsnikrep, what do you think if I used 84 cells total, and only charged around 2.45 volts per cell to keep it under the DC-DC converter max 210 volts.

What about if I put like 10 diodes in series to lower the voltage to the DC-DC converter by about 10 volts so that I can charge the LTO cells to the max? I assume the DC-DC converter will not draw too many amps and it will not be a big deal to lose a little bit of power from the diodes to have a larger battery in the car.

Or if worse comes to worse I can just pull out 4 cells from a pack and use 80 cells. The LTO cells max resting voltage is 2.56 so this would work as I should not charge this high anyway.

I could fit 3 packs plus 1/2 packs easily of the LTO cells in the battery compartment, so why not use them? I also plan on buying a spare pack so will have an extra pack anyway sitting with no use.

Should I consider doing this, or will it cause me more trouble than it is worth using such high voltage?

Last edited by insightbuyer; 09-26-2017 at 10:09 PM.
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Old 09-27-2017, 03:03 AM   #10 (permalink)
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The DC - DC converter shuts down around 220V.

Just use 84 cell charged to 2.56v = 215V approx..

Forget diodes to the dc-dc, it draws a fair bit of current..
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