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Discussion Starter #1 (Edited)
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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Discussion Starter #2
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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Discussion Starter #4

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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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Discussion Starter #8 (Edited)
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/datafiles/SCiBBrochure2014Final.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.
 

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Discussion Starter #9 (Edited)
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?
 

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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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Discussion Starter #11
Ordered another LTO pack today, this will allow me to now use 84 cells.

Waiting in the mail for:

BCM FOOLER AND INTERCEPTOR

My Meanwell power supplies and LED CC supply that should allow me to charge my pack at 2 amps. Will charge a complete empty pack in 10 hours.

Bunch of M6 4 AWG ring terminals to connect the pack in series.
 

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Discussion Starter #12 (Edited)
I received my power supplies for my charger, and also the ring terminals.

I have to figure out in what and how I am going to mount those. I also need to decide if I want to leave this in the car, or keep it outside the car.

Weight is about 4 lbs for all 5 supplies, which consist of all meanwell:
3x LRS-100-48
1x LRS-50-12
1x LPC-100-2100

The ring terminal ends seem very long, not sure why they are so long, just wasted weight as they are heavy. I will solder the wire into them as I don't have a crimper. I believe a soldered connection is better anyway.

If anyone could give advice on if I should mount the power supplies in the car or leave them outside and plug into the car from the outside with the 210 volts?

If left in the car and connected to the battery but unplugged, will they cause any errors with the car computer?

EDIT: YOU DO NOT NEED THE 12 VOLT POWER SUPPLY FOR THIS SETUP, THE VOLTAGE IS HIGH ENOUGH WITH JUST THESE 4
3x LRS-100-48
1x LPC-100-2100

I never wired in my 12 volt power supply as just the 4 I listed will charge up to 215 volts.






 

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When I made one from those components I just used a case from some old computer part that I had laying around. Many have used power supply cases. I never leave them in the car. Some have gotten CELs if they start the car with the charger plugged into the battery. I think it's better to remove it from the car.

OTOH, I recently bought a car that has one permanently mounted. It's been there for years and works fine.

Sam
 

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Discussion Starter #16 (Edited)
Are you planning on running it without a BMS?
YES, in the beginning, I will run this without a BMS. While not recommended, the cells so far all tested to move perfectly together. I am talking .001 volts together and all 3 packs. Other than the one bad cell which I will discard.

A BMS is definitely not needed for balancing.

The big issue without having a BMS is that you never know if a cell will go bad and go out of balance. That is really the big risk of not having a BMS. This chemistry is very safe, you can discharge to 0 volts, but I am not sure what happens if you overcharge a cell.

However, these cells are used and a few years old and most likely a bad cell would have shown signs like the one bad cell I detected. Highly unlikely it will just go out of whack after all this time when the cells are protected from external damage.

But I plan on doing something down the road and more research into a BMS, I'll be doing checks often of the cell voltages and leave my battery compartment opened. Hopefully, Linsight comes out and that will have a BMS, so I will at least wait until I see what is up with that.
 

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Discussion Starter #17 (Edited)
I decided I am going to build a clear acrylic case for the charger. It will look cool and also allow for easy adjustment of the voltages. At first I am just going to mount them on wood until I get the materials.

I also plan on adding this 0-300V - 0-100A display voltmeter ammeter, for only $14.80 dollars it will give me an idea of the charge amps, and voltage, amp hours out, the temperature of inside charger case.

It got good reviews and some reviewers say it is accurate, so worth the try. Would be nice to have an idea of what the charger is doing.

https://www.aliexpress.com/item/AC-300V-100A-Accurate-Energy-Meter-Voltage-Current-Power-Voltmeter-Ammeter-Greem-Backlight-Overload-Alarm-Function/32819133911.html?spm=a2g0s.13010208.99999999.263.lfKBjc

 

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YES, in the beginning, I will run this without a BMS. While not recommended, the cells so far all tested to move perfectly together.
I am debating doing the same thing. I have some C-max cells and have run them in the car for a short period of time without a BMS while I am working on my own design. My stock battery is basically dead so it would be nice to have assist again. While my cells are not as safe as yours, I would only use about a quarter of their capacity without the BMS, so I would catch any drift way before it became a problem by doing manual measurements periodically.

But I plan on doing something down the road and more research into a BMS, I'll be doing checks often of the cell voltages and leave my battery compartment opened. Hopefully, Linsight comes out and that will have a BMS, so I will at least wait until I see what is up with that.
My thread is here: http://www.insightcentral.net/forums/honda-insight-forum-1st-gen-discussion/103754-lithium-cell-swap-stock-bms-11.html

The title is a little misleading as it has evolved quite a bit, but I am doing a lithium conversion and designing my own BMS based on ATTiny's. Not as advanced as Linsight, but it has been a great experience. I tried to document my own research into BMS options, which you may find interesting, but there really isn't much out there
 

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Discussion Starter #19
I would say if the cells move together you should be OK with periodic checks. I have 280 cells in my ebike which I never put in parallel, and the cells are still perfectly balanced over 2 years of use.

The way I look at it is that worst case scenario if you have the aluminum battery cover on, you have a fire and total the car, this would only happen if you were extremely unlucky. Basically, you would be driving and hear or see smoke, and just pull over quickly and exit the car.

I wouldn't chance this in your home but not a big deal in the insight.

I found the same thing as you there really isn't all that much out there with BMS. That is why if Mudder actually made a BMS that was adjustable to different voltages, cut off voltages, etc. and was an active BMS where it charged the weak cells, he would have one of a kind BMS.

It really is surprising that nobody sells an adjustable BMS, all the BMS have set voltages. Even with a simple 3s lipo protection board, they are only available with a 2.5 volt cutoff, which is way too low. I am going to modify one so that it cuts off at 3.3 volts to use with heated electric clothing.


I'll definitely take a look at your thread, I have actually read some of it already.
 

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I posted in that other LTO thread that there's quite a few super capacitor balance boards with balancing voltages that seem appropriate for LTO cells. Wouldn't those work, as far as balance is concerned? You're using the BCM interceptor and fooler, right, so those should take care of top and bottom voltage, etc... What else would be needed - in terms of a basic setup that's more or less safe?
 
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