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LadyN Guru Joined: 26/01/2019 Location: United StatesPosts: 408
Posted: 08:30pm 28 Jan 2019
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I saw this thread https://www.thebackshed.com/forum/forum_posts.asp?TID=2979&PN=1
... and wanted to see if there was any interest in learning (and using) lithium titanate batteries?
yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166
Posted: 02:07pm 29 Jan 2019
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I have built several projects with Lithium Titanate cells.
Honestly, I cant justify the cost vs performance. 15,000 cycles and huge amps is overkill. A rapid discharge at extreme loads can be hard to manage, I found it hard to measure/guess the state of charge.
I built a portable welder and an inverter/generator that could start big loads.
Sexy as all hell but a larger lithium iron phospate bank will manage the loads for 20% of the price.
I guess I should have posted about the inverter/genset but I sold it before I took any photos and haven't got around to building version 2.0. I'm confused, no wait... maybe I'm not...
ltopower Regular Member Joined: 08/03/2019 Location: United KingdomPosts: 64
Posted: 01:26am 08 Mar 2019
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Maybe a bit late... I have a modular 36kWh Lithium Titanate battery bank setup for 48V (22 cells in series, 18 in parallel, 396 cells total) made up in 2kWh packs so packs can be used where needed.
I selected them over other lithium becase : (1) safety - they don't fail in a ball of smoke and flames (2) cycle life - forget thinking about cycles remaining, just use them (3) current handling - throw at them wahever you want (4) temperature - leave them outside sub zero, no issue, just use them (5) price - at the time they were only a "relatively" small increment on new lithium (6) cost per cycled kWh - 15yr investment timeframe they are cheapest battery
The voltage to Wh remaining is not quite linear from reference points, mid part of the curve is maybe 20-30% out.
LadyN Guru Joined: 26/01/2019 Location: United StatesPosts: 408
Posted: 01:46am 08 Mar 2019
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Sounds amazing! Any pictures to salivate at?
Exactly. My use case is not too focused on timeframe but cycle life.
How many cycles are these ones at now?
1. How much did you get the cells at for? 2. How much was S&H 3. From where?
Excited to hear more!
ltopower Regular Member Joined: 08/03/2019 Location: United KingdomPosts: 64
Posted: 09:20am 08 Mar 2019
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This is the stack of packs...
And this is the internal layout
How many cycles these have had so far, unfortunately no idea. They are still around 90Wh per cell (100%) from a previous test on the whole stack so even though they are 2015 and 2016 cells they are still all good.
Imported to UK from China, large pallet of 450 so that shipping per cell was quite reasonable, still a lot to import though, bit more than I had expected.
1. $24 per cell (yep, now quoted at $45 per cell... rockinghorse .... seems more common) 2. Over $1k (including taxes) 3. China
This is what the V to W looks like for a 28kWh setup (6 packs added since then so now 36kWh at 2.6V)
yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166
Posted: 01:39pm 08 Mar 2019
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Man, you done so much better than I did.
I paid 3 times that for smaller cells and it took 9 months to get them. Looks like I shouldn't have given up so easily, I was probably a year or two early.
thanks for the graph. that is on thing that stands out is both LTO and LFP are a good voltage match for inverters, way better than old EV cells. I'm confused, no wait... maybe I'm not...
ltopower Regular Member Joined: 08/03/2019 Location: United KingdomPosts: 64
Posted: 11:16pm 10 Mar 2019
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This is an actual discharge test from my pack when it was 26kWh, rather than an individual cell test.
The base axis is busbar voltage and the left axis is Wh per volt reduction. I think this starts to show the actual performance of the cells in a more usefull way.
The noise is due to me switching 1-4kW of heaters on and off while trying to discharge the pack in a day.
nickskethisniks Guru Joined: 17/10/2017 Location: BelgiumPosts: 458
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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Honestly, I cant justify the cost vs performance. 15,000 cycles and huge amps is overkill. A rapid discharge at extreme loads can be hard to manage, I found it hard to measure/guess the state of charge.
