Lithium Titanate (LTO) battery bank build.

[Boominburban]

If you wouldn't mind helping me to build my own that'd be great. More input is always better

Are you on any of the diy lto groups on facebook? If so, what's your name? If not, you need to be.

 

[L1ttlet]

Are you on any of the diy lto groups on facebook? If so, what's your name? If not, you need to be.

I don't use facebook. I swear if I  did I'd  be sponsored by now as it has become a very powerful tool for many things.

 

[hispls 5,000+ posts]

So I’m new to the lithium world, how is this cheaper/better then buying a northstar or limitless? All ears 

Totally different animal than AGM or LiFe PO4.   To try to condense many many hours of research into a short version:

AGM: 

cons: Very slow charge and discharge rate, terrible size and weight. 

Pros:  Tried and true, somewhat inexpensive, easy to find off-the-shelf with warranty, very tolerant to temperature extremes.

2-5 year life expectency

LiFePO4:

Cons:  Sort of expensive for the total energy stored, unknown life expectency 2000-3000 cycles (3 years?), cannot tolerate 100% discharge

Pros:  Very high charge and discharge rating, small and lightweight, easy to find pre assembled (JY, XS, etc.), easy to work with voltage rating cells.

LTO (AFAIK a variation of LiFePO4 with some titanium nano-crystals in the cathode): 

Cons:  Size and weight not nearly as good as LiFePO4, 2.3V nominal cells make useful car audio banks awkward, high charge rate but not nearly as good discharge rate as LiFePO4 (you need 120AH LTO to deliver the same burst current as 40AH LiFePO4), NOBODY is selling consumer ready banks,

Pros:   Big amp hour ratings, very fast charging (if you have enough current), big improvement over AGM as far as size/weight, 10X the cycle life of LiFePO4 20,000-30,000 cycles (15-20 years!), much better perormance at low temperature, can tolerate 100% discharge.

Both LTO and LiFePO4 are safe.  The flavors of lithium batteries that for example make your note 7 blow your balls off in your pocket are still very popular for consumer electronics because they're the highest energy storage for the smallest size/weight, those are the ones that are unstable.   Most of the LiFePO4 cells manufactured are NOT the high current rated ones we use but lower current ones fit mostly for backup power storage where you have a 1000AH bank that would deliver 100A continuous to power your house if the lights go out or overnight when solar isn't collecting or similar.  LTO is being used in a lot of EVs.   Toshiba makes an excellent cell for a couple hybrid cars and some electric busses but you cannot get them unless you're the guy manufacturing EVs and send a tech to Toshiba for their training.

 Will you be running bms on these?

Total hokum for our purposes.  Consider I'm using 240AH banks capable of 2400A charge and discharge.  Mind you, I'm only charging at 350A max but now picture a smart circuit that can pass 350A/2400A that can quickly  open the circuit if it sniffs trouble.  To do this properly would cost thousands of dollars and be a box the size of the breaker box in your house.    BMS for solar banks is for small cells with limited charge ratings.   Get a huge stack of 10AH batteries running .5C charge and discharge and you can simply use transistors to pass current and quickly shut off if trouble is detected (these BMS systems look like an amplifier with a big series of transistors along a heatsink doing the heavy lifting and some ICs doing the smart stuff. 

Otherwise cells wired parallel will self regulate.  Sadly down to the level of the weakest cell.   Catastrophic failure would hose your whole bank quickly and one dying prematurely would also rape your life expectency.  Real world you simply can't "smart" charge or manage the type of current we need for big boy car audio, absolute best you could hope to do is remove them periodically and test each individual cell.   Consider pretty much every other battery we use above 5V is multiple cells and if one fails they all go down with it quickly (traditional car batteries included).

Ive been running my own DIY LTO lithium batteries most of this year. They are awesome.Different cells though.

Different shape or a different "brand"?   YingLong is doing some really cool things with electric busses in China.

I'm  curious on the LTO builds as all i thought  there was is the lithium iron phosphate. Are these other cells safer? Charge just as fast and everything as the lithiums? I'm  gonna research these as I'd  rather build one of these then get another agm and a h/o alternator. How much did it cost ya if u don't  mind me asking? I know these builds aren't  cheap but much cheaper than buying a premade like jy or limitless one. You haven't  had any issues with this build?  So many questions on building these still.

LTO is as stable or moreso than LiFePO4 (you can find videos of abuse testing on youtube, there are no catastrophic failures).  If you can afford the size/weight of AGM I'd say stick to that.  Buy "platinum" or other premium series parts store batteries and kill them right before the warranty is up effectively getting 6-8 years out of your purchase.

Cells were low 20$ range each, plus shipping from China (roughly 2.5 pounds per cell).   Copper bar we used was roughly 200$ per bank's worth (delivered), and we put out another 200$ into nuts, washers, drill bits, cutting oil, sanding wheel, dielectric grease, and other odds and ends.  Figure also the cost of building a small box to house them.   Remember for intents and purposes you can't just apples to apples with amp hour sizes.  While the total storage is the same how much you can use before voltage drops to unuseable and how quickly you can dump that energy are totally different!  100AH LTO, LiFePO4, and AGM are totally different.  The original plan was to buy the A123 LiFePO4 cells and build up 120AH banks which would have been a fair bit smaller and lighter and probably been even better at delivering burst current than the LTO 240AH. 

Are you on any of the diy lto groups on facebook? If so, what's your name? If not, you need to be.

I found a lot of good info on electric vehicle forums and DIY "green" energy forums.  

 

[hispls 5,000+ posts]

So drilling copper bar is an absolute nightmare.  Took us almost 40 man hours to get the bar cut up, drilled and fit.   If I were to do it again I could probably get it done in a bit less time (figured out a lot of stuff the hard way) but just getting the original template piece cut was very tedious.   I'm sure the better metalworking shop you have the better this gets.   I bought the copper from Storm Power Components.  They were very helpful and fast to ship.  They offered custom cutting/machining but like anything you're out for a rather hefty setup cost.   So it would cost probably 20$ per piece to just get 20 cut for you but if you ordered 200 pieces you could probably get it down to a few bucks per piece.    China had some interesting bus options but none were terribly cost effective or practical for our purposes and I'd have still wanted some bar for the terminal end. 

Each cell was within a couple 100ths of a volt resting and banks are resting at 13.48.   We assembled 6P3S banks which will be jumped by those 4 hole bars once they're put in place.  Figured that's a more manageable size to carry around and install.

If the rain ever lets up I'll be building up some boxes for them then drilling some holes in the terminal ends to which I can bolt ring terminals.  For scale, the larger batteries in the picture are the 110AH BatteriesPlus Dekka and the small ones are ATV size ones we bought from Michael Lane a few years back on this forum.

 

[hispls 5,000+ posts]

Cells are roughly the size of a 16oz beer can (do they still even make those?), bolts are 1/2" (or whatever the metric equivalent of that is).   I've got an extra 12 cells here.  6 I bought for a friend and 6 that I may add to mine and go up to 18V

 

[Boominburban]

I am using Alterairnano cells. A 3.5ah military cell. Rated for 50c+ discharge, and a 50c charge rate. I have three 35ah batteries I have built to date.(for the Suburban) I built about a dozen others, with similar 11ah cells. I have one more 35ah battery pack to build, but I don't really need it now. So I am holding off until after World Finals.

 

[hispls 5,000+ posts]

I am using Alterairnano cells.

Interesting, can you even get those new or are all the ones on the market reclaimed from EVs?   Similar style to the Toshibas.  Busing that style cell seems complicated but the top performers are that style.

 

[L1ttlet]

That is the best info I  have read yet on LTO vs Lithium iron phosphate. I was thinking of going with life4poe cells but was reading that even with the safety valve popping if something goes array it will cause the rest of the cells to fail as well and isn't  jy and limitless and ds18 use the life4poe cells? I'm thinking with the life span and safety of LTO I'd  just want to go with them. So no BMS is needed for this type of build?  I am just wanting to run 3k-5k rms for a while of course with it running. So would 80ah suffice my system with the LTO bank and honestly I'm  not in it like y'all are just daily driver and no comps.  Although I  wouldnt mind. I can't justify spending money on chargers and stuff. But definitely in need of 80ah worth so 3p6s. Could anyone send me fully charged cells ready for assembly? I think I'd need 18 at a decent price. Still be cheaper this way than an agm and h/o alternator.  Thanx for the info, that's  really helpful. 

 

[Boominburban]

Interesting, can you even get those new or are all the ones on the market reclaimed from EVs?   Similar style to the Toshibas.  Busing that style cell seems complicated but the top performers are that style.

These are brand new cells. As are the 11ah cells from Kokam. Bussing *****, but the end results are worth it to me.

 

[hispls 5,000+ posts]

So no BMS is needed for this type of build?

I'm saying it's not really possible.  What will you use that can pass 300A to charge and 500A or more discharge that can instantly open the circuit if it sniffs out trouble?   Best you could do is possibly rig up something to sniff out voltage in all cells real time and output to a display so you can see if you have a dud cell.  There is one off-the-shelf solution out there that supposedly outputs via bluetooth but reviews are very hit or miss and everything in the GUI is in Chinese.  Anyway, there's really nothing pre-made that'll do what we need and almost all the stuff that does exist (at laughably low current levels) is all designed around 3.4V cells

So would 80ah suffice my system with the LTO bank

On paper, yes.   10C rating means they can deliver 10X the amp hour rating so 80AH can deliver 800A.  Of course the lower multiple you try to use the better and longer they'll perform.  I really need to get one installed and I'll get a far better feeling for real world results.

Could anyone send me fully charged cells ready for assembly?

Cells arrive @ 40% SOC (state of charge).   Considering your alternator will never exceed 10C you shouldn't need any fancy charging to keep them safe.

But definitely in need of 80ah worth so 3p6s

3p6s would be 120AH of these cells I have. 

Still be cheaper this way than an agm

Yes, assuming they last for 3 years you're certainly ahead of the game there considering you'd probably want at least 3 group 31 batteries to really hang with a 5K amp.   Mind you, you get zero warranty and you have the PITA factor of having to assemble things yourself.  I'm a bit concerned that we're also leaving some capacity on the table with 12V application since getting the cells up to 100% SOC would require charging 15.5 or a hair over that which many amps (and possibly some factory electronics won't like).   Optimum would be going 18V and pulling off a terminal at 5S (which would sit around 12.2V) to run everything besides your sub amp.  I may do this at some point when I have time to send out my alternator for a tune up and install an external regulator and more cable to make that happen.

These are brand new cells.

Seems the ones floating around at the consumer level are "b grade", though if you're not a proper manufacturer buying tens of thousands from the actual factory and with someone there to confirm everything who else is getting anything different?

Anyway, specs claim only 10C rating on those.   Have you tested more?

 

[Boominburban]

Yes,the 11ah cells are rated at 10c. I'm not running those. (I have, but I'm not now since I have my 35ah banks done). But they have been tested in our use to do 17-23c for 30 sec, to 12v.  I'm running a 3.5ah cell that is no longer available.That was designed for primarily military use. They were brand new in factory sealed cartons. Mine actually came at 0.00v, I had to charge them all.  Are factory rated for 35-50c+ continuous(mainly temp dependent) and 70c 45 second bursts. We have tested them to 130c for 15 second bursts. They do make two or three balancer/chargers with LTO profile already installed. Icharger X6 is one of them. ISDT BG 8S will work if you are charging at 15v+.  And  Chargery makes a unit with an LTO profile as well. ALTHOUGH, I have been running my LTO banks for over half a year now, with no balancer, and my cells are still within .01v of each other. 

And I'm charging at 15.6v to take full advantage of my cells capacity.

 

[hispls 5,000+ posts]

And I'm charging at 15.6v to take full advantage of my cells capacity.

How does the rest of the vehicle's electronics like that?  Or do you pull a terminal at 5S?   Why not up it to 18V ?  

 

[L1ttlet]

Wow this is the most informative thread so far that I  have read involving lithium. Y'all  definitely know your stuff and know far more than me. I  am now having difficulty staying up with the talk.

from what I  have gathered the cells you are running hISPLS would  not do a 14.4v charge? The one's I  left a link on with 5s would be 14.4v and 3p (your right my math was off) 120ah should be able to sustain  my system of 300-500 amp discharge for around  5mins at a time since they are technically discharging and charging rapidly.

 I  am wanting to avoid a H/0 alternator (as research into these cells says they work better with a smaller amp charge) not to mention the money saved from buying a $600 350amp alt (as well as at least $600 in agm) and then weight (suspension issues) and space to put all these.

The LTO seems like the best investment to get me by for a few yrs until they have mastered this technology and have mainstreamed production for car audio  applications.

I plan on getting a new vehicle and will be out the mula for the h/0 alternator as the lto cells can follow me from vehicle to vehicle install.

 Back to what y'all  are talking about. The SOC I thought when they are charged would be what they say they are rated on the cells voltage (ex. 3.5 volt cell @100% SOC would  be 3.5volts) I'm  not sure about all the SOC specs. Also the BMS that you were mentioning in order to work for our applications would be far to costly and large to be practical is what I  gathered.  

In that case could we (I) run a 120ah for a few yrs without a bms system and be okay and everything work fine. Cuz if a cell fails in an agm then the whole battery is destroyed, but usually has (warranty). these cells however,  would act the same as a agm cell in a battery bank and then there is not warranty and being out all the mula for those cells.

y'all  have far surpassed my knowledge in this field. Boominburban I  have always wondered if you could use those type cells in car audio applications. Looks good and alot juice. Anyway I  was hoping to build my own and not sure that I  want to now as there is so much to learn and not to mention special chargers n what not. Just now wanting the 120ah lto.

Hispls, as u mentioned they come 40% charged. So if I  hooked these up just like hooking another battery  up in my system couldn't  I  just hook up a resister like installing a capacitor for the first time? If so, would the one they sent me with the nvx 10 farad hybrid cap work for charging these?

As you were mentioning in  the 15.5v range (not worried about that as my amps can handle that) but  wouldn't  that possibly back feed into battery and even alternator and destroy it all? How would u isolate that higher charge. Not sure if I forgot a few questions as I have many and am really trying to understand all this to start making my own (safely) someday soon. 

 

[hispls 5,000+ posts]

the cells you are running hISPLS would  not do a 14.4v charge?

All LTO cells suffer from the low voltage limitation so you're sitting at an oddball voltage.  Cells are nominal 2.3V max charge 2.7 so your options are NEVER go above 14.4V charging (and have much of your usable power happening <13V) with 5S or you go 6s and either charge at 15.5 or leave a bit on the table there never fully charging them.  Most factory charging systems will put out 14.8 at least occasionally so you'd want to externally regulate to be safe if you're going 5P, of course if you're going to externally regulate why not do 6s or even 7s, pulling off a terminal at 5s for anything that won't like >15V

120ah should be able to sustain  my system of 300-500 amp discharge for around  5mins at a time since they are technically discharging and charging rapidly.

Bear in mind you're playing with the car running so 80A or whatever the alt can spare is always being used first then dipping into reserve.  Depending on your music the average power used over time is quite a bit less.   "Fast" charging depends on being able to dump a ton of current into the cells.  80A charge current would still take an hour to charge 80AH (assuming no losses).

The SOC I thought when they are charged would be what they say they are rated on the cells voltage (ex. 3.5 volt cell @100% SOC would  be 3.5volts)

There's minimum, maximum and nominal charge ratings on each.   Nominal being the average of where 80% of your usable power is coming from.... ideally you do not want to charge at maximum especially without some very precise management system; consider just a hair over max and you start prematurely chipping away at life expectancy.

In that case could we (I) run a 120ah for a few yrs without a bms system and be okay and everything work fine.

That's my plan.  Yes, one cell going tits up would wreck the rest of the bank pretty fast, as far as all the tests have shown there isn't any catastrophic (read fire or explosion) type failure possible with LTO cells.   Consider also 50% of my cost into this is hardware, so if I had to buy all new cells I don't need to buy bolts, washers, or copper again.

So if I  hooked these up just like hooking another battery  up in my system couldn't  I  just hook up a resister like installing a capacitor for the first time?

Why?  You'd be yanking out any lead battery anyway (they'd always be fighting each other) and your alternator could only possibly deliver 1C.   If you had quad HO alternators you might need to worry, but as it stands you could charge 120AH LTO bank with 1000A in @ 5 minutes and they'd be fine.   The electric busses in China use small-ish banks and recharge as passengers load and unload at each stop.

As you were mentioning in  the 15.5v range (not worried about that as my amps can handle that) but  wouldn't  that possibly back feed into battery and even alternator and destroy it all?

So there's the rub.   Who knows if the ECU on your car smokes at 15.4V?   IF some other bit in the car will react poorly?   I'd assume there's enough wiggle room from the factory that things can survive.  I've had issues with my regulator before and had 20V charging for a minute, under the hood battery was boiling but apart from the lights looking extra bright nothing seemed to go haywire.  But I'd hate to say "oh yeah, run your car at 15.5V and you'll be cool" then you smoke some hidden computer.

Anyway, options are 6s and leave some on the table (charging with stock charging system), or externally regulate.  If you're externally regulating  best to confirm that won't hurt any of the car's electronics.  I'd expect just about any alternator could charge 15.5 without trouble.

 

[wew lad 5,000+ posts]

I don't think 2000-3000 cycle is accurate for lifepo4 unless we're talking about <50% DOD and not full cycles. If it was full cycles that'd be 10+ years considering AGM's have 200-300 80-100% DOD cycles and last 3 years reasonably and up to 5+ if maintained. The claims I see are that they'll last 2000-5000 cycles with 80% capacity left but theres 0 mention of DOD and their C usage over their lifespan.

The LiFePo and LiPo I've worked with generally are used up to 70-80% capacity and discharged on average to 25-40% and we get approximately 150 cycles out of them but they are worked HARD. Near max C rating for charge and discharge and high heat. Obviously we could get up to 250 cycles out of them if we went down to ~50% capacity but that hurts flight time and is just not worth it. 

However, if the ratio is still the same and you get 2-3k high DOD cycles that's a major improvement and you could expect the cells to last 10-20 years. Obviously this is just an estimate and real research is needed but I don't think any of us have the funding for that lol plus 10-20 years in electric busses as you mentioned certainly seems like an appropriate cycle life you could sell. 

edit: I looked a little deeper and the claims from companies do say those cycle numbers are at 100% DOD which is strange to me because I've never seen a cell last that long in the real world. They're still leaving out the charge/discharge standard used during those cycles so I'm hesitant to believe it