Charging LTO at Max Speed?

Batteries, Chargers, and Battery Management Systems.
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Re: Charging LTO at Max Speed?

Post by Username1 » Mar 06 2021 5:19am

It's been a while since i put this on the back burner, but I've returned to it.

I'm wondering would the power supply linked below be suitable for charging these cells? The reason I ask is because the voltage has a narrow field, and doesn't go to 0 like other switching power supplies I've seen. For example the 36v version goes from 35 ~ 43.2V.

Say i charged 16s at 6c using the "36v" version of the power supply... I could charge them to 2.7 each or 43.2v total (the max psu voltage), but would there be an issue with the minimum 35v of the psu, since the battery would be drained to around 32v? Or would the psu be sending out 35v+ to begin with anyway?

Mean Well RST-10000: https://www.meanwell.com/Upload/PDF/RST ... 0-SPEC.PDF

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Re: Charging LTO at Max Speed?

Post by john61ct » Mar 06 2021 10:52am

There is no such minimum, the voltage output spec of a charge source is simply the adjustment range of the CV setpoint, the maximum V allowed.

2.7V is a decently gentle termination voltage, but although that chemistry can "tolerate" a 6C charge rate, slower would be more conducive to getting decades of service from a pack

IOW only charge at that high rate when you actually need to.

The actual voltage measured "on the wire" (ideally at the battery posts) will start out much lower with a depleted pack, even below 1.8V can be "tolerated" but not recommended.

So you will actually see maybe 28V over a period of time in Bulk / CC stage, the charge source is "striving" to raise the "negotiated" voltage, but that will only rise in fact along with pack SoC

until that 43V CV setpoint is reached.

You should ideally use an automated HVC termination, but if you are babysitting the charge, allow the CV stage to proceed as current falls

until it reaches say 0.1C

LTO is infinitely safer than other li-ion in the 3.6-3.8Vnominal range

but you should not allow charging to just keep going indefinitely until current flow stops, even at lower termination voltages.



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Re: Charging LTO at Max Speed?

Post by john61ct » Mar 06 2021 10:58am

You do know that 250+A is super dangerous right? Even at "only" 43V. . .

That line at 10kW requires an industrial 3-phase supply, will not be likely available off poles servicing most residential neighborhoods.

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Re: Charging LTO at Max Speed?

Post by Username1 » Mar 06 2021 9:16pm

That's good to hear that it only refers to the set voltage (CV phase). I didn't realize it was a 3 phase input. I guess that's what it meant by "3 ψ" . I know 3 phase is industrial so looks like i won't be using this power supply.

So looking at Mean Well's other power supplies, it seems the most powerful single phase (non watercooled) unit is the DPU-3200 https://www.meanwell.com/webapp/product ... d=DPU-3200. The "24v" version has 133 amps, and allows current sharing. So two of these would put out 266a which is just shy of 6c (45a x 6c = 270a). This would mean a 10s configuration charging to around 27-28v (psu max of 30v). So i think in theory i could use two separate 20a 220v receptacles connected to a dedicated 40a breaker, or maybe it would need a little more overhead I'm not sure. Regardless does that seem like a sound idea?

I guess HVC means high voltage cutoff? I'll always be stopping the charge once the CC stage ends, i won't be using CV at all. Can the power supply do this automatically, or how would you go about doing it other than manually?

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Re: Charging LTO at Max Speed?

Post by fatty » Mar 07 2021 2:34am

This thread is an interesting mix of dangerous ideas/techniques (naked charging at 10kW) and battery/charger fundamentals...
Username1 wrote:
May 13 2020 9:28pm
First reason is just because i want to. It's really cool and useful to charge an ebike in 6-10 minutes (and still have it last 10k+ charges).
Well, it may be useful. It would be helpful to understand, quantitatively, why it would be useful.
What is the usage profile?
Username1 wrote:
May 13 2020 9:28pm
Secondly this ebike will be used heavily, and instead of fitting a massive conventional battery (which could also go empty and need a long recharge), i have the ability to quickly recharge as much as i want.
It'll still be massive at 12.3kg for ~1kWh. 12.3kg of LiIon would get you 2.8kWh, so your usage profile calls for less than 3 charges, you wouldn't have to stop to charge at all.
Or, since you'd need the infrastructure to stop and charge anyway, you could also likely swap LiIon batteries. If you can get by with 1kWh/trip, you'd only need 4.6kg of LiIon.

Cost:
Let's say $80/ea shipped = 1.29Wh/$, comparable to LiIon/LiPo at retail but that's half you'd get with Headway 40152s and a quarter with Queen QB26800s, and your charging infrastructure cost will be 10x? 100x if you have to have an electrician put in and run 220V 50A?
And power cost becomes non-trivial at 10kW. If your plan has a demand surcharge, that alone may make this untenable.

As I always say, run your actual numbers first.
I would echo john and suggest to pilot this on as small a scale as possible, before scaling up. Try to hit regular milestones like maxing out a 15A, then 20A socket before running new 220V.

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Re: Charging LTO at Max Speed?

Post by Username1 » Mar 09 2021 5:28am

I'm well aware of the differences between LTO and other chemistries, and have run all the numbers already. The only downsides are energy density and cost, neither of which are an issue in my case. In exchange I get a battery with 10 minute charging, 10,000+ cycles, extreme temperature tolerance, high power capability, lack of fire hazard, and simple construction (1p configuration with just 10+ big cylindrical cells).

I'm not a fan of conventional l-ion and it's many issues. People only put up with it because of it's superior energy density. I am keenly interested in LTO, so it's partly just out of interest in addition to it's benefits. Now in terms of my specific application and why it makes sense...

Without getting into too much detail, I'll be putting the battery in a cargo type bike or scooter to transport things. Like I said, it will be used heavily (100's of km per week), and in freezing temperatures during the winter. Regular l-ion can't tolerate the cycles and temperature in this case.

I'll be going through more than 3kwh per day, so a l-ion pack would be just as big, heavy and costly, The electrical I can have done for free, so much of the extra cost will be in the power supplies. But as I said, cost isn't really an issue.

At the end of the day I'm doing something different which happens to suit my usage. I'm fully aware of the tradeoffs, and I'm set on going this route. In terms of it sounding potentially dangerous, sure but this thread was made to collect information and ask questions... I'll continue asking question and thoroughly researching how to be safe before I ever attempt it.

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Re: Charging LTO at Max Speed?

Post by john61ct » Mar 09 2021 8:19am

Do you mean the AC grid power circuits installation will be free?

Or that someone is also paying for the PSUs?

Yes HVC means no CV stage at all, just "charge to and stop".

The SoC% level at that stop point would vary greatly with the current rate, just WAG examples:

95% at 0.4C
90% at 1C
85% at 3C
80% at 5C

So, in order to get good range, capacity utilization charging, to get up past 95% SoC

the higher your Bulk / CC stage rate, the longer your AHT must be, time spent in Absorb / CV stage with a regulator holding the max V to your desired setpoint

as current level falls due to battery chemistry increasing resistance, aka "trailing amps".

The relevant endAmps setpoint then for charge termination might be say 0.01C if you wanted to get every possible mAh in there without reducing lifespan too much

or say 0.1C to ensure optimum longevity, or somewhere in between.

I would reco the latter. Anyone coming along that says "don't worry just keep charging until zero amps are flowing" I'd be very wary of listening to anything else they have to say

unless they prove themselves to be very well educated, as in a battery scientist, and also long-term experienced with using LTO hands-on.

Of course then you need a device to automate the AHT based charge termination, adjustable so you can calibrate it against the current rate.

This is the critical distinction between a proper charger, which has that stop-charge circuitry built in

as opposed to a dumb charge source like DC-DC converters and AC-DC PSUs, where stop-charge circuitry needs to be added.

Or trust yourself to sit and watch the ammeter every charge cycle, not recommended.

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Re: Charging LTO at Max Speed?

Post by john61ct » Mar 09 2021 8:34am

Revisiting this:
john61ct wrote:
Username1 wrote:So i realized i would actually need 10s (not 12) due to space. This means 24v nominal
Voltage should not be determine by lack of space.
You need to decide on your controller and motor, also wheel size, and test these out for your actual terrain

ideally with modular testing packs, say LFP or li-ion/LiPo where you can vary the voltage via xPyS layout

before building your first "production" pack.

23V nominal will in most cases mean a very slow vehicle, more like a wheelchair than a cargo bike.


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Re: Charging LTO at Max Speed?

Post by john61ct » Mar 09 2021 8:40am


Username1 wrote:If those "prochargers" can be used, they do sell a 180a version which would be 360a in parallel or exactly 6c (not sure if that can be done). I would need 2 sets of 2, with a split battery. But the battery splitting seems pretty simple to do.
Don't know if you mean parallel or serial, but there is no need for splitting in any case.


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Re: Charging LTO at Max Speed?

Post by john61ct » Mar 09 2021 8:44am

And again
john61ct wrote:I would not use cheap Chinese for that.

Ex telecom and server room secondhand much more trustworthy, stuff on eBay goes for hundreds originally cost thousands.

Lots of example here, search the threads, Eaton, Huawei, TDK Lambda, Cisco tons of ideas.

Again, $400-800 would be a realistic budget.

Of course you can start with just 3-4, then add more later.
Going to around 48V charging voltage would let you save a lot of money **and** get you very safe and reliable gear

maybe even with intelligent charging circuitry

telecom / server rooms are usually integrating their PSU systems with backup battery banks.


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Re: Charging LTO at Max Speed?

Post by john61ct » Mar 09 2021 8:51am

Again, your focus on the battery first is cart before the horse.

Get your drivetrain tested and implemented, with a large cargo box and small packs for testing, or even cheap 12V lead units

Then you will know how much of the box you need to fill with your low density LTO to get the range you need.

The fast charging is literally the very last thing to worry about.
john61ct wrote:Sorry to keep repeating, but forget the focus on the super fast charging aspect for now, prep all your infrastructure to withstand it, but get everything else solved using a 0.1-0.2C rate first.

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Re: Charging LTO at Max Speed?

Post by fechter » Mar 09 2021 8:59am

If the charger has an output that is isolated from the earth ground, you can place them in series with no problem. Best if you tap the pack at the mid point and feed each half with a charger. I did something like this for years with a lead-acid pack. My chargers weren't isolated, so I cut the ground wire off all but one of them so I could put them in series.

The bigger problem will be feeding that much power on the AC side without blowing any breakers.
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Re: Charging LTO at Max Speed?

Post by Username1 » Mar 09 2021 9:51am

I don't think the power supply is the last thing I need to worry about, it really all hinges on that. The main goal of this project is the 10 minute charge, so I'm trying to find a power supply capable of that.

I don't feel comfortable buying some high powered switching power supply from China, in terms of safety, reliability or warranty. That's why I'm looking at something mainstream and of quality like Mean Well, that can be purchased domestically.

I'm not that picky about the speed. I just need somewhere between 30-50 km/h, preferably towards the higher end if possible. I'm probably going to use the leaf motor, which is available in 3T. If I recall correctly, this would give around 35 km/h on a 24v battery and 20 inch wheels. I'll have to rerun the math to double check.

Keep in mind if the battery voltage is too high, i won't be able to charge these 40-45ah cells at 6c. The power requirement will just be too high. I need something roughly in the range of 24-36v nominal, which is somewhere around 1000-1600 wh.

For the controller I'm likely going with a Nucular. They work all the way down to 20v. A 10s battery drained to 2v per cell is right on the limit at 20v. They can also handle massive amps, which is at least handy for heavy regen breaking which I plan to take advantage of.

As I said, I WILL NOT be using the CV stage EVER. As i also mentioned a while back, it seems these cells will fill up to ≥90% capacity when charged at 6c, so that's plenty good enough for me.

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Re: Charging LTO at Max Speed?

Post by Username1 » Mar 09 2021 11:45am

For my desired top speed, and to charge these cells at 6c while under 10kw, the ideal voltage would be around 36v nominal. That's why I was looking at the Mean Well RST-10000-36 which seemed perfect except that i didn't realize it's a 3 phase ac input. The highest power single phase unit from Mean Well is the DPU-3200, but unfortunately it's only available in 24v and 48v versions.

24v is on the low end for my desired speed (though maybe acceptable), and pushing it for what the Nucular controller can handle on the low end (20v).

48v would give me much better capacity with 20 cells (2 kwh), a better top speed and controller voltage, but would require 4 units in parallel to charge at 6c (actually slightly under 6c), which is simply too much in terms of power and the amount of receptacles that need to be run. I could MAYBE run 3 together which would give me 4c, or a 15 minute charge time.

Still looking at my options for the power supply. If anyone has any suggestions, especially in the 36v range, let me know.

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Re: Charging LTO at Max Speed?

Post by fechter » Mar 09 2021 3:11pm

Look for 36v forklift chargers. A charger at this power level is going to be insanely expensive. You could easily buy a battery that is 2x bigger so you don't need to charge in such a hurry. 6C charging is asking for something to burn up.
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Re: Charging LTO at Max Speed?

Post by john61ct » Mar 09 2021 4:32pm

Mean Well is cheap chinese compared to the Western engineered stuff.

Sure it is top of that heap, so long as you're not getting fakes which are very common.

For comparison, any really good quality charger even only 12V 50-60A will cost $400+

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Re: Charging LTO at Max Speed?

Post by john61ct » Mar 09 2021 4:36pm

And sure "the whole point" might be your 6C charge rate

but then why bother with a vehicle?

Do your research with a portable powerpack for camping or traveling or when the power goes out.

But if getting a vehicle going for practical purposes is actually an essential part of your plan, then really, odds are your currently theoretical planning will evolve along the way

and doing things in the right temporal sequence might just save you lots of money overall!

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Re: Charging LTO at Max Speed?

Post by Username1 » Jun 05 2021 10:31pm

Some updates. First the power supply.

I did some research on receptacles. Nema 14-60 (240v 60a) is the highest power for home use, but it's basically never used. The 14-50 seems to be the highest found in homes, used commonly for stoves. They're also used for welding and found in campgrounds I've read. I also read that in some places anything above 50A is supposed to be hardwired according to code.

Taking these things into account it seems using 14-50 is best. That's 12kw, or 9.6kw usable when using only 80% which code requires. If the power supply is 84% efficient or better, this leaves you with 8kw of actual charging. So the practical limit of home charging is basically 8kw.

I've found some companies on Alibaba selling 8kw switching power supplies (single phase) in the voltage range needed. They go for around $1300, but I'll have to do more research to determine if the quality is good enough. I can't find anything comparable domestically, never mind the massive price tag it would probably have.

The cells

YinLong (as of just recently it seems) is now selling directly to the public on Alibaba, even in small quantities. This seems like a win in terms of getting quality cells. They also provided me full datasheets upon my request which was helpful. By the way, they're now selling a new 33140 9ah cylindrical cell which may be interesting for ebike use.

Image

Image
Last edited by Username1 on Jun 07 2021 8:00am, edited 3 times in total.

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Re: Charging LTO at Max Speed?

Post by john61ct » Jun 06 2021 1:46am


Username1 wrote: the practical limit of home charging is basically 8kw.
That's just per circuit.

There are many charge sources that accept concurrent input from multiple circuits.

And nothing to stop you stacking multiple units charging concurrently.

> YinLong (as of just recently it seems) is now selling directly to the public on Alibaba

How do you know when you are dealing direct?

So many resellers pretend to be the manufacturer

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Re: Charging LTO at Max Speed?

Post by Username1 » Jun 06 2021 3:17am

True you can use multiple circuits. I was thinking in terms of a single charger, common receptacles, and including homes which only have 60a service. That's what I meant by "practical limit".

Yinlong links directly to the Alibaba store from their main website. Those banners in my last post (just edited in the second one) are from their main website, which says to buy from them directly and has a store link.

Official website - http://www.zhyle.com/en/index.html
Alibaba store - https://zhyle.en.alibaba.com/

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Re: Charging LTO at Max Speed?

Post by stan.distortion » Jun 06 2021 6:45am

Could be worth looking at welding transformers for big amps at low cost, stick and TIG welders are almost always current regulated and MIGs voltage regulated, voltage ranges around 24v to 60v.

Anyone happen to know what's the highest charging C rate for LTO and how they'd respond to higher rates than recommended? It's for regenerative braking, the highest I've come across so far is 30C for a small 10300 cell, more like a capacitor than a battery. Needs to be small, some of the 45-60ah cells claim discharge rates up to 50C but the total weight of a pack would be far too high, total capacity only needs to be around 0.1kw/hr.
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Re: Charging LTO at Max Speed?

Post by Monte » Jun 06 2021 2:45pm

Have you considered charging at DC fast charging stations instead?

I just finished a similar battery for my bike, in a trailer. 26S1P 40Ah LTO with CHAdeMO charging.

Sadly, I didn't get to the 240A chargerate I was hoping for (I had looked at the newest CHAdeMO spec, which goes up to 400A), but 125A (max on most chargers) still gets the pack to 91% in 20min, which is actually a welcome length of a pause every 100km of cycling.

Did a full day test run a few weeks back and got 450km done in a day :)

Imo more useful to be able to use chargers on the road and only have a slow charger at home, than having a fast charger at home.


If you're really keen on the 10min charge, use 10-15Ah LTO cells instead, and have a higher voltage pack. Car chargers don't all go down to 50V, but at least here in Finland 95% of CHAdeMO chargers have worked. You'll need at least 26S to have a near-empty voltage over 50V.

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Re: Charging LTO at Max Speed?

Post by Chalo » Jun 06 2021 6:10pm

stan.distortion wrote:
Jun 06 2021 6:45am
Anyone happen to know what's the highest charging C rate for LTO and how they'd respond to higher rates than recommended?
Each cell will have a specification based not only on chemistry, but on its physical construction. If you limit to the manufacturer's spec, you should be okay.
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Re: Charging LTO at Max Speed?

Post by fatty » Jun 06 2021 7:24pm

Monte wrote:
Jun 06 2021 2:45pm
Have you considered charging at DC fast charging stations instead?

Imo more useful to be able to use chargers on the road and only have a slow charger at home, than having a fast charger at home.
This would be more useful, but he's in the US -- we don't have that density of charging stations (every 100km).

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Re: Charging LTO at Max Speed?

Post by Username1 » Jun 06 2021 9:53pm

stan.distortion wrote:
Jun 06 2021 6:45am
Could be worth looking at welding transformers for big amps at low cost, stick and TIG welders are almost always current regulated and MIGs voltage regulated, voltage ranges around 24v to 60v.
Nice idea, I'll look into it.
Monte wrote:
Jun 06 2021 2:45pm
Have you considered charging at DC fast charging stations instead?
Yes but as mentioned, there just aren't accessible enough over here.
Last edited by Username1 on Jun 07 2021 2:00pm, edited 1 time in total.

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