48V LTO Off Grid system

Joined
Dec 5, 2017
Messages
59
So after much time spent going down the HV battery packrabbit hole I have declared it too hard.

Our 48v prototype system with APC 3000VA UPS and 14kwh of VRLA works well and has components such as inverters, chargers, BMS, etcreadily available.

So we have taken a detour and are now building a 48v LTO battery pack out of 160 cells from OSN power in china. We purchased 215 cells so we have some to spare for other 12 and 48v projects.

We are building parallel packs of 8 cells to create 2.5v 240AH batteries, we will then connect 20 of these in series to get 48v, ~12kWh. The charge, float and operational voltages match very well with standard Gel cell lead acid settings common to most chargers and inverters.

I am still negotiating with suppliers but I am looking at getting a 12kwlow frequency solar inverter like this:
http://www.sacolar.com/products/info_8_itemid_18.html
https://www.must-solar.com/pv3500-4-12k-series-low-frequency-solar-inverter/
https://www.yiyen.com/product/hp-pure-sine-wave-invertercharger/

I am aware that low frequency inverters are not quite as efficient as the high frequency inverters like the PIP4048/etc but as the site is off grid we need an inverter that will tolerategenerator power without issue and I like the buffer the transformer offers for surge loads.

Our prototype system has 8kw of solar panels and the full scale system will have 16kw, this is for a family home + granny float with 3 adults and 3 children.

Regards,
Jordan
 
Low frequency inverters are generable bigger, stronger, and tougher then high frequency I read. What about pricing?
 
I'm still negotiating the final details but from all of the above suppliers I'm looking at about AU$3,000-3,500 for a 12kw solar inverter from the above suppliers, delivered to my workplace.

However a 12kw LF inverter has a shipping weight of about 90kg so you need to make sure you can unload such beast, it's not quite a slip it under the doormat affair.

Key specs:
MPPT Solar charger: 60-160A depending on model
AC Charger: 100A
Input Frequency: 40-65hz
Output Frequency: 50 or 60hz
Rated output: 12kw @ 230V AC
Surge Output:
20s: 18kw
20ms: 36kw
Start motor size: 6HP

I do not plan to test the 36kw theory, that's 750A@48v. I really don't expect to push 12kw, I just want some headroom.
 
BaronVonChickenPants said:
I'm still negotiating the final details but from all of the above suppliers I'm looking at about AU$3,000-3,500 for a 12kw solar inverter from the above suppliers, delivered to my workplace.

However a 12kw LF inverter has a shipping weight of about 90kg so you need to make sure you can unload such beast, it's not quite a slip it under the doormat affair.

Key specs:
MPPT Solar charger: 60-160A depending on model
AC Charger: 100A
Input Frequency: 40-65hz
Output Frequency: 50 or 60hz
Rated output: 12kw @ 230V AC
Surge Output:
20s: 18kw
20ms: 36kw
Start motor size: 6HP

I do not plan to test the 36kw theory, that's 750A@48v. I really don't expect to push 12kw, I just want some headroom.
Try to avoid the transformer , they use power even when on without a load . A 20kw 3 phase unit uses about 500.00 US $ just being on, @ 166.66 $ per phase.

Use run capacitors for surge, Use ten for starting a 10 Hp load - @ 7500 watts . Be sure to mount these in a sealed metal box.
If upon a failure , they pop and might catch on fire, because they contain a oil.
These do not use any current on standby . They are also cheaper than a transformer.

https://www.ebay.com/itm/TEMCo-100-...+-+100+MFD&_from=R40&rt=nc&_trksid=m570.l1313

Just curious , what kind of a discount did you get for 215 pcs and what kind of freight ???
 
I understand what you mean with the draw from the transformers, my current system with the APC transformer inverter has a parasitic loss of about 80-100w.

I am hoping the power save mode of the inverter will help with this. The brochure claims 25w standby in power save mode.

My biggest concern with the likes of the MPP PIP inverters is a known issue where they will not take power from a genset as they have a very narrow window of frequency tolerance, -+2Hz.

All of the transformer inverters I looked at had a much wider window -+10Hz.

Surge load isn't really a concern for our normal use, we have not had anything that overwhelms the 3000VA UPS in testing, including using power saws, water pumps, concrete mixers, etc. 12kw sizing is to accommodate a whole house + granny flat off-grid, in theory 8kw should be enough but the pricing difference is a token amount to know I have enough.

The inverter is only single phase, I have a couple of 3 phase motor devices, but not enough to justify a 3 phase inverter, I will just be running these via a VFD.

I'm not convinced that I received any discount on 215 cells, I purchased in March and paid 20USD/cell and door to door shipping was USD2285 to Australia, arranged by the supplier, it was a good sized pallet.

For the inverter I am using a local freight forwarder and the shipping is $477 AUD from the port in Shenzhen to my door.

I have quotes from other LTO suppliers on Alibaba now that our 3-5USD lower than OSN. All claiming to be new cells.

I have contacted Kylin regarding their $7.9USD cells but so far have not received a reply.
 
BaronVonChickenPants said:
I understand what you mean with the draw from the transformers, my current system with the APC transformer inverter has a parasitic loss of about 80-100w.

I am hoping the power save mode of the inverter will help with this. The brochure claims 25w standby in power save mode.

Trick is that for a house, you'd probably want the power always on. If you're doing a mobile place, it might be different....
Have a look at the Victron gear, the 3kW/48V Phoenix unit only uses 25W when still doing 230V out with no load. In "search mode" it's only 12W. They also have a reduced power "AES" mode.

(Might have the wrong models -hadn't picked if you're doing 110V or 230V...)
 
BaronVonChickenPants said:
I understand what you mean with the draw from the transformers, my current system with the APC transformer inverter has a parasitic loss of about 80-100w.

I am hoping the power save mode of the inverter will help with this. The brochure claims 25w standby in power save mode.

My biggest concern with the likes of the MPP PIP inverters is a known issue where they will not take power from a genset as they have a very narrow window of frequency tolerance, -+2Hz.

All of the transformer inverters I looked at had a much wider window -+10Hz.

Surge load isn't really a concern for our normal use, we have not had anything that overwhelms the 3000VA UPS in testing, including using power saws, water pumps, concrete mixers, etc. 12kw sizing is to accommodate a whole house + granny flat off-grid, in theory 8kw should be enough but the pricing difference is a token amount to know I have enough.

The inverter is only single phase, I have a couple of 3 phase motor devices, but not enough to justify a 3 phase inverter, I will just be running these via a VFD.

I'm not convinced that I received any discount on 215 cells, I purchased in March and paid 20USD/cell and door to door shipping was USD2285 to Australia, arranged by the supplier, it was a good sized pallet.

For the inverter I am using a local freight forwarder and the shipping is $477 AUD from the port in Shenzhen to my door.

I have quotes from other LTO suppliers on Alibaba now that our 3-5USD lower than OSN. All claiming to be new cells.

I have contacted Kylin regarding their $7.9USD cells but so far have not received a reply.
I paid 20 for the 30 ah one's, but you got a great price on shipping , I paid @ 19.00 each for shipping alone to Ohio
 
I did get a reply:

Before our company take 1000pcs for promotion,
so Us$8.9/PC

Now activity finished,
current best price is Us$15/PC EXW for LTO 30AH.

Still not a bad price but not as good as $7.9.

In other news after weighing all the pros and cons I decided to go ahead with the Sunrino 12kw LF transformer based inverter from Sacolar.
http://www.sacolar.com/products/info_8_itemid_18.html

Should be shipping out of China in 2-3 weeks.
 
Just an update, we have received our inverter from Sacolar, it is a monster and will be interesting to see in action.

I have also received a price update from OSN Power on LTO cells:

LTO 35Ah------Wholesale price is USD13/PC

LTO 40Ah------Wholesale price is USD16.5/PC
 
I'm considering doing something similar - importing LTO or Lifepo4 batteries from China to Australia.

How are the LTO batteries going for you? Most companies seem to sell both, but Lifepo4 are cheaper. The 10000+ cycles of LTO is appealing, but I don't really plan to be still using this in 30 years, so I'm thinking Lifepo4.

Am I missing anything? Are LTO more likely to be legitimate?
 
Unfortunately there is no straight answer, it's still a horses for courses situation.

weight per watthour LiIon, LiPo, LFP/LiFePo4 are a superior battery than LTO which are physically larger and heavier at comparable capacities, so if you are limited on weight or physical size, like an electric vehicle, LTO are probably not suitable.

Where LTO shine is their long life expectancy as well as tolerance to over/under charging.

LTO cells can be discharged all the way down to 0 volts and recharged without damage, they can be overcharged, within reason, without exploding or suffering damage. I have had 0v cells that recharge happily and hold charge, I have had cells I accidentally over charged to 3.5v that stabilised back to 2.65v and continue as normal.

LTO are very safe with no off-gassing or oozing or thermal runaway. Search Youtube for "LTO safety test"

A 5 cell LTO pack is a drop in replacement for a 12v Lead Acid battery with equivalent charge and float voltages.

You still need a BMS, however off the shelf systems designed for super caps will work with LTO calls.

We have just finished building our 48v pack, each block is 8 parallel 30AH cells, 20 blocks in series give 48v 240AH, 11.5kWh:
[img=800x600]https://lh3.googleusercontent.com/N...ldYPoc4ervW9cTcvfuqzwfvI=w1346-h1009-no[/img]

Importing in to Australia has been fairly easy, just count on spending at least half of the cell price in freight, don't forget the GST, customs charges and exchange rate on top.
 
You make some good points. I think I'll try ordering a few to test out - you got yours from OSN right? Do you know if anyone has tested out the ones from Kylin or other cheaper suppliers?
 
One of the other advantages of LTO are their high discharge AND charge rates, most cells are rated for 10C discharge AND charge, some even 15C, this makes them much more suitable to solar charging than lead acid that require trickle charge above 80%.

Yes I purchased from OSN, I did get pricing from Kylin in early October:
LTO 66160 30AH----US$9.9/PC
LTO 66160 35AH----US$13.5/PC
LTO 66160 40AH----US$18/PC

The latest pricing from OSN was cheaper than Kylin.

I purchased 215 cells in my first order which at the time was US$20 for 30AH cells:
Product Amount US $ 4472.00 AU$6211
Shipping Fee US $ 2485.00 AU$3451

GST was 10% of the product amount, so AU$621.10
Customs clearance and processing, etc added about AU$500

All up about AU$11,400 which is AU$53 per cell delivered.

You might struggle to get a decent price only ordering a handful of cells, if you search aliexpress for "lto 66160" you can delivered pricing of about $62 AUD for 30AH and $65AUD for 40AH. These prices seem about right for small quantities with delivery.

Eg: Pack of 10 cells
https://www.aliexpress.com/item/10p...umTitanate-Battery-with-wide/32947131554.html

I know there are other forum members who have purchased from OSN, and maybe someone from Yinlong, I am not aware of anyone that has ordered from others like GTK or Kylin.
 
I'm planning an LTO purchase in a few days, 330 cells for an 11s-30p pack at 24v, 1200Ah
I see you got an inverter/charger, could you share what charge settings you're using?

There was discussion on the forum about setting Absorb timing to zero and just using the bulk voltage setting to charge.

I am a little concerned about the effects of a slower rate of charge on the cell chemistry, but it definitely looks better than the AGM batteries I've worn out!
 
I haven't had a chance to dial in my inverter yet as we've only just finished the pack assembly, I was hoping to have them installed this weekend but I ran out of weekend.

But from playing around with individual cells and 12v 5 cell packs on a variable power supply I have found the following to work well:

Charge voltage 2.8v per cell
Float voltage 2.7-2.75v per cell

These settings also happen to almost perfectly match AGM charge settings when configured as 5s per 12v battery.

Others have tested, reported and graphed that the bulk of an LTO cells energy is stored between 2.4 and 2.6 volts, depending on how configurable your charger is, with your pack configured as 11s it will only just reach 2.45v per cell at full charge.
 
Thanks Baron, I'm getting more confident in the choice of LTO. These look like they might be a 25+ year pack if I treat them right!
 
Based on most of the worst case scenario brochures and sales specs, 25+ years should be a safe bet.

I understand it's still early days for LTO tech so it's difficult to predict how long they will last, I have seen rated life expectancy from 10,000 to 30,000 cycles, some even stating better than 80% usable capacity after 30,000 cycles and a 100 year shelf life.

It will be interesting to see.
 
This I am following as in about 10 - 15 Years I will be going ahead with on Off-Grid Home and this will be interesting to watch for longevity
 
So what am I missing on these LTO batteries? They seem like the perfect battery.

I'm tired of replacing the lead acid batteries on my boat every couple of years and have been looking at lithium. Stumbled on to these LTO here.. (Have 5 samples (40AH)on the way from Kylin btw.. USD20 / pc FOB for sample , 16.5 for volume. Bit pricey on air freight will need to look at ocean if I go volume.. From another vendor I got a quote of about USD2 / pc to Sydney port.. for the ocean freight piece.Clearance / gst / customs / final delivery extra but its a good guide .. but if you marry those two up its suggests port landed cells for about USD18 / pc. Not bad.Believe these are YinLong mfg.)

Based on what I've read so far these will last forever. There even seems to be a very real chance that a 5S pack will charge quite nicely, and properly, with my existing Lead Acid Charger if it is set to cool gel orAGM. Dont believe I can do that with other lithiums.

So again, what am I missing ? Isn't this too good to be true?
 
Back
Top