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LTO Powerwall
#11
where did you source the batteries? here in the region of austria/germany it is almost impossible to get those...
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#12
They were from OSN Power in China, shipped via sea freight as a single pallet and crossed fingers that they would actually arrive.

OSN may try to say that the cells are "new", they are most deffinately not, but they appear to be in a very good condition electrically and still have virtually the full life remaining.

All of the European LTO manufacturers will not sell direct and seems the same in the US, I have tried contacting all of them and spoke for a long while with one of them but still no prospect of external sales for at least 2-3 years. At the moment any LTO cells in the marketplace are recycled or manufactured in China in a small factory with limited quality control and would not touch them with a bardge pole (old English saying...)
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#13
First pack almost fully wired up withconnecting up the balancing cables after building a small test box to display the voltages for the cells.

 

Slight issue I realised after and too late was the volt meter would not alter the decimal so it stayed at 0.1V resolution...



The last cell reading is double because of the way I had to wire the volt meters as they will not power up from less than 3V so the power is stepped with the last cell reading the cell 10 and 11 combined. Will change this in future with a boost converter just for the last cell because each volt meter needs it's own -ve reference and so I could not supply all the volt meters from a single source.

Wiring is held in final position with hot glue.

 

Reverse side of the front panel, DIN rail fix with the two volt meters and switches still to install. The DB15 is flush with the front and the back filled with hot glue to hold it in place without any screws and supports the cables better.
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#14
First 9 boxes wired, charged and powering my computer at the moment. Wooo, sun power with no sun outside...



This was an earlier test with 3 of the boxe - yes, no separate breaker - testing  Big Grin  Now with 63A breaker...

 

The MGE Unit pulls hardly any power when nothing is plugged in, while the Borri units (T3 2U 3KVA) seem to pull around 70W even with nothing attached when the UPS is active. At the moment with 14% load the Borri unit is pulling about 6.5A at 81.1V so a little bit of losses in the UPS, at least it will save on a heater in the winter... Tongue




The hot-plug unit I made to check the voltages works ok, if the displays actually worked properly and moved the decimal so I had 2 decimal place accuracy, but I guess that's all you get for cheap China diaplays..  Will be making a second one with better displays and a boost for the last volt meter (powered across 2 cells and measures one for each voltmeter). Worked well enough while wiring the leads up.



Downside is that I did not connect any of the voltmeters into the battery boxes because of the accuracy and a realisation that the 30V units will have slight issues if the bus side voltage is reading 48V, which will occur with 2 pack breakers on and the third one in an off state.

Next up, a bit of soldering for the balance leads..... all 225 of them.

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#15
Running the UPS for a day now and have the battery packs unit on charge at 1300W (78.3V and 16.7A with 1A from the UPS while it is pluggeg in and 15.7A from the charger).

The Borri units I have (TU U2 3KVA) appear to have a lower cut-off voltage around 10V of lead-acid or 60V so that provides for a cut-off per cell around 1.8V and the upper 100% full reading is 13.75V lead-acid or 82.5V total or 2.5V, while the charger may go to around 14.2V lead-acid or 85.2V during the 3 step charge for the desulfation phase which would then be around 2.6V per cell.

This is why a pack size of 11s works for Lithium Titanate cells if your using it with anything that was made to work with lead-acid batteries and gives a resulting working range for the cells of 1.8V to 2.6V. The cells will work between 1.5V and 2.7V but this is similar to all Lithium cells in that you may see some issues running 0% to 100%.



Balance lead boards are in progress with fuses and resistors - still adding resistors and fuses to the 15 boards...
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#16
Our cells arrive two days ago, brand new...at the moment we are testing the same cells, Yinlong 2.3V 40Ah, our plan is to build 14P24S 48V 30kw. max output 5kw peak 10kw.
For .125C we running 2.05V -2.5V a straight line 39,7Ah... charging them higher to 2.8v brings nothing, discharging them lower than 2.0v also nothing.
Our Italian friend did the same test and with the same results and conclusions.
Max power we see is about 42Ah 1.5V-2.8V.
We are interested in your progress with balancing as we noticed that we need more than 1.2A.

My plan is to use two aluminium sheets 3 or 4mm and sandwich the cells in between.

Not sure how you build you pack, but is there really wood between the cells and the connection, or is there a nut in the wood..?
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#17
At 0.125C (5A) between 2.05V and 2.5V can you confirm that 39.7Ah (5hr) is correct because 42Ah full 2.8V to 1.5V less approx 12Ah due to 2.5V and 2.05V range makes 39.7Ah for an operational voltage range curious ?

Only wood and the 12mm thread from the cell. Good for 35A per cell without any warming.
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#18
Till now the plan is to 2.0V to 2.5V, beyond and above there is no possibility to balance the cells in this system.
Currently testing 2P5S 10Ah cells for a portable pack, with a simple balance board set at 2.7V.
For static charge and discharge there will be no problem balancing a bigger system, for a solar system it is a whole other story.
Your approach to build smaller parallel packs I had in mind when starting with LTO, but there is a lot of electronics and connections involved, that is the mean reason I will go for 14P and figure out what the best option is to balance.
If we can not find anything on the market, I wil make it myself.
Another important part will be battery protection/ and control settings for charger/inverter/generator, that wil be easiest part to build.
Main problem on this side, I did not design a pcb for over 15 years now, and to hook up the new software and dig in it cost a lot of time.
I wil start design/develop on plain pcb, and solve one step at a time.
It would be nice to find someone who is running the pcb software on daily base who can design a pcb for this system, as I am sure a lot of people sneaky reading our progress, with a almost unbeatable storage system...
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#19
After a lot of searching around for parts, inverters and charge controllers I am comming to the conclusion that 72V is currently the most unsupported system voltage. While EV and bike packs may be 72V there is a big lack of choice with solar charge controllers and inverters that will work for 72V packs. The critical issue is that there are no off grid wind charge controllers that work with 72V which are actually designed properly as wind charge controllers, not just PWM rubbish that will destroy a wind turbine or fixed MPPT voltage style.

The 72V UPS units work well and gives out a 1A charge when plugged in (would take 17 days to charge 30kWh) and pulling the power cord turns it back to battery mode, which is ok for testing and running some computers and electronics.

Charging 72V is cheap and easy via the power supply I posted separately about and the system is currently charging at 1000W from one unit, while sorting out the BMS leads and parts before contemplating re-arranging the solar to charge the packs directly rather than going through the grid and back.

Changing to 48V arrangement is now looking very appealing but a little scary as the busbars will have feed in breakers for 900A (100A x 9) if I add in the last 3 packs to make 18 in total. The real issue for concern is actually during a fault if you have say 5000A flowing the resulting magnetic field pulse created may end up pulling the busbars off the mounts.
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#20
Hello,
i bought lto 66160 too, mines are written like "excell lithium titanate" 2.3v 30ah real 25ah and sadly 2.1v
they are labeled in 2 ways:
- YL14052400208
- 104251F28200124
if someone know how to read it would be nice to know.
i paid them 9 usd/pc , how much did you?

i used a bms of electric bike programmable and the bleeding balance current is 0.2A. would be nice to have 1 or 2 A my configuration is 24S4P links of copper and having problem with the nuts that are from stronger metal than aluminum and break the terminals even at 7 Nm.

im cycling one cell to know life of it and doesnt seems to be very good compared to lifepo4 maybe like someone said they might be strongly used.

nice to contact
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