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48V LTO Off Grid system
#1
So after much time spent going down the HV battery pack rabbit 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, etc readily 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 12kw low frequency solar inverter like this:
http://www.sacolar.com/products/info_8_itemid_18.html
https://www.must-solar.com/pv3500-4-12k-...-inverter/
https://www.yiyen.com/product/hp-pure-si...ercharger/

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 tolerate generator 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
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#2
Low frequency inverters are generable bigger, stronger, and tougher then high frequency I read. What about pricing?
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#3
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.
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#4
(08-10-2018, 12:36 PM)BaronVonChickenPants Wrote: 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-MFD-u...m570.l1313

Just curious , what kind of a discount did you get for 215 pcs and what kind of freight ???
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#5
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.
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#6
(08-11-2018, 11:17 PM)BaronVonChickenPants Wrote: 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...)
Running off solar, DIY & electronics fan :-)
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#7
(08-11-2018, 11:17 PM)BaronVonChickenPants Wrote: 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
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#8
(08-11-2018, 11:17 PM)BaronVonChickenPants Wrote: I have contacted Kylin regarding their $7.9USD cells but so far have not received a reply.
Did you received any answer?
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#9
I did get a reply:

Quote: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.
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#10
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:

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

LTO 40Ah------Wholesale price is USD16.5/PC
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