LiFePo4 legit offer?

[mstasko]

@stekicar With your Chargery balance functionality being at 1.2a do you think it is able to make any difference given the battery bank size? You mention the cells arrived within 2mv which is probably in the margin of error of the meter. I wonder the cells would have stayed within that range with or without the balance function being turned on?

Also for your pack setup did you add any compression to the cells?

[stekicar]

I do not think that Chargery does any balancing with 1.2A for such a big battery capacity. I was using it mostly to monitor/tracking of each battery cell voltage connected to Raspberry Pi/Influxdb and Grafana until serial port went bust. I did not compress batteries at all. As for batteries staying balanced, I am currently using batteries 24/7 and I use roughly 3/5 of 25kW daily (25kW is about 70% of battery capacity). I just measured voltages with voltmeter on all cells them voltage is between 3.37V and 3.36V except one that is 3.32V. Here is what BMS shows for voltages:Cells voltage.jpg and on all of

[mstasko]

@stekicar that is helpful.

Where I am struggling a little bit is the BMS protection piece related to cutout voltages.
I am planning to build a 840ah bank, 48 280ah cells, 3p16s design.
My max inverter draw will be 10k or roughly 230a from the battery.
I am having a hard time finding a BMS that has a decent charge current, I'll need up to 200a (more like 100 to 150a majority of the season) and I believe the Chargery is rated for that or higher.

Would you recommend Chargey to control the cutoff relays and handle that high of a charge?

Thanks!

[Ampster]

.........
Where I am struggling a little bit is the BMS protection piece related to cutout voltages.
I am planning to build a 840ah bank, 48 280ah cells, 3p16s design.
My max inverter draw will be 10k or roughly 230a from the battery.
I am having a hard time finding a BMS that has a decent charge current, I'll need up to 200a (more like 100 to 150a majority of the season) and I believe the Chargery is rated for that or higher.

Would you recommend Chargey to control the cutoff relays and handle that high of a charge?
.....

I am not sure what you mean by BMS charge current? Small RC chargers also have balancing leads but are designed for RC helicopter battery packs. I believe that is the heritage of Chargery. I am not familiar wiith Chargery as a robust BMS in the environment of stationary packs. It may provide a good monitoring function for your pack. I do not know it it has programmable cutoff voltages.
For a while on an EV conversion I used a programmable voltage switch/relay that drove a large contactor that turned off the large charging current. It was reliable.

[stekicar]

@mstasko,
Chargery BMS unit can control two relays. One on charge side and one on discharge side. NO current passes through BMS unit itself. I have one with 600Amp shunt. But I've never used more than 250amp at a time. Chargery BMS16T, which I have, cannot control bi-stable relays so I do not use it to control my relays. I am using Raspberry Pi to control bi-stable relays. My experience with Chargery is not that great. Very good idea but it is not ready for prime time. I had problems with the unit giving wrong data (used Kw and battery capacity) on serial port which manufacturer fixed. But I had problems with serial port stopping and finally it does not work at all. I tried to update firmware with no luck. So know, I am waiting for https://shop.gwl.eu/GWL-Modular/GWL-...e-Monitor.html version 1.8 to show up and I will purchase this unit. It can control bi-stable relays, have multiple redundant safety and also will have TTL and serial port.
I also have Thornwave PowerMon (https://www.thornwave.com/collection...dc-power-meter) and this one also can control relay (only one though) for high and low voltages but it does not see each battery cell voltages.
I do not use BMS for balancing because current draw is nowhere near to EV use. My average current draw is between 20-30amps. Only when dryer runs, amps go to 200 max with everything else running in my home. I set my BMS to start "balancing" above 3.4V at charge so all those voltages in picture, on my previous post, are for battery full and absorption stage finished (there is no float stage). Here is the usage for last 24 hours:
Today.png

[mstasko]

@stekicar thanks for the info. I"ll take it into consideration. I'd be interested if you could share some photos of your setup? Trying to get a feel on how I will approach a setup given the size of the bank I am looking to do (which I believe is the same as yours, 3s16p). Thanks

[stekicar]

Here it is:
20200412_153230.jpg

[NewBostonConst]

Very nice....

[mstasko]

@stekicar Thanks for the pictures. Question on the picture that is a side shot of the battery bank, underneath the Blue Sea switch are those two relays the black boxes that have 4/0 cable attached..? if so how are you controlling them?

[mstasko]

@stekicar @ampster - Thanks for your feedback. Just wanted to let you know that I ended up ordering 64 280ah cells Deligreen on Alibaba. Was able to talk them down to $80 per cell with shipping via sea at $1200. Plan on setting up two battery banks for flexibility as 2p16.

[Ampster]

@stekicar @ampster - Thanks for your feedback. Just wanted to let you know that I ended up ordering 64 280ah cells Deligreen on Alibaba. Was able to talk them down to $80 per cell with shipping via sea at $1200. Plan on setting up two battery banks for flexibility as 2p16.

That is a good deal ($111per kWh). Did that include straps? I see Deligreen carries some brands that I have had experience with in the past. Which brand did you go with?

I am interested in what you mean by flexibility in terms of two banks? Is it the physical flexibility in layout or the ability to disconnect one bank to work on it while running your loads on the other? Some people will tell you that a strategy like that will shorten their life but I think that is less likely with Lithium. It does mean two BMSs and contactors. I am curious about your thinking to inform my strategy in the future because my AHJ requires a NEMA enclosure(s).

[mstasko]

@ampster Yes. Straps were included with fasteners. Correct. I like the idea if needed to bring one down for any maintenance. For 1+ year that has been my setup with a bank of Chevy Volt and Leaf batteries (to be sold). wrt your AHJ you maybe able to buy a used Flammable Cabinet, most if not all are UL listed and they are just as rugged or more so than a NEMA cabinet given their intended use and possibly more cost effective. Here is a guy that leveraged one for his setup: https://www.youtube.com/watch?v=lfnscM1St5Q&t=2s

Oh and the cells are ordered are manufactured by EVE: https://deligreen.en.alibaba.com/pro...37856c12HR2Y0C

[Ampster]

I did a little back of the envelope math and came up with a cost of $0.06 per kWh of usable storage over a 10 year life.
My assumptions were:
Ten year life using not more than 50% of the capacity.
Over that assumed life, one kWh of cell capacity could store and deliver 1800 kWhrs over that 10 years. If the cost of that kWh of capacity was $111 then the cost of a kilo Watt hour of usable stored energy would be $0.06 . That does not take into account the cost of solar panels and an inverter to generate that power in the first place. But if you add those costs together It still may be less expensive than energy from the grid in some high priced markets. That is the case in my energy market where the average cost is $0.20 per kWhr.

Based on the manufacturers life of 2500 full cycles, 5000 cycles at 50.% would be over 10 years giving some margin of safety. My Nissan Leaf modules are probably at 60% of original capacity and they are at least 8 years old. My point is that at a price of $111 per kWhr I will probably also sell my Nissan Leaf modules and invest in some new LFP batteries. I had considered Tesla modules but they are coming in at just under $200 per kWh. They are a more volatile chemistry and can not be consolidated into a pack as easily as these prismatic cells.

[Ampster]

@ampster Yes. Straps were included ............... wrt your AHJ you maybe able to buy a used Flammable Cabinet, most if not all are UL listed and they are just as rugged or more so than a NEMA cabinet given their intended use and possibly more cost effective. Here is a guy that leveraged one for his setup: https://www.youtube.com/watch?v=lfnscM1St5Q&t=2s

Oh and the cells are ordered are manufactured by EVE.............

That was a good video and I will be on the lookout for a cabinet like that. The other advantage those prismatics have is they are easier to configure into a cabinet. Based on the earlier post and some preliminary calculations that could be over 12 lineal feet of cells but they could be in several cells to a row and stacked several rows high to fit in a cabinet like that. I make up my own buss bars to connect the cells so I will probable continue with that strategy to reduce the risk of differences in resistance in the cell interconnections. The straps and bolts will be handy to parallel the cells before assembling them into a pack.

I will have to do some research on EVE. They resemble similar priced CATL (Contemporary Amperex Techjnology Ltd.) cells also sold by Deligreen. I have used CALBs, Winstons and Thunderskys on earlier projects, but these cells appear to have smaller form factor per kWh. Perhaps it is the aluminum case. I recently saw an interview of an American guy that served as the CTO for CATL for ten years during the time that they became the largest battery manufacturer in China. He got his start with GM and was involved with the EV-1. He also chairs some SAE committees on battery standards. He says the most important criteria is safety and that is a good reason to prefer LFP over other chemistries.

Keep us informed as you assemble your pack

[mstasko]

I think we used the same napkin for our calculations...

I also have a Leaf Gen1 pack that I have used for the past year and have similar performance. They maybe rock solid, I never needed to balance them, but they also have crummy $/kWH when compared to these latest LifePO4 prices. I actually passed on another quote that would've been under $100 per kWH (I decided to go with a vendor that others have reported decent experience.). If my order was not so large, I might of gone with them instead.

Will do, my expectation is that these will not be arriving for at my door until 30-45 days from now.

btw - here is another YT that leverages this cell form factor in a Craftsman cabinet. https://www.youtube.com/watch?v=xlxM-BcIxWE