LiFePo4 legit offer?

[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]

@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

[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.

[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!

[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 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 also did parallel all batteries for a week (because I did not have rack built). I also set BMS balancing to start around 3.4V during charging.

[Ampster]

Thanks. I did inquiring on Alibaba and some of the quotes I am seeing are crazy competitive to used cells..!
............
For your cells did you do any sort of top or bottom balancing before setting them up?

I know those prices are tempting.

I always parallel the cells for a few days before assembling them. There are advocates for both top and bottom balancing but I don't think doing that on an individual cell basis provides any marginal benefit. Maybe in an EV conversion that is going to be pushed hard but with a stationary pack there is an opportunity to extend the pack life by using less of the capacity. Doing that avoids any risk of a weak cell hitting the top or bottom before charging or discharging is cutoff.

[stekicar]

Batteries I bought are not the used ones. They are brand new, grade "B" due to 3.3V nominal voltage instead of 3.2V. They came exactly at 3.30V+0/0.02. I measured voltages, internal resistance and weight on all of them upon arrival.
I did not want to buy used ones because there is no way knowing how much they were used. I did not do any bottom nor top balancing because they came with exact same voltage.

[mstasko]

Thanks. I did inquiring on Alibaba and some of the quotes I am seeing are crazy competitive to used cells..!

Shenzhen Youngpower Technology Li

EVE A- grade 3.2v 280ah Aluminum case, priced at $82 for 48. Works out to $102/kw !
or $120 including shipping (by sea).


Looks like I'll pursue this cell type, now I need to decided on cell ah size and number in parallel that I want.

For your cells did you do any sort of top or bottom balancing before setting them up?

[stekicar]

Batteries work without any problem. I use them since November last year. I charge them up to 3.475V (upper 90%) and discharge them down to 3.15V (lower 20%) which is 70% capacity. My system is set based on charge/discharge data given by seller. Batteries have more capacity than it is stated, I never go below 3.2V even after I used 70% of available power. Batteries are grade B because nominal voltage is 3.3V instead of 3.2V. I made wooden frame out of 2x4 and place all batteries in 3p16s setup. I connected battery pack to inverters (3kW and 12 kW) and Victron solar charges through bi-stable relays which are controlled with Raspberry Pi and also with manual switches. I did not compress these batteries.

[mstasko]

Thanks for the info.

Any noticible performance hit being grade B cells, loss in ah?
what voltage range do you run the pack?
also how did you construct the battery bank, any compression or fasteners to keep the cells from moving?

I currently have a Nissan leaf pack that I’m trying to decide on expanding or selling off and going this route instead. With the leaf cells they require compression so I have them essentially fastened together so they wouldn’t be able to move I’m sure if that type of set up is required for these types of cells.

Thanks again..

[stekicar]

These are B grade (as per seller) CATL batteries with Aluminium case. I went with Guangzhou QiHua Technology Co., Ltd. Contact name was Sylvia. As for BMS I am "using" Chargery BMS16T. I bought it because it has serial port and I can communicate with it using Raspberry Pi. Communication is only one way but it is enough for me because I am just using it to monitor voltages of each cell. As for balancing, I do not think it is doing any work because it has only 1.2A capacity which I do not think it is enough for my 720Ah system. But, batteries are even with voltages. Unfortunately, serial port on BMS unit stopped working 4 months after and I cannot even update firmware for some reason. I started looking into something like this: https://shop.gwl.eu/GWL-Modular/GWL-...e-Monitor.html. This unit does not have communication port but version 1.8 will but it is still in prototype stage. This GWL unit does not have balancing capabilities.
If you have any other question, feel free to ask.

[mstasko]

Yes, I did. I got 48 of 320Ah for 720Ah total (3p16s). I am running them since mid November 2019. SInce March this year I did not use grid power except for couple of rainy days. I charge them up to 3.475V and drain them not below 3.15V (3.18-3.2 actual). So, far they are really good. Three of them came damaged so they sent replacement. And replacement came damaged... So, third time I got good ones. Actually, I ordered three more to be shippped with replacement and half came damaged and other half was in good condition.

stekicar

What brand/company did you end up going with? What is the BMS that you are using?

I am interested in this cell chemistry (LifePO4) and trying to decided between the different case types (calb, aluminum, etc) going with a smaller ah or larger ah cells, 100 vs. 180 or 200ah, etc..
Any insight welcome.

Thanks

[stekicar]

Yes, I did. I got 48 of 320Ah for 720Ah total (3p16s). I am running them since mid November 2019. SInce March this year I did not use grid power except for couple of rainy days. I charge them up to 3.475V and drain them not below 3.15V (3.18-3.2 actual). So, far they are really good. Three of them came damaged so they sent replacement. And replacement came damaged... So, third time I got good ones. Actually, I ordered three more to be shippped with replacement and half came damaged and other half was in good condition.