Alibaba.com LiFePo4 Experience

[DLTooley]

I’m just finishing off an Alibaba.com sourced 280 ah LiFePo4 battery.  

Will Prowse’s Diysolar forum is a great resource, but there is a lot of noise.  What follows are my conclusions and actions.  I’d verify for myself on that site for current conditions.  

A lot of people are buying very cheap stock that is in reality grade b, regardless of what it’s called on the site.  A lot of the daunting technical stuff is really only required if you purchase that sub par product.  

Xuba has been previously reported as good reseller.  The previous principals there, Amy Wan and her technical husband, have departed and started their own company, Luyuang. 

I paid just over $600 for the basic 4 cell pack.  They took over 2 months to arrive.  One of my purchasing criteria was the ability to inspect prior to acceptance, however the tracking numbers I was given were never used and I ended up getting a surprise drop at my door.  The product was well packaged, and undamaged - thankfully. 

For a bms I just went with the basic, non Bluetooth, $20 Daly.  The most technical part of the whole process for me was making the cable ring ends and double checking the wiring against the chinglish instructions.  

I have a Victron controller so I do get a fair portion of the data I need from that.  If you don’t have similar I’d recommend something that you can get data from, such as the Overkill Solar.  

I need to get by our library to get a kill a watt meter to do a capacity test.  Also, I’ve not been able to figure out how folks are doing their internal resistance measurements.  

My total cost, including a 600w pure sine inverter, was around $700.  That’s for a total of 3kwh used conservatively.  

I believe there are now 2kwh products available for around a grand - hopefully that’s the way the market is going.  And that the long term reliability is also there.

 

[jonyjoe303]

for internal resistance I been using the yr1030 (cost about 50 dollars) its the best tool for DIY lithium, I use it for the small 18650 cells and also lifepo4 cells and I even tested my 12 volt lead acid with it. The lower the internal resistance the higher discharge rate. It will easily find a bad cell (the one with high IR), all it takes is one cell with high IR to give you balancing problems. I tested 100's of cells with this tool, highly recommend to everyone.


One thing I would find out is how the victron is going to react if the bms activates? all the controllers mppt/pwm that I used produce voltage surges when the bms activated. The voltage surges over 20 volts destroyed any 12 volt devices connected to the battery.  No matter how careful you are, eventually the bms will activate. It was the biggest problem I had when I started using lithium.
Eventually I got the chargery bms8t because I couldnt control the voltage surges. The chargery uses mechanical relays to disconnect the solar panel when the bms detects an out of balance overcharge condition. Its not a cheap bms but it works perfect with solar and lithium.

For grade B and even grade A cells, I would definitely get active balancers. I use them on my 220ah lifpo4 which had balance issues (didnt have an IR tester when I built it) . Instead of taking it apart (160 cells), I just added the qnbbm active balancers (cost about 100 dollars for 4s) and it keeps the battery in perfect balance. The active balancers will help if you are charging at high amps, 1 of the cell usually drifts off when charging at high amps and will cause the bms to activate prematurely, these qnbbm balancers can handle up to a 6 amp differential between cells, the balancing resisters in most bms can only bleed 60ma at most which is nothing when charging at high amps.

 

[DLTooley]

I’m only charging at around .1c so I presume that’s quite low.

It’s actually not clear what the trigger settings are for the <$20 Daly. I apparently triggered it when in Victron absorb using the default Victron LiFePo4. I bled some power off with the inverter and it restarted. I’m hoping this bms device is more hardy than the smart ones.

Thanks for the 411 on the IR tester.

 

[jonyjoe303]

When it triggered did the controller cycle back and forth trying to continue to charge the lifepo4. Was the lifepo4 fully charge at that point. For the bms to activate, the battery voltage (at the terminals) would have to be a little over 14.6 volts or an out of balance condition detected. .1C charge rate (about 28 amps) would be in the high end for a cheaper bms. If the battery is in good balance as it is, keeping the bulk voltage at 14.4 volts, might prevent the voltage getting too high and triggering the bms to activate. If the bulk voltage is already at 14.4 volts and the bms activated, then more then likely an out of balance situation occured.

On the picture of the balancers I'm using an LCD meter to monitor each cells voltage. Do you have something similar in your setup. I found out that is the only way to determine how close I am to a full charge. Once each cell reaches about 3.60 volts I know I got a full a battery. It also lets me know if the battery is in balance as its charging.

I built many battery packs without the IR tester but always had balance problems or self discharging packs. It was just luck that a pack worked good. I didnt want to spend the money on the IR tester but now its the first tool I use to test all my cells. It saves time in the long run.