Anyone have experience with LIFEPO4 26650 cells?

[curtis]

I recently bought 26650 cells from battery hookup and build a 12S - 5P pack to run my 36V controller for one of my e bikes. I have 20 cells left for a 4S- 5P pack to run my 48V controller.

Capacity is a big issue with these cells as 3.8 Ah * 5 = 19 Ah and the 12S pack tripped the LVC cuttoff way before I thought. My 20Ah Lion - 18650 pack has over double the range that my 19 Ah LIFE pack has. That is because Lion is 4.2 - to 3.4V and LIFE is 3.6V down to 2.5V. I bought a 10 amp charger for portable charging.

I bought them as they are safer than Lion 18650 cells which have known to catch on fire due to thermal runaway. I have no safe place to charge them as live in a 3rd floor attic apartment with no basement or garage or outside power.

At first I thought the volt meter was defective but after research found that the standing voltage after a full charge is not even close to the running voltage.

Fresh off the 43.6V charger the standing voltage is > 42V however when I ran them using a power meter which measures voltage , current and power and peak of each during a trip. the standing voltage at 0 load was lower than 42V and after 1/4 mile was under 40V. At > 80% of the maximum amps of the controller it read around 34V. A SAG of > 5V.

The e bike was geared for 28.5 mph at 36V so should have reached > 30 mph on flat ground but only did 26 mph due to the SAG.

My question is should I build a 18S - 60V pack to run and gear a 48V 16S controller. I could order 1 more box of them. they are Tenenergy cells from Battery Hookup. Not sure if the Caps on the controller are 60V or not but I lost about 2V or > 1V just hooking them up when running 12S as 42V off the charger and > 39V when running at 0 load ?????

Basically I just want performance and compared to Lion or Lipo which is volatile battery chemistry I am NOT getting good performance. I have built several e bikes and with chain drives gearing is important so am looking at gearing for SAG voltage which is a lot lower than standing voltage. Is that what I should do or something different ?????

Since charging voltage for 12S - LIFE is 43.6V the SAG voltage under heavy load is 34V that is a 9V difference so am thinking if I gear the next bike to 48V then will need 60V of LIFEPO4 or 18S ?????

Please let me know. Anyone with experience with LIFEPO4 - 26650 cells.

Thanks.

Curtis out.

 

[hanstomatoes]

just 3.2 and add it to what ever S series and do the math Bro to make 48v you need to have 15s "in series" compare to 13s in lithium.

 

[Rocky1198]

I could order 1 more box of them. they are Tenenergy cells from Battery Hookup.

Can you post a link to the actual cells you bought?

Did you do an actual capacity test on any of those cells?
I personally never had good luck with Tenergy.
That seems like excessive sag.

That said, the nominal voltage on LiFePo4 is 3.2v
Full charge is 3.6v so for your 36v battery you need 12S to get the same as your higher voltage LiIo.

Which you did.

Do a capacity test. I'd bet your cells are significantly less capacity than advertised.
Test ONE cell under the max load rated and see what you get. If they can even handle the rated load.
Also, if you didn't test each cell, how do you know you don't have a bad one (or two) ?

My gut feeling here is the cells are not up to par.

 

[curtis]

Yea. I agree.

They seem to charge ok and do run my 1,800W brushless motor with 1,500W brushless 38 amp controller at 15S - 5P but top speed is 25 mph. The gearing is 35 mph. It did 28 mph with 13S - 7P - Lion. Since then I built a 20S LTO pack with those 18 Ah Lishen cells. Two 10S packs with active balancers. I have yet to run them on account of the bad weather. I also had to order a replacement 11T dual D bore 10mm sprocket as I got some bent teeth. The LTOs weigh almost 50 pounds so the 20" bike will be a little top heavy.

 

[curtis]

I was wrong. It was not 26650 ternergy cells. It is K2 energy cells from Battery Hookup. They are rated at 3.8 Ah per cell and I built two 6S - 5P for 36V and a 3S - 5P for 15S - 5P for 48V controllers. The problem is they are supposed to be 19 Ah but wont even go 10 miles. Fully charged the 5 in 1 meter reads 97% and after about 6 miles only 25%. Would improper solder joints cause such a loss of capacity or not ????? Also the SAG is considerable as my power meter read 40V and SAG was 34V @ 1,200W load with my e bike going up a hill. They also charge back up really fast indicating low capacity. At 25% after 6 miles a 10 amp charger 43.6V will charge to 96 to 98% in less than 30 minutes ????????

Please let me know.

Thanks.

Curtis.

 

[curtis]

I have run them well past 500 partial cycles I would imagine and work very well for loads < 40 amps. I am running dual Bafang 350W motors that pull 17 amps each and 34 amps total and the bike performs flawlessly. After 4 or 5 partial charges I will have one cell bank at 93% and all the rest at 99% or 98% on the cell meter. I simply hook up my 5 in 1 cell balancer after charging and in a minute or two the balancer beeps and then I put in on my 6S -LiPo charger at 1 amp balance and in about 3 to 5 minutes all cells are at 98 or 99%.

I am looking at building a larger 15S pack for my dedicated 54.6V - 900W - 15-amp charger. I am looking at 15S - 10P with the A123 cells. That will power my 1,000W DD hub as well as a 1,800W brushless motor and possibly a 3-kilowatt brushless motor.

Thanks.

LC. out