ebay lifepo4 batteries

[Bouteille51]

Hi all,

I am in the process of planning my first ebike build and I would need some advice regarding the "cheap" battery packs that can be found on ebay.
It will be mostly used for home-to-work commute and I would like to favor the number of cycles I can get out of my battery pack, hence my choice to use lifepo4 technology.
Ideally I would go for a ping or em3ev battery pack but I am not sure yet if I am going to stick to the ebike solution, so I'll go with a cheaper option first (I realize that one can be lucky or not with it).

In the cheap options found on ebay I am trying to compare two different packs: the "blue" one and the "grey" one, both 48v and 20ah... see attached pictures taken from ebay listings.

The BLUE one with this 'sun-ebike.com' sticker seems to be the most 'common' one. I guess this is what has been sold sold for years by sun-thing and other ebay accounts of the same company, correct ?
I saw a lot of comments on these packs here and I would be ok to try ordering a pack from them (delivery time is not a problem).

I recently realized that the GREY one is also sold by the same guys (correct me if I'm wrong) but has slightly different characteristics (see a copy-paste of both below). The price is also slightly higher but nothing significant.
I am wondering whether it is just a packaging (and marketing) difference or if there is a real technology difference between them. Do you know if the pouches/cells or BMS are indeed different, and if the stated charge/discharge rate difference are real ?

I am also surprised about the minimal discharge voltage claimed by both packs: one seems to cut off at 45v while the other one seems to cut at 41-42v...

The BMS seems accessible in the grey pack but is this a decision maker ? Probably if I need to troubleshoot the battery at some point...
I have also seen other packs with grey tape and the BMS in a grey plastic box, but much more expensive... any thoughts ?


Thank you for your help !


------------
Description for the BLUE pack :
View attachment 1
High-capacity 48V20AH LiFePO4 battery parameters:
Discharge cut-off voltage: 45V
Rated discharge current: 30A
Instantaneous maximum discharge current: 50A
Rated charging current: 5A
Maximum charge current: 8A
Battery pack size: 16*17*27cm
Battery pack weight: 8.9kg
Battery pack capacity: 20AH ± 1%
Charge cut-off voltage: 58.5V


------------
Description for the GREY pack :

Nominal Voltage 48V
Voltage Range 42 - 58.2V
Rated Capacity 20Ah
Over-discharge Voltage 2.100V( Any cell)
Over-charge Voltage 3.900V( Any cell)
Charge Voltage 60V
Open Voltage after fully charged 51V~57V (1 hour after being fully charged)
Maximum Charge Current 10A
Estimated Charge Time @5 A About 4 hours
Discharge End Voltage 41.0-42.3v
Maximum sustained work current 30A
Maximum Discharge Current 45A
Over Protection Current 60A
Temperature Rise ≤25℃
Operation Ambient Temperature
Charge 5～50℃
Discharge -20～50℃
Cycle Life ≥1200times（Cycle@23°C,0.5C ,100%DOD）
Storage Temperature Range Less Than 1 Year: -20~25°C
Less Than 3 Months -20~40°C
Weight About 8.2kg
Size 26*15*12 cm
Colour Epoxy board packaging + silver tapes (silver)
This battery is include BMS AND 5A CHARGER.

 

[999zip999]

Batteries must match the controller a controller can over discharge and kill a battery so what controller are you going to use.

 

[Bouteille51]

You are right thank you for the reminder.
I am going to use the Phaserunner from ebikes.ca, coupled to a Cycle Analyst V3.
The motor will be a Mac 8T in a 26" wheel.

At 48v, I was thinking about limiting the power to 20A (~1000W), then maybe switch to 30A (~1500W, but transiently) if I realize that I need more power.
It is probably safer not to go further than that in order to keep the motor safe.
I have no idea yet on what to expect regarding the torque etc... This is my very first build...

I read that one should limit the discharge rate to <2C with these batteries, but the lower is always the better... which made me choose these 20ah packs.

I will adapt the LVC according to the (your) recommendations, depending on the pack I choose.

 

[SniperGaulois]

Hi bouteille, did you follow up on the thread which sais Wouldn't touch him with a 10 foot pole based on what has been posted over the last year or so. Total crap shoot at best.


... If they seller isnt very well rated, and he is that far away, and there is no comprehensive review of his kit, you can presume that your battery will get problems after a year or so.

If you buy good quality 18650 pack it's a lot lighter than a lifepo and the problem with lifepo is that it isnt serviceable, if two batteyies in your pack go bad, probably the whole pack is darned.

that's why i wont buy another one myself... with 18650 you can modify the pack more easily afterwards.

 

[Bouteille51]

Hi zzoing thank you for your feedback.

I tried to read as much 'recent' threads as possible about these kind of packs.
My (maybe naive) 2 cents thinking is that hundreds of these packs are sold every year and we can only count a handful of threads complaining about quality.
Moreover, most of complaints I read about these packs relate to the shipping or short term problems (not balancing/charging during the first days).
Other users giving feedback after several months/years looked quite happy about it (retained capacity), even though they seem to aggree about a bigger sag than 'ping' batteries.

I realize that there is a chance of being disappointed with these packs but I think that I am ready to take the risk, specially if the BMS looks accessible and I can do some troubleshooting (with your precious help guys)...

Also it is cheap and I am a newbie, so even if make something wrong with this pack I won't be crying for too long
Other LiPo technology are not an option for me, too many risks and low number of 'theorical' cycles.

That's also why my question was more related about the difference between the two kind of packs rather than buying or not from ebay.
Has anyone ever opened those packs and check if what's inside is different or not ?

 

[Bouteille51]

I guess these grey packs have not been on the market long enough.
I'll give it a try and let you know (the long delivery time is not a problem for me).

Anyway, the last thing that worries me in the description is that cut off at 41-42v while the other one seems to cut at 45v.
I am surprised about such a difference for supposedly similar technology...
Do you think this is what has been programmed in the BMS ? Any comment on that ?
What would you recommend as LVC and charge voltage for these ?

Thank you for your help !

 

[999zip999]

Buy a quality pack. The others are a gamble for a 30 amp controller. Luna cycle if in usa. Em3ev from china. Why buy junk. Junk.

 

[Bouteille51]

Ok after your recommendations, I gathered some more information outside of the forum and I found horrible stories here and there (and youtube videos)...
Some of them implying the seller I was planning to buy from.

I decided to evaluate his capacity to answer messages (and give me helpful information) in case I have a problem with his pack later.
I wrote a message asking for details about the pack (cells and BMS manufacturer, or at least a reference of what makes his pack).
After insisting a bit, he could not give me any detail about the packs he is selling : "Sorry, we don't have that data".
Not really a good sign if I need top contact him about a defective pack after reception...

I will therefore not buy from him and I'll get something from a seller with a better reputation.
I could not find LiFePo4 packs on em3ev and Luna-cycle. Unfortunately, I can't afford a pack from ebikes.ca and I think that Ping has better reputation than BMS-battery and ev-components.

I'll probably go for a 48v15Ah pack from Ping which has already been very helpful when I contacted him by email.
I'll try to keep my controller to 20A, and eventually raise the intensity to 25A if needed, but no more in order to stay <2C discharge rate.

Does that sound like a better choice ?

 

[999zip999]

Most lifepo4 can not support over 25amps for long life. Yes there is high quality lifepo4, but the cost. Most manufacturers are going with 18650. They are in cans. Harder to mess up. Less cycles on paper. But a lot of lifepo4 get abused and died earlier then guesstimated cycle life.

 

[DingusMcGee]

Bouteille51,

My first 2 bike builds were at 96 v or 24 -40152 [the blue covering] LiFePO4 cells and the second was with 36 LiFePO4 cells to give 108v. Both strings were at 1p but I could get about 55 amp out for a short interval as measured by the CA-v3. I never got near the 2000 recharges that is touted because some cells would rupture juice or just go dead. They do not do well to the jarring of trail riding is what I suspect.

I have since either installed an already built battery from Luna Cycle of 18650's cells or build my own packs of 18650 cells to fit some irregular space.

The 18650's I bought are about 60% lighter than the Chinese/Headway cells based on charge density per unit weight.

I have reconfigured all the working 40152's to 2 packs at 4s8p and use them in tandem with my van's SLA deep cycle batteries for charging ebike batteries thru an inverter at remote sites. These packs produce and hold voltage at a max of 13.45v or 3.36v per cell row. I cannot get them to hold 3.65 volts per cell row for any duration.

I see no reason to go back to LiFePO4 chemistry for my ebike batteries. Think heavy cells, cells easily damaged, not suited for trim battery pack design and question how many charges you will actually get.

 

[Bouteille51]

Ahhhh
I thought that finding a motor and a controller would be the harder part but actually finding out the appropriate battery is much more difficult, specially with no previous experience...
I appreciate your help !

I wonder if your experience with short-lived LiFePo4 cells was not because you discharged your poor 15Ah 40152 with too high intensity... You used them at 55A ?

So, both of you tend to recommend not getting LiFePo4 pack (from Ping) but better a LiPo in 18650 cells (Luna-cycle for instance) ?
Maybe taking advantage of the cheaper price of LiPo to buy a cycle satiator and charge @80% will help to reach a number of cycles close to what is claimed by LiFePo4 ?

However my concerns were not only the number of cycles, but also the safety concern (fire) in case of mishandling (I have not touched a single LiPo battery yet except in my phone maybe).
I have read so much about all that on the forum... I thought I made a good choice with LiFePo4 pouches (pros: safety & cycles - cons: size & price).
Nobody is happy with LiFePo4 ?

 

[999zip999]

I have A123 20ah pouches 24s.883 cycles used with 40amp controller now 90amp. Charge to 84 volts @ 16amps. Charge in an hour. No bms just sense wires and check twrice a day. Oh 4yrs old.

 

[DAND214]

Hey, if your close to Chicago I have a 20ah and a 15ah LiFePo4 packs you can have. 20 ah is more like 12 and the 15 is a 6. They were never what they were stated at. from day one they were 20 to 25% less than rated. Cycles? less than 200. All I can say is, stay away from any dealer on Ebay if they don't live here in the states if you live here.

Luna has been great to deal with and so far the two packs I got for friends are doing fine. 18650s is where the industry is going. Stay with a good dealer and if you have a problem you will have support. If you buy from over seas your support stops as soon as the vendor gets your money.

Dan

 

[999zip999]

Ping and em3ev have support from China but not many from China have support. Yea a lot of people buying A123 20ah pouches 4 yrs ago from recall resale got shitty cells and shitty packs. China will sale anything.A lot of to good to be good.

 

[SniperGaulois]

You can perhaps try to get a pack with registered known batteries from aliexpress...

I recently tried, and it was difficult, but 90 % of people seem to have been satisfied.

On aliexpress people advertise samsung packs with basic cheap 2200mah cells by samsung/lg, 1.5-2 times lighter than best liffepo4, and if they send warehouse error, you get some money back... but don't stop there, check the cell interconnects all match they advertised power rating, before leaving feedback...

You may just get a samsung pack that doesnt overheat too much. Then, if you manage to lower the full charge rating to 4.15 you get around 100 extra cycles, and at 4.10 you get about 700-800 cycles which is comparable to lifepo, until it's at the standard 80% capacity status.

I did that recently, i got fake cells, asked for half my money back, got half my money, then realized that the pack was too hot at 1500 watts, i would have asked for 3/4 money back as it was dangerous, had to double the terminal and middle of pack wires, they were 400 watts max, my pack went to 140 or something.

With that knowledge, if you chance to get real samsung and know what to check, you can try ali express. they arent 2800mah cells, which makes huge capacities, but 2200mah is pretty cool, but treat the sellers with tweezers using the aliexpress moneyback resolution if necessary.

if you got money get a wel known mfcr. also TNT is good at taxing people and adds 25 euros service charge!!! some dudes on my seller got two packs though i got a warehouse error pack because aliexpress got a mastercard transaction irregularity kept me waiting 30 days and then i got a tnt warehouse error with generic cells.

 

[SniperGaulois]

these are so cheap nowadays, its awesome... http://www.nkon.nl/samsung-18650-inr18650-25r.html I could sell you a solderless battery box for 96/112 batteries but i have to get the project funded through kickstarter. for the moment its necessary to get spot welding stuff and nickel, or to risk soldering them with low temp solder and coolant to spray onto the cells when it's melted if you you want to not spot weld. for 300 euros of batteries it's doable. takes a day though and you have to mentally visualize all the construction, which takes concentration :|

 

[Bouteille51]

Ok I'll now consider cells instead of pouches.
My naive idea was that pouches are the future because they basically reduce the amount of lost space between cells... So they should provide a better power/volume ratio but I am wrong apparently. Maybe the fabrication process is much harder too.

Unfortunately Luna-Cycles does not ship batteries to France...
I'll consider the options offered by em3ev (but the shipping price is horrible), do you have other recommended sellers that could ship to France ?

I'll also check whether it's worth ordering individual cells (and BMS) and building a pack myself.
Looks like a new world of complexity but I like to build stuff so let's see
I saw Nkon as provider that ships to europe, any other recommendation ?

 

[DingusMcGee]

I wonder if your experience with short-lived LiFePo4 cells was not because you discharged your poor 15Ah 40152 with too high intensity... You used them at 55A ?

Under the battery specs: Max allowable discharge 10C

10C = 10 x15 150 amps. 55 amps >> 150 amps.

 

[Bouteille51]

I wonder if your experience with short-lived LiFePo4 cells was not because you discharged your poor 15Ah 40152 with too high intensity... You used them at 55A ?

Under the battery specs: Max allowable discharge 10C

10C = 10 x15 150 amps. 55 amps >> 150 amps.

Oh ok ! sorry
Wow 10C that's impressive, I was stuck in the cheap LiFePo4 pouches world where it's recommended not to go over 1.5 to 2C...