Cheap lifepo4 batteries on ebay

[hochdorf]

One or 2 month ago on ebay appeared new lifepo4 seller.
He sells batteries at low prices, has 100% positive feedback.
Does anyone know anything about these batteries?

http://cgi.ebay.com/36V-15AH-LiFePO4-Battery-Rechargeable-Charger-BMS-Power-/140578098640?pt=US_Batteries&hash=item20bb1b8dd0

 

[Cheeseboy]

Looking at the charge and discharge figures (for 48v 20Ah):

Rapid charging: Charge at 5A constant current to 57.6V±0.5V, then switch to the charging at constant voltage; the charge time should be not more than 4 hours

Max. Discharge current of Protection circuit: 20A
The protection value of Protection circuit: 60-70A (pulse)
Discharge time : 2h（10A）

And if you look at the conditions of the life cycle figures, it doesn't look too promising.

But the charge and discharge figures may just be limited by the shoddy BMS they've chosen to put on it, it's happened before.

As always, someone has to be a guinea pig, go for it if you want, I've bought a hub motor kit from this seller, it works well. Just be prepared to wait for sea shipping. mine came in around 5 weeks to Australia, so I can't complain. No tracking or anything, just turned up on my door.

 

[dogman dan]

Looks similar to a ping. But if it gets shipped for two months with the bms plugged in, it could easily arrive with a dead cell from the bms drawing it's current for two months.

So at least you want to request they unplug that thing.

 

[hochdorf]

Looking at the charge and discharge figures (for 48v 20Ah):

I mean 36v 15ah.

Maximum sustained work current:20A

Maximum Discharge Current :35A

Over Protection Current :45A

Just be prepared to wait for sea shipping.

They does not ship to my country by sea.
They ship by airmail only.

And if you look at the conditions of the life cycle figures, it doesn't look too promising.

Do you mean this?:

Cycle Life :≥1200times(Cycle@23°C,0.5C ,100%DOD)

 

[Cheeseboy]

Yes sorry about using the 48v 20Ah figures, that's the size I have on my bike.

Interestingly though, the continuous and maximum discharge rates on the 15Ah and 20Ah batteries are the same. This is a good indicator that the cells are merely being limited by the BMS, and are good for a higher discharge rate. How much higher, I don't know.

I Believe that the battery would be okay for low-medium power use, anything up to 1000 watts and it should work OK, the voltage drop would be noticeable, however, at discharge rates above 1.5-2C.

When you find out how much extra they are charging for air shipping, please let us know, that's good information for the rest of us

Do you mean this?:

Cycle Life :≥1200times(Cycle@23°C,0.5C ,100%DOD)

Yes, that is what I was referring too. If you look at the conditions that they have used in the testing of cycle life (assuming there has actually been any testing done at all) you will see that they are almost irrelevant as far as real world use is concerned.

The stated cycle life is at 0.5C or 7.5A, which is very much right at the low end of ebike current draw (270watts at 36v), as well as 100%DOD. So take it with a grain of salt.

 

[dogman dan]

Pretty much what they all do, tell you a cycle life of a pack, or even just a single cell, at 1c at most. The battery is most likely very similar to ping, but without pings track record for customer service.

 

[hochdorf]

I Believe that the battery would be okay for low-medium power use, anything up to 1000 watts and it should work OK

In europe maximum output power is limited to 250 watts.
If efficiency is for example 66% = 375 watts input power.
I have crystalyte high speed front motor and 36-48 volts 25 amperes controller, i.e. my bike is vehemently over powered. I never travel at full power on flat, only on uphills.
Over 80% of time when i travel my motor consumes 200-500 watts.

When you find out how much extra they are charging for air shipping, please let us know, that's good information for the rest of us

To finland air shipping costs 107 dollars for 540 watts/hour version.

 

[dogman dan]

You the seller Catherine? We can pretty harsh here to sellers, untill they prove themselves with customer service.

It's how you treat the guy who does end up with a defective bms or charger that impresses us. Ping got his reputation by knowing how to help guys fix a pack with a defective cell, and providing promt replacement cells or bms, or whatever is needed. Plus the technical advice how to do the work. Obviously shipping a defect battery back to China is a last resort.

Re the 1000 watts. A 15 ah battery should be big enough for a 25 amp controller if the battery is using 2c or better cells.

What's the c rate of those cells Catherine? Looking at other batteries in the same sellers store, they seem to be saying about 1.5c But 1.5 c is just about what I always recomend for 2c cells.

Question is, are these 2c cells like ping uses or 1c cells like the ping V1 packs had. If they are not 2c cells, then you need at least the 20 ah size to run a 25 amp controller.