Review of Sanyo 18650 2600mAh protected on the positive side

Thanks.

Price has been jumped up to $11.99 now!

I updated post #1.
My initial measurements of overcurrent protection were done on cell 2 only.
I later realized that one of the cells would not power my Flashlight that needs about 3A.
So I tested both cells and guess what! One cell 1 seems to be missing one MOSFET. It has half the current capability of cell 2.
Rather disappointing…

Update post #1
Added a picture of the PCB.
That cell being defective I decided to remove the clear heat shrink. The black cap fell of after that, revealing the PCB.

Thanks for the update. I'll do some testing on mine if they ever turn up..

It looks like I was lucky to get them so quickly.
On almost all DX orders I get a defective item or an item that doesn’t match the description… I’m getting tired to ask for a partial refund!

Trying to debug the defective PCB, it seems that one chip on the PCB is dead.

The voltages are the same for both chips as they are in parallel. However under load on chip gets hot but not the other.

pin 1,2: Reads VDD; Connected to positive pole of the battery.
pin 3: VDD
pin 4: GND
pin 5,6: GND
pin 7,8: Reads VDD; Connected to button top (positive)

I have no idea what pin 3 and 4 are for. They are connected to capacitors. No idea why.
Can somebody help?

I’d get a couple new ones from FT.

http://www.fasttech.com/product/1225103

2 pieces for 1½ bucks :slight_smile:

They’re 4 Ampère each

Yeah but on my cell the PCB is on the positive side, meaning that the PCB needs to have a hole in the middle like a donut. :slight_smile:

argh…of course… :Sp
sorry…

I think I’ll just use this cell in low power applications. But I’m curious to know how that chip works… And why it is connected to capacitors.

I will look that up ’cuz I am curious also. I just have to eat first.

Willing to desolder the bad pcb in order to get a picture of the back? The protection IC isn’t on the top.

I did take a look at the underside of the PCB by slightly lifting it up. There is nothing on the other side appart from markings (“18650 2TC”).

Must be a protection ic with integrated mosfet.

Nice review! Thanks for sharing. I’m a big fan of Sanyo batteries.

Too bad Sanyo was bought by Panasonic :frowning:
It’s amazing the number of good company/people in Japan considering how small it is.

my guess is they are using the capacitors as a delay (for overcurrent or overcharge perhaps?)

Correct me if I’m wrong, but a quick change of voltage on the positive side (button top) will induce a current in these capacitors.
Maybe that this current is used to detect short circuits?

UPDATE:
As you can read in the first post, one of my cells arrived with a defective MOSFET, meaning that it has only half of the current capability.
After my tests, I placed the cell in storage (3.8V) and placed it aside. Today I wanted to use it for a flashlight that uses less than 2A, but when I took it out the voltage was down to 3.5V.
I charged it back up… and realized that it self discharged. So I popped the top plastic cover and guess what: The defective MOSFET was blown up and had slightly melted the black plastic cover. It was hot (about 50°C), so that’s what caused the high self discharge.
This is not very reassuring…
In the end I removed the defective chip from the PCB and now everything is fine. You just need to be very careful not to touch 2 legs at the same time when you remove the chip…