Review of Sanyo 18650 2600mAh protected on the positive side

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lagman
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Review of Sanyo 18650 2600mAh protected on the positive side

Intro

I got my first flashlight a few days ago (Review) and needed a few 18650 batteries to go with it. I extracted 9 LG 18650 from a laptop battery pack but wanted to try/test protected batteries.

I just received two Sanyo 18650 2600mAh from DX paid 8.36USD. Ordered 18th, April. Received 14th, May.

Presentation

The protective case arrived destroyed but it did its job, the cells are in perfect shape.
Out of the box voltages:
Cell 1: 3.778V
Cell 2: 3.777V
Excellent!
Both cells are stamped with the code S04A which means the inner cell was produced during the fourth week of 2014. Very good considering they had to go to an other factory which added the PCB
The cells are 67mm long without the button top, which adds 1mm.
The added button top has vent holes, but they are quite small.

LG cell (unprotected) surrounded by Sanyo (Protected):

PCB

The PCB is on the positive side, enclosed in a strong black plastic case. The whole thing is held together with a very thin clear heatshrink. With the PCB on the positive pole there is no need for a wire to go to the negative pole so the cell is probably thinner than cells with PCB on the negative pole.
The PCB over current trips at:
Cell 1: about 2.5A
Cell 2: about 5A
I believe that the PCB of cell 1 is defective. (or is it a different PCB?)
Both PCB need to be placed back in the charger when over current is triggered.

The PCB under voltage protection trips at 2.5V and doesn’t reconnect when the load is removed. 2.5V is too low to my taste, I would rather see a cutoff at 3V as it only reduces capacity by 30mAh and increases cell longevity.
Measured internal cell resistance (DC) is:
Cell 1: 132mohms
Cell 2: 94mohms
LG cell for comparison: 78mohms

With cell 2 fully charged and a load of 3A that means that the voltage sag is 0.282V which means that there is about 0.8W of power dissipated as heat in the cell/PCB. At 4.5A it’s 1.9W.

Capacity tests

Conditions:
-Ambient temp is 20°C
-Cells are charged to 4.20V
-Cells are discharged at 1A down to 3V
-Test is performed using accucel 6 hobby charger. I know for a fact that it is inaccurate, so below is the result of the LG cell to compare.

LG cell: 2.59Ah
Sanyo cell 1: 2.59Ah
Sanyo cell 2: 2.61Ah

How do they hold their voltage? I have no way to get nice discharge curves. However after emptying the cells I put back 500mAh back in each cell and the voltages (OCV) were:

LG cell: 3.60V
Sanyo cell 1: 3.75V
Sanyo cell 2: 3.76V

This clearly shows that at a same SOC the Sanyo has a higher voltage.

Holding a voltage higher is better as it means that the energy (Wh) contained is higher. It’s also good for LED flashlights using linear regulators as it’ll keep 100% brightness longer before dropping.
Sanyo is clearly better on that point. And that proves to me that the cells are genuine.

Conclusion

Pros:
-Genuine Sanyo cell which holds its voltage high during the discharge.
-Over current protection is set just right
-Quite small in diameter and only 3mm more in length compared to non protected batteries

Cons:
-Internal resistance is quite high. That’s the drawback of protected cells.

Would I buy this again?
At 8.36USD it was a great deal so I couldn’t resist. But at 12USD I wouldn’t buy it as I can get decent (LG) cells out of a laptop battery pack for about 3USD a piece or even free if someone gives me his old pack…
If you really need protected cells however, I would recommend these if you don’t want to spend big bucks on Panasonic 3.4Ah.

Final note:
I will probably use these to power electronic things that I’m building/modifying as it will limit damage when the inevitable short circuit happens…

Please feel free to comment the way I did this review as this is only my second one.

My English isn’t perfect but I’m trying to improve it. If you see something that doesn’t sound right or is just plain wrong, please feel free to point it out! Smile

Edited by: lagman on 05/18/2014 - 18:25
Jerommel
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I never understood why they did it on the negative side, with that positive tab downward, which is not the safest idea…
They’r e rather cheap too!

MRsDNF
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Thanks lagman. Can you put review completed in the heading when your finished as I'm interested in your closing results. Cheers.

 

djozz quotes, "it came with chinese lettering that is chinese to me".

                      "My man mousehole needs one too"

old4570 said "I'm not an expert , so don't suffer from any such technical restrictions".

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Helios-
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Jerommel wrote:
I never understood why they did it on the negative side, with that positive tab downward, which is not the safest idea…

18650s vent through the top. Tho they should be able to fit a few holes in a top mounted PCB.


Counterfeit 18650s, 2,<a href=“http://

lagman
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@MRsDNF: I will. results should be online in 2 days.

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musicmagic
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well done review. thanks.

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BLightSam
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lagman wrote:
I just received two Sanyo 18650 2600mAh from DX paid 8.36USD.
How did you get them for $8.36 when the Web page says Price: US$11.99?
MRsDNF
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BLightSam wrote:
lagman wrote:
I just received two Sanyo 18650 2600mAh from "DX":http://www.dx.com/p/genuine-sanyo-18650-2600mah-rechargeable-battery-wit... paid 8.36USD.
How did you get them for $8.36 when the Web page says Price: US$11.99?

I ordered a few along time ago at this price as well when they had the special running. I don't believe that mine have been shipped yet though a number has been issued not long ago (all the details are at home).

 

djozz quotes, "it came with chinese lettering that is chinese to me".

                      "My man mousehole needs one too"

old4570 said "I'm not an expert , so don't suffer from any such technical restrictions".

Old-Lumens. Highly admired and cherished member of Budget Light Forum. 11.5.2011 - 20.12.16. RIP.

 

BLightSam
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MRsDNF wrote:

BLightSam wrote:
How did you get them for $8.36 when the Web page says Price: US$11.99?

I ordered a few along time ago at this price as well when they had the special running. I don’t believe that mine have been shipped yet though a number has been issued not long ago (all the details are at home).

Sorry I missed them. Would have gotten a few.
lagman
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Updated with capacity measurements. Enjoy!

My English isn’t perfect but I’m trying to improve it. If you see something that doesn’t sound right or is just plain wrong, please feel free to point it out! Smile

MRsDNF
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Thanks.

 

djozz quotes, "it came with chinese lettering that is chinese to me".

                      "My man mousehole needs one too"

old4570 said "I'm not an expert , so don't suffer from any such technical restrictions".

Old-Lumens. Highly admired and cherished member of Budget Light Forum. 11.5.2011 - 20.12.16. RIP.

 

my9221
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Price has been jumped up to $11.99 now!

lagman
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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…

My English isn’t perfect but I’m trying to improve it. If you see something that doesn’t sound right or is just plain wrong, please feel free to point it out! Smile

lagman
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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.

My English isn’t perfect but I’m trying to improve it. If you see something that doesn’t sound right or is just plain wrong, please feel free to point it out! Smile

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

 

djozz quotes, "it came with chinese lettering that is chinese to me".

                      "My man mousehole needs one too"

old4570 said "I'm not an expert , so don't suffer from any such technical restrictions".

Old-Lumens. Highly admired and cherished member of Budget Light Forum. 11.5.2011 - 20.12.16. RIP.

 

lagman
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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!

My English isn’t perfect but I’m trying to improve it. If you see something that doesn’t sound right or is just plain wrong, please feel free to point it out! Smile

lagman
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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?

My English isn’t perfect but I’m trying to improve it. If you see something that doesn’t sound right or is just plain wrong, please feel free to point it out! Smile

Jerommel
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I’d get a couple new ones from FT.

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

2 pieces for 1½ bucks Smile

They’re 4 Ampère each

lagman
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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. Smile

My English isn’t perfect but I’m trying to improve it. If you see something that doesn’t sound right or is just plain wrong, please feel free to point it out! Smile

Jerommel
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argh..of course.. :Sp
sorry..

lagman
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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.

My English isn’t perfect but I’m trying to improve it. If you see something that doesn’t sound right or is just plain wrong, please feel free to point it out! Smile

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

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


Counterfeit 18650s, 2,<a href=“http://

lagman
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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”).

My English isn’t perfect but I’m trying to improve it. If you see something that doesn’t sound right or is just plain wrong, please feel free to point it out! Smile

Helios-
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Must be a protection ic with integrated mosfet.


Counterfeit 18650s, 2,<a href=“http://

18sixfifty
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Nice review! Thanks for sharing. I’m a big fan of Sanyo batteries.

I’m a junky, I mod lights so I can sell lights so I can buy more light to mod so I can sell lights to buy more lights to mod.

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

My English isn’t perfect but I’m trying to improve it. If you see something that doesn’t sound right or is just plain wrong, please feel free to point it out! Smile

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

If you can’t blind them with your brilliance, baffle them with your bullcrap.

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lagman
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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?

My English isn’t perfect but I’m trying to improve it. If you see something that doesn’t sound right or is just plain wrong, please feel free to point it out! Smile

lagman
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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…

My English isn’t perfect but I’m trying to improve it. If you see something that doesn’t sound right or is just plain wrong, please feel free to point it out! Smile