This is the last of the single 18650 cells sent to me for testing by Jim - ebay UK member big_f_d_d.
I have recently purchased some 16340 cells from him, and he sent me another couple of loose 16340s to test, but hopefully I'll be able to test all the 16340 cells one after another, so that we can start seeing some 'like for like' comparisons, whereas currently my testing schedule has been somewhat random, due to jumping cells I have been sent to test to the front of the queue.
This Sony cell is a bit of a departure for me - IMR cells aside - as it is obviously a bare laptop cell, or possibly for power tool use, and has not been converted in any way for use in lights. So no protection circuit, no button, no aftermarket wrapping, and the stock wrap does not extend to the bottom of the cell. It is common for cells that are intended for use in packs to have an entirely bare base in order to make welding/soldering the cells together easier to do.
Testing equipment
A quick re-cap of the equipment used for testing: -
I will be charging cells with an iCharger 106B+, and discharging and testing internal resistance with an iCharger 208B. Two chargers are used for speed and convenience – one cell can be charging while a second is being discharged (not relevant in this instance). I use the same charger for each step to ensure consistency in conditions between tests, so that results are comparable.
Voltage is measured with a Precision Gold WG 020 multi-meter, dimensions with a Precision Gold digital calliper, and weight with a Neva digital scale stated to be accurate to 1/100th of a gram.
The base of the cell is attached to the charger via a 12” 16AWG cable with a large, strong magnet soldered to it. The positive button is attached via a magnet (if it adheres well) or via a crocodile clip. The positive contact on this cell appeared to be aluminium, with the high strength magnet wanting to pull to the shoulder of the cell. A smaller, weaker magnet was attached to the contact, and then the strong magnet was attached over that. Internal Resistance did not appear to suffer as a result.
Results at a glance
Sony US18650GR 2550mAh unprotected
Provided for testing by Ebay UK member ‘big_f_d_d’
Big_f_d_d does not currently have this cell listed on his ebay page, so I cannot comment on pricing.
|
Cell 1 (1) |
Initial voltage on receipt |
3.79V |
Measured length |
65.01mm |
Measured width (max) |
18.30mm |
Weight |
46.42grams |
Internal resistance at initial voltage |
93mOhm |
Capacity from initial voltage down to 3.00V @ 0.5A |
1148mAh |
Internal resistance after storage charge |
99mOhm |
Capacity from 4.2V down to 3V @ 0.5A |
2421mAh |
Capacity from 4.2V down to 3V @ 1.0A |
2346mAh |
Capacity from 4.2V down to 3V @ 3.0A |
2345mAh |
Capacity from 4.2V down to 3V @ 5.0A |
2291mAh |
(1) This is a single cell provided to me for testing, rather than a purchase that I have made.
Construction
As has been stated, this is a bare cell intended for the construction of laptop or power tool battery packs. As such, there is no protection circuit, and no button. The positive contact is an aluminium plate, pretty much flush with the shoulder of the cell. It is about the same size as the positive contacts on an AW 2600, 2900 or 3100mAh cell.
There should be issues using this cell in a light with a raised or spring contact at the head, but with a flat contact or a light with physical reverse polarity protection, this may not be suitable.
The wrap is thin, and with a tape like consistency, but does not appear brittle. The cover does not wrap around the base, so you need to ensure that the inner diameter of your battery tube is anodised, or other wise lined to protect contact, and that the anodising isn't worn.
With no protection circuit, the negative contact of the cell is the case of the cell's canister, and as such is steel - there should be little concern about wear and tear.
Light compatibility
Light |
Characteristics |
Fits |
Functions |
Olight M20 |
Wide tube, spring at head, sprung plunger at tail cap |
Yes |
Yes |
SWM T20CS |
Short tube, dual springs |
Yes |
Yes |
Jet IIIM |
Wide tube, raised contact at head, tail spring |
Yes |
Yes |
Fenix TK15 |
Two-piece tube – narrow at head. Short tube, short spring at head. |
Yes |
Yes |
Fenix TK11 |
Narrow tube, tail spring only |
Yes |
Yes |
Eagletac G25C2 |
Wide tube, sprung plunger at head and tail (minimal travel at the head end), physical reverse polarity protection |
Yes |
Yes (2) |
Nitecore IFE2 |
Narrow tube, physical reverse Polarity protection |
Yes |
No (2) |
(2) Despite the cell's flat contact, and the Eagletac's physical reverse polarity protection, this cell did work in the G25C2, and allowed all modes to be accessed. However, the cell was not compatible with the Nitecore IFE2's physical reverse polarity protection.
Charger compatibility
Charger |
Fits |
Functions |
4Sevens single bay |
Yes |
Yes |
Trustfire TR-001 |
Yes |
Yes |
Ultrafire WF-139 |
Yes |
Yes |
Ultrafire WF-188 |
Yes |
Yes |
HXY-042V2000A |
Yes |
Yes |
XTAR WP2 II |
Yes |
Yes |
Pila IBC |
Yes |
Yes |
Jetbeam/Sysmax Intellicharge i4 |
Yes |
Yes |
Internal resistance
Cell |
Voltage |
Internal resistance |
Sony US18650GR |
3.79V (as received) |
93mOhm |
Sony US18650GR |
3.74V (storage charge) |
99mOhm |
FJD 2600mAh #1 |
3.72V (storage charge) |
143mOhm |
FJD 2600mAh #2 |
3.72V (storage charge) |
138mOhm |
Ridbatt 2600mAh #1 |
3.74V (storage charge) |
129mOhm |
Ridbatt 2600mAh #1 |
3.74V after initial capacity test (storage charge) |
135mOhm |
Ridbatt 2600mAh #1 |
3.74V after all testing complete (storage charge) |
117mOhm |
Xtar 2600mAh #1 |
3.85V (as received) |
139mOhm |
Xtar 2600mAh #2 |
3.79V (as received) |
136mOhm |
Keeppower 2600mAh #1 |
3.78V (as received) |
123mOhm |
Keeppower 2600mAh #2 |
3.78V (as received) |
119mOhm |
Hi-Max 2600mAh #1 |
3.79V (as received) |
153mOhm |
Hi-Max 2600mAh #2 |
3.80V (as received) |
163mOhm |
Conclusion
I like to see a cell for flashlight use to have a protection circuit, and the addition of a button assists with light and charger compatibility. On an entirely personal level, I have had encephalitis, leaving me with a poor memory, easily distracted, and I loose track of things at a drop of a hat, hence my reliance on protection circuits. That isn't to say that I wouldn't use this cell, but I would want to be using a light with a circuit board with a low voltage cut out, or at least some kind of low voltage warning. Having said that, this cell isn't being marketed for use in lights, so I can't really criticise it, but it is some thing to consider if you do decide to use bare cells in a light - do you trust yourself to keep track of how long the light has been on? Will the light grow obviously dim before the battery has overdischarged? Will the light cut off or warn you of low voltage.
I'm also not keen on the wrap not extending the full length of the cell, and hence representing a potential shorting risk, but again, that's just a consequence of using a laptop cell in a light. This could easily be resolved by the purchaser, by adding a second layer of wrapping.
Beyond that, you have my normal bug-bear - at 0.2C, the cell's capacity was a fair deal lower than stated, and in this instance, there is no protection circuit to blame for having used some of the power, or increased internal resistance.
Having mentioned internal resistance, this remains in two figures, but as mentioned above, this is most likely just due to the lack of a protection circuit.
Despite the somewhat reduced capacity - quite possibly indicating that this is not A grade stock, and hence why it is not in a laptop pack as we speak - this cell appears to perform well. The relatively low internal resistance is allowing it to maintain capacity well as discharge rate increases, with almost 2300mah of the original 2421mAh remaining at a 5A discharge rate. If you have a suitable light for this cell, with low voltage warning or cutout, and no ano wear in the battery tube, then this should perform well for you.