Cell interchangeability - cgr18650c vs us18650s

Hello everyone.

I would like to ask a small newbie question.
Recently I've acquired a minidisc player that works off a Sony LIP-12 battery.
The battery was dead, and using an AA unit would make the player too big, not to mention how much batteries it eats off for a music addict like me

So I cracked open the battery and found a SONY us18650s STG inside.
After some usual fiddling of getting it off, I used the salvaged zinc foil and some electrical tape to connect a new cell to the original controller.

However I am having a hard time understanding the batteries specs.

Replacement Panasonic datasheet - http://www.rosebatteries.com/pdfs/Panasonic CGR18650C.pdf
The only info I've been able to find about the original sony one - http://www.rcgroups.com/forums/showthread.php?t=69352

It appears to me it will be fine to listen to the player off that cell, but would it be OK to charge it inside the player?
And won't the fact that I use electrical tape to secure the foil to the cell affect anything?
Maybe anyone could suggest a better way of connecting the cells, assuming I don't have any battery welding equipment, and the space inside the player is very very limited?

Thanks in advance.
- Ak.R.

The Datasheet suggest this is simply a vintage ICR Lithium battery. Current ICR cells have significantly higher capacity (up to 3600mAh). Higher capacity simply means longer run time. I can think of no reason why you could not replace the existing cell with a much higher capacity 4.2 volt cell as long as it fits.

The charge characteristics shown are fairly typical of an Li-Ion cell. The only drawback I can see to charging replacement inside the player is the time it will take. That may be an issue if the charging circuit incorporates any sort of timer for overcharge protection. That's not common on Li-Ion charging circuits however.

18650 cells exist with terminals or wires on them, or can be easily made. As far as the choice of cells goes. Avoid any cell that ends with fire (Trustfire,Ultrafire etc). Stick with well known manufacturers, Sony, Panasonic, LG or Samsung 4.2 volt cells. The maximum available current from any of the current generation of ICR 18650's is far more than your device will ever need, so High current IMR cells would be overkill. For external charging, virtually any quality 4.2 volt charger rated for 1 amp charging or less should be fine. Single bay quality chargers are available from reputable manufacturers like Nitecore and Xtar at quite reasonable prices.

Probably be relatively pricey, but someone like BatteriesPlus may be able to make and sell you a LiIon 18650 with terminals. You might also ask Mountain Electronics if they can help (www.mtnelectronics.com). I doubt welding on a terminal is any more difficult than welding on a button top. They are also commercially available. see http://www.batteryjunction.com/tenergy-37-2200-pcb.html this is a protected cell, which you probably don't need (protection adds to the cost). Amazon also sells 18650's with solder tabs for less (no protection circuit).

Both seem to be early 18650s, similar to my 2004 Sony VAIO pack that had 8 2002 Sony 2000mAh cells inside and all work decently today.

I would think that unless something was amiss with the OEM pack/holder, you could just use any flattop cell?

Chris

Another point worth mention. If the device has a fuel gauge to predict remaining runtime then the gauge might not work too well if you replace it by a much higher capacity cell, or a cell with a very different shape discharge curve. You can find discharge curves for many modern cells on HKJ's site.

mattheww50 said:

18650 cells exist with terminals or wires on them, or can be easily made. As far as the choice of cells goes. Avoid any cell that ends with fire (Trustfire,Ultrafire etc). Stick with well known manufacturers, Sony, Panasonic, LG or Samsung 4.2 volt cells. The maximum available current from any of the current generation of ICR 18650's is far more than your device will ever need, so High current IMR cells would be overkill. For external charging, virtually any quality 4.2 volt charger rated for 1 amp charging or less should be fine. Single bay quality chargers are available from reputable manufacturers like Nitecore and Xtar at quite reasonable prices.

Click to expand...

Yeah, it seems that whatever cells end with -fire, also end up making one eventually, from what I've read so far.
So my method these days is just going around local websites and collecting people's old laptop packs, it turns out very cheap even if only one of the cells is working, and since I don't use any flashlights on 18650's just yet, I don't need the protection or high current capabilities.
However the original battery pack claims to be rated 3.6V on the outer case, does that mean my cell will always stay undercharged, or is it just an average standard value?

ChrisGarrett said:

Both seem to be early 18650s, similar to my 2004 Sony VAIO pack that had 8 2002 Sony 2000mAh cells inside and all work decently today. I would think that unless something was amiss with the OEM pack/holder, you could just use any flattop cell?

Click to expand...

You can have a look at some of the photos I posted at my blog here -> http://www.vladkorotnev.me/blog/lip-12-recell/
The Sony LIP-12 has a controller stuck to the side of the battery, and both terminals on the side as well, with a sliding protective cover.
I'm looking forward to going to a local electronic store this week and checking out what 18650 holders they have (they are exactly like AA holders, unprotected, just bigger size) and if it fits with the original controller (or can be made to fit), then I'd rather use one of those than electrical tape...

Gauss163 said:

Another point worth mention. If the device has a fuel gauge to predict remaining runtime then the gauge might not work too well if you replace it by a much higher capacity cell, or a cell with a very different shape discharge curve. You can find discharge curves for many modern cells on HKJ's site.

Click to expand...

Yep, it seems to have went a bit off. When I put the cell in, AFAIR, it was at about 3.2 V, and the player shows about 50% battery. I let it charge a bit (about an hour) and it showed a full battery after being unplugged for about a minute but then went back to 50% when I put in a disc. Then again, poor contact might be the case, which is why I'd rather get a holder soon.


Lucky enough that this is just a single-cell pack, no balancing or anything needed, yay~

The 3.6 volt figure is nominal. Unlike NiCd or NiMh cells, Li-Ion cells are not constant voltage during discharge. The typical range is 4.2 (there are some 4.35 volt cells out there) to about 3.0 volts, although there are some cells that are designed for discharge all the way down to 2.5 volts. If you are going to power a device with a Li-Ion cell, it needs to be capable of operation at any voltage from 4.2 volts down to something around 3.0 volts. The 3.6 or 3.7 volts (which is the typical 'label' on ICR cells these days) is kind of the average voltage during the discharge cycle.

akasaka said:

Yep, it [fuel gauge] seems to have went a bit off. When I put the cell in, AFAIR, it was at about 3.2 V, and the player shows about 50% battery. I let it charge a bit (about an hour) and it showed a full battery after being unplugged for about a minute but then went back to 50% when I put in a disc. Then again, poor contact might be the case, which is why I'd rather get a holder soon.

Click to expand...

Probably the best chance of avoiding confusing the fuel gauge is to swap the cells at the same low voltage, between 3.0-2.5V, so that the gauge will have a chance to learn the capacity on the next cycle (if it has that capability). Even that may not work well if the new cell has chemistry different enough to radically alter the shape of the discharge curve, since the gauge firmware may have been programmed with parameters that depend upon that shape.

Totally not sure, but replacing it to the same voltage would have been impossible since the original cell was at 0.86V when I cut it out.
Not sure if it can learn either. I'll just use a voltmeter periodically to check it.

mattheww50 said:

The 3.6 volt figure is nominal. Unlike NiCd or NiMh cells, Li-Ion cells are not constant voltage during discharge. The typical range is 4.2 (there are some 4.35 volt cells out there) to about 3.0 volts, although there are some cells that are designed for discharge all the way down to 2.5 volts. If you are going to power a device with a Li-Ion cell, it needs to be capable of operation at any voltage from 4.2 volts down to something around 3.0 volts. The 3.6 or 3.7 volts (which is the typical 'label' on ICR cells these days) is kind of the average voltage during the discharge cycle.

Click to expand...

I am no expert, but I've devoted a good bit of thought on how I would deploy my old 18650's as I fooled around with them the last couple of years.

I think mattheww50 made some important points above. From the sound of it, your battery is inside your music player - that implies a couple of things to me:
Likely, the battery is probably naked and the player itself has the battery protection circuitry.
Likely, the battery is recharged by circuitry in the player itself (like a typical cell phone).

So, the most important performance parameter for suitability (aside from safety, etc.) are charge voltage and cut-off voltage of the replacement battery. Capacity is important, but lower capacity cells wont be killed by the music player. Where as, wrong cut-off or wrong charge voltage may get the replacement cell killed in no time.

If I am facing this problem, I would use an adjustable power source and see at what point the music player cuts off the battery. The current going in should suddenly drop to zero as the voltage is being adjusted down slowly. If it is still drawing current at below 2.6V, you need to get batteries with protection circuit. If you seeing the sudden drop off, now you know the ceiling for the cut-off voltage as you shop for your replacement. If (for example) the music player doesn't cut out till 2.6V, and you get a battery that can discharge only till 2.8V, your replacement battery will be killed fairly quickly. However, if the music player cuts out at 2.8V and your battery can go down to 2.6V, life is good. Your battery has lower cut off than your music player's cut off.

Likewise, I would test at what voltage the music play stop "charging" and what is the charge current. This one is harder to test. I know the likely stop points are 3V (LiPO), 3.6 volt, 4.2V, and 4.35V. I give it a good resistive load (typically, my prefer loads are 12V incandescent auto lights of various wattage since I have a good collection of them in my garage) and my DMM as amp meter as well as volt meter. Now you know the charge voltage of the replacement battery you need. Ideal is of course they are the same. If not, you want to make sure your bettery has higher stop-voltage than the actual.

Now you have the 3 data points:
- The discharge cut-off voltage.
- The charge current (less important to know)
- The charge-full voltage.

As to the capacity, it depends on how much you want to spend.

As I said, I am no expert, but these three data points I would want to know before shopping for battery. Cut-off voltage and charge-stop voltage needs to be right.

Not only the player has a protection circuit (not sure about that tho), but also the original battery pack did. And I did not remove it.

It would be helpful if you posted some photos showing the internals of the Sony LIP-12, esp. showing any internal circuitry it possesses.