Blame the Battery ....

[Battery Guy]

Also, in my quick investigation it appeared that the majority of actual cell manufacturers do not produce cells smaller than 18650.

Most of the lithium-ion cell manufacturers in China are going after the commodity markets (i.e. standard cylindrical and prismatic cell sizes) or the specialty LIP (pouch cell) markets. It wouldn't surprise me if there were only a handful making the "odd" cylindrical cell sizes because the market for those cells is very small compared to the other cell sizes.

Interestingly, I keep hearing rumors that several of the Japanese battery companies will be getting out of the standard 18650 commodity cell business because they are having a hard time competing on cost.

It is a very interesting time to be in the battery business.

Cheers,
BG

 

[Mr Happy]

As a matter of interest, I caught a segment on "How It's Made" on the Science Channel concerning the manufacture of lithium ion cells. The example used was a US manufacturer where the lithium was mined, transported, processed and made into cylindrical cells here (there) in the USA.

I didn't catch the name of the manufacturer, but it would be interesting to know who it was and if those cells are available in small quantities anywhere (the normal application was automotive, I think).

 

[qwertyydude]

It's possible the American battery on How it's Made was A123 Systems. Great technology and the safest as they won't explode but very limited in power density, only about 1100 mah on an 18650. Great cell to use if you need high current discharge as 18650 A123 cells can manage over 30 amps continuous discharge, and 4C recharge rate.

 

[Battery Guy]

It's possible the American battery on How it's Made was A123 Systems. Great technology and the safest as they won't explode but very limited in power density, only about 1100 mah on an 18650. Great cell to use if you need high current discharge as 18650 A123 cells can manage over 30 amps continuous discharge, and 4C recharge rate.

A123 18650 and 26650 cells are made in Asia.

The Sanyo UR18650W significantly outperforms the A123 18650, both in terms of power capability and total capacity/energy. See a comparison here.

Cheers,
BG

 

[forexer]

If the PCB is tripped does it render the cell useless forever? Or does the PCB reset itself after awhile under right conditions. Does the PCB trip when due to over charging / over discharging or doe sit also trip when the cell's temperature gets too high.

 

[old4570]

If the PCB is tripped does it render the cell useless forever? Or does the PCB reset itself after awhile under right conditions. Does the PCB trip when due to over charging / over discharging or doe sit also trip when the cell's temperature gets too high.

If the Protection Circuit is tripped :
Get another cell , and connect the two in parallel , Positive to positive , and neg to negative , for about 1 second .. It might take a few tries , but hopefully it will re-set the protection circuit .
Unless the protection circuit has been damaged some how .

 

[forexer]

If the Protection Circuit is tripped :
Get another cell , and connect the two in parallel , Positive to positive , and neg to negative , for about 1 second .. It might take a few tries , but hopefully it will re-set the protection circuit .
Unless the protection circuit has been damaged some how .

What are the most common parameters for the PCB to be tripped? And what does connecting the cells in parallel do to restore the circuit?

 

[old4570]

What are the most common parameters for the PCB to be tripped? And what does connecting the cells in parallel do to restore the circuit?

Ok its usually over discharge ...

Connecting the cells feeds power to the protection circuit , and usually the battery voltage has increased [ bounced back with no load ] so the circuit remains open and the battery can be charged ..

Less common , would be overcharging , a short , to much current , some have thermal protection , so to much heat .

Over discharge is the main one ...

 

[forexer]

Ok its usually over discharge ...

Connecting the cells feeds power to the protection circuit , and usually the battery voltage has increased [ bounced back with no load ] so the circuit remains open and the battery can be charged ..

Less common , would be overcharging , a short , to much current , some have thermal protection , so to much heat .

Over discharge is the main one ...

You've been very helpful to a newbie like me:thumbsup: Last question: What's the optimal voltage a average cell should be discharged to. Would you say no lower than 3V? I'm guessing the PCB kicks in at around 2.5ish volts?

 

[old4570]

3v max ! , some are rated lower , but there is very little power left in the cell bellow 3v , and there is the possibility of doing damage to the cell .

The protection circuit ? Some kick in around 2.75ish , dont quote me on that . and a few actually kick in just bellow 3v , 2.5v is a little low ...

Many here try to avoid going under 3.5v , as decent performance seems to drop of around this point , and doing so long term [ going under 3.5v ] may accelerate the degradation of the cell structure of the battery ...

 

[LuxLuthor]

If you look at battery discharge curves, when the cells are empty, their voltage drops quickly and like a rock under load. As such, they spike down so quickly to reach the low voltage protection trigger, whether it be 2.5 or 2.8V and then rebounds back up to a safe 3.1+V that it does not damage the cell to any degree.

The problem comes when people use very low current applications that drifts down much slower towards the trigger low voltage protection so it spends more time below 3.0 V, or the person who repeatedly keeps using a battery that is empty before recharging. Some PCB's have their own reset voltage, so it it hits 2.5V and breaks the circuit, when the battery rebounds back up to 2.9V, it resets the protection break without having to do any external parallel connection or recharging.

 

[Norm]

, some have thermal protection , so to much heat

Which batteries have this feature? This is something that I wasn't aware of.
Norm

 

[Battery Guy]

Which batteries have this feature? This is something that I wasn't aware of.
Norm

Most 18650 lithium-ion cells have a Positive Thermal Coefficient (PTC) device built into the crimp assemble. If the cell get's too hot, or too much current is drawn from the cell, the resistance of the PTC increases and limits the amount of current that can be drawn from the cell. The PTC is reversible, so when the temperature decreases, the PTC "resets" and the cell is back to normal.

The PTC is typically thought of as a safety feature to prevent thermal runaway caused by an external short circuit.

It is worth noting that some high power 18650 cells, such as those in many power tools, do not have a PTC because it restricts current flow too much.

The PTC should not be confused with the Current Interrupt Device (CID), which is also incorporated into the crimp assembly. The CID is activated when the internal pressure of the cell gets too high. When the CID is activated, a metal contact within the vent assembly is torn, opening the circuit so that no current can pass. Usually, CID activation occurs concurrently with vent activation. The CID and vent are not reversible in a lithium-ion cell, so the cell is effectively dead forever when this occurs.

Hope this helps.

Cheers,
BG

 

[LuxLuthor]

Most 18650 lithium-ion cells have a Positive Thermal Coefficient (PTC) device built into the crimp assemble. If the cell get's too hot, or too much current is drawn from the cell, the resistance of the PTC increases and limits the amount of current that can be drawn from the cell. The PTC is reversible, so when the temperature decreases, the PTC "resets" and the cell is back to normal.

The PTC is typically thought of as a safety feature to prevent thermal runaway caused by an external short circuit.

It is worth noting that some high power 18650 cells, such as those in many power tools, do not have a PTC because it restricts current flow too much.

The PTC should not be confused with the Current Interrupt Device (CID), which is also incorporated into the crimp assembly. The CID is activated when the internal pressure of the cell gets too high. When the CID is activated, a metal contact within the vent assembly is torn, opening the circuit so that no current can pass. Usually, CID activation occurs concurrently with vent activation. The CID and vent are not reversible in a lithium-ion cell, so the cell is effectively dead forever when this occurs.

Hope this helps.

Cheers,
BG

Is that the part that runs the highest risk of being damaged when people solder various cells (I'm mainly talking NiMH, but there is also a "crew of CPF members" that believe they can safely solder even to Lithium Cobalt)?

 

[Battery Guy]

Is that the part that runs the highest risk of being damaged when people solder various cells (I'm mainly talking NiMH, but there is also a "crew of CPF members" that believe they can safely solder even to Lithium Cobalt)?

While both the PTC and the CID are located within the crimp assembly, they are in different locations with respect to the current path. The PTC is connected to the negative electrode, and therefore the can. The CID is connected to the positive electrode lead, and therefore the "button". So it would be very hard to damage the PTC by soldering to either end of the battery. The CID is typically made of aluminum, and should not be damaged by soldering, at least not directly. If the process of soldering causes an internal short circuit, the pressure in the cell could rise and the CID would activate, permanently disabling the cell. So if you know people that this has happened to, tell them that they were damn lucky the cell didn't explode in their face.

My biggest concern about soldering to lithium-ion cells is the possibility that local heating might melt part of the separator or the thin insulation material that covers the leads to prevent shorting inside the cell.

Cheers,
BG

 

[VidPro]

Beep
Li-Ion Batteries for $500 Alex
The PCT resistance materials
What is, Not connected to the can

or should we say not always connected?
http://www.molalla.net/members/leeper/liion1.png
it would be sorta difficult for some of the cylindrical li-ions i have seen apart to have the PCT connected to the can, when the plates are right there down the sides, and the bottom on a good cell is gapped , so i can solder to them without messing up the internals
its not rocket science, look how easy they are to dent on the bottom of the actual cell , for example.

mabey it is in some? but that statement just didnt make enough sence to me.

and LUX since when can you spot Weld without ANY heat, or do the metals just melt together via electronmigration You should Not solder to li-ion cells, unless you can do it as fast as a spot welder

 

[LuxLuthor]

and LUX since when can you spot Weld without ANY heat, or do the metals just melt together via electronmigration You should Not solder to li-ion cells, unless you can do it as fast as a spot welder

Yeah, I use magic fusion.

All factory battery packs are spot welded, and the flash weld is so quick, I can immediately touch my finger on top of the weld spot, and perceive no heat. It's like magic.

 

[VidPro]

Yeah, I use magic fusion.

All factory battery packs are spot welded, and the flash weld is so quick, I can immediately touch my finger on top of the weld spot, and perceive no heat. It's like magic.

i solder so hot and so fast, that only a little smoke comes off my fingers when i touch the top of the solder spot , and most of that is just steam :laughing:

i am now up to about 400+ solderings of li-ion without a single lost Ma. and most of the stuff i wouldnt use a spot welder even for because i use lots of copper, and it is redundant to put tabs on, as opposed to direct. I would not use spot welding for raw wires, that doesnt wrap the wire in conduction, and i hate crimps. I cant see doing different for the parts and pieces i use. even if i toss on protection, i dont have manufactured metal strips of the exact lenght and all. its not manufactured.

 

[Battery Guy]

or should we say not always connected?
http://www.molalla.net/members/leeper/liion1.png
it would be sorta difficult for some of the cylindrical li-ions i have seen apart to have the PCT connected to the can,

Oops, my bad. You are correct that the PTC and the CID are both on the positive terminal. Sorry about that.

when the plates are right there down the sides, and the bottom on a good cell is gapped , so i can solder to them without messing up the internals

The bottom of most cylindrical lithium-ion cells has a plastic spacer, perhaps what you are referring to as being "gapped". However, I have seen many cell manufacturers, usually cheap ones. that stick the jelly-roll right into the can without any kind of spacer or protection other than the extra separator hanging off the edges of the electrodes.

its not rocket science, look how easy they are to dent on the bottom of the actual cell , for example.

Not rocket science, but you need to know what you are doing and have decent equipment. My fear is that people will attempt this with cheap soldering irons, insufficient experience and inadequate respect for the potential safety implications.

I put soldering to lithium-ion batteries in the same category as mixing battery types. There is nothing magic about, and if you really pay attention and know what you are doing, you can do it safely. However, it is best to keep it to yourself

Be safe VidPro, and please where some kind of eye protection when you are soldering to any kind of battery.

Cheers,
BG

 

[CKOD]

Yeah, I use magic fusion.

All factory battery packs are spot welded, and the flash weld is so quick, I can immediately touch my finger on top of the weld spot, and perceive no heat. It's like magic.

It's definitely nice how there is pracitcally no heat going into the battery top. Put together 2 18650 packs for 2 flashlights I'm assembling and it came out nicer then wiring and solder even with my 80w iron here would have.

Though some of those heavy copper bus bars that RC guys use in their packs look nice and I would consider soldering with paste (or maybe just strips of really fine solder if paste isnt handy) if I needed the low resistance that such a bar would provide.

Anyone here that assembles pack for their own use put protection PCBs on the pack?