1S 1000mAh LiPo for £1.59

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SteveT

Senior Member
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srnet

Senior Member
Quote;

WARNING: Soldering Lipoly Cells takes a degree of skill and experience. Do not attempt to solder your own packs if you are not confident in your soldering abilities. No Warranty is implied or given once you have soldered the cell tabs. Please check cells for warranty purposes prior to soldering.
 
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g6ejd

Senior Member
Dangerous (literally) things. I charge mine in a LiPo charging bag since I had a unit burst into flames, akin to an incendary device - basically (as I did) most people panic because they go up in flames so quickly.

Used extensively in model aircraft. See films on youtube for the effect of one going wrong...
 
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srnet

Senior Member
boriz said:
They only 'burst into flames' when severely mistreated.
Click to expand...
True, any mistreatment that may cause a Lipo to explode is serious.

But its so easy to do.

Take the simple Lipo which is the subject of this post, its got no protection circuit, so severely mistreating it is as simple as leaving the PICAXE gizmo its powering on, letting the battery go flat, and then trying to re-use it.
 
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boriz

Senior Member
Allowing a LiPo to completely discharge is severe mistreatment. It will never recover and should be disposed of. Attempting to recharge it is a waste of time, aside from the possible dangers.

A smashed wineglass can kill you. Yet they seem common enough.

Used properly, Lithium batteries are as safe as wineglasses.
 
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Jeremy Harris

Senior Member
All the scaremongering about lithium cells makes me chuckle, especially when you look at all the hypocrisy about.

Pretty much every single household in the UK has many lithium cells of this size or bigger. Laptops, 'phones, portable appliances, you name it, they all have lithium cells. Pretty much all of them use the same cell chemistry (LiCoO2) as these HK cells. Most have greater capacity. Virtually none of these appliances have protection circuitry built-in to the cell or battery pack, they pretty much all rely on the appliance/charger looking after the cell. If you don't believe me, then take apart a laptop, 'phone, ipad or whatever battery and take a look. 9 times out of 10 you won't find anything smart inside the battery pack.

The risks are no worse than for any other high energy capacity battery. If you don't over-charge the cell (in this case take it over 4.2V cell terminal voltage), don't discharge any cell below about 2.5 to 3V, don't short the cell out and don't try to charge a cell that has discharged below the lower cut-off voltage then they are safe, in fact based on the evidence of many tens of millions of them in use around the world, they are very safe indeed, arguably safer than car batteries.

The fear and worry here is driven by fear of the unknown, rather than reality. If we were to invent lead acid batteries today they would be seen as terrifyingly dangerous things, I'm sure. Who in their right mind would entertain the idea of something that gives off an extremely explosive gas mixture when being charged, that can release large amounts of energy if shorted, and which relies on highly corrosive and poisonous materials like sulphuric acid and lead in order to work?
 
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srnet

Senior Member
Jeremy Harris said:
If you don't believe me, then take apart a laptop, 'phone, ipad or whatever battery and take a look. 9 times out of 10 you won't find anything smart inside the battery pack
Click to expand...
I cant recall not finding a protection circuit inside a Lithium Ion phone\camera battery.

Just took another two old ones apart, both had protection circuits inside them.

Luck of the draw I guess.
 
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manuka

Senior Member
Well said Jeremy! However see this "lithiums aloft" account & ponder...

But back at ground level -todays dirt cheap cell phones increasingly tempt just for their lithium battery & dedicated mains charger. Here in NZ the "Warehouse" chain sells the Nokia 100 new at NZ$19 (~£10). At that low price you can ignore the phone features & simply use it merely to smart charge the BL-5CB 3.7V 800 mAh battery.
 
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Jeremy Harris

Senior Member
srnet said:
I cant recall not finding a protection circuit inside a Lithium Ion phone\camera battery.

Just took another two old ones apart, both had protection circuits inside them.

Luck of the draw I guess.
Click to expand...
I've similarly just stripped an old Nokia pack (3.7V single cell) and it hasn't got a BMS inside, neither has the pack I pulled from my old Loox pocket PC, or the big pack from my old Benq laptop. Even the duff Makita drill pack I've pulled apart doesn't have a BMS, , just a service indicator board that counts the number of charge cycles (it stores data from the Makita charger) and has an "electronic" fuse that gets "blown" by the charger if three attempts are made to charge it when a cell has gone down. None of these packs had any active intervention to control charge or discharge current or voltage, they rely 100% on the appliance or charger doing that.
 
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srnet

Senior Member
Do you know of any modern, i.e. new Lithiums that do not have the protection circuit ?

I was looking at this for the satellite where we dont want the protection circuit as there may be a requirement to get a couple of amps out of the battery for a few seconds to melt a bit of fishing line for an antenna release mechanism.

All the camera Lithiums I currently have (and are small enough for the application) Canon 4BL, 6BL, Kodak Klic 7002 all have the protection circuit.
 
hippy

hippy

Ex-Staff (retired)
Jeremy Harris said:
None of these packs had any active intervention to control charge or discharge current or voltage, they rely 100% on the appliance or charger doing that.
Click to expand...
That has been my experience also.

I think the real fear of people using such batteries derives from that; that people will use them without taking the precautions they should, will treat them like traditional batteries when there are higher risks involved.

There is little problem with anyone using anything in a safe and proper manner. It is use in unsafe or an improper manner which presents problem, raises concerns and causes fears. It is not the people who understand what they are using and doing which anyone is trying to protect but those who don't.
 
J

Jeremy Harris

Senior Member
The pack I've just pulled apart is the common Nokia BL4C/5C. Nothing in it except a single cell and what might possibly be a thermal switch (hard to tell because it was embedded in the plastic top cap). No circuitry of any sort inside it.
 
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Jeremy Harris

Senior Member
hippy said:
That has been my experience also.

I think the real fear of people using such batteries derives from that; that people will use them without taking the precautions they should, will treat them like traditional batteries when there are higher risks involved.

There is little problem with anyone using anything in a safe and proper manner. It is use in unsafe or an improper manner which presents problem, raises concerns and causes fears. It is not the people who understand what they are using and doing which anyone is trying to protect but those who don't.
Click to expand...
I think you're spot on. There are many, many examples of lead acid battery explosions around, in fact I suspect most of us will have heard a tale or two about someone blowing one up, most often by pulling a lead off during a fast charge. I saw it happen once, when I was a teenager working part time on a garage forecourt. The garage was closing up for the day and one of the mechanics just grabbed the leads from a battery on charge and pulled them off. The battery exploded, embedding bits of plate and terminal 15ft up in the workshop roof. The guy was lucky that the blast went upwards and he was some distance away when he yanked the leads off.

We've become accustomed to those hazards, and now take them for granted, because we understand how to minimise the risk of them happening. Given a bit of time and familiarity we'll similarly get used to using lithium cells safely, I'm sure.
 
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srnet

Senior Member
Jeremy Harris said:
The pack I've just pulled apart is the common Nokia BL4C/5C. Nothing in it except a single cell and what might possibly be a thermal switch (hard to tell because it was embedded in the plastic top cap). No circuitry of any sort inside it.
Click to expand...
And embedded inside the top cap is ?
 
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Jeremy Harris

Senior Member
srnet said:
And embedded inside the top cap is ?
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Just what looks like a thermal switch, a tiny bimetallic disc type one AFAICS, mounted on what looks like a very tiny PCB that also carries the three gold plated connectors. There's certainly nothing there that could handle the sort of power dissipation needed for an over-charge protection circuit.

I've designed and built a few lithium BMS circuits and the big problem is that, however you choose to do it, the protection circuit ends up having to dissipate a fair bit of heat. The simple way to make a cell work with a dumb charger is to have a shunt that's triggered on at full charge voltage, but that then dissipates all the charge power, so runs warm. Another way is to turn the charge current off, using a series switching device, when the cell reaches full charge voltage, but that then dissipates heat during charge.

The best way seems to be to use a switched mode constant current/constant voltage circuit, but this then gets too big and expensive to incorporate in a small single cell.
 
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srnet

Senior Member
My BL5C has the tiny metal thing, 3 gold pads one the small PCB.

Plus 8 SMT resistors\capacitors, a diode and two black bob SMT components.

What are all the SMT components for ?
 

Attachments

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Jeremy Harris

Senior Member
Interesting that these are different. There aren't any components on mine (I tried to photograph it but it's too fuzzy), just what looks like a tiny bimetallic thermal switch.

There's no way that those tiny components on yours can actively manage cell safety, as IIRC the phone can charge one of these batteries in an hour or two, so the BMS circuit would have to handle at least 300 to 400mA, and either shunt around 1.2 to 1.6 W at full charge or dissipate the difference between the charger voltage (6V I think) and the cell voltage through the charge period (so around 0.7W to 0.9W). This seems highly improbable to me, given the small size and the fact that these components are embedded in solid plastic (assuming your battery is constructed like mine).

My best guess is that these components do something similar to the circuit in the Makita power tool packs. In that case the internal pack circuit just signals to the charger that the cell is OK, using an additional connection. This would explain why there are three connections on the Nokia pack, the + and - go directly to the cell (in my case via the N/C thermal switch) and the third connection may then be a signalling port, so the cell can send a "I'm healthy" signal back to the charger. I've looked closely at the Makita system and this just measures each individual cell voltage and if they are all within limits it sends a signal to the charger to tell it that it's safe to charge. If any cell is too low a voltage, then it allows the charger to have three attempts at charging, for just a few seconds at a time, and if the low cell doesn't promptly come up the internal circuit "blows" and internal "fuse" and renders the pack a brick, but refusing to send the "OK to charge" signal to the charger.

Circuits like this don't offer any inherent protection from short circuit or over-charge, the appliance relies on the charger and appliance circuitry to do that. They do simplify the charger a little, though, by moving the cell monitoring function to the cell terminals, where it's most effective.
 
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srnet

Senior Member
For a single cell battery, why would you need so many components for a 'cell good' indication ?

The battery voltage is available on the terminals and a temperature sense device need be no more than a single SOT component.

I have just tested a low voltage power down circuit for the satellite board, uses two SOT devices and a resistor. At low voltage the load is disconnected. I am loosing 3mV across the MOSFET switch at 100ma, so at 400ma, the SOT device a mere handles 1.2mW, I think it can cope.
 
J

Jeremy Harris

Senior Member
srnet said:
For a single cell battery, why would you need so many components for a 'cell good' indication ?

The battery voltage is available on the terminals and a temperature sense device need be no more than a single SOT component.

I have just tested a low voltage power down circuit for the satellite board, uses two SOT devices and a resistor. At low voltage the load is disconnected. I am loosing 3mV across the MOSFET switch at 100ma, so at 400ma, the SOT device a mere handles 1.2mW, I think it can cope.
Click to expand...
If the circuit is similar in function to the Makita one, then it not only checks cell voltage, but also records that data and uses it to signal to the charger that there may be a problem. The Makita pack circuit also records the number of charge cycles, and apparently this data can be read from a pack by a Makita service centre. The Makita charger can send a signal back to the battery that effectively bricks it, by setting some sort of non-resettable fuse that then means that the pack cannot signal to a charger, so cannot be charged with a genuine Makita charger. In practice, you can still charge a bricked Makita pack by using a non-Makita charger, one that doesn't rely on getting the "OK" signal from the pack. I've done this (very carefully) and have resurrected a bricked Makita pack, that seems to work fine. The big problem is that, despite all the cells in this pack seeming to be OK now, it still won't charge with the Makita charger. I'd dearly like to try and decode the signalling format and then try and find a way to reset this "fuse", but don't want to have to buy a new pack in order to do it!
 
J

Jeremy Harris

Senior Member
srnet said:
Here is a Lithium Ion Single Cell Protection circuit, same size as the one in the Nokia 5C but with even fewer tiny components !

http://www.ayaatech.com/shop/?type=detail&id=826

Protects (or at least alleges to) against over low volts, high volts, over current, copes with up to 7A discharge.
Click to expand...
The question that needs to be asked is, what degree of protection does it really offer?

Note that it has no balance current, so it does not work as an over-charge protection shunt. It seems to use a series switch to offer a degree of cell protection during charge, but realistically, how much heat can such a circuit get rid of? Is it reasonable to expect a tiny circuit like this to dissipate 0.5W or so when encapsulated inside solid plastic?

The dissipation problem is the really big issue with cell protection circuits, or battery management systems. I've looked long and hard at the problem (for high capacity battery packs) and designed and built a couple of shunt type BMS systems that work, but have come to the conclusion that it's safer, and easier, to just use a good CC/CV charge profile (with cell level voltage monitoring), combined with a low cell voltage over-discharge cut out or warning.
 
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srnet

Senior Member
Jeremy Harris said:
The question that needs to be asked is, what degree of protection does it really offer?
Click to expand...
Well, I would assume it offers the protection stated, low volts, high volts and overcurrent.

As an example of what similar devices can do, look at this data sheet;

http://www.sii-ic.com/en/product1.jsp?subcatID=5&productID=1794

"The S-8211C Series are protection ICs for single-cell lithium-ion / lithium-polymer rechargeable batteries and include high accuracy voltage detectors and delay circuits.
These ICs are suitable for protecting single-cell rechargeable lithium-ion / lithium-polymer battery packs from over charge, over discharge, and over current."

And all this in a 1.8mm square SMT blob.

Look at the application circuit on page 26. To the SMT blob, add a couple of MOSFETS, 2 resisters and a capacitor and your done.

Cant see how heat dissipation could be an issue, modern MOSFETS can have extremely low on resistances so only a couple of mW max with the battery on, and with the battery off, the MOSFET heat dissipation would be as good as zero.
 
J

Jeremy Harris

Senior Member
srnet said:
Well, I would assume it offers the protection stated, low volts, high volts and overcurrent.

As an example of what similar devices can do, look at this data sheet;

http://www.sii-ic.com/en/product1.jsp?subcatID=5&productID=1794

"The S-8211C Series are protection ICs for single-cell lithium-ion / lithium-polymer rechargeable batteries and include high accuracy voltage detectors and delay circuits.
These ICs are suitable for protecting single-cell rechargeable lithium-ion / lithium-polymer battery packs from over charge, over discharge, and over current."

And all this in a 1.8mm square SMT blob.

Look at the application circuit on page 26. To the SMT blob, add a couple of MOSFETS, 2 resisters and a capacitor and your done.

Cant see how heat dissipation could be an issue, modern MOSFETS can have extremely low on resistances so only a couple of mW max with the battery on, and with the battery off, the MOSFET heat dissipation would be as good as zero.
Click to expand...
OK, let's say that you have a standard Nokia 5.7V, 800mA charger (which is just a DC power supply) and that the charge time is 2 hours (pretty typical for most older 'phones), with a cell capacity of 800mAh (small by modern 'phone standards, this size cell is now up around 1100mAh or more). That means a charge current of 0.4A. If we assume a series protection circuit, then the pass FET is regulating the 5.7V down to between 3.7V and 4.2V depending on the state of charge of the cell. The pass FET dissipation is then going to vary between 0.8W and 0.6W, depending on state of charge (it could be more than 0.8W if the cell starts off lower than 3.7V).

Clearly you're not going to dissipate this sort of heat inside that small plastic moulding on top of the cell, so the way around it is to use an external charge regulator to control the charge current, which is, in practice, what these things usually do. In other words, the internal cell circuitry isn't really managing the cell, it is still reliant on external circuitry in the appliance or charger to do that. In the case of these small Nokia BL4C/5C series packs, the major part of the charge control is in the 'phone, rather than the charger, so that the 'phone can use the full charger power to operate whilst the cell is charging.

There's no getting away from the fact that somewhere you need to drop the voltage difference between the charger and the cell terminal voltage during charge.

What these protection circuits do is the easy part, they just disconnect the cell from the terminals if the cell voltage falls below the low voltage cut off during discharge, or above the high voltage cut off during charge. The appliance/charger still needs to do the critical CC/CV charge profile job.
 
S

srnet

Senior Member
Jeremy Harris said:
What these protection circuits do is the easy part, they just disconnect the cell from the terminals if the cell voltage falls below the low voltage cut off during discharge, or above the high voltage cut off during charge.
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Good we are agreed then.

Modern Lithium Ion batteries can and do have protection circuits in them and they use tiny SMT components.

Proper charge control is of course a separate issue.

But I am still looking for a phone\camera battery that does not have one of these protection circuits inside, ideas anyone ?
 
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Jeremy Harris

Senior Member
srnet said:
Good we are agreed then.

Modern Lithium Ion batteries can and do have protection circuits in them and they use tiny SMT components.

Proper charge control is of course a separate issue.

But I am still looking for a phone\camera battery that does not have one of these protection circuits inside, ideas anyone ?
Click to expand...
Yes and no. If you try and charge one of these cells outwith the appliance, then the protection circuit may very well not protect the cell. The key to it doing its job is that it relies on the appliance doing the donkey work by limiting the charge current and voltage. For example, if you tried to charge a cell at a higher current, this rather simple little voltage switch may not know you were doing that (it only measures cell voltage usually, rarely it may measure discharge only current), so may well then allow the cell to blow.

As I mentioned above, the genuine Nokia BL4C pack I took apart yesterday doesn't have an internal circuit, just a thermal switch. The Pocket Loox pack similarly doesn't have a protection circuit, neither does the Benq laptop pack, although both of these may well be too big for your needs.

I take it you're after a good brand name pack (for reliability) that fits to a holder, rather than is soldered in? If it only has this sort of crude voltage detector circuit and FET switch, does that cause a problem? At a guess, an ordinary 'phone battery must be able to deliver an amp or so peak, maybe more, as full Tx power for GSM is around 1W or so (so maybe 3W in to the Tx), plus the screen power of another W or so. Might be worth testing a decent 'phone pack to see when the over-discharge trip operates, as I would hazard a guess that it might well be above the 2A you need to operate the deployment mechanism.

The alternative might be to just use a single bare cell from a reputable manufacturer. The cheap HK cells mentioned here aren't great quality, they are more often than not "seconds" from a reputable production line. You may well be able to source a good cell brand like Kokam, though, that would do the job. Genuine Kokam cells are excellent, I have some bigger ones that are around 5 years old and which have held up remarkably well, even through all my initial experimenting with management systems.
 
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srnet

Senior Member
I have tested the over current trip in these protection circuits. I wasted a couple of batteries in the process. I would not be on the hunt for a Lithium battery without the protection circuit if it was not a problem. Besides without exact details of the particular protection circuit fitted to the Lithium cell, and its current trip limit, its not worth the risk.

The packaged cells are also lot easier to deal with (mount) than the bare cells. Packaged cells have those nice gold pads to solder wires to. If I really wanted a bare cell its not too difficult to disassemble one of the packaged ones. But then you have the bare tabs to deal with.

Besides, if protection circuits are fitted to so few Lithium batteries, it ought not to be difficult to find one without the circuit.
 
S

SteveT

Senior Member
All right, they may not be the best LiPo in the world but how about http://www.hobbyking.com/hobbyking/store/__11874__ZIPPY_138mAh_20C_Single_Cell_.html

Spec.
Capacity: 138mAh
Voltage: 1s / 3.7v
Discharge: 20C Constant / 30C Burst
Weight: 6.6g (including wire, plug & case)
Dimensions: 37x26x3.2mm
Discharge Plug: JST

or
http://www.hobbyking.com/hobbyking/store/__24920__Turnigy_nano_tech_260mAh_1S_35_70C_Lipo_Pack_QR_Ladybird_Genius_CP_Mini_CP_.html

Spec.
Capacity: 260mAh
Voltage: 1S1P / 1 Cell / 3.7V
Discharge: 35C Constant / 70C Burst
Weight: 8g (including wire, plug & case)
Dimensions: 32x20x7mm
Discharge Plug: Walkera two pin
 
J

Jeremy Harris

Senior Member
I've probably got around 100 HK packs, of various types, in use or lying around here. They sell under a couple of names, Turnigy and Zippy, and an acquaintance (who works for an EV company) passed on the tip about most of their cells being B grade from a big manufacturer, following a visit he made to see HK a year or so ago. The best A grade cells they sell are their "Nanotech" range, that are, apparently, very good quality and have earned a good reputation for reliability and performance. The others tend to be pretty variable; out of all the cells I've bought from them I now reckon on adding around 10% to every order to allow for duds (it's not worth the shipping cost, and HazMat fees, of returning dead packs, and they don't accept returns to the UK, as a rule, only to China).

High reliability is, presumably, going to be a pre-requisite for the satellite application, so the cell used presumably needs to be of known provenance (which is why I suggested getting a Kokam cell earlier). The failure modes I've seen in HK cells have been low terminal voltage on arrival, failed alumising on the packaging, leading to corrosion within the laminated cell enclosure, failed sealing around the end enclosure welds, leading to leaks and air/vapour ingress and obviously "puffed" cells where the electrolyte/carrier has boiled off internally at some point.

Personally I don't think I would risk either a Zippy or Turnigy brand cell in the satellite application, but, based on what I've heard from others (and the inside tip from the acquaintance who saw their production facility) the Nanotech cells might be an option. This fairly light and small 750mA Nanotech cell might be an option, and comes with a connector, so there is no requirement to solder to cell tabs: http://www.hobbyking.com/hobbyking/store/__20386__Turnigy_nano_tech_750mah_1S_35_70C_Lipo_Pack_Fits_Nine_Eagles_Solo_Pro_180_.html

I've not tested enough tiny consumer goods prismatic packs to say for sure which have internal FET switches and which don't. It's clear that any pack designed to deliver a fairly high current almost certainly won't use them, due to the problems already mentioned, but then very few tiny packs are designed to be able to deliver anything over around 0.5 to 1C, and it looks as if you are looking for 2C+. One very common "protection" technique used in consumer lithium cells is to design them to have a high internal resistance. This is the tactic used by Sanyo/Matsushita/Panasonic for their very high performance 18650 laptop cells. Because the cells are only required to deliver around 0.2 to 0.3C maximum in service, they've deliberately made the IR high (a pretty massive 0.085 ohms per cell, for a 3Ah nominal capacity). The internal resistance then acts as an effective current limit, by causing the cell terminal voltage to dip, reducing the discharge current, if a low resistance load is applied. This might present a problem with your high current deployment burn-through system, so may be another reason to not go for tiny consumer-goods cells.
 
S

SteveT

Senior Member
The second one I listed above IS a nanotech with a rating of 35C constant 70C burst (I wish they would change that term) all for £1.75. Not too expensive to have a look at.
 
J

Jeremy Harris

Senior Member
SteveT said:
The second one I listed above IS a nanotech with a rating of 35C constant 70C burst (I wish they would change that term) all for £1.75. Not too expensive to have a look at.
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Yes, I know, but its capacity seems too low for the application, I think. I get the feeling that srnet needs around 800mAh, based on the discussion about the small 'phone packs. I may have that wrong, and maybe the much smaller capacity one you linked to would be OK, but my assumption that a bigger capacity was required was the reason for my link to the 750mAh version.
 
S

srnet

Senior Member
Battery capacity is not a real issue, average current consumption is only 75mahr, and with a 50min dark/light cycle you only need to store 62mah. Obviously using a 62mah battery would be a poor choice, with 100% discharge every 100mins, it aint going to last long.

I have quite a variety of Lithium Polymers, most of these dont come with protection circuits although some of the smaller ones do.

There are space rated Lithium Polymers out there, I had a discussion with ClydeSpace about it and if there was one at the size needed (max dimensions 40x40mm) we would source from there. But no-one has built a satellite this small before (notionally a 50mm x 50mm cube) so its no surprise there are no space rated cells in this size, yet.

There is a small Lithium Ion button battery that an ESA study identified as suitable for space flight;

http://www.thebatterystore.com/powerdiscpd245037v200mahli-ionrechargeablecoincell.aspx

But max discharge current is only 400ma.
 
S

srnet

Senior Member
boriz said:
Used properly, Lithium batteries are as safe as wineglasses.
Click to expand...
Sure, but they need extra precautions that would not be needed for Alkalines or NiMh, batteries that would commonly be used in PICAXE circuits.

To quote from the WikiPedia page on Lithium Ion batteries;

Safety requirements

If overheated or overcharged, Li-ion batteries may suffer thermal runaway and cell rupture.[52] In extreme cases this can lead to combustion. Deep discharge may short-circuit the cell, in which case recharging would be unsafe.[citation needed] To reduce these risks, Lithium-ion battery packs contain fail-safe circuitry that shuts down the battery when its voltage is outside the safe range of 3–4.2 V per cell.[35][44] When stored for long periods the small current draw of the protection circuitry itself may drain the battery below its shut down voltage; normal chargers are then ineffective. Many types of lithium-ion cell cannot be charged safely below 0 °C.[53]
 
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