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Forum Index : Microcontroller and PC projects : LiPo's for projects like the Game*Mite
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thwill Guru  Joined: 16/09/2019 Location: United KingdomPosts: 4042 |
Hi folks, I note a couple of Game*Mites have been constructed either with recycled vape LiPo's or old mobile phone batteries ... is this safe ? Up until now I've been using eBay LiPo's like these https://www.ebay.co.uk/itm/354254105023? with what I understand is some safety circuitry in the little PCB that is packaged on top of them, possibly duplicating some of what is already included on the TP4056 charger modules I use: https://www.switchelectronics.co.uk/products/micro-usb-5v-1a-tp4056-li-battery-power-charger-module-with-protection?variant=45334951657781. Can I just buy a ubiquitous (and cheaper) Nokia BL-5C, solder wires to its +/- terminals (ignore T) and charge it via a TP4056 ? Best wishes, Tom Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 9122 |
The "T" pin is connected to an internal circuit that allows the phone to know the capacity of the battery (resistive divider). The battery has full charge/discharge protection so, in theory you could do away with the tp4056 module if using one of these but duplicating it should be no issue |
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bigmik Guru Joined: 20/06/2011 Location: AustraliaPosts: 2914 |
G’day Tom, All, I have a small collection of salvaged Lipo’s I have collected from my daughter’s friends who otherwise just discard their vapes (electronic cigarette replacements). There are a myriad of batteries available in them. From the 15 or so I have personally collected they range in capacities of 280mAh to 1400mAh. As to safety? Well they look identical to the other ‘generic’ ones you see on Fleabay, Aliexpress etc. Note that NONE of the batteries I have collected have protection circuits so I would always use one in conjunction with a protection module, like the TP4056. I have only put a few into service but I think common sense should prevail when repurposing these lipo batteries. Solder very carefully to them and insulate the solder joins with that yellow ‘kapton’ tape, then heat shrink over the battery and leads to prevent them from being pulled loose. If we didn’t put these salvaged batteries to use they will just litter the streets and be added to the already growing landfill piles. One wonders how many discarded batteries are sitting there just waiting to be told “Unleash thy power” and create fires and explosions. Previous to my daughter collecting these for me, I have seen them littering the streets as people just throw them on the ground and not even dispose in a garbage bin (not that that is safe anyway). Re. The Nokia BL-5C batteries, when we were designing the Game*Mite, I found much to my surprise that it wasn’t as easy to source Lipos as it used to be so went looking at the BL-5C batteries but these are not as common locally or quite expensive to buy. Many sellers are either not even shipping to Australia or are charging many times the price of the batteries for shipping so obtaining these lipos is either costly or difficult. I am NOT advocating that people should salvage these batteries but if they do, PLEASE TAKE CARE AS THESE CAN BE VERY VOLITILE, shouting intended. Kind Regards Mick (the big one) *** EDIT That small clone hand held game unit we bought to investigate whether we could use the case or not uses a BL-5C battery and they only connect to the outer pins, I think the original Nokia battery would have had in built protection but as to whether the clones do or not is debatable, you should have no issues using a TP4056 with them any way. I haven’t researched but I always thought the extra tab on them (T) was a thermistor. And went low or high if the temperature got too high but i could be wrong there. Mick Edited 2023-10-22 10:35 by bigmik Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6798 |
Something to watch is that the TP4056 modules come, by default, with a maximum charging current of 1A. That implies that the minimum capacity of any battery that you use should be 1Ah (unless it is rated for 1A charging). This is why I paralleled two 550mAh batteries, it wasn't just to get longer running time. You can change a resistor on the TP4056 to change the charging current, but it's SMD and hence fiddly to do so. As Mick (the big one) says, the vape cells are not protected, however suitable charge and discharge protection is on the TP4056 module. Running two or three unprotected cells in parallel should be fine providing that the maximum current drawn doesn't exceed the maximum allowable for a single cell. This is because you can't guarantee that all cells will remain operational. The cells have to have identical capacity and should be voltage balanced before connecting them in parallel (to avoid large surge currents). For the first few charges keep a very close eye on the cell temperatures. If any start to run appreciably warmer than the other(s) it could be a problem cell. Never charge this setup unattended. Parallel connection has the advantage that the cells will self-level their terminal voltages so weak cells will generally simply fail to add current to the available output. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| bigmik Guru Joined: 20/06/2011 Location: AustraliaPosts: 2914 |
Hi Mick, That is an interesting point I will check out the TP4056 modules tomorrow. Mick Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6798 |
It's one of those cases where a through-hole resistor is superior to SMD. It would make it far easier to program the charging current. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| bigmik Guru Joined: 20/06/2011 Location: AustraliaPosts: 2914 |
Mick, All, I have had a look and I agree they are set for 1A charge (which is way too much for the one I just made with a 280mAh Lipo) The good news it is the easiest resistor to change. In this image it is R3 on the bottom row of the board.  To change the charge rate, remove this resistor (not difficult, heat both sides with a hot soldering iron then hold one side and it will move away easilly enough) and replace with the correct value (if you are OK with SMD work). If you are not confident with SMD work a small 1/4W resistor can be soldered from the left hand side pad of where R3 was removed from to any GND point, I suggest the large - pad at the very left hand bottom corner of the above image. Use this table to select the desired charge rate, which if isn’t known is generally half the rated capacity of the battery, ie 1000mAh battery should be set to charge @ 500mA.  It looks like it should be a fairly straightforward rework. Regards, Mick (the big one) . Edited 2023-10-22 20:59 by bigmik Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 9122 |
Interesting, I'll put a 1.2k resistor in series with a 10k trimmer on my design and possibly a shorting link which can be open for non-rechargables |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 4042 |
So if you are charging a 1000mAh battery @ 1 mA (1.2k resistor) are you in the "hmm, you'll get away with that but your battery won't thank you" region or the "running around the house with your hair on fire" region ? Do you need to use these discrete values or can I pick from standard sizes and use a 2.7k resistor for this size of battery. And am I correct in thinking it looks like an 0805 ? Best wishes, Tom Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 9122 |
Charging at 1C is normally considered safe (1mA/maH) although sealed consumer items (phones) normally charge much slower than that. At 1C you definitely shouldn't charge unattended. |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6798 |
A lot of "trickle" chargers run at C/10, so 100mA for a 1Ah battery. At that rate a flat battery reaches charge in 10 hours. That's fine if the battery isn't flat but is a bit long for some people. C/5 is also fine and will only take 5 hours. Some of the larger cells (typically for drones etc.) are rated for c*1.5 or even C*2. They warm up quite a bit during charge and have a shorter life - and charging must *always* be supervised. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Bleep Guru Joined: 09/01/2022 Location: United KingdomPosts: 509 |
You do need to keep in mind that the 1A charge is a maximum, it will taper down as the battery voltage increases, the battery charger should never allow a cell voltage higher than about 4.2V in a lot of cases the USB probably won't be able to supply 1A anyway, especially if connected to a computer, so personally I'm not going to get too worried about it. Regards Kevin. |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6798 |
A LiPo charger is a constant current unit. The initial current is the maximum preset by the charger and it falls during charge, quickly at first then more slowly. The terminal voltage stays virtually constant at 4V2 throughout charging. End of charge is detected by the charge current suddenly falling from a low point to about zero. The charger then cuts off and the terminal voltage slowly starts to fall. At some point this fall is usually used to retrigger the charging process, but the current will be very low and will eventually cut the charger off again. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 4042 |
I'm trying to figure out what would be a sensible value to fit on the modules I include in any future kits (TBH 1.2k doesn't sound like a particularly good choice full-stop). We recommend a 1000 mAh battery but have no control over what a user might actually fit (or guarantee they will read any corresponding advice in the manual), so 2.7k? 3.3k? 4.7k? Best wishes, Tom Edited 2023-10-23 06:59 by thwill Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| bigmik Guru Joined: 20/06/2011 Location: AustraliaPosts: 2914 |
Hi Tom, All, I did a little research on Google and it is a bit confusing to say the least. Most sites state that the recommended safe charge rate is 1C, however these sites all seem to pertain to hobby cells for cars and helicopters etc. I have struggled to find information for the ‘loose’ single cell flat pack style we are using so does this 1C charge rate still apply to these? I did read somewhere else that it best to charge a Lipo @ 0.5C to 1C. By far the most prominent advice seems to state 1C charge rate, ie. 1000mA for a 100mAh cell. You recommend a 1000mAh battery, I would suggest to leave the TP4056 as it is. If you want to set to a ‘safer’ charge rate of 0.5C or 500mA, from the table above (taken from the TP4056 datasheet) this would be achieved by using a 2k2 resistor (yes it appears to be a 0805 size). In my first build (now in AndrewG’s hands) I used a 1400mAh battery, I am happy at the default of 1000mAh. However, on the unit I just built, I used a paltry 280mAh and I WILL be fitting a different resistor for it (probably a 4k7 ohm). BTW I tested the run time on my unit with the 280mAh battery fully charged and the unit ran for 1hr59m sitting at the menu screen with a 3.2” TFT screen, I did start with playing Vivaldi at max volume but it stops playing after a couple of minutes and I wasn’t going to constantly keep re starting the music demo so I let it sit. I didn’t specifically measure the charge time but is was very quick at about 15m from ‘dead’. It is too fast for this battery. From your 1000mAh battery you should get 6-7hrs of play from a charge. Regards, Mick Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2135 |
I think there is a typo in that. The definition of 1C is the current required for 100% of charge capacity in 1 hour. So for a 100mAH cell 1000mA is 10C and would lead to a short life. For a 280mAh cell a 0.5C rate = 140mA for near full capacity in 2 hours. So far no one seems to have measured the actual battery current while charging. I haven't used this chip but in the past I have found actual charge rates can differ significantly from the datasheet. That seems best to me. On PCBs using the module the trimer and resistor could be on the PCB with a wire link to the resistor pad on the module - after removing its resistor. Edited 2023-10-23 10:21 by phil99 |
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| bigmik Guru Joined: 20/06/2011 Location: AustraliaPosts: 2914 |
Hi Phill, All, YES, there is a typo, I meant 1000mA for a 1000mAh cell (the type Specified for the Game*Mite). Regards, Mick Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6798 |
The actual charge current varies with time so measuring it is only useful if you are plotting a graph. :) I know I said the charger is constant current, but it is actually CC/CV, meaning that at the beginning it is constant current but it changes to constant voltage later. I think this shows the general idea. 1C is normally considered to be the maximum charging current. Most batteries will handle this without a problem. Most aim for 0.5C - 1C, it's not that critical and C is pretty vague anyway. It also changes with age. Reducing the charge rate down to as low as 0.1C is fine but below that you gain nothing - it just takes longer. Modern cells aren't like lead acid, where you store them on a trickle charge. We actually shut the charger off now. Lithium cells get a bad press. Most of the problems are caused by either poor, badly designed chargers or mechanically damaged batteries. The first case can lead to severe overcharging and consequent overheating, the second to shorts between the layers of cells - the DC equivalent of shorted turns on a transformer. Lots of current in a small space. It's also not helped that manufacturers will insist on jamming their batteries into the smallest possible space, not allowing enough cooling for the charging process. Couple that with fast chargers and you may have problems. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| robert.rozee Guru Joined: 31/12/2012 Location: New ZealandPosts: 2350 |
my advice regarding Li-Ion cells: 1. be cautious of (18650 cylinderical) cells coming from dubious sources - mostly through the mail from china. these cells may well be recycled from used battery packs, with protection circuits added, new endcaps, and heat-shrink outer covering. while they may be fine and perfectly safe, they may equally not be. 2. cells chemistry may be designed for 4.0v, 4.1v, 4.2v, or occasion 4.35v maximum charging voltage. this is not always easy to distinguish if the cell has been recycled and repackaged. or they may be LiFePO4 chemistry (what is colloquially called "lithium ferrous"), in which case their maximum charging voltage is around 3.6v. 3. you can substantially extend the service life by reducing the charging voltage applied. for instance, using 4.0v with a cell designed for 4.2v. this generally only has a minor impact on usable capacity. 4. you can gain a moderate safety advantage by reducing the maximum charging current. for instance, instead of 1C, reduce it down to 0.2C. HOWEVER, if you do this you still want to keep the charge termination current pretty much the same. 5. avoid over-discharging cells, as while not necessarily dangerous, doing so risks substantially reducing the lifespan of said cells. 3.0v per cell is a safe minimum voltage for a Li-Ion cell. LiFePO4 can tolerate a tad lower at 2.5v. upping the minimum cutoff voltage can help extend the service life of a cell, while only moderately impacting usable capacity. and advice for the TP4056: while it is a pretty neat device that removes a number of uncertainties (read - potential mistakes) from charger design, there are a couple of major limitations to the device that must be kept in mind... (a) you can not adjust the charging voltage limit. it is fixed at 4.2v. hence it is unsuitable for cells that are designed for 4.0v or 4.1v, and must NEVER be used with a LiFePO4 (3.6v) cell. even charging a 4.1v cell with a 4.2v charger may lead to an undesirable outcome. (b) the charge termination current is fixed at 1/10th of the maximum charging current. so if you reduce the maximum charging current too much then there is the risk that charging may never terminate. this may lead to an undesirable outcome. (c) if you are drawing power from your cell at the same time as you are charging it you risk effectively 'float charging' the cell indefinitely. needless to say, this may lead to an undesirable outcome. one very good approach, in my opinion, is to use Li-Ion 18650 cells with an external charger such as the Nightcore D4. keep an eye on the cells for the first few times you charge them, and if you find one or more get excessively warm then DISCARD the offending cell(s). another approach is to construct a 'conservative' charger that has a reduced maximum charging voltage and moderate (0.2C) maximum charging current. include a timeout on charging, and if possible add a lockout mechanism to prevent charging while current is being drawn from the cell. such a lockout may be as simple as a 3-position on-off-charge switch. and btw - i have read that lithium-based rechargeable cells can form dendrites. alas, these can lead to undesirable outcomes, even in cells that are just sitting disconnected :-( cheers, rob :-) Edited 2023-10-23 22:02 by robert.rozee |
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| lizby Guru Joined: 17/05/2016 Location: United StatesPosts: 3150 |
What is the "undesirable outcome" which may occur from this (sorry to go OT, but my particular interest today (since I considered it in bed during a wakeful night) is about using a 100Ahr 12V LiFePO battery with attached charger to power an inverter and thence a well water pump, thus avoiding a transfer switch if mains power drops out). ~ Edited 2023-10-23 23:05 by lizby PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed |
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