I have dozens of old cell phone batteries that I would like to try to repurpose. I googled the answer but didn’t find anything consistent.
You can buy lithium polymer batteries for DIY purposes from places like SparkFun that come with a PCB protection circuit attached to the battery.
Do these types of cell phone batteries contain circuitry similar to the one on the green PCB, or is it the circuitry inside the phone?
If so, is the best way to just use a charge management IC like the MCP73831 for charging? If not, how can these cells be practically utilized? The Apple mobile phone battery also has three or four pins, two of which are obviously power + and -, and the other two are status indicators? What exactly are these other two pins used for? What is the best way to handle these batteries when using them in a hobbyist DIY environment?
EDIT Also, I only want to use the battery for low current purposes (a few hundred milliamps max) and most of them are from unused phones.
These batteries do have built-in protection, but not the kind you see on Sparkfun batteries. They have thermal protection required for battery charging and sometimes a low-battery cutoff to prevent over-discharging of the battery. However, there is no overcurrent protection , overvoltage protection, or protection against novice abuse…
You have two pins for + and – (simple) and a temperature pin to detect if the temperature rise is at normal levels. This ensures that the battery will not explode while charging. In practice, you read this as a variable resistor.
This feature isn’t used very often as they usually try to maximize battery capacity, especially with modern smartphones, but it’s not uncommon for older, not-so-smart flip phones like mine 🙂
Obviously, charging a lithium polymer battery is a risky thing to do without the correct settings. Disclaimer: I do not recommend charging your battery without an approved charger.
Having said that, one can charge it using any LiPo-compatible charger. Cell phone batteries usually only have one cell, so charging them is very easy. It should check the battery voltage and divide it by 3.5 to 4. This will indicate the number of cells connected in series. Then use an unbalanced charger to charge the battery to the appropriate level. If charging for the first time, assume you need to use a multimeter to check whether the battery is getting hot via a remote circuit., additionally one may want to do this outdoors where a fire or explosion in the battery won’t harm anyone around it.
Seriously, just throw them in the recycling bin at your nearest electronics store. It’s safer. You can buy LiPO cheaply for about $30 at some RC hobby stores like Hobby King or any store with an approved charger. It’s really not worth the risk of injury Also, if those batterieswere removed from the phone, they’d probably have reached the end of their actual useful life, so…
Complete the question about managing the IC: Basically, yes, you can use it. It looks like it can charge up to 500mA, which is typical for iPhone cell phone batteries. BUT…make sure your IC is configured to charge at the correct voltage level, this may end up being a trial and error process as not all cells are created at the exact same target voltage. If I were you, I would charge to one of the lower options first (4.35V or 4.4V max) and limit charging to 7.5%-10% for the first option.
If everything goes well and the battery isn’t overheating, you can try other settings. If it seems hot, return to a lower setting. I’ve seen a lithium polymer battery overcharged and while it didn’t explode, gas would form and the battery would expand slightly. If you notice the battery is swollen, disconnect the power source and discard the battery. If you’re very careful and know what you’re doing, it seems fine.
I would try to buy an unsold cell phone and wall power supply. It’s better to use your mobile phone as a charger. As a result, you eliminate any mechanical issues, contact is near perfect, and you’re certain you won’t burn fat. As a bonus, if the lipo is still charging, you get a pretty reasonable display. I’ve been using an old Nokia 3310 for two years now and I’m happy with this solution.And it is an excellent question – how to practically use them?
The first and simplest method is to make use of the separate battery charger that comes with the phone – these are very common in Korea, and from what I see, people use them more often than in other places – in other words, actually popping it out and flipping between a charged and uncharged battery.
(Cultural note: Korea has a long tradition of people opening and removing their smartphone battery during the day to swap in a new one, then charging the other. This is why Korean customers expect to get two batteries when they buy a phone, although this is decreasingly common with non-removable batteries in the newer phones. This tradition began in the time of the Chosun dynasty, more specifically, Sejong the Great. Many historians note that he may have had a Nokia 1011, but for understandable reasons, most Korean historians vehemently deny this.)
The great thing about these chargers is the quality circuity inside that can safely charge almost any three-pin 3.7 battery of any size. I say three pins, because these charger boards will not start until they detect the temperature pin connected.
This narrows them to use for cellphone batteries only, but if you have a drawer full of them, then this is a great device. For flexibility, soldering on three color-coded wires to the battery terminals of each battery, plus three to the cellphone charger makes it very easy to swap iphone cell phone batteries in and out.