![]() ![]() We’ve seen this done with iPhone batteries, and we’ve also seen things like makeshift pin header-based holders for smartphone cells. One small thing to keep in mind – while older Nokia batteries have a third pin, it’s not a thermistor pin – instead, it’s a fixed-value cell identification resistor. ![]() Most importantly, you get a battery with an active supply chain, which means you can design it into your project mechanically and electrically, and not fear a redesign a few months in when all local stock of a very specific cell suddenly runs out. With a smartphone cell, you get a protection circuit, usually a built-in thermistor and often a one-wire or I2C fuel gauge. You can source these contacts from online repair shops, LCSC, Aliexpress and probably more. If you’d like to make your device repeatable by others and make battery sourcing simple, perhaps work around LiIon shipping restrictions, or if you’re a garage startup itching to get a small prototype batch out of the door, smartphone batteries are a good bet.Įven more, there’s not much preventing you from putting the same contacts used by phones onto your PCB. However, shopping for smartphone batteries in your local stores is still worthwhile if you need a small cell to power your device.įor instance, user-replaceable batteries are still manufactured and sold for numpad phones from manufacturers like Nokia, with cells typically around 1000 mAh, more than enough for a small ESP32 or Pi Pico project that spends lots of time asleep. Of course, we’ve all seen a phone battery die earlier than the phone did, and in many modern phones, the cell is glued-in and harder to extract. Smartphone Batteries A Viable Source A radio rebuild project using a Nokia batteryįirst underappreciated source of LiIon cells, specifically pouch cells, are smartphone batteries. Let’s see what your options are beyond laptops. However, a 18650 cell might not fit your project size-wise, and thin batteries haven’t quite flooded the market yet. Taking laptop batteries apart, whether the regular 18650 or the modern pouch cell-based ones, remains a good avenue – many hackers take this road and the topic is extensively covered by a number of people. But what if you don’t have any LiIon cells yet? Where do you get LiIon cells for your project? With 18650s being so readily available, finding a battery from a reputable manufacturer should always be a priority.In the first article, I’ve given you an overview of Lithium-Ion batteries and cells as building blocks for our projects, and described how hackers should treat their Lithium-Ion cells. Try to avoid rewraps, as the batteries that are used for them may change at any given time. Until further notice, any battery that is not rated according to these two rules can be assumed to be falsely rated. At the same time, no 18650 with a capacity at or over 3000 mAh, will have a CDR over 20 amps. There is (still) no 18650 with a CDR over 30 amps. Going over the ratings of reputable manufacturers, you will notice a pattern: there is always a trade-off between CDR and capacity. While this rating is sometimes overstated on battery wraps, this doesn’t happen as often as it does with discharge ratings. One mAh is equal to the charge transferred by a steady current of one milliampere flowing for one hour. Always look for the CDR of a battery, and cross-check ratings with online sources.Ĭalculated in mAh (milliampere-hours), the capacity of a battery signifies its running time. This is not a rating that should be taken into account when considering a battery, as it is often times misleading. It is the maximum current that a battery can supply in short intervals (that are most of the times not mentioned on the rating). One good example is the maximum discharge rating (or maximum discharge current), which may even be the only rating on the wrap. Rewraps and Chinese manufactured batteries will often overstate the CDR, or use other ratings instead of it. When accurately rated, it signifies the current that a battery can be safely discharged at a continuous rate without taking damage or reducing its capacity. This is the rating that is used by reputable electronic manufacturers, and the one rating that we can use to compare battery discharge. ![]()
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