The hobby R/C model airplane/boat/car world has embraced “LiPo packs”, which look like this: 12V to drive a motor or relay, and much higher currents of 1A or more. Sometimes, you may need much higher voltages, i.e. Many sensors work well in the 3.0.3.3V range, some support a larger range – as long as all components are used in their operating range, we’ll be fine. The LPC8xx series works from 1.8.3.6V and so will the RFM12/69 radio modules, for example. When making battery choices, it’s also important to consider what voltage range all parts of the circuit will support. LiPo (Lithium Polymer): these rechargeable cells supply 3.7.4.2V and have a very high energy density – advantage: available in a wide variety of sizes/capacities (also as cell phone packs) – disadvantage: needs some care, since the internal resistance is very low (a short can produce high currents on “unprotected” cells).Coin cell: the most common one is the CR2032 (20 mm round, 3.2 mm thick), and delivers a nice 3.0V – the disadvantage is that most coin cells have limited power (200 mAh) and are single-use, leading to recurring replacement and waste disposal.These can be used either through a regulator with fairly little voltage drop / loss, or as is if the voltage range is known to be acceptable across the battery’s entire lifetime. AA and AAA: single use alkaline provides 1.5V, and rechargeable NiMh around 1.2V, so in both cases we’ll need two or three of them in series to produce 2.4.3.6V, roughly.Let’s focus on the small ones first, since the aim here is to power small wireless nodes, spread out in an around the house: photovoltaic cells (yep, same Volta as before) ![]() batteries, both single-use and rechargeable.When the signalling doesn’t use wires, then the most practical option for power is to also provide it without wires. A lot of the work at JeeLabs is about wireless communication.
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