Question: How can you make battery powered electronics last longer?

Tom Rooney answered on 2 Jun 2020: last edited 2 Jun 2020 11:13 am

This is a very good question and one that engineers are looking at all the time!

Essentially there are three ways to look at the problem – Improved Electronics, Improved Batteries and Alternative/Supplementary Power Sources:

1) Make the electronics more efficient – This can be broken down into further approaches:
a) The electronic components themselves – select or design components that run on lower voltages and draw fewer microamps.
b) Work rate – Whatever your system or device is doing, design into its processes and coding a more efficient work rate. To do this identify the tasks that require the most power and reduce the time it needs to do this or the frequency of this action.

In the field of underwater transponders Sonardyne have spent a great deal of effort on working on this as our hardware is at the bottom of the ocean running on its internal batteries for its lifetime, In order to maximise the time the unit is operational for (between 1 and 6 years!) we have designed the electronics to work very efficiently. The most power demanding elements for our transponders is communicating with other transponders and taking environmental measurements (as the sensors need to be powered up); therefore we have programmed in a greater element of autonomy and AI into the processor functions to keep both of these actions to a minimum.

2) Make the batteries more efficient. There is a huge worldwide effort in this regard:
a) Rechargeable batteries – Lithium alloy batteries are improving all the time to reduce size, increase power density, maximise duration and minimize charging time. However this is a complicated issue with many problems:
i) Lithium is a highly volatile element and these batteries have a significant risk of fire in the event of battery failure. As Lithium reacts with water, even the moisture in the air can fuel the fire and attempts to extinguish using water can make the situation far worse.
ii) Lithium and the other rare metals used in the battery design are sourced through open cast mining and large scale industrial manufacturing processes that produce large quantities of carbon and other toxic waste products – Electric powered cars for this reason are not as eco-friendly as you may think.
iii) Rechargeable batteries have a limited life – you only have so many charges and re-charges before the power density begins to fade. Smart chargers and battery telemetry data help monitor and manage this die-off but before long your electronic system will begin to last less time on each charge.
iv) Toxic waste – when it does die you have to dispose of it somehow and it contains some pretty toxic compounds and chemicals that need to be processed correctly to recycle them or render them harmless to the environment.

b) Replaceable batteries – Chemical batteries have been around for a long time and these too are being improved. Again, they have issues though:
i) They have a finite life. When you use up the power in a chemical battery you have to replace it (like the Alkaline Batteries in a toy) when its gone its gone.
ii) Toxic waste! A traditional power cell you’d use in a toy also contains some pretty toxic compounds and chemicals that need to be processed correctly to recycle them or render them harmless to the environment.
iii) Greater power density! However they do have one advantage over rechargeable batteries. For their size they have a greater power density than Lithium based rechargeable cells, and that power is sustained for longer during its life. A rechargeable battery’s voltage drops off gradually in the last 20% of its charge which can affect the electronics’ performance; a replaceable battery’s voltage dies off in the last 5% of its life (which is longer anyway) so you get a more reliable performance for longer.
v) New chemical batteries coming on to the market. People are looking at molten salt batteries and other forms of sustainable replaceable battery designs. There is a UK company (metaletrique) that have designed an exciting battery that uses an inert (non-toxic) electrolyte liquid, aluminium anodes and air – the battery is a quarter of the size of a comparable Lithium unit and produces four times the power density. Once the anodes are depleted they can be replaced four times using the same electrolyte, and after that the liquid can be recycled to have the aluminium extracted, purified and turned back into anodes. They recently drove an electric powered delivery van 1500Km on a single battery charge! So perhaps a smaller version of this type of battery might be the answer to your question.

3) Supplement the batteries with another source of power – depending on the environment or application your electronics are operating you could consider having a supplementary power source built in to your device. Things to consider are:
a) Photovoltaic Cell (Solar panel) – If your device has access to sunlight this is an easy addition to make that will keep your device running for much longer. If designed correctly you could run on solar alone and only need the battery as a “keep alive” supply.
b) Wind Turbine – If your device is going to be used outside or in a place where there may be sufficient airflow (like inside a ventilation system or on a vehicle) you could consider a turbine. There are some small efficient on the market or you could design your own!
c) Water turbine – as above but for water or other fluid flow.
d) Motion generator – If your device is in a dynamic setting then fitting a small generator that creates power when it’s moved is worth looking at. High quality wrist watches have been using these devices for decades and, depending on the scale of your device, there are many types that could be used to supplement your battery power and make the system more efficient. One form of motion generator is a dynamo, a small generator that converts rotational energy into electricity.
e) Electromagnetic induction – if your device is to be used in a setting that has an electromagnetic field (such as near power cables) you may be able to tap off some of this energy right out of the air and use it to power your device!
f) Permanent Magnet motors – Look on YouTube for many demonstrations of these at work. A motor driven by permanent magnets and a small exciter voltage can drive a much bigger generator to give impressive outputs. Maybe a smaller scale version (maybe using nano technology) is the future of sustainable power for electronic devices!

I hope this has been a useful answer – Like I said it is a huge subject so a very good question to ask.

In essence the solution to most problems in this area will lie in a combination of ALL of the answers above.

Tom