If I have a set of rechargeable batteries, I count myself lucky if I can get them to last for more than 2 years. Yet there are many spacecraft out there, which use their batteries much more regularly than me, and yet they have batteries that still work after years. How are they able to maintain the lifespan of these batteries for such an extended period of time?
This document provides a bunch of useful information on the topic. Some applicable quotes:
Space missions impose several critical performance requirements on batteries and fuel cells. Batteries required for space applications must be capable of operating in a hard vacuum and withstand severe launch environments (vibration, shock, and acceleration). Space applications also require batteries that can provide maximum electrical energy in minimum weight and volume
Long cycle life (> 30,000 cycles) is the critical driver for orbiting spacecraft, and long active shelf life is the driver for planetary probes (> 7-10 years). Radiation resistance and operation at temperatures as low as -80°C is essential for some planetary missions. No single battery system can meet all these complex requirements.
The Ag-Zn battery was the first choice in the early days of space missions. The Ni-Cd battery became the major energy storage device over the next 20 years because of its long cycle life. The Ni-H2 battery started to play a role in the 80s.
There is also plenty of information about the longevity of power sources. For example, the Space Shuttle didn't use batteries:
The space shuttle requires a power source that can provide 6-12 kW for 2,000 hours. Batteries cannot satisfy this application, as the required battery weight would be prohibitive. The application can and has, however, been met with an alkaline fuel cell operating on hydrogen and oxygen stored separately in cryogenic tanks. International Fuel Cells is providing alkaline fuel cells for the shuttle orbiter applications. This system has been in use for the past 18 years. Plans are underway to replace the alkaline fuel cell system with an advanced PEM-based system. The replacement of the hydrazine-powered auxiliary power unit (APU) with an electric APU powered by 100-150 kWh Li-ion batteries is also underway.
I won't just copy and paste the whole thing here, but it's a good read, with lots of rich information on the topic of batteries in space.
Generally speaking, there's a couple of things that should be done to prevent this from happening.
- Order good batteries. This helps, to an extent, but isn't a sure thing.
- Try to keep the thermal limits of the batteries within limits. Don't allow the batteries to get too warm, or too cool, and vigorously monitor this.
- Charge the batteries fully, but don't overcharge them. This is probably one of the big reasons that consumer batteries fail. It is actually common for them to be somewhat overcharged, which is why most batteries are noticeably warmer after they are done charging. They aren't super overcharged, but this does contribute to wear and tear.
- Minimize the depth of discharge. Essentially, charge your batteries when you have used less than a third of their capacity. You are much more likely to have issues if you completely discharge your batteries.
If you do all of these things, your batteries will last longer. The same goes with personal electronics, by the way. Of course, making sure your battery is charged in an optimal manner can be a very difficult and time consuming matter, which is why more systems don't do it (Every battery is a bit different).