Types of Batteries for Robots and Robotic Designs

Introduction

Choosing the correct battery system for your robots is important since each type uses a different type of battery. Several need smaller ones, whereas others can need larger ones. And so we're asking about the quality of batteries. Here's a comprehensive guide to the forms of robot battery systems.

Our primary emphasis will be on rechargeable batteries and the first word that is sure to come into your mind is 'lithium batteries;' the most widely used rechargeable batteries. If you choose anything under budget, the lead-acid batteries will suit the bill or you might choose lithium-ion or lithium-polymer batteries. Non-rechargeable batteries are expensive in any direction in the long run.

1. Lead-Acid Batteries 

Lead-acid batteries are usually cheap and come in large capacities too. You can find them in larger platforms that don’t require tremendous power but need lots of energy capacity. You’ll find them in solar power systems, UPS, etc. However these are only available in increments of 6V and 12V, are super heavy and have low capacity per weight unit. They also take longer periods of time to charge and lose capacity if left in storage. Lead acid batteries used in automobiles, trucks and boats have a high content of toxic and highly corrosive sulfuric acid. The lead from these batteries can be recovered through smelting.

2. Nickel Metal Hydride Batteries

If you want to go for a cheaper option but lighter than lead-acid batteries, nickel-metal hydride batteries are the ones for you. They’re quite popular for their low internal resistance and the good power-to-weight ratio and are far safer than Lithium-based cells. You’ll find them in airsoft guns, cheap toys, AA/AAA replacements, digital cameras, etc. Disadvantages include a higher self-discharge (around 50% higher than NiCd). They also have a limited service life and do not absorb over-charge well. A nickel metal hydride battery, abbreviated NiMH or Ni–MH, is a type of rechargeable battery. The chemical reaction at the positive electrode is similar to that of the nickel–cadmium cell (NiCd), with both using nickel oxide hydroxide (NiOOH).

3. Lithium-Ion Cells

Lithium-Ion Cells are relatively safe and have a higher energy density so they are suitable for electronic equipment that requires longer time between charges while still consuming more power. Their rates of self-discharge are also low and are very lightweight. They’re used in powering electronic gadgets such as mobile phones, laptops and tablets etc. However, one major disadvantage to them is their cost i.e. they can be quite costly and they will also suffer from aging. Plus they require extra protection from being overcharged and discharged.

4. Lithium Polymer Batteries

Lithium polymer batteries are usually lightweight and come in packaged form, a collection of single cells with a balance plug and the main power plug. They are available in a wide range of voltages as well according to the required usage. You’ll find them in combat robots, RC airplanes, and drones, laptops and phones even.

Keep in mind however that they can be very dangerous if not handled with care. They should be properly stored and maintained. They can also be quite pricey. Now we’ll discuss some battery specifications you should know about.

Battery Ratings

All batteries will come with a list of voltage ratings and capacity ratings in amp-hours or milli-amp hours. Some will also come with a discharge current rating (C-rating) or burst current rating.

5. Lithium Polymer Battery Ratings

• Voltage/Cell Count:

LiPo batteries include series (S) and parallel (P) cells. The basic ones are labeled as 1S and if not labeled they’re automatically assumed to be 1S i.e. a single set of cells in series. The nominal voltage of a LiPo cell is 3.7V and so if a cell is “2S” i.e. two cells in series, its voltage would be 7.4V. Similarly, it would be 18.5V for a 5S pack.

• Capacity and C Rating:

Capacity refers to how much power the battery can hold whereas ‘C rating’ refers to the measure of how fast a battery can be discharged safely without harming the battery. Most batteries you’ll find today come with two C Ratings: A continuous rating and a burst rating (the burst rating is only applicable in 10-second bursts, not continuously).

Let’s say you have a 1000mAh battery pack labeled as 25C/40C. It has the capacity to handle 25A continuous or 40A bursts (usually for a couple of seconds up to 10 seconds). These ratings tend to drop at larger capacities. C ratings above 50 are common for batteries less than 1000mAh. Usually, a 500mAh 75C/150C battery can handle 37.5A continuous and 75A bursts.