Battery

A battery is a component that can store and supply electrical energy.

Battery Comparison Table

Battery	Type	Nominal Voltage (VDC)	Capacity (Ah)	Weight (lbs)	Size LxWxH (in x in x in)
Interstate 12 Volt 8 Ah Sealed Lead Acid Battery (SLA)	Lead Acid	12	8	5.11	5.95x2.56x3.86
Interstate 12 Volt 12 Ah Sealed Lead Acid Battery (SLA)	Lead Acid	12	12	9.42	5.93x3.84x4.02
Interstate 12 Volt 18 Ah Sealed Lead Acid Battery (SLA)	Lead Acid	12	18	13.85	7.2x3.0x6.6
Interstate 12 Volt 26 Ah Sealed Lead Acid Battery (SLA)	Lead Acid	12	26	20.7	6.9x6.55x5.0
Interstate 12 Volt 35 Ah Sealed Lead Acid Battery (SLA)	Lead Acid	12	35	24	7.7x5.16x6.62
Interstate 12 Volt 55 Ah Sealed Lead Acid Battery (SLA)	Lead Acid	12	55	37.5	9.02x5.43x8.89
K2 12.8V LiFePO4 Battery Pack 11.1Ahr	LiFePO4	12.8	11.1	2.86	5.94x2.53x3.83
Shenzhen 12.8V LiFePO4 Battery 42Ah	LiFePO4	12.8	42	13.45	8.7x6.9x4.7
K2 25.6V LiFePO4 Battery Pack 9.6Ahr	LiFePO4	25.6	9.6	5.5	4.5x3.5x6.6
LiPo Battery 7.4V 2200 mAh	LiPo	7.4	2.2	0.30	4.13x1.29x0.67
LiPo Battery 11.1V 2200 mAh	LiPo	11.1	2.2	0.41	4.05x1.30x0.94
Polymer Li-ion Battery 7.4V 3650mAh	Li-Ion	7.4	2.2	0.37	5.5x3.7x0.3
Polymer Li-Ion Battery 11.1V 1800 mAh	Li-Ion	11.1	1.8	0.27	3.4x2.0x0.67
High Power Polymer Li-Ion Module 11.1V 5Ah	Li-Ion	11.1	5	0.69	3.1x2.8x1.0
High Power Polymer Li-Ion Module 11.1V 10Ah	Li-Ion	11.1	10	1.3	6.5x2.5x1.3
High Power Polymer Li-Ion Module 22.2V 10Ah	Li-Ion	22.2	10	3.3	6.3x3.0x2.8

Selecting Batteries for a Robot

K2 25.6V LiFePO4 Battery

When selecting the appropriate batteries for your robot, you need to size them by voltage to match the desired motors and motor controller. You will also need to take into consideration the maximum current output and the battery type and capacity.

Voltage Rating

Our motors are rated for either 12V or 24V. Incorrectly providing a 24V source to a 12V motor will immediately cause permanent damage. If only connected for a short period of time the observed damage will be limited to a whining sound when the motor is moving. A prolonged over-voltage condition will cause catastrophic damage to the motor and this may pose a significant risk of fire, injury, or death. Be sure that the appropriate power is applied to the motors. If the motors receive insufficient voltage, say 12V to a 24V motor, the motor will either move very slow or not at all.

In order to distribute the weight of a battery evenly across the robot, its common practice to use multiple 12V batteries to prevent the robot from favoring one side while driving. For a 12V motor system, the batteries will need to be connected in parallel and for a 24V system, they will need to be connected in series.

Note: When using a multiple battery system, always be sure that each battery is individually fused.

Maximum Current Output

When selecting the appropriate battery source, it is wise to be sure that the battery can produce the amount of current needed by your motors and motor controller. Take, for example, Dimension Engineering's Sabertooth 2x12 motor controller. It has two channels and each channel is capable of outputting 12A so for the motor controller to be able to supply a total of 24A to a pair of motors the battery providing power to the system must be capable of supplying that amount of current. It is important to note that the motor system may not be the only major component in your system. Be sure to account for the additional loads on your system, such as a computer, control system, sensors, and a radio.

Note: For many hobby RC motors, the batteries will be marked with a C rating. This rating will indicate the maximum continuous current discharge that the batteries are capable of. The C rating is a multiplier that can be applied to the battery capacity to get your maximum continuous discharge. For example, a 2,000mAh 10C battery can output a maximum of 20,000 mA or 20A.

Battery Type and Capacity

There are two main types of batteries that are discussed here: Lead Acid, Lithium. Lead-acid batteries are the cheapest out of the two. These are the batteries that you typically see in a car or a truck. They do not require special circuit protection, only a fuse. The downside is that they are large and very heavy.

The second type are Lithium batteries. You will typically see in most electronics today. They are lighter and more compact than lead-acid batteries and are the go-to battery type for RC robotics. One caveat with Li-ion batteries is that they require specific under-voltage circuit protection to prevent the battery from dropping too low. If this happens the battery will be unrecoverable. Most of our Lithium batteries contain the necessary circuit protection to prevent this from happening. Most of the cheap RC batteries you see listed online, do not.

There are several kinds of Lithium batteries. Lithium-ion is the most common (and the most unstable). Lithium-ion require extreme care so they do not overheat, etc resulting in a fire or explosion. A more stable battery is LiFePO4 chemistry as in our K2 25.6V 9.6 AHr or K2 12.8V 11.1AHr batteries. These batteries are much more stable and an excellent choice for powering robots, but they are more expensive.

On the topic of battery capacity, it is commonly measured in mAHr (milliamp hours). This is a measurement of how long it would take to discharge the battery if it outputted 1mA of current. Larger batteries are typically measured in AHr which is mAHr divided by 1,000. So, a 12V 2000 mAHr (2AHr) battery will last twice as long, under the same conditions, like a 12V 1,000 mAHr (1AHr) battery.

Power and Battery Wiring

When wiring your batteries to your robot there are concerns you must address. Namely, what output voltage do you need and how you are going to charge the batteries. When using two 12V batteries you will need to wire them in parallel to power 12V motors and in series to power 24V motors.

The key things to consider are what voltages do you need and how much power The driving force for the main battery will be the motors. We typically use 24VDC motors, they run at half the current for the same power as 12V motors so smaller wires, motor controllers, etc. Do you need a separate battery for the controller or on-board computer? How are you going to get those voltages (multiple batteries, voltage regulators, etc.)? How much of a load will be on each voltage so your batteries and/or regulators are sized properly? This will help you size your batteries: simple math. If you have a 1Amp load and a 10Ahr (10,000mAhr) battery, the battery will run for 10 hours in theory.

Robot Battery Chargers

When ordering a robot kit as a base for your project, we offer appropriately sized chargers for the supplied batteries. When picking out your own chargers, it is absolutely critical that you pick the charger with the correct voltage and battery type. Not selecting the appropriate charger will be a fire hazard and cause permanent damage to the battery, charger and your property.