There are several battery types that will successfully power your VH12 Hexapod. The batteries you choose will affect how long the robot will run, recharge time, etc.

This article explains your options.

Battery Safety Tips

Rechargeable batteries are by far the most cost effective and environmentally friendly kind of batteries, but some simple safety rules are recommended:

Never, ever put non-recharegable batteries in a battery charger!
If you are using rechargeable batteries, make sure you are using the right kind of charger for the batteries you are using. Follow all manufacturer recommendations.
Never leave batteries charging unattended. Never charge batteries "overnight". It is safest to charge batteries in a place that will not be damaged by heat, just in case the rare instance of a damaged battery overheating during charging occurs.
Investing in a "smart" charger is well worth the extra cost, as they will generally keep your batteries in much better shape than "dumb" chargers. You can buy a dumb charger for under $10, but if it damages your batteries so they can't hold a charge, did you really save any money? A good smart charger is about $25 but will keep your batteries running for many hundreds of chargers. Don't be penny wise and pound foolish!
If you are charging batteries, it is normal for them to get warm, but if they feel hot, if smoke is coming off them, if you smell a "burning plastic" type odor, if you see sparks, or if they appear to be swelling, disconnect the charger immediately from the wall socket and wait for things to cool down.
If there is any visible damage to a battery or if it appears to be swelling, stop using it immediately and do not attempt to recharge it.
Some kinds of rechargeable battery cannot be disposed in the trash but must be recycled, follow all instructions and markings on the battery and follow your local community recycling practices.

Gamepad: Any kind of 9v battery

The gamepad has minimal power requirements and can be powered by either non-rechargeable or rechargeable 9v batteries. Alkaline, NIMH, NICAD, or LION batteries will all work fine for the gamepad. The gamepad was designed to fit a standard 9v battery in its battery compartment. You can expect several hours of usage. Do be sure to turn the gamepad off when not in use.

Only Use Rechargeable Batteries for the Robot

Non-rechargeable batteries, such as alkaline batteries, cannot produce enough current (amperes) to drive the robot reliably.

The major types of rechargeable battery used today are Nickle Metal Hydride (NIMH), Nickle Cadmium (NICAD), and Lithium Ion (LION).

The robot comes with a 9v battery clip and a six-cell AAA battery holder that uses a 9v snap connector. However, you can find 6xAA battery holders with 9v snap connectors if longer battery life is desired.

Below we discuss the different options for the robot.

Do Not USe 9V Lithium Ion Batteries

A 9V Lithium Ion batteries that look like standard 9v batteries might be tempting to use in the robot, however in general they cannot provide enough current (amperes) safely. For example, a 600 mAh LION battery can only safely output about 1 to 1.2 amps. It might actually work in the robot, but it will get hot and its lifespan will be compromised, and it may even become a safety issue.

So, we do not recommend 9V transistor battery sized LION batteries.

6xAAA Rechargeable NIMH or NICAD Batteries

You can use a 6xAAA battery holder with a 9v snap connector to power the robot using NIMH or NICAD batteries. Typical battery life for continuous use would be 15 to 20 minutes for a battery with 1000 mAh capacity.

6xAA Rechargeable NIMH or NICAD Batteries

You can use a 6xAA battery holder with a 9v snap connector to power the robot using NIMH or NICAD batteries. You can expect 30+ minutes of continuous usage using these batteries. However, because AA batteries are about twice as heavy as AAA batteries, they do put a little more stress on the servo motors.

Two 18650 Size LION Batteries

The "18650" battery is commonly used in flashlights and these are made to output current which easily is enough for the robot. Two in series will provide 7.4 volts nominal and, while more expensive than other options, can provide very long battery life for the robot. For example using two 3000 mAh 18650 cells you can expect over an hour of continuous use.

Note that these batteries require special chargers. You can find 2 x 18650 battery holders, but you will need to solder on an appropriate connector.

Other Options for Advanced Users

If you know about batteries and wish to design your own system for the robot, here are some factors to bear in mind:

The robot requires 2 amps during typical use but may spike up to 2.5 amps for short periods.
The voltage regulator requires 6.5 volts input to keep the servos powered at 5.0 volts nominal, so do not design a battery system with less than about 6.5 volts output at 2 amps. Running the servos with too low voltage may shorter their life.
The maximum recommended battery voltage is 12.0 volts, beyond that the 5v regulator used for the servos might be damaged and the Arduino Nano onboard regulator (which is fed directly off the battery, not the 5v regulator used for the servos) might overheat.

Example 1: the robot will run quite well on two AA LIFEPO4 batteries (which have 3.2v nominal cell voltage and when charged will meet the 6.5 volt minimum, and can output easily 3 amps). You would probably need to get a 2xAA battery holder and solder on a 9v clip, or make a converter to go from 9v clip to some other battery connector such as JST or Tamiya. Note that LIFEPO4 batteries require special smart chargers and preferably balance chargers.

Example 2: You could use two 9v LION batteries in parallel by making a custom battery clip modification to the robot, thus doubling your battery life in a convenient 9v form factor. 9v LION batteries are lightweight and two would easily fit in the battery area of the robot.

Vorpal The Hexapod Battery Recommendations

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