12V Battery Health Analyzer (NiMH, 3000mAh)

Using the Battery Health Analyzer

To use the Battery Health Analyzer:

1. Ensure that your battery is charged and at room temperature.
2. Plug your battery into the Battery Health Analyzer. The Battery Health Analyzer will report back the battery’s current voltage, and the LED will be green.
3. When you click the MODE button, the LED will change to blue, and it will display the numerical value of the connected battery’s internal resistance, measured in milliohms (mO).

NOTE: The Battery Health Analyzer may get warm after several concurrent tests. In this case, the Analyzer will display "HOT", followed by the number of degrees °C it must drop before another test can be performed.

When is a Battery “Bad”?

The most important effect of a battery’s IR is voltage drop. When your robot pulls current from the battery, the internal resistance means that the voltage will drop (see “What is Internal Resistance?” below). The amount that it drops will increase with a higher IR.

That’s why we recommend that FTC teams use their batteries in order from lowest IR to highest in competitions. After using a battery in a match, put it on the charger, and once it's charged, use it again. Keep your best batteries early in the queue so they get the most use, and keep the highest IR batteries for practice and rare matches.

Some robots pull much more current than others; as such, robots that draw less power don't require nearly the amount of care with battery health as others. If your robot design is pushing to get all you can get out of your battery, you should make sure to bring only the best batteries to your matches. For most teams and robot designs, however, a middle ground is reasonable.

Low-Power Robots

• Use 3-6 motors
• Use a few servos
• About one arm/lift
• Consistent & efficient motor ratios

Can use almost any charged battery (in working order). Consider moving batteries out of circulation if IR is >200mO.

Average Robots

• Use 6-8 motors
• Use a few servos
• About one arm/lift
• Consistent & efficient motor ratios

Can use batteries even after a few years of heavy use. Consider moving batteries out of circulation if IR is >160mO.

High Power-Draw Bots

• Use 7-8 motors
• Use many servos
• Multiple arms/lifts
• Motor ratios maximize power

Use only the best batteries! Consider moving batteries out of competition circulation if IR is >130mO.

What is Internal Resistance?

Batteries are built to last—but not forever! While you can bet that your batteries will maintain their form and function throughout many charge cycles, tiny electrochemical changes in your batteries will accumulate over time and cause an observable increase in each battery’s “internal resistance” (IR).

Batteries with a higher IR are more likely to reduce a robot's performance. That’s because of the direct effect on voltage, which is calculated by multiplying current by the resistance (Ohm’s Law, written as voltage = current X resistance). As a result of this relationship, when a robot draws current, the IR will cause the voltage drop. Higher IR values produce greater drops in voltage, and voltage drops result in reduced performance.