Battery Basics 101

[Namuna]

There's been quite a lot of Forum traffic with questions pertaining to Batteries, so let's try and makes some sense of it all...

In this thread we're going to touch on the following subjects:
- Bit Battery Dimensions
- Nicad vs. NiMH
- Voltage & Amperage
- Charging

-Bit Battery Dimensions
The stock Bit Char-G/Microsizer battery is a 1/3AAA scale, 50mAH Nicad battery. One of the most common upgrades for the Bits is a higher capacity NiMH battery (like a 1.2v 150mAH NiMH battery).

The '1/3AAA scale' size is very misleading because that is NOT an industry standardized size and that means there can be a significant variation in actual physical dimensions between one manufacturers 1/3AAA size vs. another. The best way to shop for an upgraded battery is to go by physical dimensions...In order to fit (without modification) into a Bit chassis, the size has to be '10mm Diameter x 16mm Height' (or smaller). This is IMPORTANT to note because there has been some talk about a company that offers a 210mAH 1/3AAA size battery...But it has a height of something like 21mm (which is too big to fit a Bit).

- Nicad vs. NiMH
IMO, go with the NiMH batteries. They have higher capacity, no toxic chemicals, and prices are relatively cheap. I won't go into full details about the differences, there's PLENTY enough info out there on the Net about the 2 types and their differences.

Also note that while the stock battery on a Bit Char-G is NiCad, the charger on the remote handles the NiMH batteries without problems.

- Voltage & Amperage
Okay, let's put some sense into what 1.2v and 50mAH means...To simplify things:
~ Voltage(abbreviated as 'v') = Speed
~ Milliamps (abbreviated as 'mA') = Runtime and Torque/Acceleration

The PCB (aka circuit board) of the Bit regulates the Milliamps (aka current) going to the motor, which means having a higher capacity battery (like a 150mAH battery vs. a 50mAH) will make no impact on motor performance except to be able to maintain that regulated current for a longer time (meaning longer runtime between charges). If you were handy/brave enough to tamper with the resistors on the PCB and change how much current was going to the motor, then you’d in turn change how much torque was imposed (think of torque as acceleration).

On the other hand, the PCB does NOT regulate the Voltage to the motor, so putting a higher voltage battery in the Bit will equate to ALL the voltage going to the Motor and in turn the motor will produce more revolutions, faster (in other words, SPEED!).

A term heard often around the Forums is ‘2.4v’ or ‘Dual-Cell’ or ‘Dual-Battery’ Mod…They are talking about taking 2 batteries (make SURE they’re both the same voltage and milliamperage) and connecting them in Series (when connecting multiple batteries in ‘series’ the voltages add together, but no change to the milliamps. If you were to connect the multiple batteries in ‘parallel’, then the opposite is true; the milliamps add together, but the voltage stays the same)…Considering the information above, you know that this 2.4v Mod means lots of SPEED increase right?

- Charging
Here’s the rule of thumb when charging batteries…First, set the voltage as equal as possible to the cell/pack voltage. Then take the capacity of the battery (in milliamps) and divide by the charge rate (in milliamps) and then add 20% and the result is how long (in hours) it will take to fully charge the battery. Let’s take, for example, a 2.4v Dual battery pack with a 150mAH rating. Now, let’s say you had a 2.4v charger that charges at 500mA…[150/500 = .3] then [.3 + 20% = .36] so it would take .36 hours (or a little less than 22 minutes) to fully charge the pack…Roughly

The 20% is a sort of ‘leeway’ given because charging batteries and the chemistries and variations make this NOT an exact science (as a matter of fact some people say to actually add 50% for inefficiencies!)

The stock charger on a Bit puts out 2,500mA at 1.5volts for 45 seconds, per charge cycle. If you do the math in reverse, you’ll see that a single charge only fills a stock battery to about ½ capacity! So doing 2 consecutive charges will produce a SIGNIFICANT increase in runtime!

Alright, I think that should give a decent idea of how it all works with Batteries.

If you have any questions, concerns or corrections, feel free to post.