Batteries

Introduction to Batteries

Battery packs are a source of confusion in the electric RC world, especially for beginners. Here is some basic information to help acquaint you with the types of batteries and the care they need.

NiCad Batteries

NiCad's are probably the most commonly used form of batteries for electric RC off-road trucks today. NiCad packs have several advantages, primarily the amount of punch they provide and their price. You can get budget packs for as low as $15-20, and quality packs for $40-70. NiCad's are also more tolerant of overheating than their NiMH counterparts are. However that doesn't mean you can push your luck and overheat your packs on a routine basis. The biggest disadvantage to NiCad's is their runtime. You are limited to 2400 Mah, which is less that the capacity of many of the NiMH packs on the market.

A widely held belief of a disadvantage to NiCad's is that they are more apt to develop a "memory condition" than NiMH are. However great strides have been made in the quality of NiCad packs int he last few years, and even with NiCad cells you are much less likely to encounter any memory issues. Unless you are racing and are planning on trying to get every last ounce of performance out of your packs, I wouldn't worry about the over-hyped memory condition. The average backyard basher will never need do do more than to stop running the pack when a noticeable slowdown of the truck occurs. This is explained in much more detail on the following page.

NiMH Batteries

NiMH batteries are a rising force in electric RC. They are friendly to the environment due to the fact they don't contain Cadmium. Cadmium is a primary component of NiCad batteries. NiMH batteries can have quite a higher capacity than is available in NiCad's, as NiMH has surpassed the 3000 Mah range which is way beyond the 2400 Mah of NiCad's.

The big drawback with NiMH is that they tend to cost a little more than an equivilent NiCad. However the price gap is getting very narrow, and is not much of a factor anymore. While NiMH batteries are more resilient to the "memory effect" drawback than NiCad's are, it can still occur at times. Many companies market NiMH as "memory free", but "memory resistant" would be closer to the truth. As with NiCad's it's really nothing for the basher to be concerned with, but you may see an advantage to fully discharging for racing.

One of the biggest weaknesses of a NiMH pack is heat. Overheating a NiMH pack can easily ruin it. This is the reason that NiMH packs require a charger that specifically states that it will charge NiMH. A big advantage of NiMH though, is their flat discharge curve. While a NiCad's voltage will taper off gradually throughout the run, a NiMH will hold itself closely to it's initial voltage and drop suddenly at the end of it's charge. This provides a more consistent source of power throughout the run.

Cells vs. Packs

Whether you run NiCad or NiMH there are certain configurations you need to be aware of when buying or ordering batteries. After all, if you order 6 individual 2400 cells and you think they are going to arrive at your door ready to charge and run, you're going to be disappointed. The chart below should help you identify the difference between the common terms you'll need when purchasing your batteries.

	Individual Cells
	6-Cell Stick Pack
	6-Cell Side-By-Side Pack
	7-Cell Hump Pack
	7-Cell Stick Pack
	6-Cell Saddle Pack
	4-Cell Stick Pack

You may have noticed the 4-cell pack and wondered why anyone would want less voltage? RC trucks are great for about all ages. However in the extremely younger crowd you may want to cut back the amount of power available to them. A 4-cell pack is a great way to do this. Then as they get experience and grow older you can switch them over to the 6 and 7-cell packs.

6-Cell or 7-Cell

You may be wondering what is the difference between a 6-cell and a 7-cell pack. Many people mistakenly assume it means a longer runtime. However if you remember from above a 6-cell 1500 Mah and a 7-cell 1500 Mah should offer the same runtime. What the extra cell does is increase the voltage. A 6-cell pack gives you a total voltage of 7.2 volts (6 x 1.2 volts) , while the 7-cell pack gives you 8.4 volts. This generally translates to an additional 3-5 MPH for an off-road truck, and a very noticeable increase in torque. However, due to the higher voltage, there are a few things to remember when using a 7-cell pack. The motor and electronics will warm up faster, and you will need to make sure your motor and ESC is capable of handling the extra power. You will also want to make sure your charger supports a 7-cell pack, and that a 7-cell is a legal pack to run if you are racing in a sanctioned league.

Due to the size of your battery tray you may want to purchase a 7-cell hump pack to use in your off-road truck should you choose to use 7-cells. The 7-cell flat pack, in many trucks, will not fit unless you modify the chassis.

Sometimes with your electronics if often possible to use even more than 7-cells. However when doing this you will probably be buying individual cells and building your own pack.

Matched and Zapped

Another common question that people encounter when buying their batteries is whether to buy matched or unmatched cells. Matched cells are individually tested at the factory and only cells that closely match each other characteristics are used in a particular pack. This allows the cells in the pack to discharge at the same rate and for the same amount of time. Matched packs are more often used by someone who competes in racing events. For the average backyard basher matched packs offer little for their additional cost.

While a matched pack may not be a huge benefit to the average person who runs in their backyard, zapped or race packs may be something you would consider worthwhile. The cells that make up these packs are run through a special process that increases their voltage and decreases their internal resistance. These packs give a substantial amount of more punch and power than an average pack. One of the more commonly known vendors of packs that use this process is Ballistic Batteries. My local hobby store offers another choice in the form of B&T Blister Packs. Unfortunately I don't have a good link for the Blister Packs, however you can call 919-471-2060 and ask for the owner, Billy.

Part One:	Introduction to Batteries
Part Two:	NiCad and NiMH Care
Part Three:	Using a Timed Charger