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What you need to know about Lithium Polymer Batteries! If you have a specific question you would like to see answered here please email us at promatch@frontiernet.net
What is the best Lipo choice for me? This depends on what you are using the battery for. If you race competitively you will certainly want a higher "50C+" rated battery. If you are a casual racer or just backyard bashing you will be fine with a 25C rated battery. We do not recommend using lower than a "25C" rated battery pack as voltage drops may cause radio gliches. If you are using 2 2S packs in a 1/8th scale buggy or Truggy we recommend using at least 40C rated packs or higher as these types of vehicles draw very high amounts of current. What is the "C" rating? The "C" rating is a number that battery manufacturers use to rate the maximum amp draw a pack will withstand. It has been reported to me that the parameters for establishing this rate are as follows. The manufacturer measures the highest amp rate at which a battery will yield 80% of the stated capacity of the pack. So let's say for a 5000 mah 50C pack, it would yield at least 4000 mah of capacity when discharged at 250 amps from a fully charged state to a cutoff of 3.0 volts. It says nothing of what damage was caused to the pack after this test, only that it accomplished the test once. Take from this what you want. The "C"rating of a pack is probably the most ambiguous measure performance that I have ever seen. Hopefully in the future a "real world" measure of performance can be established. Some companies really inflate this rating so it is important to understand that the "C"rating is subjective. A higher C rating from the same manufacturer should give you better performance and longer cycle life. Also remember that buying a lower "C" rated battery and running it in a high current draw application such as 1/8th scale cars will overstress the battery and cause the pack to "swell". What does the "S" stand for in a "2S" or "3S" Pack? The "S" stands for the number of cells in the pack. A 2S pack is a 2 cell pack and is rated at 7.4 volts. A 3S pack is 11.1 volts, 4S 14.8 volts and so on. Basically each cell is 3.7 volts. Why does my 2S pack charge to 8.4 volts? The "rated voltage is a median number used by the industry to rate the average voltage of a battery cell. When fully charged each cell in a Lipo pack will reach 4.2 volts. The lowest voltage you should discharge your lipo packs to is 3.0 volts per cell (6.0 volts for a 2S pack). I personally recommend a minimum voltage cutoff of 3.2 volts per cell. What is the plug attached to the small wires coming out of the pack for? This is the "balance plug" and is inserted into the output balance port of the battery charger. It allows the charger to adjust the current so that each cell in the pack reaches the same (4.2) voltage at the completion of the charge cycle. Make sure the balance ports match the balance plug on the battery pack as their are a few different types of balance plugs. The most common is an XH plug and is found on most brands of Lipo chargers. Adapter for different types of balance plugs are available and many chargers come with different balance adapters. What do I do with the balance plug when I'm running the battery? Nothing. The balance plug is only used for balancing during charging or discharging. What do I do after using the packs? After you are done using your Lipo battery make sure you unplug the battery from the car! Leaving a Lipo battery plugged into the speed control (even with the switch off) for extended periods of time can cause the voltage to drop too low causing permanent damage to the pack. Make a habit out of removing the pack from the vehicle and putting the pack into a lipo bag. Just put it in a cool dry place. If you don't plan on running the pack for a month or longer charge or discharge the pack as necessary to get the pack to 3.8 volts per cell. For example a 2S pack should be at 7.6 volts. This is referred to as a storage charge. A trick for extending the life of a Lipo packs is to place the pack in a plastic storage bag and put it in the Refrigerator. Allow them to return to room temperature before charging them. Never ever ever leave a Lipo in a hot car! Although Lipo's are designed for a maximum temperature of 140 degrees F, a temperature of just 104 degrees F for an extended period of time (<24hrs) can cause "puffing" and will cause permanent damage to the pack. Cooler is always better.
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