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Juice

Whether you like it or not, your bot does indeed have to move to be competative and no, you can't control it by telekenesis. You need to have an onboard power source giving all kinds of juice to your bot's various systems. Here is a handy-dandy table that shows various ways to power your machine of destruction.

What is it?	Pros	Cons	What's it good for?
NiCad Cells	Beefy, efficient, fairly high discharge current, light	Contain cadmium, expensive, need special chargers, need to have many in series (1.2 volts each)	Main power supply, receiver batteries
NiMH cells	Very light, very efficient	expensive, need special chargers, discharge current lower than NiCads must have many in series (1.2 volts each)	Receiver batteries, lightweight main power supply
Sealed Lead-acid batteries	available in 2, 4, 6, 12, and 24 volts, cheap, very high discharge current, very high capacities available, can use any decent power supply as a charger.	Very heavy, very innificient at high discharge so you need more capacity	Main power supply in higher weights, 12 volt power source for NiCad charger
Lithium Ion batteries	3 volts each, light	hard to find, very expesive, don't like high discharge rates	high-voltage systems, receiver batteries
Gasoline	Obscene power to weight ratio for fuel and engines	battlebots limit on fuel amount, explosive, stalled engines die, need to run fuel lines, fumes	Spinning weapons, hydraulic pumps
Compressed Gas	Can provide huge bursts of power, high power to weight ratio	Low limit on amount that can be stored, fairly dangerous, cannot be used for long periods of time	lifter weapons, tosser weapons, hammer weapons.

So you want to buy some of this stuff, eh? well you can get NiCad and NiMH packs from www.battlepack.com and all kinds of Sealed lead-acids from www.arcade-electronics.com.

Now choosing your source of power can be a very trying and arduous journey. The most obvious choice for batteries is sealed lead-acid because they are so cheap. this was the road Strange Brew was going to take before we realized the true cons of them. A SLA as it's known is usually labeled in how many amp-hours it stores. a 20 amp-hour battery can put out one amp for 20 hours. on SLAs their capacity is usually determined by a 20-hour discharge rate. On paper, a 20 amp-hour battery could do 1 amp for 20 hours, or 20 amps for an hour, or 40 amps for a half hour, or 80 amps for 15 minutes, or 400 amps for 3 minutes. This is NOT the case. As the discharge current rises, the effective capacity drops. A SLA's effective capacity for a 3 minute drain is about 40-45% of it's rated capacity, so divide the capacity roughly in half to find out what its in-box capacity would be. Weight is another issue. A SLA battery will weigh roughly one pound for every rated Amp-hour at 12 volts, so to get 6 amp-hours realistic run time at 24 volts, you'll be blowing about 25 pounds on just batteries. They are definately not suited for the lower classes, but plenty fine for the upper ones. Most can be charged, however, by any power source that can put out about 13.5 volts.

NiCads are a different story. Though they cannot source as much current as a SLA battery, they can do high current much more efficiently. a 3-minute discharge current for a NiCad isn't much different from their 20 hour discharge capacity. NiCads don't, however, store much energy alone. The most common NiCad batteries used by roboteers store 3 amphours at 1.2 volts. This low voltage requres many of them to be wired in series to get the necesary voltages to run high-powered motors. That means 20 cells for 24 volts, and that's only for 3 amphours. Anything over a lightweight wedge will need more than 3 amphours, so you need to wire the packs in parallel. That's 40 cells for 6 amphours at 24 volts. Luckily you have people like www.battlepack.com to assemble these packs for you. NiCads also put out a lot of heat when they are discharged at high current, so they need to be well insulated and sometimes need active cooling (like a fan) to keep them happy. They also cost quite a bit more than SLAs: a 24 volt, 3 amphour NiCad pack costs about 138 bucks assembled. That sounds like a lot, but it's worth it. It's in-box capacity is similar to that of a 7 amphour pack of 2 SLAs, which would likely weigh over 15 pounds. The nicad pack weighs only about 3 pounds. As for NiMH packs, think of them as diet NiCads. They weigh even less per amp-hour, but cannot put out as much current. For the record, Strange Brew runs on 2 24volt 3amphour NiCad Battlepacks.

Not seen as often as often as they used to, gasoline engines offer the peak in prolonged power-to-weight ratios. The Rotax 277 as used in White Rabbit puts out an awe-inspiring 26+ horsepower but when stripped down weighs less than 15 pounds. You can't top that. But gas engines have their own downfalls. If they are stopped, they stall and must be restarted by either an electric motor or by hand. Their torque curves are exactly the opposite of electric motors: max torque at max rpm, no torque at 0 rpm. If they are used to spin a kinetic impact weapon, their spinup time will be slower but it will be much harder to slow down once it is up to speed. Gas engines also need some sort of clutch to disengage them when their rpm goes below a certain level (idling) so they cannot be stalled. Gas engines also cannot be controlled by solid-state electronics like the speed controllers control electric motors. They need to have their fuel valves manually opened by a servo which is just another thing to go wrong. On top of all this battlebots has a limit on how much fuel a robot can store onboard (not the case with batteries). Gasoline engines were used on White Rabbit, Sunshine Lolibot, Half Gassed, and Botknocker 19.

Last but not least is Compressed Gas. Compressed gas can produce phenomenal amounts of power in a fairly small space. Unfortunately, it cannot be stored in large volumes easily and as far as the gas itself is concerned it does not have a very high energy-weight ratio. Compressed gas, such as nitrogen or carbon dioxide, is not suitable for drive because of the heavy limitations that are put on its storage in battlebots. It is best suited for intermittent duty tasks in linear actuators (Translation: use it in pneumatic cylinders). A pneumatic cylinder weighing 20 pounds and running full pressure CO2 gas can produce over 70 horsepower for a split second, enough force and speed to propel another bot several feet into the air (such as the case with Toro, T-minus, and The Matador). Compressed gas can also be used to store energy in puncture weapon linearly (a spear such as Rammstein) or angurally (a hammer/spike such as Killerhurtz).