Specifications
solution. These typically cost between $50 and $120 and are available in sizes from 40 amp-
hours to 120 amp-hours. Be sure to use a deep-cycle battery as regular lead-acid batteries are
not designed for discharge on a regular basis. For field battery capacity up to 2880 watt-hours,
the lowest cost solution is to use two 6 volt golf car batteries. These typically cost about $140
for a pair and are rated at 6 volts and 220 amp-hours. The Exide E3600 is one readily avail-
able battery of this type.
Note: the higher capacity batteries can weigh up to 70 pounds. For example, Exide E3600
weighs 62 pounds. If anticipate problems moving batteries of this weight, then you may choose
to use multiple smaller batteries instead.
I do not recommend connecting field batteries in parallel. If you accidentally connect the batter-
ies incorrectly, it can result in an explosion which will spray sulfuric acid over a wide area. It is
safe to connect them in series, however, as a reversed battery will only result in less voltage at
the output.
7.4.5. Field battery charger (optional)
Most high-end battery chargers will also charge a lead-acid battery. Some examples of this are
the Great Planes Triton, the Schulzes, and the Orbits. The charge rate is usually limited to
about 5 amps on these chargers, so they will take a long time to charge high-capacity field bat-
teries.
A better choice is to use a dedicated lead-acid battery charger. Be sure to select a good quality
battery charger which includes an automatic cutoff feature. These battery chargers will avoid
overcharging and "boiling" your battery and subsequently causing early battery failure.
Vector Manufacturing makes good battery chargers for this purpose. They use switching power
supplies, digital voltage readouts, and a multi-stage charging algorithm for faster charging. The
VEC1088 will charge at up to 12 amps, and the VEC1092 will charge at up to 35 amps.
7.4.6. Portable generator (optional)
If you fly larger helis, you may want to use a portable generator instead of a field battery and a
field battery charger.
Honda manufactures a line of very quiet generators which are ideal for use at flying fields. The
Honda EU1000i uses a four-stroke engine, is rated for 1000 watts of AC output, has a noise
level of only 53-59 dB and will run from 4-8 hours on a single tank. The older discontinued
Honda EX350 and EX650 are also good choices for a portable generator if you can find one.
These use two-stroke engines so oil will need to be mixed with the gasoline. These generators
output a square wave instead of a sine wave, so some equipment may not work well with it. Be
sure to test before you buy one.
Yamaha manufactures the EF1000iS which is rated for 1000 watts of output, and is also a very
quiet (47-57db) generator.
The 12 volt output of most portable generators is very weak, so the AC output should always
be used for charging batteries. Portable generators should be run at least 30 minutes a month
to keep the generator properly lubricated internally.
7.5. Electronic instruments
7.5.1. Digital voltmeter
A DVM is very useful for monitoring the voltage of the battery packs. If you are having trouble
Support Equipment
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