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battery-powered machines, and that includes
everything from cell phones and laptops to
automobiles and aircraft.
But high energy-density storage is
intrinsically dangerous, and pushing
the envelope too far or too fast can lead
to unintended consequences. As Boeing
recently learned with their 787 Dreamliner,
an oversight in battery design can put users on the
sidelines rather than in the action. When the planes’ high-
tech, high-efficiency lithium-ion batteries started shorting out
and causing fires, the Federal Aviation Administration (FAA)
promptly grounded the Dreamliners. Despite this recent bad
press, lithium-ion batteries offer advantages. They have a high
power-to-weight ratio, can charge more quickly and offer more
desirable cycling characteristics.
While at least one DPV manufacturer has made the leap to
lithium-ion batteries, most use conventional sealed lead-acid
batteries, which are fairly reliable but still carry some risk.
During the charging process, hydrogen gas is generated as a
byproduct, and it can accumulate in explosive concentrations.
To counter that issue, a catalytic element is generally added; it
combines atmospheric oxygen with the hydrogen before the
concentrations reach dangerous levels. However, incidents have
occurred in which systems failed and explosions resulted. To
avoid such situations, divers must observe proper precautions
for maintenance and operation of DPVs.
Performance Points
When comparing DPVs, many aspects of performance should
be considered. Start with the overall quality of construction.
Depth ratings are a sign of robust design, but pay attention to
bearings and seals, as these contribute directly to reliability.
Most DPVs have multiple speed settings, which helps
conserve battery power and increase utility.
Overall weight and buoyancy are also important. Most DPVs
weigh between 20 and 40 pounds, with higher performance
models being heavier. Instrumentation such as depth alarms
and battery-power meters can help divers maintain a margin of
safety in their dive operations. High on the list of desired
characteristics should be ease of maintenance, charging time
and availability of parts. Also keep an eye out for accessories
such as lights and variable-buoyancy systems.
The Training Trap
One of the keys to safe scooter diving is proper training. It
might be tempting to think that little real training is actually
needed — that operation is simply a matter of point, pull and
party. In reality, a DPV adds a whole new set of potential risks
to diving activities. First among these is the potential for rapid
ascents and descents, with the attendant risks of decompression
illness and barotraumas. It can be difficult to make needed
buoyancy adjustments while scootering, and so unintended
separation from the DPV could leave a diver in a seriously
over- or under-buoyant condition, leading to excursions to
unintended depths. Furthermore, because DPVs allow divers
to travel so much farther in the brief timespan of a dive, a
mechanical failure or human error could leave a diver stranded
far from the planned exit point. This is a particularly significant
consideration for cave divers.
Among the challenges that come with DPVs is maintaining
buddy contact between divers (zipping around doing barrel
rolls can be absorbing), so resist the tendency to get separated.
There are also the aforementioned hazards associated with
routine maintenance (i.e., battery charging), which means
established protocols must be followed to minimize the risk of
explosion. So before you grab the horns and wrestle the aquatic
mechanical bull into the bay, take some specialty training to get
a handle on the basics of safe operation and maintenance.
Diver propulsion vehicles can seriously redefine fun and
performance in our underwater world, but with heightened
performance comes heightened risks. With the right knowledge
and training, we can sidestep the risks and enjoy the ride. AD
For divers willing to spend some money, get a little training and properly maintain the device,
a DPV offers an extended range and serious underwater fun.
STEPHEN FRINK
FRANKLIN VIOLA/COURTESY DIVETECH