Description of the Project:
Mount solar panels on the Black Mountain Interagency Hotshot Crew Vehicles to
demonstrate feasibility of using rechargeable batteries during operational periods and to
reduce usage of disposable AA batteries. For a full technical description please refer to
the proposal document.
Hotshots are extremely mobile crews that use their vehicles as a home base they do not
have the luxury of being able to drop a battery into a wall charger each night in order to
avoid using disposable batteries. We have designed a system that will allow them to use
rechargeable batteries to power their radios as well as provide other safety and waste
reduction benefits. The system will pay for itself in only one season using rechargeable
batteries versus the cost of AA batteries.
Implementation Process:
Procurement of the solar panels and installation was accomplished prior to the Hotshots
leaving for their first off forest tour. Jim Shepherd supervised the installation of the
charge controllers and the solar panels with the assistance of several of the permanent
hotshots. The mounts for the panels were fabricated to prevent overheating the panels
and shortening their lifespan as they are mounted just above the AC units over the cab
(see photo1 and 2). The solar panels procured provide a rated 40 watts at 12v to the main
vehicle batteries through a charge controller whenever there is full or partial sunlight.
The Hotshots reported that this part of the system has worked flawlessly for the entire
summer.
There were several setbacks with the chargers in procurement and function. We received
one of the 12 volt, 6 bay, gang chargers for the radio batteries, quite quickly after
contacting RELM wireless (see photo 4). They informed us that this was a unit not
available to the general public as it is still in engineering development (this may have
changed in the intervening year). We tested the unit thoroughly in the radio shop for off
line power drain and also for charging draw before install. The unit seemed to perform
well, so we proceeded with the install in the crew vehicle and the order of the second
gang charger. Several weeks after the install the Hotshots reported multiple fuse failures
seeming to originate with the radio battery charger. Upon investigation it was found that
the strain relief on the 12v power cord for the RELM charger was not sufficient and had
caused a short in the cable (see photo 5). Jim Shepherd fixed the short and designed an
improved strain relief that has worked well for the rest of the season and eliminated the
fuse failures (see photo 6). We provided feedback to RELM Sales on this strain relief
problem, but are following up with their R&D department (pictures etc.) to make sure
they rectify the problem before production.
The most significant setback in full implementation of the project was the long delay
between ordering and receiving the second 12v radio battery gang charger. The order
was placed in April and the unit was not received until around the 15th of September.
There seems to have been some communication breakdown between our verbal order and
several follow up emails with the RELM Sales Department and getting the unit built,
tested and shipped to us by their Research and Development Department. Once received
the charger it was installed on the second crew vehicle to complete implementation.
Costs to date:
The following are the expenditures
- $1029.60 Two 12v six bay radio battery gang chargers
- $492.80 Two 40W solar panels
- $83.00 Two 12v solar panel charge controllers
- H-T contribution
o 8 hours of install time and 2 hours admin time
o 10 rechargeable radio batteries
Benefits realized to date/ projected benefits:
The crew members on the Black Mountain Hotshots report that they have been using
rechargeable batteries. They have not been able to fully make the switch because of
being short one 12V gang charger. The second charger was delivered late in the fire
season so now they can start next year’s season using rechargeable batteries nearly
exclusively. There was also a problem for a portion of the season with the first charger.
The strain relief on the power supply cord was not sufficient, resulting in a short in the
cord and blown fuses. With some diagnostics the problem was found and corrected in
house at the H-T radio shop. The insufficient strain relief was reinforced with a heavy
duty solution with hot-glue and heat shrink (see photo 6). This solution seems to have
work very well and when the second unit came in we preempted the problem before
sending the charger unit out to the field.
The hotshot crew expressed interest in the possibility of using lighter weight, longer
lasting and smaller lithium batteries that have become available. These batteries also
have the benefit of no memory effects from charging at any phase of use. As the prices
come down this battery technology would be ideal for the fast-and-light nature of Hotshot
operations (see photo 3). These batteries weigh one third less than the AA clamshells
that all hotshots have been carrying to date. Another of the other great benefits of this
type of battery is the dramatically increased battery life. One 3800mAh lithium battery
could last for up to two weeks based on average usage and about a week on heavy usage!
I believe that Black Mountain will be trying out several of these batteries this year.
Before this solution even evaluating the batteries was not possible.
One other benefit that has been seen is the system’s capability to maintain the charge on
the crew vehicles main batteries. Each vehicle has multiple deep-cycle heavy duty
batteries for starting the engines and running the onboard equipment. Like any vehicle
these batteries are normally charged with the engine driving an alternator which produces
the DC voltage that is required. When the vehicles don’t run for a significant period of
time… as in the off season there is a possibility of discharging these main batteries fully
and ruining their capacity to hold a charge. The source of this discharge is the myriad of
small electronics and computers included in all modern vehicles that draw a slight charge
whether the vehicle is operating or not. Upon receiving from the manufacturer the crew
vehicle they had this problem with their main batteries, i.e. they were inoperable. As I
understand it during the time that the vehicles sat for their first winter they also had
battery problems. Since the vehicles have been fitted with our solar system that
maintains the batteries there has been no further trouble. In fact this spring as they were
taken out of mothballs they fired right up. This result in and of itself gives a large
environmental benefit, (not having to dispose of those large lead acid batteries). This
technology also provides another margin of safety for the crews since the vehicle
batteries are kept always at an optimal charge with solar energy even if they are away
from their vehicles for multiple days.
One of the things that we haven’t been able to accomplish is dissemination of our project
by MTDC Tech Tips. We have not heard back from them even though we made a
submission during their annual call for projects. We have and are following up with
other contacts in the “Greening the Forest Service” movement to try and get some
publication of the project. Even though we have not been able to get published, word of
mouth in the Hotshot community is heating up. We have responded to five or six
requests for descriptions of the project and suspect that many more Shot crews will be
interested this year as they see our solar panels and talk to those who know about the
project.
One of the possible improvements to this system to improve it’s portability to other
mobile firefighting platforms is creating several sizes of 12V gang chargers. Engines of a
variety of sizes that carry three to five firefighters could use a 2 and/or 4 bay variant of
our gang charger. Also the Hotshot Superintendent or similar vehicles that carry several
passengers could use a 2 bay gang charger. There is currently on the market a single bay
12V charger for mobile applications for vehicles and crews that only need that
functionality. Also a variety of solar panels are available for these various applications
which are relatively inexpensive and would provide all of the functionality described in
our application to Hotshot crew vehicles. Another improvement for reducing the impact
of alkaline AA waste is to think about switching the “backup” clamshell to long-life,
long-storage, and lightweight lithium AA’s that are readily available in the consumer
market. These batteries, when used as a back-up could last for a whole season or even
longer and reduce the need to throw away so many alkaline AA’s.
Many thanks to the Region 4 “Green Micro Gant” team who evaluated our project and
felt it merited funding. We hope these results will spur a change in the firefighting radio
users to try out using rechargeable batteries both at their home units and on incidents.
There is significant trepidation by some to make the switch, but it is easier on the
environment and… you can always carry a back-up clamshell with AA batteries.
Source: DOI