By Robert Avsec for FireRescue1 BrandFocus
Fire departments are always looking for power equipment that’s lighter, takes up less compartment space on its fire apparatus and more ergonomic (i.e., less of a physiological stress on the firefighter carry it and using it). With the introduction of lithium-ion (Li-ion) battery packs capable of powering those tools (e.g., saws, hydraulic rescue tools and fans/blower) manufacturers have successfully addressed those desires. It’s no wonder that Li-ion battery packs have become the portable energy storage of choice for fire departments around the globe.
But that popularity has come with a cost. Fire departments that have gone the “Li-ion route” to power their portable equipment have experienced a significant increase in their operating budget; some larger departments have seen their investment in Li-ion battery pack exceed $100K. With many fire departments now moving into their second generation of Li-ion-powered tools, the leaders of those departments have a growing concern: How to increase their ROI (return on investment) for Li-ion battery packs?
Many of those fire department leaders are growing uncomfortable with a paradigm where Li-ion batteries have been viewed as consumable items. Increasingly, fire department leaders have a desire to understand Li-ion batteries better, use them smarter, and dispose of them safely when that time comes.
A Quick Primer on Li-ion Batteries
Many people think that a higher voltage means more power and that’s not the case. Power is measured in watts (W), and watts are calculated by multiplying voltage (V) by the current (amps or A). So, while It’s feasible to get the same power from say an 18V battery and a 54V battery, the 54V pack can do it with 2/3 fewer amps than the smaller 18V pack.
Now power is nice, but firefighters are more interested in how long a battery pack will power the tool they’re using (i.e., run-time). For that, firefighters need to understand that runtime equals watt-hours: How many watts a battery can deliver for one hour? To calculate watt-hours, multiply the voltage (V) by the rated amp-hours (Ah) of the pack.
The typical Li-ion battery pack is constructed using several cylindrical cells, similar in shape to the AA batteries in your TV remote, but the similarity ends there. An Li-ion battery pack is not only much larger, it packs a Li-ion “chemical cocktail” that supply a greater energy density, unlike the low energy density, but cheap, alkaline battery that you buy for that TV remote.
Battery cells are not perfectly identical production machines, think of them as “chemistry in a can.” Manufacturers of Li-ion battery cells use the term nominal to describe an industry standard they use to rate the approximate mid-point voltage of their batteries (i.e., essentially, the average rating of the cells produced with a certain chemistry). Generally, all commonly used Li-ion battery cells have a nominal voltage of 3.6V. There are many options, beyond voltage, for cells with different amp-hour ratings. And there are different maximum discharge current ratings, depending on how long a manufacturer wants the battery to last on a specific tool and how fast the battery pack can use its energy (i.e., higher power) during a tool’s operation.
Manufacturers of Li-ion battery packs get increased cell voltage by assembling several individual cells in series. To get the voltage for such a battery pack, you multiply the individual cell voltage (3.6V nominal) by the number of cells in series. For example, a 10S battery pack configuration ─ ten cells in series ─ becomes a 36V battery (ten cells times 3.6V per cell). To increase amp-hours (Ah), a battery pack assembler will connect cells ─ or a series of cells ─ in parallel to achieve their run-time targets. For example, for a 2P (2 cells in series) configuration, using 4.0 Ah cells, results in an 8.0 Ah battery pack (Two cells times 4.0 Ah/cell equals 8.0 Ah).
Power Equals Heat
With the increased use of Li-ion battery packs to power tools, it is well known in the battery world that high discharge currents (amps) result in heat. For short runtime applications like hydraulic rescue tools (typically short burst < 30 seconds) or power tools (e.g., drills or saws for < 10 seconds) there is little time to develop much heat, so battery packs do not necessarily need to be designed to manage, or even measure, internal heat levels.
Most firefighters should know, based recent fire incidents involving electric vehicles (EV) and fire suppression training for EVs, that Li-ion batteries don’t “play well” with high heat. When they do ignite it’s nearly impossible to extinguish due to their internal fuel source (lithium does not needing additional oxygen to burn). Firefighters should avoid using any Li-ion battery pack outside of its designed heat range.
Avoiding Heat Buildup with Li-ion Battery Packs
The best way for firefighters to avoid heat build-up problems with Li-ion battery packs is to ensure that they only use the battery pack that was designed by the manufacturer for the tool they are using. To emphasize this point, let’s look at the difference in power requirements between a hydraulic rescue tool and a PPV fan/blower.
Typical vehicle extrication consists of a series of cuts and spreads, often shared amongst two to three tools ─ each with its own operational specialty (e.g., cutter and spreaders). This means that the electrical load is “shared” across the battery packs of the tools in use, each of which might only be engaged for less than 30 seconds at a time (Cut pillar. Cut hinge. Place cutter down. Grab spreader. Proceed to roll dash forward). When each tool is being used, the battery packs in those other tools have the chance to cool.
A Li-ion battery pack, even if maximizing its discharge capacity, does not develop enough heat to worry about in 30 seconds ─ assuming the manufacturer has designed a battery management system that regulates the maximum discharge current to within the safe limits of the specific battery cell model used in their pack.
After turning on a PPV fan/blower, however, a firefighter expects it to run at full speed for at least 30 minutes (1,800 seconds, or 60 times longer than a typical rescue tool operation). Not only that, but to move more than 12,000 cfm (20.000 m3/hr.), a PPV fan/blower needs about 2 hp (1.4 kW). To deliver this much power for the expected runtime from a rescue tool’s 176 Wh battery pack, a PPV fan would require five of these packs to hit the mark. This difference in operational run-time is where the major differences exist between the Li-ion battery packs used for a hydraulic rescue tool and a PPV fan/blower.
Improving Your Fire Department’s ROI for Li-ion Battery Packs
RAMFAN has been building fans for firefighting since the 1980s ─ first developing the ultra-high-pressure shipboard “desmoking” fan for the U.S. Navy ─ and is now today’s industry-leading manufacturer of battery-powered PPV fans/blowers for the fire service. With that experience, RAMFAN has developed the PRO Connect, better battery management system (BMS) for the Li-Ion battery packs used in its products.
Using RAMFAN’s proprietary wireless connectivity technology, PRO//connect simplifies the lifecycle management of Li-ion battery packs for its next-generation of firefighting tools using the latest near-field communication (NFC) and Bluetooth low energy (BLE) technology. PRO Connect gives firefighters the ability to track the condition of their battery packs over time, measure internal conditions, track cycle counts, upgrade BMS firmware, troubleshoot problems, and even conduct basic maintenance of their battery packs.
All RAMFAN battery packs will be equipped, as standard spec, with PRO//connect hardware integrated into the packs and will work with the PRO//connect mobile application—available in both iOS and Android versions.
