Fully Charged

Battery power comes to the Fire Service, but gaps still exist on the way to full adoption.

For the better part of a decade, we’ve all become acutely aware that CO-emissions have been linked to increasing cancer rates among first responders. The combination of this realization and the advance of energy storage into the realm of affordability has allowed firefighting equipment and vehicle manufacturers to integrate lithium batteries into the tools and trucks that we rely on to get the job done.

As more equipment types are made available with battery-electric power, a new challenge is on the horizon—charging these increasingly powerful tools quickly enough to get us back in service for the next call. When thinking of charging, whether its rescue tools, fans, flashlights, or entire trucks, we need to simplify down to the common denominator—electrical power consumption measured in Wh.

Largest Consumers

The truck itself is obviously the largest power consumer in your kit. The Pierce Paccar MX-13, for example, is 510 hp—or 386 kW. This would require a battery pack 4 times larger than a Tesla—just to run for one hour at full power. To complicate things, the North American fire service preference for custom chassis apparatus will make this a challenge as it is quite expensive to develop an electrified chassis. Expect partnerships with third-party battery manufacturers or a move towards commercial chassis from builders such as Tesla, Nikola, Daimler, etc. Rosenbauer’s RT is available ($1.2m for a small pumper) and claims impressive specs, including the ability to charge itself with an on-board diesel engine as well as up to 18 kW of output to external power consumers (i.e. high powered fans, etc.).

Needless to say, despite the cool tech coming out from our European brothers and sisters, it will take a few more years yet to get a reasonable solution to full electrification of the fire apparatus. Until then, hybrid systems employing onboard lithium battery banks for powering all systems without belching CO out the back and small ultra-low-emission generators for continuous charging capabilities when remaining energy levels exceed minimums. These capabilities can be achieved now with an appropriately specified apparatus using one or more lithium batteries together with an inverter and charger. If using any more than 100 Ah of lithium, an onboard charging generator is recommended to achieve full charge before your next call. Your 120V 15A shore power is only delivering 1.8 kW—which would charge a Tesla in 56 hours or a single 200 Ah lithium battery in 1.5 hours from empty, neither of which is acceptable when your next call may happen in the next few minutes.

The largest power consumers on the truck, other than the truck itself, are PPV fans. The larger output models are typically gasoline-powered, but with an eye on eliminating carcinogenic CO emissions from the fire ground these will need to be supported—electrically—by the apparatus if high volume airflow capabilities are to be maintained as a tactical tool. The ability to support high power equipment, such as a 18-24” PPV fans with equivalent airflow to today’s gas-powered models, while still hitting CO elimination targets will require a complete apparatus design consideration to become a platform rather than a simple, drivable toolbox. This will mean lots of lithium onboard the apparatus with high output inverters—capable of at least 115V/240V output, or higher voltage 3-phase, to get the current down to a reasonable level so as not to require large diameter cable runs. A compact generator, as small as 2-cylinder 3 kW, can be sufficient to work as a dedicated charging solution to refuel the lithium banks on an extended operation or en-route back to the station for when peak alternator output time is insufficient to full recharge the batteries.

Other large consumption onboard systems that require near full-time operation include air-conditioners, clean cab filtration, and a variety of tool chargers. Obviously, if you want to go CO-free the a/c cannot be belt driven. The smallest electric air conditioners on the market consume about 2 kW at max power. Add that to the several battery chargers you have on board for rescue tools, PPV fans, and power tools, and you’ll run through a single 200 Ah lithium battery in about 30 minutes. Energy consumption adds up quick when you start paying attention to the electrical efficiency of every item on board your apparatus.

Zero Downtime

As first responders, we don’t always get the luxury of waiting for battery tools to recharge before we use them again. The concept of “Zero Downtime” may be new to those in departments that have yet to deploy battery-powered equipment, but you’ll soon learn that battery charge time is critical and not all batteries, or chargers, are created equal. With gas-powered hydraulic rescue tool power units or PPV fans, refueling takes all of 30 seconds. After a full use of a high-powered battery tool, time to charge can take 2-6+ hours, depending on the battery size, charge current, and whether or not on-tool charging exists. The best solution to maintain Zero Downtime across your equipment fleet is to select equipment with swappable battery packs. This does require extra batteries, but the equipment can be back in service within seconds instead of hours.

Many departments are adopting battery-powered equipment without fully considering the infrastructure required to achieve Zero Downtime.

When are the chargers active?

On shore power.

This could take more than 6 hours to recharge, once plugged in.

On alternator power.

En route driving times are often insufficient to fully charge a battery.

Always active AC.

AC output from inverter, designed to remain active in the station, while en route, and on scene, is an ideal solution to maintain continuous battery charging capabilities for new-generation tools.

How much time is needed to charge?

MATH WARNING: Battery amp-hours divided by charging amps equals time to charge from empty.

Truck Battery: 200 Ah / 60 A = 3 hours

PPV fan: 8 Ah / 3 A = 2.7 hours

Rescue Tool: 7 Ah / 3.3 A = 2.2 hours

The Art of Generator Design

Many combustion generators in the North American fire apparatus market are designed for external output only. This means they are not setup for charging or powering internal systems, but setup to power outlets, extension cords, and maybe scene lighting.

The most efficient generator installation would be a fully integrated system, where the generator itself can be mounted anywhere, a remote-control panel used for operations, and it is wired to power chargers, inverters and outlets throughout the vehicle. Both DC and AC demand can be powered by the same generator if setup properly, and when a transfer switch is installed the AC power can seamlessly switch from on board to shore power automatically when plugged in back at the station.

Instead of sizing generators for directly connected full-time use while on-scene—most of which are fixed speed engines, can be loud and waste tons of fuel—consider a bank of lithium iron phosphate (LiFEPO4) batteries to supply silent, zero-emission electrical power through an inverter coupled with a compact, dedicated charging generator to recharge those batteries when they drop to a low voltage point. Inverters can be sized up to 12 kW, plenty to power an extended operation using multiple tools. Runtime will depend on how many batteries you have on board. Six lithium batteries will power 12 kW output for an entire hour of continuous load—which is quite unlikely as most tools are used intermittently.

Spec for Tomorrow

Fire departments who are planning to move towards battery-powered tools should deeply consider charge time as a key factor before jumping in. Charge times are not just a simple brand comparison, and often cross over into entire apparatus design. If 2-6 hours is too long to charge between calls, then better charging infrastructure onboard the apparatus may be a better solution.

Today, most battery-powered firefighting tools use batteries smaller than 200 Wh. The fastest chargers available will recharge 200 Wh in 2 hours or less. Tomorrow’s tools will be more powerful, requiring larger batteries for the same operational runtime.

• Charge times, by battery size:
  • 100 Wh: 1.0 hour (small power tool battery)
  • 200 Wh: 1.6 hours (rescue tool battery)
  • 300 Wh: 2.4 hours (PPV fan battery, <1hp)
  • 400 Wh: 3.2 hours (High performance PPV fan, > 1hp)
  • 500 Wh: 4.0 hours (Large output PPV fans, >2 hp)
  • 2000 Wh: 1.2 hours (single lithium truck battery, lead acid replacement)

Fire apparatus are expected to remain in service for 20 years. They should be designed, as much as possible, to support the electric tools that are expected to drop in the next decade—or risk early obsolescence and subpar performance of tools and tactics as technology evolves.

Departments have always been first movers in their communities to stay ahead of the evolving risks they may encounter—in industry, structure types, etc. A new threat to these departments needs to be prepared for, one which many have overlooked until now, in how to support their tools to maintain mission readiness while still checking the boxes of firefighter health and local community green agendas.