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BATTERY COMPATABILITY: Why is it critical to specify purpose-built battery packs for firefighting PPV fans?

Since we launched the original RAMFAN EX50Li in 2017, we’ve been writing a story that has never been written before in the firefighting industry. From a clean sheet design, we mapped out what basic requirements would be necessary to integrate into our fan design.

Some were easy: Compact dimensions, lightweight, 15+ year useful life as our loyal users have come to expect, shroud integrated lighting and rehab misters to ensure max performance without extra stuff to store, etc. Basic fan design check boxes that we’ve learned over the last 50 years.

Others required a deeper questioning of the application: How, specifically, do firefighters use PPV fans? Average runtime of a tactical vent operation? How much power does a fan need to have for most scenarios? How much battery capacity does a fan need to deliver this power for a reasonable amount of time without having to rely on an extension cord? How will they charge batteries? Where/when will they do it? Are there batteries available to buy that are suitable for the application—or must we develop our own?

As it turns out, the answers to these tough questions led us down a path where there were very few resources available. So…we developed our team to include some of the most knowledgeable electronic engineers in the entire industry, and we set out to either find the answers to our questions—or if that fails, to develop our own solutions. And now, we’re on a path of innovation that is redefining the boundaries of what is possible with cordless tools.

 

Power Requirements.

We’ve been building fans for firefighting since the 1980s—from developing the ultra-high-pressure shipboard desmoking fan for the US Navy to today’s industry-leading battery-powered PPV fans. Throughout this time, we’ve learned from firefighters around the world that most ventilation tactics require between 12,000 cfm – 20,000 cfm (20.400 – 34.000 m3/hr)—as tested per AMCA 240 standards. To produce this much airflow, fans require more than 1.5 hp (1.1 kW). Early generation battery PPV fans were all less than 1 hp (0.75 kW), primarily due to the lack of available motors and supporting electronics in this size range. For the EX150Li, we developed a 1.9 hp (1.4 kW) brushless motor and controller package to meet the challenge.

Heat Management

Perhaps the most critically important factor of developing a battery-powered tool is ensuring the battery is designed to remain safe throughout the performance envelope of the intended application. When pushing 1.9 hp, or even 0.9 hp in the smaller EX50Li, the current (measured in amps) required to maintain this power can be quite high—and is continuously high throughout the 30-45 minutes of expected runtime. Some measures must be designed into the packs to maintain a margin of safety.

In the battery world, it is well known that high discharge currents (amps) result in heat. For short runtime applications like rescue tools (<30s) or power tools (<5s) there is very little time to develop any heat, so battery packs do not necessarily need to be designed to handle, or even measure, internal heat levels.

Well, as most firefighters should know from recently popular EV (electric vehicle) fire suppression training, lithium-ion batteries are little cans of chemistry…and they don’t play well with high heat. Even worse, if they do ignite its nearly impossible to extinguish due to their internal fuel source, not needing additional oxygen to burn. In short, beware of battery packs that are used outside of their designed heat range.

Both the R2 and M1 series battery packs from RAMFAN have several heat management features that are very important to understand.

  1. Battery cells are specified for 35A maximum continuous discharge current (per cell) to ensure a high margin of safety. This is one of the highest in the industry, and the Samsung 21700-40T is known to be simply the best available, with Very High Capacity and Ultra-High discharge capabilities.
  2. Every pack we build includes multiple thermistors (digital temperature sensors) throughout the pack to monitor real-time temperature of cells during operations.
  3. Our proprietary BMS (battery management system) is designed specifically for the fan in which it will be installed—including the high power, high discharge and sustained runtimes that firefighters expect from it. The processor intakes data from multiple sensors throughout the pack—reading temperature of cells, current (A), and voltage—and processes hundreds of times per second to ensure the battery pack stays within a predefined “safe zone.”
  4. Our hard-anodized aluminum housing is not just for durability. It is an active 360o heatsink which is constantly pulling heat from inside the pack to equalize with ambient temperature.

Lots goes into the design of our packs, so that our customers do not need to worry about the safety aspect of their own equipment. Beware of manufacturers that use packs built for other applications, as they may not be designed for the realities of PPV fan deployment.