KNW-127
Battery Selection and Battery Safety
By Earl Pack – AE5PA
(Written 12/16/2013; Updated 1 Jan 2020)
updated 04 Aug 2025 and Mar 2026 by Paul Smith (K5PRS)
to update chemistries
Good Evening, fellow ARES members. Today we discuss battery selection and battery safety for amateur radio emergency communications. Reliable power is essential for keeping communications active when commercial systems fail. We will examine common battery types, highlight new technologies useful for field operations, review selection guidelines, and cover critical safety procedures.
Amateur radio operators work with many battery types. Each chemistry has specific charging and safe-use requirements. Charging details and chargers vary so check charging instructions carefully. Lead-acid batteries remain common in emergency service due to their high capacity and low cost, making them suitable for long-term communications and home backup power for radios and DC lighting. Newer battery chemistries are changing these preferences by offering better performance in portable and field deployments.
The most common battery types include alkaline, nickel-based (nickel-cadmium and nickel-metal-hydride), lead-acid, lithium-ion, and lithium iron phosphate (LiFePO4).
Which Battery to Use
AA-size non-rechargeable alkaline and rechargeable nickel-based batteries are the most common for handheld transceivers. They are also available in AAA, C, D, and 9-volt sizes. These provide a readily available emergency power source with good shelf life that can be purchased almost anywhere.
Nickel-based batteries, such as nickel-cadmium, deliver several hundred charge-discharge cycles. Although more expensive initially, they become cost-effective over time and perform well in field use when solar panels or other recharging sources are available.
Plain lead-acid batteries supply large amounts of instant energy and are standard in automobiles. They are heavy, however, which limits their suitability for field deployment. Deep discharging quickly damages them, so a generator or other charging source is often necessary for extended operations.
Lithium batteries are smaller, lighter, and offer the highest power capacity for their size. They power handheld transceivers, GPS units, and cell phones. Lithium batteries also provide the longest idle lifespan of any current chemistry.
Deep-cycle lead-acid batteries, often called marine batteries, deliver longer-term energy before voltage drops and support hundreds of discharge cycles when properly maintained.
Variations of lead-acid batteries include wet-cell (flooded), gel-cell, and absorbed glass mat (AGM). Gel-cell and AGM batteries cost more than flooded types but are lighter for equivalent capacity, produce less explosive hydrogen gas, and cannot spill acid. They are safer but they require special chargers. AGM batteries are particularly versatile for standby power because they hold a charge longer, offer greater lifespan, and tolerate many charge cycles. Deep-cycle AGM batteries that are not discharged below 60 percent can last for hundreds of cycles.
New Battery Technologies for Ham Radio Field Use
LiFePO4 batteries deserve strong consideration as a replacement for heavy lead-acid batteries in field and emergency kits. These batteries provide several key advantages:
- Longer lifespan, typically 2,000 to 5,000 charge cycles
- Higher efficiency, with 90 to 95 percent round-trip efficiency for more usable power
- Greater safety, with reduced risk of thermal runaway compared to other lithium chemistries
- Significantly lighter weight for the same energy capacity
- High power density with minimal voltage drop under load
- Faster charging, which benefits field operations
- Wide operating temperature range, typically from -20°C to 60°C (note that charging below freezing requires care)
A built-in battery management system (BMS) adds to the cost but protects the battery and enhances safety. For most ARES deployments or extended grid down emergencies, the advantages outweigh the higher initial price.
Emerging technologies to watch include lithium manganese iron phosphate (LMFP), which offers improved energy density while retaining the safety and longevity of LiFePO4. Sodium-ion batteries are gaining attention for their lower cost, excellent safety profile, and strong performance in extreme cold. Although currently better suited for stationary storage, sodium-ion options are becoming viable for certain portable applications as energy density improves. Solid-state batteries promise even higher safety and energy density but remain largely in prototype stages for widespread ham radio use in 2026. Something to keep an eye on.
Buy the battery with the greatest reserve capacity or amp-hour (Ah) rating possible, balanced against cost, weight, and size constraints. Nickel-based and lithium packs, along with deep-cycle batteries, usually list an Ah rating. A 50 Ah battery can theoretically deliver 5 amps for 10 hours or 10 amps for 5 hours. For a radio drawing 50 watts at 12 volts, the current is approximately 4.17 amps, so a 50 Ah battery could support about 12 hours at 100 percent duty cycle (though your radio probably can’t). Actual runtime is shorter with lead-acid batteries due to inefficiency, age, temperature, and recommended depth of discharge.
Practical Hints for Extending Battery Life
The longer a battery sits without recharging, the greater the potential damage. In extreme heat or cold, even 24 hours can be too long, so store batteries properly. Auto batteries experience temperature extremes, so run vehicles periodically to keep them healthy. Keeping auto batteries on a constant trickle charge is ideal for battery health.
Recharge batteries immediately after use and maintain them with managed trickle chargers. Follow manufacturer recommendations carefully for nickel-based and lithium batteries.
Avoid deep discharges with plain lead-acid batteries, as repeated deep cycling shortens their life. When powering a radio from a vehicle battery for extended periods, use a timer and periodically start the engine to recharge it. For long stationary assignments, employ a separate deep-cycle battery to preserve the vehicle’s starting battery. If no solar charger is available, jump the batteries periodically and keep both topped off. Trust me, it is no fun finding that your battery won’t start your vehicle at the end of a remote, 8 hour shift.
Undercharging causes sulfation and damages lead-acid batteries. Avoid operating batteries in temperatures above 100°F or below 32°F. Use the correct charger for each chemistry—gel-cell and LiFePO4 require specialized chargers. Be aware of small constant power drains in handheld transceivers and GPS units even when turned off; store batteries separately from devices. Fully discharged alkaline batteries can leak corrosive acid—never leave them installed in equipment.
Safety Tips
Never store batteries in a bag or pocket with metal objects, as shorts can cause fires. This risk is especially high with 9-volt batteries that have exposed contacts. Tape over the connectors or use a snap on connector from which the wires have been clipped. Never dispose of batteries in fire, as most will explode. Do not overcharge lithium batteries—always use the proper controlled charger. Install fuses as close to the battery as possible to protect wiring from shorts.
Specific Safety Tips for Lead-Acid Batteries
Lead-acid batteries can deliver up to 800 amps of instant current, enough to cause severe burns or death. Remove all jewelry when working near them. Shorting terminals can blow a post off the battery with force comparable to a bullet. Wear safety goggles—acid in the eyes requires immediate flushing with water for 30 minutes and prompt medical attention. Wash acid from skin immediately. Battery fumes are explosive, so keep sparks and flames away and provide proper ventilation during charging.
When connecting to a vehicle, attach the positive lead first and the ground last to minimize sparking. Disconnect the ground first. Never make live connections with the load turned on. Keep children away. Use proper lifting techniques, as these batteries are heavy. Avoid using long metallic tools that could bridge terminals. Protect the battery top so equipment cannot fall across the posts.
A properly selected, maintained, and charged battery is a reliable source of power for home emergency or field communications. Every ARES member should maintain at least one suitable battery, along with necessary cables, jumpers, and chargers, in their radio go-kit.
Battery technologies continue to evolve rapidly. LiFePO4 has already transformed field operations by reducing weight and increasing runtime, while newer options like LMFP and sodium-ion promise even better performance in the coming years.
After all, in the middle of a prolonged activation, the last thing you want is your battery quitting before the storm does. And remember, a well-charged battery is like a good net control operator—it keeps everything running smoothly when the conditions get tough.
Batteries are constantly being improved and new chemistries are routinely coming into common use. If you become aware of new battery technologies that need to be incorporated into this training, please let me know (Paul Smith, k5prs, k5prs@aol.com)
That is the end of tonight’s training. Are there any comments, questions or suggested additions?
Thanks, this is (callsign) clear to net control.
Send corrections, modifications, updates or suggestions to k5prs@aol.com