LiFePO4 Batteries for Ham Radio: Sizing, Charging, and Real-World Runtime

Lithium iron phosphate batteries changed portable ham radio. Before LiFePO4, we carried 20-pound sealed lead-acid batteries that gave maybe 60% of their rated capacity and died after 300 cycles. Now a 6-pound battery delivers 100% usable capacity for 2000+ cycles.

But there's a lot of confusion about sizing, charging, and what you actually need for a day of operating. I've used LiFePO4 packs for POTA, Field Day, and backup power for three years. Here's the practical stuff.

Why LiFePO4 Specifically

Lithium-ion comes in many chemistries. Why LiFePO4 for radio?

• Voltage match: A 4-cell LiFePO4 pack runs 12.8V nominal (13.2V full, 12.0V empty). That's almost exactly what 12V ham equipment expects. No voltage regulator needed.
• Flat discharge curve: Voltage stays between 13.2V and 12.8V for about 80% of discharge. Your radio sees consistent voltage throughout operation.
• Safety: LiFePO4 doesn't thermal runaway like LiPo/Li-ion. You can puncture one without fire. Important when it's bouncing around in a backpack or vehicle.
• Cycle life: 2000-5000 cycles to 80% capacity depending on brand. That's daily use for 5-10 years.
• Temperature tolerance: Discharges from about -20°C to 55-60°C, depending on the maker. Charging below 0°C damages cells unless the pack has low-temperature charge protection or heating — important caveat.

The only downsides: slightly lower energy density than lithium-ion (heavier per Ah) and higher initial cost. For ham radio use, neither matters enough to choose differently.

Sizing: How Many Amp-Hours Do You Need?

This is where people either massively overbuy or show up to a POTA activation with insufficient power.

The math:

Average current draw × hours of operation = amp-hours needed

Typical radio current draws (approximate, at 13.8V):

Mode Radio RX Current TX Current SSB 100W IC-7300, FT-891 1.5-2A 20-23A (peaks) SSB 50W IC-705, G90 0.5-1A 4-6A SSB 10W (QRP) IC-705, KX2 0.3-0.5A 2-3A FT8 100W Any 100W HF 1.5-2A 20A (constant during TX) FT8 10W QRP rigs 0.5A 2A VHF FM 50W Mobile rigs 0.5-1A 8-11A VHF FM 5W Handheld 0.1-0.3A 1.5-2A

Critical point: SSB is intermittent. You transmit maybe 30-40% of the time during a ragchew, less during a contest (unless you're running a frequency). FT8 at 100W is the battery killer — 15 seconds TX, 15 seconds RX, continuously. That averages about 11A sustained.

Example calculation — POTA activation, 2 hours, 100W SSB:

Assume 30% TX duty cycle:

• TX: 0.3 × 2 hours × 21A = 12.6 Ah
• RX: 0.7 × 2 hours × 1.8A = 2.5 Ah
• Total: ~15 Ah needed

A 20Ah LiFePO4 handles this with 25% margin. Comfortable.

Example — Field Day, 8 hours, 100W mixed SSB/FT8:

Assume 50% duty cycle (contest pace):

• Average current: ~11A
• 8 hours × 11A = 88 Ah needed

That's a big battery. Or two 50Ah packs in parallel. Or operate at lower power — 50W cuts TX current roughly in half.

My Recommendations by Use Case

Casual POTA/portable (2-4 hours, QRP-50W): 12-20Ah. Bioenno 12Ah or Dakota Lithium 18Ah. Fits in a backpack. Weighs 3-5 lbs.

Serious POTA/contest portable (4-8 hours, 100W): 30-50Ah. Bioenno 30Ah or SOK 30Ah. Needs its own bag but manageable. 8-12 lbs.

Field Day / Extended operation: 100Ah+ or multiple smaller packs. At this point consider a solar panel to supplement. A 100W solar panel on a sunny day can offset most of your consumption.

Home backup (when grid goes down): 100-200Ah. Keep the radio running for days at receive-mostly duty cycles. A 100Ah pack at pure receive (2A) lasts 50 hours.

Brands I've Actually Used

Bioenno Power: The ham radio battery company. They make packs specifically sized for our use cases. 3Ah to 100Ah+. Good BMS, consistent quality. Prices are premium — about $1.50-2.00 per Ah for smaller packs.

Dakota Lithium: 10Ah and 18Ah are popular for portable ops. Decent quality. Slightly cheaper than Bioenno.

SOK Battery: Good value for larger capacities (100Ah+). I run a SOK 100Ah for home backup. No complaints after 18 months.

Budget options (Ampere Time, Redodo, etc.): These work. I have a Redodo 20Ah mini that's been fine for a year. But the BMS quality varies. For critical applications (emergency backup), I'd spend more on a known brand.

I'll be honest — for packs under 30Ah, Bioenno's ham-specific sizing (with Anderson Powerpole connectors pre-installed) is worth the premium. For larger packs (100Ah home backup), the budget brands are fine.

Charging Best Practices

Voltage: Charge to 14.4V (3.6V per cell) for a full charge. Some people charge to 14.0V (3.5V/cell) for longer cycle life at the expense of about 10% capacity.

Charger: Use a charger specifically designed for LiFePO4. Do NOT use a lead-acid charger — the charge profile is wrong and can damage cells or trigger BMS shutdown. Float voltage for lead-acid (13.6-13.8V) is below LiFePO4 full charge voltage.

Good chargers: Bioenno dedicated chargers, Genasun GV-5 (also does solar MPPT), any charger explicitly marked for LiFePO4.

Temperature: NEVER charge below 0°C (32°F). This plates lithium metal on the anode and permanently damages the cell. Most good BMS units will refuse to charge below freezing, but don't rely on it — some cheap ones don't have this protection.

Discharging below freezing is fine. Capacity drops somewhat but no damage.

Storage: Store at 50-60% charge (about 13.2V). Not full, not empty. LiFePO4 self-discharge is very low — a stored pack loses maybe 2-3% per month. Check voltage every 3-6 months during long storage.

Solar Charging in the Field

A solar panel + MPPT charge controller extends your battery life dramatically for full-day operations.

My portable setup:

• 100W foldable panel (Bioenno or Renogy)
• Genasun GV-5 MPPT controller (optimized for LiFePO4)
• 20Ah LiFePO4 pack

On a sunny day, the 100W panel produces 5-7A for 4-6 hours. That's 20-40Ah of recharge — more than enough to offset a full day of 50W SSB operation. Even on cloudy days I get 2-3A, which covers receive current and some TX.

The panel doesn't need to fully charge the battery — it just needs to put back roughly what you're taking out. This extends a 20Ah pack from a 3-hour battery to an all-day power source.

Common Mistakes

Over-sizing. A 100Ah battery for a 2-hour POTA activation means you're carrying 20 lbs of battery you don't need. Match the battery to the actual use.

Ignoring the BMS. The Battery Management System is what protects the cells. Cheap packs sometimes have BMS that cuts output at 30A continuous — fine for QRP, not fine for 100W rigs that draw 23A on SSB peaks. Check BMS continuous discharge rating.

Series connection without matched cells. Don't put two 12V LiFePO4 packs in series for 24V without a BMS designed for the combined pack. Individual pack BMS units don't communicate and cells will drift.

Leaving connected when not in use. Your radio draws standby current even when "off" (many rigs draw 30-50mA for memory retention). Over months, this can deep-discharge a small pack. Disconnect when storing.

Expecting SLA behavior. LiFePO4 voltage doesn't correlate to SOC the same way lead-acid does. Between 13.2V and 12.8V you're somewhere between 20% and 90% full — you can't tell from voltage alone. A coulomb-counting battery monitor (Victron BMV-712 or similar) is the only accurate way to know your state of charge.

The Bottom Line

For most portable operators: a 20Ah LiFePO4 pack handles a half-day of operation at any power level. Add a solar panel for full-day autonomy. Keep a 100Ah pack at home for emergencies.

Total investment: $150-200 for a quality 20Ah portable pack. That's less than a decent antenna analyzer and arguably more useful for getting you on the air from anywhere.