If you own a YAESU FTA-450 or FTA-550 and the battery no longer lasts through a full day of aviation communication, the good news is that the radio itself may not need any major repair. One of the strongest design features of these radios is their replaceable battery system.
The original SBR-12LI battery provides 1,800mAh, while YAESU has subsequently replaced it with the higher-capacity SBR-39LI 2,200mAh lithium-ion battery. For owners looking to restore battery life, the SBR-39LI replacement battery is therefore one of the most practical upgrades to consider.
Short answer: the FTA-450 and FTA-550 are still highly serviceable aviation handheld radios, and battery replacement is unusually simple. The SBR-39LI battery offers a convenient way to replace an aging original battery without opening the radio.
YAESU FTA-450 vs. FTA-550: What’s the Difference?
The FTA-450 and FTA-550 share essentially the same battery architecture, so the main reason to choose one over the other is functionality rather than battery performance.
YAESU FTA-450
The FTA-450 is primarily designed for aviation VHF COM communication.
Its typical applications include:
- Air-to-ground communication
- Airport communication
- Pilot-to-ground communication
- Aviation-band monitoring
- 200 memory channels
- NOAA weather reception
It is a straightforward choice if your priority is reliable aviation communication.
YAESU FTA-550
The FTA-550 adds navigation-oriented functions to the FTA-450 platform.
It supports:
- VHF COM
- NAV reception
- VOR
- ILS
- 200 memory channels
- NOAA Weather
- A larger dot-matrix LCD
This makes the FTA-550 more attractive to pilots and aviation users who want navigation capabilities in addition to communication.
From a battery replacement perspective, however, the two radios are very similar.
Original Battery vs. SBR-39LI
The original battery associated with these radios is the YAESU SBR-12LI.
Its key specification is:
| Battery | Capacity | Chemistry |
|---|---|---|
| SBR-12LI | 1,800mAh | Li-ion |
| SBR-39LI | 2,200mAh | Li-ion |
YAESU’s documentation identifies the SBR-39LI as the replacement for the SBR-12LI.
That makes the SBR-39LI battery particularly interesting for owners of older FTA-450 and FTA-550 units.
You can check the SBR-39LI replacement battery when looking for a replacement for an aging original pack.
The capacity increase is approximately:
2,200 ÷ 1,800 ≈ 1.22
In other words, the nominal capacity is about 22% higher.
That does not mean real-world runtime will always increase by exactly 22%, because radio power consumption depends heavily on transmit time, receive time, scanning, display brightness, temperature, battery condition, and transmission power.
Nevertheless, the larger capacity gives the SBR-39LI more energy reserve than the original 1,800mAh pack.
YAESU FTA-450 / FTA-550 Battery Life
Battery life specifications for aviation radios should always be interpreted carefully.
YAESU’s published test condition uses a repeating duty cycle of:
- TX: 6 seconds
- RX: 6 seconds
- Standby: 48 seconds
This corresponds approximately to:
- 10% transmitting
- 10% receiving
- 80% standby
Under this type of test condition, the FTA-550/FTA-450L can achieve approximately 13.5 hours with a fully charged battery according to the manufacturer’s operating documentation.
That is a strong result for an aviation handheld.
However, 13.5 hours should not be interpreted as 13.5 hours of continuous transmission.
Aviation communication normally involves relatively short transmissions followed by periods of listening and standby. Therefore, the published figure is much more representative of normal aviation communication than a continuous-transmission test would be.
What Determines Real-World Battery Runtime?
Actual runtime varies considerably depending on how the radio is used.
| Usage | Relative Battery Consumption |
|---|---|
| Standby | Low |
| Occasional reception | Moderate |
| Scanning | Moderate |
| Long-duration reception | Higher |
| Frequent transmission | High |
| Continuous transmission | Very high |
For normal aviation communication, a healthy battery can provide excellent operating time.
For intensive two-way communication with frequent transmissions, however, the battery will drain considerably faster.
This is one reason replacing an old battery can make such a noticeable difference.
Why the SBR-39LI Is a Practical Replacement
The main advantage of the SBR-39LI battery is not simply the number printed on its label.
A replacement battery restores the radio’s energy reserve and eliminates many problems associated with an aging lithium-ion pack.
An old battery can develop:
- Reduced capacity
- Increased internal resistance
- Greater voltage sag
- Shorter operating time
- Unexpected shutdowns
- Poor transmit performance
A new SBR-39LI battery can therefore be considered both a capacity upgrade and a reliability-oriented maintenance item for an older FTA-450 or FTA-550.
The FTA-450 / FTA-550 Also Supports Six AA Batteries
One of the most useful design features of these YAESU radios is the optional SBT-12 alkaline battery tray.
The tray accepts:
6 × AA alkaline batteries
This provides an important backup power option.
Imagine arriving at an airport, preparing for a flight, or operating in an environment where charging facilities are unavailable. If the rechargeable battery is depleted, six fresh AA alkaline batteries can provide an alternative power source.
For aviation equipment, this kind of redundancy is valuable.
It means the rechargeable battery does not have to be the only power source you carry.
Important: Do Not Charge Ni-MH Batteries in the SBT-12
The SBT-12 should not be treated as a universal rechargeable-AA battery pack.
YAESU’s documentation warns against using rechargeable batteries in the alkaline battery tray because the tray does not provide the appropriate charging protection required for Ni-Cd or Ni-MH cells.
Therefore, do not install six Ni-MH AA cells and then connect the radio to its charger expecting the batteries to charge safely.
The SBT-12 should be used according to YAESU’s specified battery type and operating instructions.
For backup purposes, properly stored AA alkaline batteries are the straightforward option.
Low-Battery Indication
The FTA-450 and FTA-550 monitor battery voltage.
When battery voltage falls to approximately 6.0V, the low-battery indicator begins flashing.
This provides an important warning that the battery needs attention.
If your radio is several years old and the low-battery warning appears much earlier than expected, the battery should be one of the first components to investigate.
A Critical Symptom: The Radio Reboots When You Press PTT
One of the most useful troubleshooting clues is this:
The radio works normally until you press PTT, then the display goes off and the radio restarts.
This does not automatically mean the mainboard is defective.
A weak battery can cause exactly this type of behavior.
When the transmitter starts, current demand increases significantly. An aging battery with high internal resistance may be able to power the radio during standby but fail to maintain sufficient voltage during transmission.
The result can be:
PTT → high current demand → voltage drop → protection response → restart
YAESU documentation identifies insufficient battery power as a possible cause and recommends checking the battery condition and voltage.
If a battery has been in service for many years, replacement should be considered.
Why a Battery Can Show “Full” and Still Be Bad
This is one of the most misunderstood aspects of lithium-ion battery aging.
An old battery may appear to charge normally and display a full charge, yet the radio can still shut down when transmitting.
The reason is internal resistance.
The relationship can be simplified as:
V = Voc − I × R
Where:
- V = loaded battery voltage
- Voc = open-circuit voltage
- I = current
- R = internal resistance
As the battery ages, internal resistance generally increases.
At rest, the battery may still measure around 7V. But when the transmitter demands significantly more current, the voltage can fall sharply.
Therefore:
A battery that can be fully charged is not necessarily a healthy battery.
This is particularly important when diagnosing an older FTA-450 or FTA-550.
FTA-450 / FTA-550 Battery Replacement Difficulty
The battery replacement procedure is one of the best aspects of this radio design.
DIY difficulty: ★☆☆☆☆
You do not need:
- A heat gun
- Suction cups
- Plastic pry tools
- Soldering equipment
- Battery adhesive
- Screen removal
- Mainboard disassembly
The battery is a removable external pack.
This is very different from modern smartphones, where battery replacement often requires opening a glued display or rear cover.
For owners who prioritize long-term maintenance, the FTA-450/FTA-550 design deserves a high score.
How to Replace the FTA-450 / FTA-550 Battery
Replacing the battery is straightforward.
Step 1: Turn Off the Radio
Switch off the FTA-450 or FTA-550 before removing the battery.
Do not remove the battery while the radio is operating.
Step 2: Locate the Battery Lock
Look at the lower section of the battery.
You will find the battery latch and the LOCK / UNLOCK mechanism.
Step 3: Move the Lock to UNLOCK
Slide the locking mechanism until UNLOCK is fully visible.
This releases the battery.
Step 4: Press the Battery Latch
Press the battery pack latch and lift the lower portion of the battery away from the radio.
Step 5: Remove the Old Battery
Remove the SBR-12LI or existing battery pack from the radio.
No special tools are required.
Installing an SBR-39LI Battery
Installation is essentially the reverse procedure.
- Align the top of the battery with the battery compartment.
- Position the battery against the radio.
- Press the lower part into place.
- Slide the locking mechanism.
- Confirm that LOCK is fully visible.
After installation, make sure the battery is mechanically secure.
The battery’s rubber sealing material should also be checked for proper positioning.
A replacement SBR-39LI battery should be installed as a complete battery pack rather than modified internally.
Check the Rubber Seal When Replacing the Battery
The sealing interface between the battery and radio is easy to overlook.
Before returning the radio to outdoor service, inspect the sealing material for:
- Deformation
- Cracks
- Detachment
- Excessive aging
- Incorrect positioning
Do not casually remove or discard the original sealing components.
For aviation and outdoor use, mechanical fit and environmental protection are important.
Do Not Open the SBR-39LI Battery Pack
There is an important distinction between replacing a battery pack and repairing the battery cells.
The recommended procedure is:
Remove old battery → install complete replacement battery
It is not:
Open battery → replace cells → rebuild pack
Do not attempt to:
- Open the battery casing
- Replace individual lithium cells
- Spot-weld new cells
- Modify the protection circuit
- Increase capacity by changing cells
- Rebuild the battery yourself
Lithium-ion packs can present significant safety risks if short-circuited, damaged, incorrectly assembled, or improperly protected.
For an aviation communication radio, modifying the battery pack is especially difficult to justify when a complete replacement pack is available.
Should You Buy an SBR-12LI or SBR-39LI?
For most owners, the SBR-39LI is the more interesting option.
SBR-39LI
Advantages:
- 2,200mAh capacity
- Official successor to the SBR-12LI
- Higher nominal capacity
- Suitable for restoring runtime on older radios
- Convenient complete battery-pack replacement
SBR-12LI
Advantages:
- Original 1,800mAh specification
- Familiar original battery type
However, because the FTA-450/FTA-550 platform has been on the market for many years, finding an old-stock SBR-12LI does not necessarily guarantee better battery health.
For an older radio, battery age can matter as much as nominal capacity.
That is why the SBR-39LI replacement battery is worth considering when the original battery has significantly degraded.
What to Check When Buying a Replacement Battery
Do not choose an aviation-radio battery based solely on mAh.
Check:
- Exact compatibility
- Nominal voltage
- Physical dimensions
- Contact arrangement
- Protection circuitry
- Temperature protection
- Mechanical locking structure
- Battery production date
- Overall battery quality
Avoid batteries that require you to cut wires, solder connectors, or modify the radio.
For the FTA-450 and FTA-550, a complete compatible battery pack is the better approach.
Does the New Battery Need “Activation”?
No special old-style battery activation procedure is normally necessary.
There is no reason to perform repeated:
- 12-hour charging cycles
- Full discharge cycles
- Three-cycle “activation” routines
A practical procedure is:
Install → fully charge → use normally → monitor performance
Lithium-ion batteries generally benefit more from avoiding excessive heat and unnecessary deep discharge than from deliberate full-discharge cycles.
FTA-450 / FTA-550 Battery Maintenance Tips
To maximize battery service life:
Avoid excessive heat
High temperatures accelerate lithium-ion battery aging.
Avoid unnecessary deep discharge
Do not repeatedly operate an aging battery until the radio shuts itself down.
Store spare batteries appropriately
If the radio will not be used for an extended period, avoid leaving the battery completely discharged.
Keep a backup power option
For aviation operations, carrying a properly prepared backup battery or the appropriate AA battery solution provides useful redundancy.
Monitor unusual PTT behavior
If pressing PTT causes a sudden shutdown or restart, investigate the battery before assuming a radio electronics failure.
FTA-450 / FTA-550 Repairability Score
| Category | Rating |
|---|---|
| Battery removal | ★★★★★ |
| Battery installation | ★★★★★ |
| No radio disassembly required | ★★★★★ |
| No heat gun required | ★★★★★ |
| DIY difficulty | ★☆☆☆☆ |
| Factory replacement option | ★★★★★ |
| AA backup power | ★★★★★ |
| Outdoor practicality | ★★★★☆ |
| Battery troubleshooting | ★★★★☆ |
| Overall serviceability | ★★★★★ |
The biggest advantage is simple: you can replace the battery without opening the radio.
FTA-450 or FTA-550: Which One Should You Choose?
If your priority is straightforward aviation communication, the FTA-450 is sufficient for many users.
If you need:
- VOR
- ILS
- NAV reception
then the FTA-550 is the more capable choice.
From a battery perspective, however, there is little reason to choose between them based solely on battery performance.
The more important questions are:
What battery is installed?
How old is it?
Does it maintain voltage during transmission?
For an aging radio, replacing the battery can have a greater practical effect than attempting to diagnose more complicated electronic faults.
Final Verdict: Is the SBR-39LI Worth It?
The YAESU FTA-450 and FTA-550 remain particularly attractive from a maintenance perspective because their batteries are not permanently glued inside the radio.
The original SBR-12LI provides 1,800mAh, while YAESU has moved to the SBR-39LI 2,200mAh as its replacement battery.
Under YAESU’s specified TX/RX/standby test cycle, the FTA-450L/FTA-550 can achieve approximately 13.5 hours of battery life with a fully charged battery. Real-world runtime will vary according to transmission frequency, reception time, scanning, temperature, and battery condition.
The SBR-39LI therefore makes particular sense for owners whose original battery has become:
- Short-lived
- High-resistance
- Unreliable during transmission
- Prone to voltage sag
- Several years old
The SBR-39LI battery is also much easier to install than the batteries found in modern smartphones and many sealed electronics.
The complete process is essentially:
Power off → UNLOCK → press latch → remove old battery → install SBR-39LI → LOCK.
No radio disassembly is required.
The additional SBT-12 six-AA alkaline battery option is another major advantage, especially for users who need a backup power strategy.
For flight training, aviation operations, or emergency communication, the best setup is not simply “the highest mAh battery.” A reliable SBR-39LI battery, combined with an appropriate backup power solution, provides a much more robust approach.
Overall verdict: ★★★★★ for battery serviceability.
If your FTA-450 or FTA-550 is still functioning well electronically but its original battery has become unreliable, replacing the aging pack is one of the simplest and most worthwhile maintenance upgrades available.
FAQ
1. What battery does the YAESU FTA-450 use?
The FTA-450 originally used the SBR-12LI 1,800mAh lithium-ion battery, with the SBR-39LI 2,200mAh subsequently becoming the replacement battery.
2. What battery does the YAESU FTA-550 use?
The FTA-550 uses the same basic battery system, including the SBR-12LI and its SBR-39LI replacement.
3. Is the SBR-39LI compatible with the FTA-450 and FTA-550?
The SBR-39LI is identified by YAESU as the replacement for the SBR-12LI used with this radio family. Always verify the exact radio model and battery compatibility before purchasing.
4. How long does the FTA-450 / FTA-550 battery last?
YAESU’s published test condition gives approximately 13.5 hours under a 6-second TX / 6-second RX / 48-second standby cycle. Continuous transmission will produce substantially shorter runtime.
5. Can I use AA batteries with the FTA-450 or FTA-550?
Yes, the appropriate SBT-12 alkaline battery tray can accommodate six AA alkaline batteries.
6. Can I put Ni-MH batteries in the SBT-12?
The SBT-12 should not be used as a rechargeable Ni-MH battery pack. Follow YAESU’s specified battery and charging instructions.
7. Why does my FTA-550 restart when I press PTT?
A weak or aging battery may not be able to provide sufficient current during transmission. Voltage can fall sharply under load, causing the radio to shut down or restart.
8. Should I open the SBR-39LI and replace the cells?
No. Replace the complete battery pack rather than opening and rebuilding a lithium-ion battery.
9. Is replacing the FTA-450 / FTA-550 battery difficult?
No. The battery is externally removable and can be replaced without opening the radio or using specialized repair tools.
10. Where can I find an SBR-39LI replacement battery?
You can check the YAESU SBR-39LI replacement battery for a compatible replacement option.