Choosing the Best Battery for the FMS J11 Twin 70mm EDF
The FMS J11 is powered by two 70mm 12-blade EDF units, two 3060-KV1900 inrunner motors and two 80A ESCs, all drawing from one 6S battery. This single-pack arrangement is more convenient than the dual-battery layouts used by many larger twin EDF jets, but it also places a demanding load on the selected pack.
FMS recommends a 6S 5000–6000mAh battery rated at 50C or higher with an EC5 connector. That is a useful starting range, but capacity alone does not determine whether a battery is suitable. Installed dimensions, actual weight, voltage capability, discharge performance and the ability to achieve the published 145–150mm center of gravity are more important than the number printed on the capacity label.
This is why the collection includes both standard LiPo batteries and lightweight Lightning LiHV packs above 6000mAh. A conventional high-capacity battery may add enough weight to increase the takeoff roll, reduce low-speed flexibility and raise the landing speed. A lightweight LiHV pack can provide additional capacity while staying within a much more practical weight class.
FMS J 11 Battery Options by Flying Style
| Battery range | Best for | What to expect |
|---|---|---|
| 5000–5200mAh | Lighter, more responsive setup | Closer to the standard FMS configuration, with easier rotation and a more agile feel. Requires the most disciplined flight timer. |
| 5500–6200mAh | Balanced everyday flying | Adds useful capacity and reserve while remaining within or close to the conventional recommended range. |
| 6700–7200mAh LiHV | Lightweight high-capacity setup | More usable capacity without the typical weight of a conventional battery in this class. Check CG, charger mode and system voltage before flight. |
5000mAh: The Lighter Performance Setup
A 5000mAh 6S battery is the natural starting point for the FMS Twin 70mm EDF J 11. It keeps the nose lighter, helps the aircraft rotate more readily and gives the full-flying stabilizers a more responsive feel. This capacity is especially suitable for a maiden flight, performance-oriented flying or pilots who prefer a setup close to the manual.
The trade-off is a relatively narrow flight window. Real-world twin 70mm flying can use a 5000mAh pack quickly, especially during repeated full-throttle passes, vertical climbs or hot-weather operation. A conservative timer of approximately three minutes is a sensible starting point, followed by adjustment based on landed voltage and returned capacity.
The CNHL G+Plus 5000mAh 6S 70C provides a particularly useful balance of weight and output, while the Black Series offers a value-focused alternative. The Racing and G+Plus high-discharge versions are suited to pilots who place greater emphasis on voltage stability during sustained high-power operation.
6000–6200mAh: The Balanced FMS J11 Setup
A 6000mAh or 6200mAh battery is a strong middle ground for this aircraft. It provides more reserve for the landing circuit and an occasional go-around while avoiding the extreme weight of many traditional 7000mAh-class packs.
This capacity range works particularly well for scale-style flights with smooth passes, moderate throttle and the detachable ordnance installed. The additional weight can make the aircraft feel more deliberate, but that character also suits the large Flanker-style airframe.
The Black Series 6000mAh is the straightforward conventional-capacity choice. The Racing Series 6200mAh adds a higher discharge rating for pilots who use more aggressive throttle or want greater voltage support under the combined load of the two EDF units.
Why a 7200mAh LiHV Can Fit the FMS J11
The manual’s 5000–6000mAh recommendation should not be treated as an absolute capacity ceiling. It was written around typical battery construction, where additional capacity usually brings a substantial increase in both mass and physical size.
The CNHL Lightning LiHV 7200mAh 6S 120C changes that calculation. At approximately 149 × 52 × 50mm and 800g, it is close to the size and weight of many conventional 6000mAh 6S LiPo batteries while providing 20% more rated capacity than a 6000mAh pack.
That makes it a particularly strong fit for the FMS J11 battery compartment and a realistic way to increase usable energy without turning the aircraft into an unnecessarily heavy setup. Its dimensions allow practical installation, while its weight remains compatible with achieving the aircraft’s recommended balance when the pack is positioned correctly.
The benefit should be understood as greater reserve rather than a guaranteed proportional increase in flight time. A heavier aircraft may require more throttle, and the actual result will still depend on flying style, external ordnance, temperature, battery condition and the number of full-power manoeuvres performed during the flight.
LiPo vs LiHV for the FMS Twin 70mm EDF J 11
| Feature | Standard 6S LiPo | 6S LiHV |
|---|---|---|
| Nominal voltage | 22.2V | 22.8V |
| Maximum charge | 4.20V per cell | Up to 4.35V per cell |
| Main advantage | Simple, familiar charging and broad compatibility | Higher usable energy and lightweight capacity options |
| Important check | Correct 6S mode and EC5 connector | LiHV charger mode and confirmed maximum system voltage |
A Lightning LiHV battery may also be charged only to the standard LiPo limit of 4.20V per cell when a more conservative voltage is preferred. In that case, it behaves more like a standard 6S pack and does not provide its full LiHV energy advantage.
Before charging to 4.35V per cell, confirm that both ESCs and the complete onboard power system can accept the resulting fully charged voltage.
FMS J11 Flight-Time and Battery Management
The approximately four-minute duration listed for the aircraft should be treated as a reference rather than a guaranteed timer setting. A light-throttle scale flight and an aggressive speed flight can produce very different remaining capacities, even when the same battery is used.
For the first flights, set a conservative timer and begin the landing circuit before it expires. Avoid using the final reserve for repeated high-speed passes. The J11 can glide, but a heavy twin EDF has less room for correction after the battery voltage falls sharply.
Telemetry is especially useful in this model. Pack-voltage callouts, low-voltage alarms and post-flight capacity checks provide a better picture than relying on elapsed time alone. Adjust the timer gradually after several flights with the same battery and a consistent flying style.
Battery Weight, CG and Runway Length
Begin with the published 145–150mm CG. A slightly nose-heavy maiden setup is generally more predictable, but excessive forward weight can increase the takeoff roll, make rotation more difficult and require greater speed during the landing approach.
After installing any battery, support the aircraft at the specified CG with the landing gear in the condition stated by the manual. Confirm that the battery can be secured without compressing the cells or placing strain on the power leads.
Heavier setups benefit from a long, smooth runway. Grass and gravel increase rolling resistance, consume more battery energy during takeoff and introduce a greater risk of foreign-object ingestion through the lower air inlets. Removing the detachable ordnance for the maiden flight or for operation from a rough runway can reduce risk and slightly improve performance.
FMS J11 Battery FAQ
What battery does the FMS J-11 use?
FMS specifies a 6S 5000–6000mAh battery rated at 50C or higher with an EC5 connector. Lightweight CNHL LiHV batteries above 6000mAh can also be practical when their dimensions, weight, voltage and installed CG are suitable.
Is 5000mAh enough for the FMS J11?
Yes. A 5000mAh pack is the lighter standard choice and suits performance-oriented flying. Because both EDF units draw from the same battery, start with a conservative timer of approximately three minutes and adjust it using post-flight voltage and returned-capacity data.
Can the FMS J 11 use a 6200mAh battery?
Yes. A suitable 6200mAh EC5 pack provides more landing reserve than a 5000mAh battery and is a strong balanced option for scale flying. Confirm the installed CG and ensure the battery is secured correctly.
Can I use a 7200mAh battery in the FMS J11?
Yes, when the battery remains sufficiently compact and light. The CNHL Lightning LiHV 7200mAh measures approximately 149 × 52 × 50mm and weighs about 800g, placing it near the weight class of many conventional 6000mAh packs. It fits the J11 well and can achieve a practical balance when positioned correctly.
Will a larger battery always give a longer flight?
Not in direct proportion to capacity. Additional weight can require more throttle and may offset part of the expected flight-time gain. A larger pack is often most valuable because it provides a safer reserve for landing and a go-around.
Can I charge a 6S LiHV battery with a normal LiPo charger?
The charger must support the selected charging voltage. A LiHV pack requires a dedicated LiHV mode to reach 4.35V per cell. It may be charged in standard LiPo mode to 4.20V per cell, but it will not deliver its full rated LiHV capacity.
More Batteries for Twin EDF Jets
Explore more LiPo batteries for EDF jets or compare the full range of 6S LiPo batteries with EC5 plugs for other high-power RC aircraft.
Important: Always confirm battery dimensions, weight, connector, charger mode, maximum voltage and CG before flight. Do not select a battery by capacity or discharge rating alone.
