Fullsend 6S 6000mAh Li-Ion: Holy Grail of long range FPV

Lithium-ion or Li-ion batteries generally have a higher energy density than other battery chemistries, including LiPo. This means that Li-ion packs can store more energy in the same physical size, allowing longer flight times and increased range. For example, by comparison, the iFlight Fullsend 6S 6000mAh weighs just 608 grams, and a LIPO battery with the same power weighs 865 grams.

LiIon batteries are also favored for their stability and longer life span. LiION cells are less prone to swelling or catching fire than Li-Po cells. Unfortunately, they aren’t perfect. While LiION packs have a max 30-40C discharge rate, LIPO packs can have up to 200C. A higher discharge rate is essential for racing and freestyling. Not all drones can be used with LIION packs; you should test it with the AMP drain on the screen, and if your power needs exceed 150A, you should avoid using LiION batteries.

As Li-ION batteries have a lower bottom voltage than LIPO batteries (2.5V/cell vs 3.0V/cell), you need to make a few adjustments to avoid all kinds of warnings in BetaFlight OSD. Under the “Power & Battery” tab, you need to change “Minimum Cell Voltage” from 3.3V to 2.9V and “Warning Cell Voltage” from 3.5V to 3.1V. Turning on “Average Cell Voltage” monitoring in the OSD tab is also essential. It would be best if you were near home and preparing to land when the average cell voltage is around 3.0V. Remember that flying and rest voltages differ so that you will be left with some safety reserve energy after landing.

iFlight Fullsend LR 6S 6000mAh Li-Ion battery review

Disclosure: I received this long-range Li-ION pack in a product review collaboration with iFlight. Although the battery was offered for free, all opinions in this article remain mine, and the sponsor did not influence me.

iFlight’s Fullsend LR LIION battery product range includes 6S 8000mAh (12xINR21700-40T), 4S 3000mAh (4xINR18650-30Q), 6S 4000mAh (6xINR21700-40T), and 6S 6000mAh (12xINR18650-30Q), so I was surprised to open the package and find inside a 6S 4500mAh/99.9Wh pack (not listed on their website). Looking to unravel the mystery, I discovered that airline companies have strict regulations regarding lithium-ion packs over 100 wh. Probably, this is why the battery was “mislabeled”. After removing the protective foam inside the box, I found two more labels, one with 6000mah and one with 4500mah.

The Fullsend 6S 6000mAh LiION pack measures 137*56*38mm and weighs around 610 grams. It uses twelve pieces of high-quality Samsung INR18650-30Q cells connected in a 6S2P configuration. Practically, two 6S 3000mAh batteries are connected parallel to double the storage capacity. The package feels solidly made with nice enveloping. The battery claims to provide up to 35C continuous discharger rate. Yes, this is not a race pack, not a freestyle, but a cruiser pack.

Being close to 14cm (5.5″) long, it can’t be installed on top of any FPV drone. On my nine-inch Chimera 9 ECO, there was enough room to install it, but on my six-inch Volador VD6, I needed to remove the GoPro mount to make space for the battery.

Technical specifications

Fullsend LR 6S 6000mAh Li-Ion: Performance – Expected flight time

To evaluate the true capacity of the FullSend LR 6000mAh battery, I discharge it down to 2.6V per cell with a discharge current of 3A (0.5C). At this discharge rate, the pack stayed cool, avoiding energy wastage. The measured capacity was approximately 5880mAh. When charged back, the capacity was 6726mah but this value is more based on estimation. The FullSEND LR’s measured internal resistance (IR) was around 9-11mΩ/cell.

After the bench tests, I installed it on my 9″ long-range drone. The take-off weight was about 1400 grams. You will need two 30cm long velcro straps to secure it to the frame. When you fly such heavy birds or race quads with LIION packs with low discharge rates, you feel you are flying on Jupiter with high gravity. If you push the throttle level higher, cell voltage drops significantly, and a low voltage alarm appears on the screen. After 18 minutes of flight, I landed when the cell voltage dropped to 3.1V. Probably, it still had energy left for an additional 2-4 minutes of flight. Even 30 minutes after landing, the battery was still warm to the touch, which never happened with LIPO packs.

I recommend not abusing LI-ION packs by over-discharging (below 2.5V/cell) or over-heating them using excessive throttle; you don’t want to kill your 100-buck battery. If you use them properly, they will serve you for several hundred flights.

Pricing and availability

The FullSend LR 6000mAh LI-ION pack can be ordered from the manufacturer’s website for $119.99 (€143,79 from the EU warehouse). If you need an even higher capacity, the 8000mAh version with INR21700-40T cells is priced at $149.00 (€178,49 from the EU warehouse). Before ordering, I suggest you ask about delivery options, as Lithium batteries over 100Wh are regulated as a hazardous material in many countries.

6000mAh LiION vs 6000mAh LiPO: Which is best for long-range FPV?

The choice between LiPo and Li-ion batteries depends on the specific requirements of the drone application, considering factors such as weight, energy density, discharge rate, and lifespan. In the table below, I compared the most important parameters of the Fullsend 6000 LiION and 6000 LIPO batteries.

Fullsend LR 6S 6000mAh Li-ION: Alternatives

The GEPRC VTC6 18650 6S2P promises similar performance but uses a different form factor. Despite using similar Samsung cells, it is about 30 bucks more expensive than this FullSend. Another alternative would be the URUAV 6000mAh 15/30C 6S Li-ion, which also has a more cubic shape. The Lumenier NAV 6000mAh 6S has the same longish form factor and promises up to 50C burst discharge rate, which is the best in its class.

You can make your own LIION packs way cheaper than buying ready-to-use ones, but a spot welding machine will be needed. To ensure the best performance and reliability, it is recommended to use good-quality cells from Sony, Samsung, or Panasonic. One genuine INR18650-30Q cell is about 5$, and you need 12 of them to make a 6S 6000mAh pack, so without calculating the price of welding and wrapping, you can build it for around $60.

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