Review: DemonRC Fusion 4S 1500mAh LiPo Battery – 666C

Today we are testing the Fusion 4S 1500mAh LiPo battery from DemonRC. It’s labelled 666C which is joke as it’s the devil’s number. This is funny but it doesn’t tell us what to expect though so it would be interesting to find out how it performs.

Further Reading: The basics of LiPo battery for beginners


  • Cell Count: 4S
  • Capacity: 1500mAh
  • C Rating: 66C – 133C
  • Balance lead: 5cm
  • Discharge wires: 12AWG, 9cm
  • Size: 88x35x33mm
  • Weight: 190g

Battery Comparison

We will be testing and comparing the performance of the following batteries:

  Shops Weight Price
DemonRC Fusion 4S 1500mAh DemonRC 190g $32
Acehe Formula 4S 1500mAh GetFPV 189g $36
Tattu 4S 1550mAh Amazon 178g $21

Testing & Results

Internal Resistance

The IR values are measured by my iSDT charger after they are fully charged. All numbers are in mΩ, the higher, the worse.

  Cell #1 Cell #2 Cell #3 Cell #4
Fusion 5.5 5.7 5.5 5.7
Formula* 6.5 6.8 6.5 6.5
Tattu 6.5 7.2 7.0 7.1

* Interesting observation, the IR of both the Formula and Tattu have gone up slightly compared to last time I checked, although I haven’t used them since my last review. This confirms that IR does go up over time.

Actual Capacity

The Fusion is actually a 1580mAh pack, close to 1600mAh. Capacity is measured by discharging the battery from 4.2V to 3.5V per cell during flight.

Discharge Performance Testing Format

To test the performance of the batteries, I flew around this race course multiple times. The routine includes a 5-second WOT punch out (100% throttle), and low throttle cruising the rest of the lap.

Current and voltage are measured where the red dots are, the data will help determine the performance of the battery, for example, how much power the battery can provide, how bad the voltage sag is, and how fast the voltage recovers from a “punchout”, etc.

Voltage Comparison

Pay attention to the voltage sag at each punch out, the lowest voltages.

The Fusion has outstanding performance in terms of voltage sag, it held up the best in punchouts. The Formula has really close performance, but it seemed to take a couple of laps to catch up. It’s was only 8°C so it’s probably affected by temperature more than the Fusion?

Power Comparison

Power is the product of current and voltage.

The clear winner is the Fusion, it consistently provided the highest power through the whole flight in all 3 batteries we tested.


The DemonRC Fusion 4S 1500mAh seems to be an excellent battery from the test: low and consistent IR, provides outstanding power and handles voltage sag like a champ.

I am surprised that it actually out-performed the more expensive Acehe Formula, which is also one of the top batteries out there in terms of performance.

If you are in Europe, you can’t go wrong with the Fusion :) Highly recommended!

4 thoughts on “Review: DemonRC Fusion 4S 1500mAh LiPo Battery – 666C

  1. Thomas Jorgensen

    Will you recommend this DemonRC batteries for Freestyle flying?
    If no then witch batteries do you recommend for freestyle FPV

  2. Mike

    The link to the Tattu battery you provide is the 45C version, not sure if the link is to the wrong battery or if you are comparing a high end battery to Tattu’s lowest end. It would have been more of a fair comparison to use at least the Tattu 75C or even the R line 100C.

    1. Oscar Post author

      The prices are clearly stated, the Tattu in this test are cheap, so people understand why the other two batteries are more expensive.


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