In this test, I wanted to see how much heat actually builds up inside a hardcase LiPo battery compared to what we measure on the outside. Using a Spektrum hardcase pack, I removed half of the case to directly access the cells, allowing for side-by-side temperature readings.
Measuring the Temperature Difference
I discharged the pack at a high rate until the internal pouch cells reached around 60°C (140°F). On the case surface, however, the temperature was only 48–55°C—a difference of up to 12°C. This confirms that the plastic case acts as an insulator, preventing accurate surface readings of the true internal temperature.
| Measurement Location | Temperature (°C) | Observation |
|---|---|---|
| Exposed Cell Surface | 59–60.8 | True internal temperature |
| Hardcase Surface | 45–55 | Up to 12°C cooler due to insulation |
Why This Matters
If you’re only checking the outer shell of your LiPo pack, you might assume it’s running cooler than it actually is. In reality, the internal cells could already be beyond the safe 60°C limit—posing risks to both performance and safety. THis is also a matter of how well the temperature of the cells are conducting to the hard case shell. Poor heat transfer will show up as an even cooler operating battery pack.
Safer Testing Methods
Here are a few ways to estimate LiPo temperatures more reliably:
- Use a softcase pack first: Select one that has roughly the same internal resistance and performance factor compared with your hard case pack. Run it aggressively and check its peak temp. If it’s under 60°C, the hardcase version should remain within safe limits under similar loads.
- Add headroom: When measuring the outer case, assume the internal cells are 10–15°C hotter. This is an indirect method to measuring temperature and can drastically incorrect.
- Direct monitoring: The most accurate way is to install a temp sensor directly on the cell or use a smart LiPo with built-in temperature tracking.
Final Thoughts
This experiment highlights why external readings don’t always tell the whole story. Hardcase LiPos may seem cool to the touch while their internal cells approach dangerous temperatures. Always measure carefully and leave safety margins when running your RC vehicles hard.
If you’d like full access to the raw data and comparison sheets from my battery tests, consider joining my Patreon community. Members of Tier 1 or 2 get access to the calculator that can determine the C rating of a battery based on IR and capacity.