We have been hearing good things about LiHV batteries, which is reportedly better than traditional LiPo, especially for mini quad racing. I ran some tests and tried to find out which battery is better.
Many thanks to Aircraft-World.com for sending me the Hyperion HVLi batteries for testing.
What is LiHV battery?
LiHV (or HVLi) stands for “High Voltage Lithium Polymer”. It’s a similar to LiPo battery but allows you charge it up to 4.35V per cell safely.
When you charge LiHV batteries like standard LiPo to only 4.20V per cell, they perform pretty much similar. However when you charge them fully to 4.35V per cell you get the following advantages:
- With a fully charged HVLi battery, voltage is higher than normal LiPo’s (on a 4S, HVLi is 17.4V, LiPo is 16.8V), therefore your motors will run harder at higher RPM, and your quad can fly faster theoretically
- Secondly, LiHV can store more energy than LiPo per weight, so theoretically (again) you get longer flight time. Hyperion (the company that makes these HVLi batteries I am testing) states there is a 10% increase in capacity than standard LiPo’s of the same size and weight
- Lastly, good quality HVLi has lower voltage sag on high throttle
Can you charge your normal lipo to 4.35V?
So you might wonder: “can I over-charge my normal lipo to higher voltage like 4.30V or even 4.35V, to get more power and longer flight time? ” The answer is NO!!! That’s extremely dangerous and very likely to cause fire because of the different cell chemistry.
How to charge HVLi?
Before you buy any HVLi batteries, you should check your charger first as not every existing charger can charge HVLi batteries.
Some chargers don’t have HVLi as a battery type, but allows you to charge up to 4.3v/cell. Still, It’s best to have a charger that has a setting for LiHV specifically, for example this IMAX X150.
You should NOT charge HVLi together with standard lipo, when you over charge LiPo over 4.2V per cell you might get a fire. Chargers are unable to detect whether you have plugged in HVLi or normal LiPo so be extra careful not to mix them together.
HVLi Batteries I am testing
These Hyperion HVLi packs come with standard XT60 Main connectors, with JST-XH Balance connectors. The discharge lead is 14AWG silicon wire.
When comparing to normal LiPo of the same capacity, LiHV’s are smaller and lighter due to the higher energy per weight.
- Hyperion 4S 1800mAh 40C – 178g
- Turnigy Nano-Tech 4S 1800mAh 65C – 228g
And here is the smaller 1400mAh pack.
- Hyperion 4S 1400mAh 40C – 142g
- Dronelab 4S 1500mAh 50C – 157g
Testing and Comparing of HVLi and LiPo
I tested and compared the Hyperion 4S 1800mAh and Turnigy Nano-Tech 4S 1800mAh. I ran the test twice, the first time I was just hovering, and the second time I did some med-high speed cruising.
Here I hovered the quad at one place, and only landded when “consumed mA” reached 1800mA – the specified battery capacity. (I removed the GoPro to get a bit longer hover time)
- Hyperion: 10:45
- Turnigy: 9:09
I was expecting they would land at about the same time, given both are the same 1800mAh capacity, but interestingly NO! The Hyperion lasted about 96 seconds longer than the Turnigy.
My guess is the weight of the batteries, the Hyperion is 50g lighter than the Turnigy, and the motors pull less current when just hovering. The power graph confirmed this, as you can see the quad has to work harder (higher power) to stay in the air when carrying the extra weight.
Another thing to notice is the voltage of the batteries throughout the whole discharging cycle. The voltage of the HVLi is higher than the LiPo initially, but towards the second half of the process, it was gradually getting closer to that of the LiPo.
Fun fact: After we have drawn 1800mA from the Turnigy Nano-tech, its voltage was still pretty high at 14.4V (3.6V per cell). That suggests it actually might be larger pack than specified by manufacturer. (maybe 1900mAh?)
Fast Flying Test
In this test I was flying around with 70% to 80% throttle constantly. The higher voltage improved the responsiveness and speed of the quad. You can see that from the power graph, the quad was able to pull out more power from the LiHV than LiPo overall.
However I didn’t notice much improvement on flight time compared to the Nano-Tech LiPo, probably because I was pushing the quad too hard.
Similar result to the hover test, where we see higher voltage at the beginning, but they converged towards the end. That suggests the battery would give your motors higher RPM and less voltage sag, thanks to the higher initial voltage, but probably similar performance to the LiPo’s in the 2nd half of the pack. I think this is something you need to take into account when doing endurance races, where you need to decide when is best to change batteries.
*Note that the Turnigy battery I was comparing against with is nearly a year old so discharge rate is worse than new packs. I don’t have any new 1800mAh LiPo packs so that’s it.
HVLi for your Fatshark Goggles
I also tested a 2S HVLi pack, which is designed for Fatshark FPV goggles – 2S 1300mAh 2C-4C. They look exactly the same to the original LiPo pack that comes with the Dominator Goggles I have, but the HVLi can power on your Goggles for much, much longer!
I tested the following 3 x 2S batteries, and here is the result:
- Fatshark 2S 1000mAh (Stock Lipo) : 0:50:10
- Turnigy 2S 1300mAh: 2:37:26
- Hyperion HvLi 2S 1300mAh: 2:52:42
The Hyperion is able to power the goggle on for nearly 3 hours straight! Very impressive :)
Note that I did this battery mod on my goggles batteries for easier charging.
Update Feb 2017 – Longevity Issue
After some use of these HVLi, they seem to have pretty short life cycle: after about 30-40 discharge cycles, the cells are starting to swell, and they don’t hold full charge anymore. They get really hot after a fast session. Normally for a decent standard LiPo they should hold up 300+ cycles.
So at this point, I don’t think I will buy anymore HVLi for day to day flying and practice due to the lack of longevity. However for special events like races, I might still consider them for the outstanding performance.
Extra Discussion: When getting new LiPo batteries, do you do the “Break-in procedure” to “maximize” Lipo performance? Leave you thoughts on the forum :)