Lithium based batteries are everywhere in RC. The performance that we are able to get out of these packs are incredible compared with all past battery technologies. Within the last few years a new style of LiPo based battery has emerged. It is known as the Lithium Polymer High Voltage battery pack. The pack is commonly referenced as LiHV, identifying that it is a high voltage based lithium battery.
High Voltage Battery Pack
LiHV Battery Pack Specifications
Lithium high voltage batteries have a higher nominal and peak cell voltage. LiHV per cell peaks at 4.35 volts where a typical LiPo battery has a peak voltage of 4.20 volts. The nominal voltage of a LiHV battery is 3.8 volts whereas the nominal voltage for a typical LiPo is at 3.7 volts.
Voltage cut off for a LiHV battery pack is the same as a standard LiPo battery pack. The absolute minimum voltage that a cell should get to is 3.2 volts. However, in practice the battery should not be discharged past 80% of its total capacity, Discharging a LiHV further will degrade the lifespan of the pack.
In order to charge a LiHV cell, your charger must have the capability to do so. Not all chargers are capable of charging to 4.35 volts per cell. This is a must in order to receive any benefit from a high voltage Lithium battery pack. Under no circumstance should you ever attempt to charge a standard LiPo battery pack to 4.35v per cell.
Application of LiHV Battery Packs
LiHV battery can virtually be used in any RC application. There are a few notes to consider about its applications, however. The batteries do only increase the amount of voltage by a small amount. The amount actually only ends up being about 3.5% when looking at the peak voltage. However, this is not the only amount of performance that you will end up seeing with these battery packs. The other side of the coin is the current. When you are requesting the motor to spin faster RPM’s due to the increase of voltage, the result will be an increase of current. Overall you may expect a performance increase of around 8-10 percent on average.
LiHV are not going to work for every setup
A setup designed around a standard LiPo battery pack may not have the headroom for increased performance. There are a handful of stock setups running near maximum capacity. If the setup is already pushing the limits it’s not a good idea to use the pack in your application. A good quality RC product should always have enough headroom where LiHV won’t over tax the system.
If you plan to use LiHV to grab an extra 10% more power, just be certain that your system can withstand the increase in performance. More heat buildup in the motor and ESC is a certain.
Are LiHV Batteries Worth it?
Let’s get to the point of the article. There’s no doubt about it. LiHV batteries offer better performance from a voltage standpoint in comparison to standard LiPo batteries. The voltage difference is subtle but adds up very quickly as you increase in cell cell count. Increasing voltage can certainly lead to an increase in performance by raising the total amount of output motor RPM.
Increase RPM’s by LiHV or just a higher Kv?
I personally setup all of my RC’s specifically to the voltage that I plan to run. If I want more RPM’s out of the motor, I simply increase the kv of the motor. When I looked at HV batteries for a specific setup, my decision was to just get a new motor with a slightly higher Kv rating. I know that the motor will easily outlast the lifespan of the battery pack.(Typically 3 years) I didn’t want to have a dedicated battery for just one RC vehicle. It would be different if all the battery packs I own were LiHV based. However, these packs are not mainstream. (Yet) It’s certainly possible that the market can turn and LiHV become more mainstream.
Proven Performance
LiHV have not yet proven themselves in any RC racing league. In fact, there are many clubs and racing leagues that strictly prohibit their use.
I haven’t been able to put the HV packs truly to the test. However, reading up on some test data has shown me that HV packs haven’t yet proven themselves well enough in the performance department to warrant their use.
In conclusion I just don’t feel that LiHV are worth their value today for me. Perhaps in time things will change. This conclusion is not for everyone. I’m sure there are setups out there that will be able to squeeze a bit more power out and this is the only way to do it efficiently.