Im sure you have all seen the trend in racing, LiPo is being killed off at most tracks in exchange for LiHV, for that oh-so sweet extra 0.15V Per cell (4.35V per cell max charge LiHV VS 4.20V per cell max charge LiPo). Its no secret that more voltage equals more power and speed, and that is why we buy bigger batteries for the bigger and faster RCs in our lives. But what makes these LiHV batteries different? Do I need to treat them differently? Well as someone who go into LiHV about a year ago and has done extensive research and testing to see just how different they are, I now have enough information to let you guys know what is up with this newer battery technology.

So, what is LiHV? Well, in reality the basic chemical and materials makeup is no different than a standard LiPo, although most LiHV options tend to be "Graphene" models with a very small mount of the element infused into the cell construction to boost performance. However, Graphene models are also available in standard 4.20V LiPo packs, so this is in fact not a difference, its just that LiHV models are made for racing and so they tend to be higher-end, more expensive batteries with more features.

So what is different about LiHV then? Well, to be honest, NOTHING. See in reality, most standard LiPo cells can take 4.35V without exploding, but it will degrade the lifespan of the cells rather quickly and there is a BIG chance of an explosion when overcharging a standard LiPo and you should NEVER try this. So wait then, how do LiHV deal with the extra voltage? Why is it safe on LiHV and not standard LiPo? Well simply put, its the quality of the cells put into the packs. The cells that get chosen to go into LiHV packs are ONLY the absolute best, most resilient, and most powerful cells a manufacturer has to offer, which is why the packs are so expensive. There is simply NO WAY to make a LiHV pack cheaper than a standard LiPo with the same number of cells and capacity. These LiHV cells are also tested before being sold, with batch samples undergoing hundreds of cycles to full 4.35V and then being completely discharged before being deemed safe to sell and label as a LiHV pack.

So how do I care for these LiHV packs? Nearly the same way you care for standard LiPos with one exception. Some of you may remember that I did an experiment a while back and posted my surprising results to the RCTech forums. This experiment showed that dropping voltage to absolute minimum 3.0V per cell actually slowly damages a LiPo pack over time, and that most LiPo packs will actually hit their rated capacity going from full charge 4.20V per cell down to about 3.3-3.4V per cell. These tests were performed on new batteries, all of which had either never been cycled or had been cycled less than 20 times. Batteries are a CONSUMABLE item and do not last forever no matter what you do and will loose capacity and performance as they degrade over time, its simply an unfortunate fact that cannot be avoided. This showed why those who set their LVCs on their ESCs to minimum 3.0 per cell were having so many LiPo issues for so long. Well, with LiHV unfortunately the news gets a bit worse. Some manufacturers will even label LiHV packs to say "DO NOT DISCHARGE BELOW 3.3V PER CELL!!!" Well this label DOES exist for a real reason. As with LiPo, manufacturer instructions have once again mis-lead us.

With testing, I was able to determine that MOST LiHV packs hit their capacity rating when being discharged slowly at under 0.5C discharge rate from full 4.35V per cell to roughly 3.40-3.50V per cell. Now luckily the "bottom of the fuel tank" is only slightly higher than the standard LiPo so I have been running with my same 3.4V per cell cutoff as I always have, despite running LiHV batteries. Its such a small difference that the LiHV packs should not suffer degradation, especially considering that when on throttle, your pack voltage sags and so when LVC occurs, voltage usually bounces back up to 3.5+V per cell by the time I stick the pack back on the charger.

As for Storage Voltage, 3.80-3.85V per cell is still perfectly safe for both LiHV and LiPo, so do not worry about making any changes here.

One last thing, lets talk longevity. Because LiHV packs are just over-charged, very high-end standard LiPo cells, I imagine you are concerned about the lifespan of LiHV in general. Well, there is a bit of reason for concern, but you can compensate, let me explain. Lithium-Based batteries do not enjoy voltage change in general. Despite the fact that the entire reason for their existence is to be a BATTERY whose sole purpose is to be charged and discharged, all Lithium cells degrade when charged or discharged, PERIOD. The amount of degradation depends on a number of factors including how hot you get your battery, how fast you set your charge speeds, and our topic today will be how far you charge and discharge your batteries. You can look up hundreds of articles that will tell you that LiHV does not last anywhere near as long as standard LiPo, so lets see if we can alleviate some of that degradation...

You see, if you did very tiny cycles to your LiPos or LiHVs, like charging to just 4.1V per cell and discharging to just 3.8V per cell, your Lithium batteries would actually last thousands and thousands of cycles before needing to be replaced. However, this would make for extremely short run times, so short that most would find it unacceptable. The average 5000mAh bash LiPo would become a puny 2000 or even less mAH pack. So, what is a good balance? What is the ideal voltage start and ending for a cycle? Well, since standard 4.20V cells are much cheaper, just go ahead and charge those to standard full charge and try to set your LVCs to 3.4V per cell. A standard, slow-ish charge rate of 0.5-1.5C will ensure maximum lifespan, and of course don't mistreat them. This practice should yield a LiPo that lasts for about 500-600 cycles, or roughly 4-5 years for the average basher who runs once per week with 2 packs and 2 cycles per pack that he/she alternates between so they don't have to drag a charger to a bash spot or can charge one pack while running the other. LiPos and LiHV do have shelf life limits. After a few years sitting around any LiPo or LiHV will degrade badly so the best way to get the most bang for your buck is to make sure you buy batteries you will actually use regularly.

As for LiHV, because they are overcharged cells, the less you push past 4.20V per cell, the longer they will last. I personally charge my LiHV packs to exactly 4.31V per cell. Why such an odd number? Well any battery regardless of chemistry will drop a slight bit in voltage when unplugged from the charger because the act of "shoving amperage" into a battery has the same effect of a motor causing voltage sag, only in the opposite direction. My goal is to be as close to 4.30V per cell as possible when my vehicle starts up. This still gives me a noticeable advantage over competition running standard LiPos but prevents some of the degradation caused by the over-charging. Unfortunately I have not used LiHV long enough to have fully degraded a battery to be sure about this, but performance is still above a brand new standard LiPo after a year and so I believe this is a good sign so far. Just as with standard LiPo, do not abuse or over-discharge the pack.

I hope I was able to help some of you guys considering the LiHV route. Not all tracks conform to strict IFMAR and ROAR rules so there are plenty of ways to see the advantage on a track. Get out there and have fun with RC!