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LRC: Hi Chris! Thank you so much for chatting with us today about batteries! Let’s start out talking a little about Venom and their lineup of batteries. (What all batteries does Venom offer? How long has Venom had batteries? What makes Venom one of the best? Etc.)
Chris: Hi Mike, thanks for the opportunity to discuss this with you.
Venom had very humble beginnings having been started out of a garage with the Venom Temperature Monitor for nitro engines in 2001. In 2002 Venom introduced it’s first NiMH and NiCD batteries. Back then, as is still true today, Venom focuses on selling high quality batteries at realistic prices. We took on LiPo battery packs almost since the beginning when LiPo battery technology first began to make an impact on Radio Control vehicles about 7 years ago. Since then we’ve carried a variety of packs for all your RC needs big and small, land, sea and air. We have evolved with the technology in these few short years and the results show. We are one of the top selling brands of rechargeable RC battery packs in North America and our products are found in more than 50 counties globally.
What has made us so strong in this market is a combination of unequaled customer service, high quality product, very reasonable prices and our Universal Battery Connector System hasn’t hurt either.
We stopped selling Nickel Cadmium batteries in 2010, both because of the shift to Nickel Metal Hydride / Lithium Polymer and the environmental concerns around the NiCD chemistry. Venom still offers NiCD batteries, however most of our product line is now LiPo oriented. We carry many ROAR approved packs like our new 70C 2 or 4 S 5300mah packs for racing. We also have Lithium Iron (LiFe) packs for transmitters and even mini packs for park fliers.
Chris: That’s right and that is a very good observation. The main thing to understand about LiPo’s and what they offer is called energy density. The more power you can pack into a smaller and lighter pack the better off you are for pretty much any application you can think of. There are some benefits to using a lighter pack such as;
1) Lighter overall weight to meet the minimum race weight limit
2) The opportunity to adjust weight distribution or bias of the chassis – huge tuning benefit
3) Increased power to weight ratio – huge performance benefit
The cons could be;
1) The vehicle can be too light and not handle as well as it will with more weight
2) The battery pack must be a higher C rate and sufficient capacity to provide both the runtime and punch the driver needs
3) The higher C rate packs can be expensive
4) Depending on the chassis you might have difficulty in keeping the pack in place adequately because chassis are not designed around these packs at this time.
LRC: When trying to decide which battery is right for your application (onroad, offroad, 1/10 scale, 1/12 scale, bashing, etc.), what are some key things to take into consideration?
Chris: I think that the individual needs to look at the vehicle and decide based on both use and cost. RTR vehicles do not need high C rate packs and therefore you can bank that savings into more packs with higher capacity and cycle them for more driving time for example. If you’re racing or think about racing then you can consider spending more money on high performance packs so look for the higher C rate and lower capacity packs because again you’re looking to save weight to increase performance.
Of course its awesome to have the highest possible punch and power for bashing so you can climb and jump just about anything. If that’s your thing then you want the highest C rate and more capacity so your power system isn’t lacking but you may learn quickly that your vehicle’s motor and ESC can’t take full advantage of what the battery can deliver!
LRC: There has been all sorts of batteries hit the market with 90+ C ratings. Some say these batteries offer no more punch and performance than something such as a 60C or 65C battery unless ran at higher temperatures. Is this true?
Chris: That is a tough point to prove because the average guy will not test to the levels needed to see the benefits or the shortcomings of this claim. The reality about C rate is that it’s the prediction of the packs ability to deliver a certain amount of power, to put it simply. What you should see in a high C pack compared to a low C pack is the packs ability to deliver the required power instantly while keeping the highest voltage under load and simultaneously not over heating for the duration of the capacity and use of the pack…does that make sense? In other words you can look at the C rate as a measure of the packs ability to keep up with your needs. At some point the numbers don’t make sense and your system will never demand 300-400+ amps but your system will demand 110 amps right now in an instant. A few minutes into a race, a good pack will not break a sweat and it will deliver the power you require until the finish.. Of course set up is extremely important and we can discuss race strategy and set up using LiPo batteries another time.
As for temperatures this is a safety point with me and as a result we have a general policy to keep operating temps below 120F. The reason for this is for thermal runaway and failure prevention. Above 140F a LiPo pack’s chemistry can become self- feeding and begin to get hotter even after the pack has been disconnected. We call this “Heat Soak,” a state where the excited molecules continue to generate heat after the pack has stopped providing power. We have all experienced this whether you realize it or not. A pack can get about 20 or more degrees hotter after it is disconnected so if its already over 140-150F for example then there is a real chance of cell damage and/or total failure.
In all of our testing at typical ambient temperatures between 70-100F there is no reason to run packs hotter or preheat them to get better performance. A LiPo pack in this condition will self heat up to about 90-100F and operate there until its discharged at which time the added stress will bring the temperature up.
Venom packs deliver their rated current at maximum C rate and not exceed 120F under load in most cases, that is our standard. There is no need to operate at any higher temperature and due to other limiting factors you would risk a failure at the next weakest link, for example the plug and wires unsoldering themselves due to the high heat transfer. Some new cell chemistries do allow for a slightly higher temperature range of operation but you must know what those limits are and the manufacturer should supply that information to be certain. The bulk of the LiPo packs out there right now will not handle higher temps and you must understand this, read the labels!
In cold weather there is a benefit to preheating your pack up to 90-100F before use. The reason for this is that the battery will not deliver its best power until it reaches its most effective operating temperature under load in use. LiPo’s hate cold weather! Rather than waste track time warming up the pack and falling behind from the start of a race, if you preheat the pack in the pits to 90-100F and then run it you will be better off than the next guy for sure, at least for the first couple minutes while his pack is warming up to compete. As a general rule if the weather is colder than 70F then preheat your packs to get the best performance for that day.
Safely preheating batteries can be as simple as keeping the pack in your pocket or coat or placing it on the dash of your car. You can also use tire warmers but those can get too hot so you need to know what peak temp they get to before you attempt that and limit the power used to regulate the temperature. Please beware of any loose metallic articles in your pockets or even a metal watch touching the plug of any battery pack you might place in your pocket!!
Chris: That’s pretty straight forward…. 1C. The best thing to do is follow the 1C rule. The 1C rule is to take the capacity divide it by 1000 and then multiply that number by 1. The factor 1C is provided by the battery industry and is a standard figure.
So for example;
5000mah / 1000 = 5
5 x 1C = 5 Amps
Charge at 5 Amps
If a pack is rated for 5C charge rate then;
5000mah / 1000 = 5
5 x 5C = 25 Amps
Charge at 25 Amps
The higher charge rates are where you get into a hard time finding or affording the equipment to charge a pack at those higher rates.
If you follow this standard then you won’t harm your packs and you will protect your considerable investment. The moment you start to fast charge them, 2C-5C and above, if they are not rated to do so you are effectively reducing their service life. Buyer beware, all LiPOs charged above 1C will have a shorter service life than those treated with respect and charged no higher than 1C, period. There are packs designed for fast charging and these are OK to follow the manufacturers recommended settings but keep in mind you need a good charger system/set up to do this safely and you will not get the total number of charge/discharge cycles that give the same window of performance as compared to the same battery always charged at 1C. The only reason to fast charge is for saving time. If you’re not in a hurry then charge at 1C even if the pack is meant to be charged faster, it will last you longer. A typical discharged pack should not take longer than about 1 hour to charge unless your balance charging it.
Some guys are crossing over their old NiMH habits and applying them to LiPo technology….DONT! LiPo’s have their own behavior and requirements and you must know this to be safe and get the most from your LiPo packs.
LiPo packs do not see any significant temperature change during charging unlike NiMH packs which peak charge at 120F! If you do see an increase in temperature there is a problem unless a manufacturer has specified this is normal and I’m not aware that any do at this time.
LRC: Obviously balancing a battery is good for it, but how often does it REALLY need to be balanced?
Chris: If you have a pack that has been balanced to start off with then it depends on the quality of the cells over a period of a few cycles. This can vary between packs from the same production line and from brand to brand so you really just need to pay attention to your packs. Use a balance checker with readout and it will display the individual cell voltages in a couple seconds. Why is this important is the next question. Because ESC’s are not reading this and managing the cells while in use. For example if your 2 cell 7.4V pack has a low cell when the LVCO (Low Voltage Cut Off) built in to many of today’s ESCs activates, the ESC will see the average of the cells voltage together as one value, not individually. If one cells voltage is 2.8V and the other one is 3.2V then the average is 3.0V and the ESC will cut off as specified or as you have set it. What the esc has also done is allow one cell to drop to a dangerously low voltage most likely damaging that cell and you could see it begin to balloon. The difference between these cells is only .4V, but as a rule you should balance your packs when they vary about 0.1 to 0.15 between cells. If you balance charge them about every 5 cycles or after heavy use then you should be fine. Just pay attention to the cells individually and decide when to balance charge.
LRC: Now let’s talk discharging. What is the best way to discharge LiPo’s, and how often should this been done?
Chris: There are a few ways. You can use your charger if it has a discharge feature, however that usually takes a long time. I use my old set of lamps from the NiMH race days and plug in a balance checker to display the voltage per cell. This method takes a little less time than a charger at 1 amp. I discharge at about 3 amps. What you’re doing is putting the packs to bed for the time they are stored between uses.
LRC: If a battery is going to sit on the shelf for an extended period of time (2 weeks or more), should the battery be charged or discharged?
Chris: Discharged. This is important to do so the chemistry is more stable while stored. LiPo batteries do not like to be stored, they like to be used and cycled so to protect them it’s a very good idea to discharge your packs to about 3.5-3.7 volts per cell. If the pack sits for a long time then check them periodically because the voltage will decay and if it drops below 2.8V per cell you now have a paper weight. We call this a “cold failure” and a cell could balloon in this condition.
Many of todays chargers have a “Storage Mode”and our chargers like the Venom Pro Charger and Pro Charger Plus have this feature built in. You can use this mode to prepare the pack for storage or do it manually but whatever you do keep an eye on things at all times.
LRC: What do you think will be the next big breakthrough in batteries for racing?
Chris: That’s a good question and manufacturers are testing new chemistry all of the time so I would look to that area to yield the next generation of race packs. High Energy Density, compact LiPo packs and high current capacity is the basic direction these packs are going so I expect to see more of this in the future.
Chris: We started in batteries and we are a leader in this segment, however we’re not going to rest on that for 2012. This year Venom will be releasing a new generation of race packs that will offer super high sustained voltage under load, however they will offer lower long-term cycle life. There’s almost always a trade off right? You can also expect to see some pretty cool new chargers with features never offered by anyone to my knowledge before. Rest assured, Venom’s going to continue to surprise and deliver cutting edge batteries and charging systems to power all your modeling needs. Stay tuned, we’re just getting warmed up!
LRC: Thank you so much Chris for taking time with us today, is there anything you would like to add?
Chris: It’s a very exciting time to be in this hobby whether you’re a consumer or a manufacturer. We are seeing the benefits of several outside technologies coming together into one industry simultaneously. We have never in the history of RC had this much power, performance, reliability and variety so if any of this peaks your interest, then now is the best time to get involved. Please support your local hobby shops and talk to the people of this great hobby. There is so much to learn and great people to meet and mentor you so you have the best possible experience and maximum fun. After all, it’s called a hobby for a reason so enjoy it at this incredible time!
Thanks to Mike and LiveRC for bringing this information to the public and supporting our efforts. From all of us here at Venom we wish you all a Happy New Year and the best of luck in your RC efforts in 2012.
Hey Racers! Keep the shiny side up and remember one thing… Venom’s got your back!
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