Text by Jay Kopycinski
Photos by Cheap Battery Packs
Name: Mike Frederick
Business: CheapBatteryPacks.com
Location: Hillsboro, Oregon (just outside Portland Oregon)
Products: Custom high performance packs for any RC (or any) application and pack building materials for the do-it-yourself crowd. Nimh, Nicad, and, Lipo technologies.
RCC: How long have you been into RCs and how did you get started in the hobby?
Mike: I got into RC because of my fascination of flight. I went to my local hobby shop and picked up an electric flying wing (called a Zagi) and was hooked. From there I got into RC helis and cars (both gas and electric). I had no training and did not know anyone into RC when I started. I had to teach myself to fly. But after starting I quickly found others who where into it. These relationships later helped start my business.
RCC: How did you get started providing batteries for fellow hobbyists?
Mike: I started the company about 5 years ago. When searching for batteries for my Zagi I was shocked at how expensive they were and how few choices there were for batteries. With a little research and a lot of questions I found some sources I could work with. I learned quickly that not all batteries are created equal and started to zero in on specific products that I knew would be needed. I felt if I’m happy with them then others would too. So far it seems as though I was right.
RCC: Have you seen a growth in interest from customers wanting packs specifically for RC crawlers?
Mike: Yes - this market has grown quite a bit for us over the past year. I have two employees who are very much into it and have helped spread the word about us.
RCC: Can you give us some tips on what specs we should consider when choosing a cell or pack for a crawler?
Mike: Since crawlers are very customized I would consider the pack when designing your crawler. Do you want it to sit low or high? How much weight do you want to carry? What type of motor system will you use and how much power will it require? There really is no limit. Since we specialize in custom packs we can build any strange pack you could possibly think of for a crawler. In essence, that is why we exist. Most packs found at local shops are just your barebones basic packs. You will have to butcher them to get them to fit for a crawler.
RCC: Is there anything a hobbyist shouldn’t do when designing a custom pack?
Mike: Determine how much power you think you’ll need. Crawlers tend to draw lower current then other RC applications so most can run off smaller cells like 2/3A or 4/5A, which are easier to work with. But take the basic measurements of a single cell and visualize or actually mock up where they will be placed. From that you can take measurements from one cell to the next if the pack will be sprawled all over the chassis. Or if you can cluster the cells into a more typical pack, simply sketch it and let us know.
Either way, a simple diagram is always best. A sketch should contain orientation of the cells, how you want the wire to exit and travel, and how long the wire leads should be (including between nodes of cells if applicable). But there really is no limitation as long as you can show us how you want it. How big is too big? That is really up to you -- if you can use large SC cells and don't mind the weight and have a spot for them, then go for it.
RCC: Can you briefly describe the advantages or disadvantages of using a Nimh cells versus Lipo cells?
Mike: To simplify -- Lipos offer more power in a smaller package in both area and weight. We call this energy density. The ratio is almost 3:1. Meaning it takes 3 Nimh cells to equal one Lipo cell of the same capacity. For flight, this is a big deal. For crawlers, the low profile of Lipo cells might mean a cleaner fit. Also, only 2 cells (7.4 volts) will usually work for crawlers. But Lipos are more fragile and finicky than Nimh, not to mention more expensive. There is more support equipment (balancers) needed. So Lipos, for many, might not make the most sense. I would say that if you need to be at a certain weight, then Lipos will help lower your weight. But other than that, for crawlers, I am not sure what other advantages there may be.
RCC: We’ve all heard of Lipo batteries that have exploded or caught fire…..is this still a concern today?
Mike: Lipos only catch fire if charged improperly or due to charger/balancer failure, both of which are very hard conditions to recreate. Most of the "movies" you see online are created. Meaning, someone creates the condition on purpose then films it for a "see what can happen" affect. The only other concern is shorting them. If a Lipo is damaged, they can short and we have seen where a punctured Lipo can catch fire. This would be bad news if it does this near something flammable. But Lipos don't spontaneously combust. Something will cause this condition.
So, if you use Lipos: #1) charge in a safe area (Lipo sack is a good investment), #2) when running them and damage occurs remove them from your vehicle (if safe) and put them in a fire safe environment, and #3) never ever charge them in your vehicle (basically #1 again). Hazardous conditions are not common and it would take something very sharp and metallic to cause the Lipo to combust via puncture. In my opinion, Lipos are very safe and we have yet to have any issue with one. Not one of our Lipos has caught fire. But it is always best to keep an eye out.
RCC: Is there any reason for a crawler to consider using Nicad batteries these days?
Mike: Nicads are hearty critters, but there is no power advantage. Nicads can handle a higher charge current which some people like. But, the large capacity that Nimh offers usually more than offsets that. Nimh are simply better when it comes to power delivery these days, but this depends on what type of NIMH you are using. Not all batteries are the same, so only high drain cells (our specialty) should be used for any RC applications.
If I had to say some negatives of Nimh -- they self discharge quicker and don't like to be left uncharged for super long periods. It’s always best to store them fully charged if you plan on not using them for a while. They also don't like to be left on a trickle charge forever either. So, it is best to peak charge them just before use.
RCC: Can you provide any buying tips on choosing a battery charger for a crawler?
Mike: Peak charger, Peak charger and Peak charger -- we are amazed at how many people still use wall chargers or older Nicad chargers for their NIMH packs. A good peak charger will last years and will keep your packs running at top performance. I see many of you spending tons on your crawler but cheap out on the charger. If you are going to run electric then treat the part that fuels your cells with some priority -- the Hyperion 5i (or 5i ac/dc if you don't have your own DC power supply) are great buys. They actually do Nimh, Nicad and Lipo -- even if today you don't want Lipo, you may decide next year you do. I know that wall chargers are under $20, but I have seen hundreds of bucks lost due to wall chargers cooking batteries. I guess it would be like buying a nice high performance sports car but getting 2nd hand $10 tires. What's the point?
RCC: Where do you see the future of RC battery technology going from here?
Mike: From a battery perspective we will see continuing development in the Lithium technologies. There are different chemistries within the Lithium market place. Iron (Fe), Manganese (Mg), and some others are making their way out there. Like A123 Lion (still a Lithium technology). The next big step in Lipos will be faster charging. LiFe (Lithium Iron like A123) can be charged in 18 minutes. So there is some neat stuff just coming out now. Capacities are growing too and we should still see some better energy densities as well.
On the Lipo scene, most people only seem concerned about discharge rates (10C, 20C etc). Currently we are at 30C with 50C bursts. this means that a 2000mah cell @ 30C discharge = 60 amps current (2000 x 30 = 60,000mA = 60 amps). This could have a burst of 100 amps. This is very impressive. I expect to continue to see the C ratings increase but level off in the next year. Most people will not need 30C. After all, at 10C you will be done in 6 minutes. At 30C, it’ll be 2 minutes. So who wants to play for 2 minutes? But these ratings are also an indicator of advancement and durability. High discharge cells tend to do very well at lower discharge rates, which simply means more cycle life. That is always good. More cycles equals better value over time.
RCC: Lots of great info Mike. Thanks for your time and valuable tips!
