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Old 04-09-2008, 12:04 PM   #1
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Default Tenergy 3800s, Decent Battery, Great Bargain.

Long before recent reports of tainted products such as lead paint in kid’s toys and anti-freeze in toothpaste, I noticed a general lack of quality control in many of the consumer products being shipped to the U.S. from our communist oversees trading partner, China. It was back in the early ‘90s, when despite the recent history of the Tiananmen Square Massacre and ongoing human rights violations, then president Bill Clinton advocated and won the restoration of China’s “Most Favored Nation” trade status. That, coupled with China’s own ongoing economic reforms, led to the ever increasing influx of Chinese made products that we see today. Remember when Walmart boasted about their “American Made” products? You’d be hard-pressed to find anything in that store made in the United States today. So now as a consumer, I usually have two choices when I go to make a purchase, buy Chinese or come home empty-handed. And as long as that’s the case, I try to make the best of it.

All Chinese-made products are not created equal, but many are. And I don’t like paying more for something if I can get an equivalent quality product for less. Ebay is an interesting place to find growing businesses specializing in the resale of new products made in China, and www.All-Battery.com is one of them. I had never heard of Tenergy cells before. I got started in RC around 1988 and back then everyone pretty much ran Sanyo SC, SCR or SCE NiCD cells. Occasionally, Panasonic came up with a competitive cell to counter but then Sanyo would make an improvement and everyone would jump back on their wagon. In 2006, I re-entered RC car racing after a sabbatical that lasted several years. I needed to purchase new batteries because my old SCRC 1700s just weren’t holding much of a charge. As I shopped around I noticed that there were a far greater selection of batteries but one thing they had in common is that they are almost all made in China. I opted for the Intellect 4200 cells that were popular at the time and those performed very well. Now only two years later and really only one summer’s worth of racing, those packs aren’t holding near the charge they started with despite having been properly maintained and stored. That’s nowhere near the lifespan I’m still getting out of my Sanyo SCR 1400 pack I purchased somewhere around 1993. So in shopping this time around I thought I’d give Tenergy a chance. If they don’t last, so what; if I can get the same amount of use from them as I did the Intellect cells for a fraction of the price, it’s worth a try.

Performance is a separate issue and I didn’t expect much. That led to a pleasant surprise that the Tenergy 3800 NiMH cells are really pretty decent cells. I needed some 4-cell packs to get into the new U.S. Vintage Trans Am class. I took one bad cell off an Intellect pack, put the spare in the glow starter for my planes, and I had my main pack. Now I only needed two qualifier packs that could last 5 minutes in my TC3. I spotted the Tenergy cells on Ebay, and looked up www.All-Battery.com. They had a weekly special of one 9.6V, 3800 mAH for $16.99. Such a deal! That’s an 8-cell pack I can break apart and rebuild into two 4-cell packs for $8.50 a piece, not including shipping. I already owned a roll of cheap shrink wrap I bought at American Science and Surplus, and the Dean’s connectors and battery bars came off the packs in my recycling box. One bonus was that the pack came with a Dean’s connector, but since the wire was 14 gauge, and the ones off my old packs were 12 gauge, I didn’t use it. Not bad to have a spare though. I don’t think the Dean’s “style” connector that came with this pack is the genuine article. The dimensions and make up of the plastic are slightly different. However, it does mate perfectly to my existing connectors.

For my pseudo-scientific experiment, I used my reborn 4-cell Intellect 4200 as a reference. I cycled it a couple of times using my Duratrax Ice charger and then set it for a 10 amp discharge with a 0.9 volt per cell cut-off. The Intellect pack gave me a discharge rating of 3223 milliamps and 1164 seconds of runtime at just over 4.8 average volts. The internal resistance measured at 35 milliohms. I ran the discharge cycle within two minutes of peaking the pack on a 5 amp charge.

I cycled each of the new Tenergy 4-cell packs a couple of times using the same charging and discharging methods as the Intellect. The two packs performed very close to each other which was expected since they came from the same 8-cell parent pack. The average of my cycles yielded a rating of 2646 milliamps, 956 seconds of runtime at 4.26 average volts. The internal resistance measured at 65 milliohms. I think they still need a little breaking in.

At the conclusion of this experiment I didn’t think much of the Tenergy cells mainly because of the average of only 1.07 volts per cell. That was disappointing performance considering my Intellect pack was still yielding 1.2 volts per cell. The high internal resistance numbers I think also made the packs get very warm when charging and discharging. I kept an open mind as I knew there wasn’t a whole lot of control behind my tests. What I really wanted to know was how the packs would perform in my TC3 and whether or not I could get 5 minutes of runtime with reasonable power delivery. The completed 4-cell Tenergy pack weighed 225 grams (7.9 oz) compared to 315 grams (10.8 oz) for the Intellect, so hopefully the weight savings would help make up for some of the performance difference. Also, the cell dimensions are slightly smaller, allowing me to move them closer to the center of my car and gain better side to side balance.

I waited for a nice day. Early Spring in Chicagoland this year has been pretty harsh and we had significant snowfall as late as March 21st. Once we finally had a decent day, I prepped the car with a CO27 stock motor and went out the street to give it a whirl. I brought my egg timer set for 5 minutes, laid out an imaginary course in my head and proceeded to drive. The car had good power and speed. My final gear ratio of 5.23 was a little low but it gave the car some pretty decent top end, albeit at the expense of acceleration. My biggest concern was the power holding through the runtime. About 4 minutes into my run, I had to stop. An older woman walking her dog on the sidewalk fell as she was distracted by my little 1965 GT 350 Mustang that she called, “so interesting.” Her dog got away. I offered to help her up but she was more concerned about her little Maltese, “Muffin,” so I chased it down and apologized for distracting her.

Now back at the car I was wondering what I should do to continue my test. I decided to set the timer for another 5 minutes and just see what it could do. To my surprise, I was able to make it to the beeper while still holding enough speed to keep up with the occasional car driving down my quiet suburban street. “Wow! So now let’s drive this baby ‘till it dumps,” I thought. After about another minute or two of driving the car had noticeably less power, but that was more than ten minutes of driving so far. Not bad for an eight and a half dollar pack! I think I must have been driving for more than 15 minutes when the pack finally dumped. Because the structure of the U.S. Vintage Trans Am class puts more cars into a single heat, I don’t expect that the parking lot tracks I’ll visit will have more than a single main. So the only thing I’ll likely be competing for in the qualifiers is starting position. Anyone that has ever raced on a parking lot at their local hobby store knows that in an 8 minute main, starting position will mean very little. So I concluded that I can confidently use these batteries to complete the five minute qualifiers. We’ll see how it goes after an actual race. Maybe I’ll post an update.

Along with the 9.6 volt pack I also ordered two, four-packs of NiMH 2600 AA cells that each came with a free case. The cases were worthless as one arrived broken and the other was cracked and snapped the hinge the first time I used it. But the batteries themselves seem to be holding up very well in my Spektrum radio. My total order was $40.53 including the $13.58 for the AA cells, $16.99 for the 9.6 volt pack and $9.96 for S&H. Anyway you break it down, that’s a lot of “funtime” for less than the price of most 4-cell packs from a hobby retailer. I’ve been checking the www.All-Battery.com web site regularly under their weekly specials and haven’t seen a repeat of this price that I got back in March. However, at the time of this write-up, they are offering the same pack with a Tamiya “style” connector for $21.99 and free shipping. That’s actually a slightly better deal than what I got less the Dean's connector and when the S&H is factored in. My order was packed well, shipped quickly and I was able to pay with PayPal from their website. “Bashers” and occasional parking lot racers don’t need ROAR approval, so I think these cells are a reliable solution to the less dollars, more fun equation.

Last edited by beemerfan; 04-09-2008 at 01:08 PM. Reason: error in text
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Old 04-10-2008, 03:32 PM   #2
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Very, very comprehensive test you have here!

I was also looking at the Tenergy cells, but I saw several reports of people who bought the cells and said that they were "over rated." However, the price difference makes up for it, as you said.

This sort of reminds me of Ethanol gas...haha, I'm sure you know why
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