United RC Race 32 & X32 Micro Battery Packs

by The JANG | October 18, 2004

Overview

In a departure from my usual format, this review covers not one, but two products, both United RC 6-cell racing battery packs for Mini-Ts and Micro RS4s.

The "Race 32" features United RC's specially-branded KAN-based 1050mah cells, while the "X32" uses the relatively new GP1100 cells. The "32" in these names refers to the configuration, 3 rows of 2 end-to-end butted cells. This is in contrast to the more common configuration of four cells side by side with two laid end to end across one side (United offers this configuration in their Race 42 and X42 packs). The "32" setup uses three direct end-to-end cell connections and two battery bars, whereas packs in the "42" configuration have three battery bars plus one patch bar or wire. Racers tend to favor the "32" configuration knowing that shorter connections and less of them will give you less resistance and less things to physically split apart or short out. Enough of the descriptive stuff, though -- it's time to try these packs out.

Quantitative Tests: The Stage

Now, I like gut feelings. I like being able to say something "seems" really good. However, I know that my gut feelings are not going to help a single reader out there win a race or make an informed purchase decision. Rather than telling you all that "I love these batteries -- they feel fast," I decided to get serious. Real serious. Experimental results were collected over the course of three very long and lonely Sundays. I broke in the battery packs for 3 charges each and recorded 49 individual speed runs and two runtime runs per pack. I didn't just test the United packs, either. To have something to compare to, I assembled my own "32" pack made from a set of the same generic, no-name green "1100mah" 2/3A cells a lot of the big- and small-name micro & receiver pack manufacturers use. This would serve as a baseline.

Here are the settings I used for the speed & runtime tests:

Speed measurement: A 4' wide, 50' long speed trap was measured out and marked on asphalt and high-quality video was captured from a vantage point aligned with the midpoint. Successive straight runs were made in zero-wind conditions and start and end points were captured in freeze-frame analysis with 0.033 second precision.

Runtime measurement: For each of the runtime tests, a just-charged pack, warm off the charger, was installed and the truck was immediately run nearly continuously until its speed had diminished to under an estimated 10mph. The overwhelming majority of the time was expended on straight, WOT (wide-open [full] throttle) runs up and down a 200-300ft stretch of asphalt, braking at each end enough to safely turn around, and immediately returning to full throttle. Otherwise, I only stopped when I needed to scratch my chin really bad, or after the occasional traction roll that I frantically ran to recover from.

Quantitative Tests: Results

The speed figures are very compelling; the X32 comes out a clear winner, and the generic pack a clear flop. Granted, nearly 21mph is pretty zippy for such a tiny little truck, but given the option, I'd take 17% more speed in a heartbeat.

The differences in runtime between the generic and United RC packs are also pretty dramatic, but the wide spread between the two figures for each of the three packs tested prevents me from declaring a decisive victor between the Race 32 and X32. The 18min. high of the X32 trounces the 16.5min. low of the Race 32, but the other two runs were equal. I took a few other runtime measurements as well, but they were taken at different stages of battery break-in, so I had to discount them. I would really need to run in large, continuous circles at one throttle level to trim down the variation and come up with a true scientific result.

There was also a marked difference in rate of peak loss between the United RC packs and the generic pack. In one speed session with the generic pack, top speed dropped from an initial measure of 22.3mph (the highest recorded on that pack) down to 20.4mph in just six passes, after which it plateaued. In contrast, the Race32 had 8-, 6-, and 5-run sequences with 0.14mph or less drop in top speed, a delta so small that it could easily be attributed to measurement error or hitting a couple extra tiny bumps in the asphalt. The X32 had a 6-run sequence (covering around 1/4 mile of ground) in which the last four runs were tied for highest speed, and a 4-run sequence in which the last two were tied for fastest.

Subjective Notes

First off, I need to note a very embarassing annoyance that I had to put up with during the tests of the control ("generic") pack. Simply put, it could not handle the amp draw of the Mamba system on Race timing. The initial voltage drop on launch was significant enough that the controller's adaptive power threshold logic would kick in (described to me by Shawn Palmer of Castle Creations as a battery-saving device) and the truck would simply stutter along at a snail's pace. I had to roll on to the throttle to get it going, on every charge. Evidently this was not a fluke -- Castle tells me the powerful Mamba really needs "quality cells," and now I see why. Only on the mildest power setting was there none of this stuttering with the generic pack. Neither of the United RC packs, on the other hand, had this problem past the first breakin charge.

On the subject of off-the-line "punch," to be honest I couldn't tell the difference between the Race32 and X32 because the Mamba system let the truck drag its tail every time without fail, given any decent amount of traction. The only difference out of the gate between packs was with the generic pack which, as I mentioned, suffered too much voltage drop and led to stuttering as the controller tried to save the pack from its own impotence.

Build Quality

From my understanding, United RC is a small, privately-owned company. You wouldn't know it from looking at their packs, though. Shrink-wrapping is done laterally and longitudinally around the entire pack, completely covering the cells and leaving very neat ends that blend into the outer contours. The wires come out at a well-planned spot and are straight and equal in length, with very neatly-attached connectors. The labels are even printed at a fine resolution.

Never content to leave good enough alone, I took an X-Acto knife to one of the packs to slice off the shrink wrap and see what it's really made of. I tried prying the end-to-end cells apart with medium-firm pressure, to no avail. Good, solid connections there. The bridges across banks were very thin metal bars thoroughly soldered at each end. I've seen many packs that use a small pattern of tiny tack welds to secure the battery bars, and the United RC pack's solder joints inspire far more confidence. Better connections mean less resistance, more runtime, lower pack heat, and less glitching.

Discussion

The points I've covered above should speak for themselves. In the end, it comes down to which you want, really good (Race 32) or great (X32). For most, the decision will be based on price. The Race 32 is $20.00 from UnitedRC.com direct with pre-installed Dean's connector (please don't get a high-quality pack and run the puny little HPI connectors, please?), while the X32 is $25.50. If you want to win tough races, I say you should skip Super Sizing your fries for a week and spend the extra $5.50 for the X32's. If you're just a basher looking to spend as little as possible, you can find bare-bones packs on the Internet for much cheaper. You get what you pay for.

The bottom line? The United RC Race 32 and X32 are both well-built quality packs which yield excellent real-world results. It's no wonder that United RC packs and cells are used and recommended by many of the top small-scale R/C racers around.

Race 32		X32

Contact Info

United RC, Inc.
Loganville, GA, USA

http://www.unitedrc.com/

770.764.URCI (8724)
cs1@unitedrc.com