ASK Cub Reporter, A Weekly Q & A Session- Version 09.30.2010

Here I am, still saving the world from gasholes, one at a time…
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Bigsquid
I am having a problem keeping the clutchbell bearings in my OFNA Pirate from blowing up. Any ideas what I am doing wrong?
I like the new look of your website.
Earl

Cubby– Ofna Pirate eh? Damn those things have huge tires. Tell ya what, here’s your problem- it’s nitro, and nitro sucks. Convert it over to electric, they don’t use clutch bells at all, so problem solved. And yes, you’re welcome.

Next…

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Hey Brian, my friend at the track says that the more mah a battery pack, the more power it can put out. Isn’t mah just the capacity of the battery not the power?

Eddie

Cubby– Sorry Eddie, Brian is busy writing up his dissertation on the effects that gravity have on Planck time, so I’ll answer this one. We’ll start with some basics for the noobs reading…

What does mah even stand for? milliampere-hour
One mah is one-thousandth of an amp hour.
Generally in our hobby, the higher the mah of a battery, the longer runtime you will get.

Mah is generally measured via a 1C discharge.

The higher the load on a battery, the less efficient a battery is, resulting in more energy being lost as heat. So a battery that might test out at 2000 mah at a 1C discharge (2 amps), may only test out to 1500 mah at an 8C discharge (16 amps).

Generally, the higher the mah of a battery, the more power it will put out (with power equaling voltage times amperage).

But, like always, there is ALWAYS a but…

Let’s say we take two different brand 2S Lipo battery packs. One is from brand “X”, and the other is from brand “Y”. The brand X pack is rated at 4000 mah capacity, while the brand Y pack is rated at 5000 mah. As a “general” rule of thumb, the brand “Y” battery should not only give you more runtime, but also more power. But we all live in that pesky “real” world, and that is NOT always the case. Due to several factors, the brand X pack might actually put out more power, and also give longer runtimes under heavy loads than brand Y. But for you as a consumer, there is no way you’ll know that unless you’ve had the opportunity to actually test both packs.

For example from real world testing- I’ve tested probably a dozen different “1000 mah” cells on a West Mountain CBA. Some tested as low as 730 mah (making the cell “over-rated”), some as high at 1300 (“under-rated”) at 1C (1 amp). That is a huge variation in capacity between cells all labeled at 1000 mah. Perhaps the variations were due to manufactures fudging the numbers (in some cases likely, in others, I high doubt), or perhaps they were due simply to quality control issues, I don’t know. What I do know is most Asian battery manufactures “shoot” for performance specs plus or minus 2 percent, which in the case of a 1000 mah cell would be 20 mah. From first hand testing experience, the better manufactures get closer to around 5 percent (50 mah in this example), the worse ones, closer to 20 percent (200 mah).

The moral of all this is- from what I’ve seen from first hand testing, don’t always believe what’s on the sticker.

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If you’ve read down this far (through all the mumbo jumbo above) you are one hell of a good man. 🙂

That’s it for this week, shoot me your questions (no matter how asinine) to Cubby at BigSquidRC dot com!

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