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ASK Cubby, 03.05.2014, Version- Digital Questions Converted to Analog Answers

“Backyard Bash-Racing

Hey Cubby,

I got a backyard track that I built for my buddies, my sons, and me to “race” on. We rarely have enough people to turn marshal so we just race around and when someone gets rubber side up, we all just drive over and someone flips them over (we all have SCT’s, try doing that with a buggy lol), then we take off racing again. That way we are always bunched up for maximum tire rubbing fun because someone always tanks it every couple laps. Anywho, once in awhile we do get enough people to show up and have some semblance of a real race. I am looking into getting a cheap timing system. Do you have any recommendations? I know you are not a fan of “real racing”, but this is definitely not that. Nitro, electric, 2wd, 4×4 altogether. Only rule is “NO crybabies”. If you are ever in the NW Ohio area, stop out! I attached a clip of the “Vickery International Harvest .500″ (it was in October).

Thanks,

Dustin P.”

Cubby- Yo hey congrats Dustin, you’ve just won our coveted “Letter of the Month”, thus entitling you to a free BigSquidRC t-shirt. Hit us up with your snail-mail and shirt size for the hook-up.

Soooo… how did you win “Letter of the Month”? By not only displaying how much fun it is when things don’t get too serious, and by the cool video that you attached to your email. Your track looks like tons of fun, it is covered in grass, which has good traction yet results in minimal tire wear, and those huge banked corners are off the hook. Yes, I wish I could get some laps in, it looks that fun. Also, your single “No Crybabies” rule is perfect. The more rules there are, the less fun everyone is going to have.

To get to your actual question… what is a good cheap timing system? First a warning. Every time you “up” the professionalism (like adding a timing system), the further you will get away from the fun you are having right now. Like the good times you are having now? DON’T CHANGE ANYTHING.

But… should you really think a timing system will add to your fun, I would go super old school. I would skip transponders and a loop and do hand scoring. Now, I am far too lazy to Google an old school hand scoring program (where you literally hit the number 2 on the keyboard when car #2 crosses the line, hit the number 4 for car #4 etc), but they should be easy to find, and best of all, they should be free. The only cost you will have it supplying some junky old computer to score with, and none of the guys “racing” will have to deal with all the hassles of running a transponder.

Thanks for the email Dustin, your Bash-Track proves that it is still possible to have fun racing rc cars.

Check out the video here:


“Ask Cubby

Cubby,

I have a question about charging lipos. I am a little confused about charging and balancing batteries. I have read that you should balance them every time you charge them, is this true? I have also read you should charge them at the lowest rate you can but I also read you should charge at the highest rate you can. Could you help clear this up.

Kevin McK.”

Cubby- Hey Kevin, thanks for the email. You wouldn’t believe how many LiPo questions we receive every week.

First up, should you balance charge every single time? In the early days of using Lithium based packs in rc cars they didn’t even come with balance ports. Back in those days it was impossible to balance charge, you simply hooked up the primary wires to your charger and let’er rip. Now days every single pack comes with a balance port, as does every charger. The upside to balance charging is ensuring that none of the cells will ever get over-charged. Over charging a Lithium cell is dangerous business, and balance charging prevents this. On the downside, balance charging can take extra time, not much, but slightly longer. Should you balance charge every time? IMO yes, the upsides far outweigh the down.

What’s better, a slow charge rate, or a fast one? I am not going to answer this from a “I heard it on the internet” perspective, I am only going to answer this from knowledge I have learned first hand. I hate to give out information without cold hard facts to back it up, but in this case I’ve never found the hundreds of hours of free time to do the required testing to back up how I feel about charging with graphs off our West Mountain CBA.

So here it goes… IMO slow charging a LiPo results in longer pack life. For example, if you charge a Happy Flower 2S 2000 40C pack at half a C you might get 200 cycles out of it. On the exact same pack you might only get 50 cycles if you charge it at 5C. Once again, that is just my opinion. The biggest downside? It might take over 2 hours to charge a pack at half a C.

My opinion on fast charging a LiPo- they get slightly warm resulting in lower IR and higher output voltage, not a ton, but a little. That can be a big deal in “stock” classes where the pitiful 17.5 motor that racers are running can really benefit from another .2 volts of input power. Of course charging at a quicker rate will result in faster charge times, charging at 6C you can often have charge times of around 15 minutes, which is awesome if you don’t have many packs and want to get in a lot of driving time. But… if you are running a high horsepower brushless system, or running on high cell counts, any slight bump in voltage will only make it harder to control your truck, and IMO the faster charge time will reduce a pack’s usable amount of cycles.

So… what rate should you charge your LiPo? That’s up to you my friend, weigh the various upsides and downsides to see what works best for you. We typically charge at the maximum recommended rate to save time, but no faster.


And there ya go ya bunch of freaks, that’s it for another ASK Cubby. Submit your questions/rants/illiterate banter to Cubby at BigSquidRC.com. If your letter makes the big time you’ll get something free, yes, free.

YOUR Cub Reporter

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Posted by in Ask Cubby, cubby on Thursday, March 5th, 2015 at 9:38 pm

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