ASK Cub Reporter, 04.19.2012- Your Reasonable Questions, My Putrid Replies

Hi Cubby, I read that charging a lipo at a higher amperage will make my truck faster, is that true or false?

Travis P.

Cubby– Hola Travis, thanks for taking the time to shoot us an email.

So… will charging a Lipo battery at a higher/faster rate result in higher output voltage under load, thus making your truck faster? Well I am not about to “guess” and give you an answer, nor am I going to regurgitate crap I’ve read on-line and give it to you as a reply. I decided to do some real world testing (Mythbuster style) and find out for myself.

The day before testing I discharged our “test” pack at a 1C rate and let it rest overnight. The next morning I charged our test pack, a Turnigy 2S 65C 6000, at a 1C rate (6 amps). The instant the pack was done charging it was placed on our West Mountain CBA and tested under a 6C load (36 amps). Why 6C? Why not. But seriously, I used 6C because it gives approximately a 10 minute runtime, roughly what people in the field expect to get while running their trucks now days. After the pack was discharged it was allowed to rest until the next morning when I charged the pack again, this time at the highest rate I could, 20 amps. As soon as the pack was done charging (this took 28 minutes on a Hyperion 720iNet3) the pack was placed on the West Mountain and discharged again at 6C (36 amps).

Here’s a few stats from the test…

1C (6 amp) Charge To 6C (36 amp) Discharge Test
Ambient Temp- 70 F
Pack Temp At Start of Test- 70 F
Pack Temp At End of Test- 95 F
Capacity- 6086 mah
Runtime- 10.17 minutes

20 Amp Charge To 6C (36 amp) Discharge Test
Ambient Temp- 70 F
Pack Temp At Start of Test- 75 F
Pack Temp At End of Test- 97 F
Capacity- 6056
Runtime- 10.12 minutes

Result of the test? As you can see from the graph below the Lipo put out less voltage, therefore making your truck slower, when charged at a higher rate. The pack actually put out higher voltage under a 36 amp discharge load, with a slightly longer runtime and a lower temp after being charged at only 1C (6 amps). For instance, at the 5 minute mark during the discharge, the pack charged at 1C (6 amps) put out 7.08 volts, while it only put out 7.04 volts at the 5 minute mark after it was charged at 20 amps.

So… to finally answer your question… based on just this one test I would have to say that no, charging your Lipo at a higher rate will not make your truck faster.

However…

1. A sample size of 1 isn’t nearly enough to be considered “scientific” in any way. Perhaps if I come up with 100 hours or so of free time (LMAO) I will dedicate the proper time to seeing if my initial test was remotely correct or not.

and…

2. If my sample size of 1 truly does indicate that a lower charge rate results in higher output voltage under load, the difference in voltage may very likely be very small. Using the example of the 5 minute mark I listed above- the voltage difference was .04 volts. 4 hundredths of a volt is a very small difference, a difference that would be nearly impossible to tell while driving on the track.

hpi e10 drift car
I was wondering can i run 2s lipo battery on a stock e10 setup with the brushed motor?
Chad K.

Cubby– Yo what’s up Chad?

Can you run a 2S Lipo battery on the el-cheapo RTR brushed motor/speedo in your HPI E10 drift car? Of course you can. Your car will be a lotttttttt faster on a decent Lipo than when running the included POS 2000 mah 6 cell NiMH.

But should you? The speedo that came in your HPI does not come with built in Lipo low voltage protection. Every Lipo battery manufacture recommends to not over discharge their packs. Without some sort of protection you might very well drive too long and over discharge the Lipo.

Also… a Lipo makes your car faster because it is putting out higher voltage to your motor. This higher voltage will reduce the life span on your stock 27 turn brushed motor.

I run Lipo’s on brushed RTR’s all the time without any issues. Of course that is my job, to destroy rc equipment, so I am not going to recommend you do the same. What I will recommend to you is to buy a Lipo alarm (typically under $20), hook it up to your car, then go enjoy some newly found Lipo power while you are out drifting.

That’s it for this week ya freaks, submit your letters, questions, answers, and unopened bottles of vintage 2000 Warhol Dom to Cubby at BigSquidRC dot com!

YOUR Cub Reporter