Thread: Question Clear some things up for me? (Batts & Motors) View Single Post
Apr 25, 2011, 10:55 PM
The 6 P principle works for me
Ventura CA
Joined Aug 2007
986 Posts
Quote:
 Originally Posted by Aleriance Hey everyone I have a huge topic that I don't understand... BATTERIES AND MOTORS. I did read the complete guide on Li-Pos but I still need some clearing up. Where do I start? 1) Does increasing voltage increase your vehicle's top speed? Is this a good idea? 2) If "C" means discharge rate of a Li-Po, Would a lower "C" last longer during drives or did I misunderstand? 3) "S" represents the number of cells in a Li-Po? 4) The higher the mAh, the longer run time? 5) What are Kv in a motor? 6) What does say "20T" mean in a motor? (I drive RC buggies) Any explanations would be greatly appreciated. Thank you all so much.
First off, welcome to RCGroups! Also happy to see that you are reading various threads. There is also a "search" feature that works pretty good.

1. in general motors have "kv" ratings. For instance, a motor with a "kv" of 1000 will (with no load, i.e. just the shaft turning and nothing attached to the shaft) will turn at 1000 rpm for each volt of electric that gets to the motor. If 2 volts get to the motor then 1000 X 2 = 2000 rpm. When you add more voltage you get more rpm. There is however, a limit as to how much "power" a motor can take in and put out AND still be efficient (say 80% efficiency or better). A good electric setup is all about matching the components to the job. I am not a rc car person however there must be some good set up info in the car section.
2. Lets say you drive your car for 10 minutes and the battery is completly discharged, what is that average discharge rate? LiPo's are rated in Ah (Amp Hours) and there are 60 minutes in an hour. 60 / 10 = 6 or the avg disch rate is 6C. With 2 batts of the same capacity but different "C" ratings, they should last about the same amount of time however as they are getting low on power the higher C rated battery may heatup less since it probably has lower internal resistance and since it will loose less power due to lower internal resistance, it may run a little bit longer and hold/output a higher voltage towards the end as compared to the lower C rated batt. WARNING! just because a mfgr says their batt is a "25C" rated batt does NOT guarantee that it is! Check for reviews of the batts that you are interested in!!!!!
3. See post #4.
4. Think of amp/hours as gallons of gasoline. 1 Ah, 1 gallon. 2 Ah's, 2 gallons. The more gallons you have the longer you can run and as posted above more amp hours means a bigger battery that will weigh more and may or may not fit in the space available!
5. See #1, above!
6. no comment!

Sorry for being long winded! Hope I helped!