08-20-2012, 10:59 AM | #1 |
Quarry Creeper Join Date: Jun 2012 Location: Vancouver, WA
Posts: 223
| School me on batteries
I have a 2200mah / 20c 3s lipo running a brushless hobbies LT4 ESC and Tekin Pro4. I am seeing delays when pulling on the throttle forward and reverse. I am needing a higher C rating battery? Is comparing a C rating on a battery to torque and the mah rating as the horsepower a safe bet? |
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08-20-2012, 11:39 AM | #2 |
Rock Stacker Join Date: May 2010 Location: Boise
Posts: 68
| Re: School me on batteries
Depending on which Pro4 you're running, that is way underpowered. MAh is capacity, and C is current. C is multiplied by amp hours to determine safe recommended current load. 2200 MAh is 2.2 amp hours (move the decimal over three spots.) So 20c 2200MAh is capable of 44 amps load. I haven't had much luck finding the actual watt rating of the Pro 4's but using the SC4x specs, assuming the 4.5=4600, 5.5=4000, and 6.5=3300... 4.5T=900w 5.5T=815w 6.5T=745w Amps are watts divided by volts. As volts go down, amps go up, so I'll use 3.8v/cell as the nominal. So... 4.5T on 2S = 900/7.6=118 amps 5.5T on 2s = 815/7.6=107 amps 6.5T on 2s = 745/7.6=98 amps 6.5T on 3s = 745/11.4= 65 amps That being said, I think the Pro4's pull more juice than the SC4x motors. If you want to stick with 3s 2200mah, I'd look for a minimum of 40c, for 88amp capability. The higher the better. If you go higher in capacity, you could get by with a lower C - i.e. 4400mah 20c also = 88amps. Think of the C rating as the carburetor CFM. If you're trying to power a big block 454 with a 650 CFM carb, it's not going to be happy. And mah is the size of the gas tank. ***Edit*** Well, having too high of a CFM on a carb can cause problems too... Not so on C rating. You could run a 100C battery with a 10 amp load. Only downside is increased size/weight due to the heavier duty cells and wiring. Last edited by tocsin; 08-20-2012 at 11:45 AM. |
08-20-2012, 11:47 AM | #3 |
owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down!
Posts: 20,290
| Re: School me on batteries
Great reply tocsin, I would also say the battery is under rated for best performance. going forwards to backwards is the hardest you can hammer on a system.
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08-20-2012, 01:31 PM | #4 |
Quarry Creeper Join Date: Jun 2012 Location: Vancouver, WA
Posts: 223
| Re: School me on batteries
Okay, that does make a lot of sense. I don't want a massive pack I have to figure where mount but still want some decent run time out of it. At least it had enough juice to twist my front driveshaft I will be shopping for a battery as well. |
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