Hi JPBLUE1000,
welcome to the dark (faster more powerfull, heaps more torque) side.
Most motors are rated in KV. KV is a denotation of how many Revolutions that motor will do per volt supplied. You should also find that the motor will be given a maximum RPM. In the case of the Castle 2028 Motor in the conversion it is 30 000. This is useful when building your own system because it lets you work out if the voltage you want to run is suitable for the motor you have or vice versa. There is no point in having a motor that is only rated for 10 000 RPM if the voltage you are going to be running is going to spin it to 60 000RPM. Generally most motor will not have a amp rating but will normally come with a continuous and max wattage rating. The 2230 i used in my conversion is rated for a maximum of 10 000 Watts
LIPO batteries are rated in Voltage (number of cells or "S") , discharge and Charge capabilities ("C" rating) and storage (mAh Mili amp hours). All of this information is very important, it will have a great impact on how your system will run perform and is i believe the most critical part of the system. A good quality battery can make a poor system perform at its potential, a poor quality battery can make even the most expensive systems perform badly.
atmo3624 said that 8s is what you need. What is implying is that you need a battery of 8 cells. All lipo cells are rated at 3.7V per cell, an 8s pack has a nominal voltage of 29.6V. however when a lipo battery is fully charged the voltage will be 4.2V per cell.
C rating.
One C rating is one of what ever that battery capacity is. If you have a 5000mAh battery pack (regardless of voltage) than one C is 5000mA or 5amps. This is important because it tell us how many the Amps the battery can discharge safely, and at how many Amps the battery can be charged at safely. For now lets stick with Discharge. If you buy a battery that has a discharge rating of 65C and a capacity of 5000mAh, than that battery pack can safely discharge 325A (65C X 5000mAh = 325000mA 325000ma / 1000 (to convert to Amps) = 325A )
PUTTING IT ALL TOGETHER.
I wanted to convert my Leopard 4 to brushless, i knew i needed a big motor to do it so i went to the NEU website (I really like their motors and their customer service) and picked the biggest motor they do as a conventional inrunner a 2230. I knew i wanted to run 12s of batteries in my model, so i looked at all the 2230 motors and noticed they are rated for 40 000RPM. I than looked at the KV of all the motor and one motor the 1Y is rated at 725 KV. By doing some simple maths 40000/725=55, I now know that i can run that motor up to 55Volts. 12s is 44.4 so i am in the range i want to be in. That is motor sorted. On their website it has all the motor max voltages.
So 44.4 X 725 = 32190RPM i am in the range i want to be in safely.
Now we know the KV, the maximum wattage from the website (10 000) and the voltage. I can work out how many Amps my system should pull at 10 000W on full Voltage.
Amps = Wats/Volts
= 10 000/44.4
= 225Amps.
I need a battery that can put out at least 225 Amps if not more continuous. I like using thunderpower batteries and have had a lot of success with them. They do a 65C battery.
Amps = C X mAh/1000
= 65 x 5000/1000
= 65 X 5
= 325Amps Continuous.
All that is working off of our maximum system voltage. But we know that as we use our electric model the voltage will begin to decrease. I have my low voltage cut off set to 3.0V per cell. We simply run through the maths for max system amps to determine what the max amps will be.
3.0X12=36V
10000/36=277Amps
From this we know what the max our system should pull is at its lowest voltage. Our batteries are still in the safe range, we need to pick a speed controller that will be able to handle that amperage and voltage. Find a brand of controller you like (I picked MGM) and they do a speed controller that can handle 400Amps Continuous, and up to 63Volts. My system is well within its limits.
That is the way i have always worked out my brushless systems if i am designing one from scratch. It has always worked very well for me, my motors and speed controllers last well, i have good temps and my batteries last.
One final note on batteries. NOT ALL BATTERIES ARE EQUAL!!
You will see that some batteries are rated at 150C. Is that continuous, burst and at what voltage. There is no regulation, industry standard to say where a company has to rate their lipo pack or at what voltage. If you get a pack that is rated for 80C but that is only at 2.0V per cell. AT 3.7V per cell it might only be 20C. It is useless as the pack never drops to that voltage. Remember a LIPO BATTERY SHOULD NEVER EVER EVER BE DISCHARGED BELOW 3.0V PER CELL. Serious damage to your components, your model or worse to you could occur.
Lipo Batteries is one of those things you get what you paid for. I have had good results from Thunderpower, Hyperion and flightpower packs. They are not the cheapest or the most expensive but i have found that they have the truest readings and the most reliable. I hear a lot of people saying they will only use turnigy packs because if it does go bad and puff the pack is cheap to replace. That is all well and good if you pick it early and the pack is on your bench, what if it is in your car or worse your hand.
I know that there is a lot of info and i have only glossed over most stuff if you need any help or have any questions please post in this thread or PM me if i can answer it i will.
