Amperage and MAH how is it doubled ?
 

I have done a lot of reading and have not seen a FAQ sticky on this.
I am very frustrated just trying to figure out what size lipo I NEED for my new project car. (Castle Monster combo 2200kv) 9 lbs car, 4WD, mostly street bashing speed runs and rally hard pack driving, speeds in 50's

The big problem is I read and hear different stories about Series and Parallel.

Hobby shop owner says if it's in Series "everything is doubled, including amperage
Another guy says if it's in parallel the MAH it's doubled.

For Example Two 3s 3000mah 30c lipo in series becomes 6s 6000 60c.
flip side Two 3s 3000 30c in parallel becomes 3s 6000 30c.

SO I ask you guys What is the true answer on this and where is the calculator to figure what continuous amperage do I need to run ?

Another confusing lipo issue is one lipo will say 30c at 67amps and another will say 30c at 81 amps.
I was told it depends on how many cells are in series or parallel in the battery. Problem is many batteries onle say C rating.


Castle creations told me they recomend that I run 33c for my setup. But what is the true amperage and if putting lipos in series is best then what C / amp do each batt. need?

Appreciate the help

Ok...

Series involves linking all the cells plus to minus. So the entire pack spec will mimic a single cell. So a 6s or 2 3s packs wires in series is the same thing.

eg, 6, 3000 30c cells wired in series will give you a 6s 3000 30c pack.

Parallel wiring takes 2 sets of X number of cells wired in series and wires both pos and neg of those X number of cells together.

eg, you have 2, 3s 3000 30c packs and after you wire them in parallel you will have 3s 6000 30c.

C rating refers to the ability of the cell to produce amps. It is simply a number that you multiply by the pack's amp capacity rating to determine what the pack can output.

eg, the 3000mah 30c pack can output 90amps. You get this by multiplying the 30c by the packs AMP/hr rating (3000 milli amp hour-mah = 3 amp hour)

So 30 x 3 = 90

So you see that the packs capability is related to both its capacity (mah) and the C rating. Voltage is not important when doing the math for pack amp discharge.

Total available power is determined by finding the discharge capability (as shown above) and multiplying it by the pack voltage.

So our 6s 3000 30c pack would be capable of 1998 watts. 22.2v (=6s) x 90amps = 1998 watts.

It's hobby shop employees/owners like that who set up such views of ignorance regarding ALL other hobby shop employees. linc certainly straightened this out.

Thank you lincoln
I know about series and parallel wiring
But now you have lost me with the watts at the end. SO I Multiply Volts X Amps to Figure Watts right ?
Just need calculation for KV into Watts



The hobby owner was showing me how he was just put in Garage magazine for being the first hydralic guru for low riders and how his Slot car track runs on car batteries in parallel. So I wanted to believe him.

Yea, he was definately wrong.

The only somewhat confusing part of all of it is parallel. 2 3S 3000mah packs in parallel will be 3S 6000mah, like pimp said, but it would still be 30C. Differance is, the amps double as well, just not the C. Its pretty simple one you think about it. A 3S 3000mah 30C pack is 90 amps, but a 3S 6000mah 30C pack is 180. Still 30C, but when the MAH is doubled, so is the amperage since C x Ah = amps. Got it?

Thank u squee,
Wow , thank you for putting it into that example, it makes more sense and easy to folow.
But that is weird to figure, that MAH double and amps double but not the C rating. I thought the C rating had to do with the amp output..?
So what importance is C rating, how is it used ?

How about in series, whats that equation ?
I may want to use two 3s in series

thank you for your help, it really

In laymans terms...C rating is basically like the valve size on your garden hose. You can change how fast the fluid goes through it (Amps), and you can change the pressure behind it (Volts), but that valve is always only going to open up so far, thus only allowing so much water through....

Wow!!! cliffnotes version :lol: i like it!!!!

Watts is pretty easy, it is just volts x amps. Watts are a good indicator of total power available.

You can figure that a vehicle of a certain size and weight will draw X number of watts. Main issue is figuring what wattage you need to get the job done. It is usually best just to post up the setup you plan to run and the desired result. The the rest of us who had done something similar can offer insight.

More example:

say you want 2000 watts, and plan to run 4s - 2000/14.8 = 135.13 amps. If you figure that is what you need at the tires, and the motor is 85% efficient, you will need about 2353 watts from the battery to get the job done - 2000/.85 = 2352.94, or you can take the 135.13 amps/.85 and get 158.97 amps needed from the battery at 4s.

So as you can see, to get 2000 watts at the tires with and 85% efficient motors you will have to have a 4s pack capable of 150 amps, so a 5000mah 30c lipo should do the trick (as long as the specs are true to the pack's performance...).

Tire weight and vehicle weight play the biggest part in figuring the amp draw a system will determine. You have to move the chassis weight around with the motor, so it stands to reason that lighter is better. Wheel weight is also a big factor, as a heavier wheel/tire will need alot more power to get moving that a smaller lighter tire. That is why we can get away with smaller lower torque motors in buggies, while truggies/MT need a big torque motor to get those big tires moving.

I think I got it, except for, if I do in series do I need a lower C than if I do in parallel to equal the same amperage ? or I guess that always stays the same ?

Are these equal ?
Two 5000 3s 30c in series = 5000 6s 30c 150amps

Two 2500 3s 30c in parallel = 5000 3s 30c 150amps

I have it all figure out except for above AND how to figure what a 2200kv motor needs in watts ?

its equal amp wise, but obviously the 6s is double the power as voltage is 2X.

Another way to keep is straight in your head is just noting that a given battery equals a discrete amount of energy (& power.) Hooking two batts in series or par does not change the total amount of energy, ie it is two units.

EG. Energy equals power*time or (voltage*amps) * time.
A 3S 5Ah cell equals--> 3*(3.7V) *5Ah= 55.5Wh (watt hours)

So if you take two packs, the total Energy is 111Wh no matter what.

Series: ie 6S 5Ah--> 6*3.7V*5Ah=111Wh
Par: ie 3S 10Ah --->3*3.7V*10Ah=111Wh

You know the guy at the hobby store was FOS, bc according to him:
2x 3S 3Ah packs in series = 6S 6Ah... try the math
3S 3Ah= 33Wh => two packs =66Wh
LHS "magic packs": 6S 6Ah= 133 Wh... nope, fail. You didn't somehow create energy just by changing wires. If you could you'd solve the world's energy problems and win several Nobels for overturning fundamental laws of physics. lol

woosh over my head. I'm not at that level yet.

So regardless of Series or Par I still need a 30c which ever way I go ..?

If the 2200kv is 1250 watts DO I just need 1300 watts of battery power ?

You might not need 30C. That would depend on the mah of the pack. And to answer your question earlier, the C rating refers to the cells. a 3000mah 30C is still gonna be a 30C cell no matter how many there are. Thats gonna be 90 amps, but if you put 2 in parallel, that will the 6000mah. Still 30C since the cells haven't changed, just the number of them. 6000mah 30C would be 180 amps. Get it? Its still 30C since thats what the cells are rated at. The amps just raises because the mah raises since there in parallel.

If you think you need 1250 watts of power to the wheels and you plan to use a motor that is 85% efficient then you will need some thing like 1500 watts of battery power

1250/.85 = 1470

Now the problem iswhere did you get the 1250 from? Someone told you that? Doing the math will get you the numbers, but there are no hard and fast rules on what numbers apply to what vehicle due to the giant amount of variables.

Best to list your setup and intended use and we will do our best to suggest alternatives for lipo power.

I can see bursts of 1250w. Around 250w is much more common for average power draws in truggies/MT. After all, 1250w on a 6s 5Ah battery will only get you about 5 minutes of runtime...