5c lipo battery help

[hobbimaster]

Here's a question someone might have already tried. If I already have a 3C lipo (11.1v) 4000Mah, and I want to try running 5C can I simply purchase another 2C 4000Mah (7.4v) and wire it in series with the 3C to get the 5C total voltage, will this work? Right now I have a MGM 16018 and run 2-orion 4800 lipos in a series harness. Is it absolutely necessary that the Mah match, Lets say I wanted to run the 3C 4000Mah, with the 2C orion 4800mah. Would the lipo cut off cut the packs out before the 4000mah pack get too low?

[sikeston34m]

Originally Posted by hobbimaster

Here's a question someone might have already tried. If I already have a 3C lipo (11.1v) 4000Mah, and I want to try running 5C can I simply purchase another 2C 4000Mah (7.4v) and wire it in series with the 3C to get the 5C total voltage, will this work? Right now I have a MGM 16018 and run 2-orion 4800 lipos in a series harness. Is it absolutely necessary that the Mah match, Lets say I wanted to run the 3C 4000Mah, with the 2C orion 4800mah. Would the lipo cut off cut the packs out before the 4000mah pack get too low?

The answer is No, probably not.

The ESC is only going to be looking at the Total voltage output. It only see one big battery pack. Since it's not looking at individual cell voltage, the lower capacity packs are going to run down first. The higher capacity packs are still going to have some left at this point. Kinda like this:

Cell 1 = 2.5
Cell 2 = 2.5
Cell 3 = 2.5
Cell 4 = 3.8
Cell 5 = 3.8
Total is 15.1 volts

If you have your low voltage cutoff set at 15 volts, at this point, you're still not on the cutout. Cells 1, 2, and 3 are critically low.

I'm not sure if this is how the exact numbers would work out. But you will over work and over discharge the 4000mah pack and it won't live very long at all.

One other thing, the "C" rating of a pack is it's Continous Discharge rating for Amperage.

Example: A 10C 4000mah pack

10C X 4 amps hour = 40 amp continous rating

I hope this helps.

Just to break down what the mah rating is:

Mah is how much current the battery can produce for a given time frame.

1 amp hour is 1000 mili-amp hours. So hypothetically, A 1 amp hour battery can sustain a 1 amp draw for 1 hour.

These numbers can be played with in a number of ways to do estimates.

[hobbimaster]

Do you think using the 3-cell 4000 MaH pack with another 2-cell 4000 MaH pack wired in series stand a chance? I can see what you are saying about the different packs not working using different capacities. I'm just trying to avoid buying a 5-cell when I have this 3-cell lying around.

If you match the brand and capacity it will be fine. One tip, C is a discharge rating. When you are referring to 5 cells in series, it's 5s, not 5c.

[Patrick]

How old is your 3s 4000mah pack and how much use has it had?
You can use a 3s pack with a 2s pack of the same mah and type wired in series (that's what I have in my truggy), but it's best not to use old cells with new cells. Otherwise the same thing that sikeston34m was talking about in the first half of his post could end up happening.

[hobbimaster]

The pack itself is a Maxamps maybe 4-6 months old, But I only used it maybe 6 times since the 1/10 buggy I put it in was basically uncontrollable.

[hobbimaster]

BTW, will a motor run cooler as voltage is increased? I want to use a neu 1512 2.5 and have read the motor gets hot as compaired to a 1515 1y.