I don't understand this.

[Maxists The Baddist]

I'm looking at flightpower batteries on helihobby and the 6s1p says 4900 mah and 22.2v. The 4s1p is 1800 mah and 14.8v. Are there different cells in these batteries? I think each is 3.7 right. Times the number of cells to get the voltage. But why do they have different mahs?

[Jermo]

it all depends how they are connected, serial, parallel, or complex.
Jermo

[MarkD]

They're both set up in Series

3.7*4 = 14.8V
3.7*6 = 22.2V

The amperage is because they use differing amperage cells ie 4900Mah for the 6S1P pack and 1800Mah cells for the 4s1p pack

[Maxists The Baddist]

Every cell is 3.7V. So can the manufactuer just choose whatever Mah they want the cells to have that form the pack? Asking because I'm just amazed at all the different combinations. Also trying to get a grip on how to decide what stuff to buy for an electric.

[Pinecone]

Cells come in various mAH from different manufacturers. So you can get pretty mcuh what you want, but unless you want to order 10,000 plus cels, you can't get ANY mAH capacity. The brands we buy are not the people who make the cells (except possibly Kokam), they are people who buy cells and assemble packs.

But each cell is nominally rated at 3.7 volts (3 - 4.2 volts over the useable/safe range).

[Maxists The Baddist]

Say you buy a 1800Mah pack like the 4s1p. Does every cell have 1800Mah capacity? And what does the 1P mean?

[Pinecone]

Yes. 1P means 1 parallel. 4S1P means 4 cells in series, none in parallel. 4S2P would be 8 cells, two sets of 4 cells in series, wired in parallel. If you started with 1800 mAH cells, you would end up with 14.8 volt, 3600 mAH capacity.

Series adds the voltages together. Parallel adds the capacity, and amperage.

If the above packs were 1800 mAH 10C cells, the 4S1P would deliver up to 18 amps. The 4S2P would be able to deliver 36 amps.

[Maxists The Baddist]

Now what does the C mean? I've read about the peak burst in Cs that a pack can deliver.

[Graeme]

One "C" is the pack's amperage when fully charged. 1C for a 650mAh pack is 650mAh. A rating of "5C continuous/10C burst" would mean that it can withstand 3.25 amps continuously, and a 6.5 amp burst.

[Pinecone]

Think of it more as X times C, with X being the capacity of the pack in Amp-Hours.

If you r pack si 650 mAH capacity, that is 0.65 AH (divide by 1000). If 10C, that means 0.65 times 10= 6.5 amp is the maximum safe amp draw the pack can deliver.

So it you try to hook it up to a motor setup that draws 10 amps, you will kill the pack.

Also the further you run the pack from its max amp rate, the longer it will last (as in cycles before it dies) and higher the voltage delivered.

[Maxists The Baddist]

Does C stand for current. And is current a number of amps at a voltage?

[Graeme]

Yep, that sounds like a good way of saying it since it's not a fixed value, (e.g. C=650mAh on a 650mAh pack, and C=2200mAh on a 2200mAh pack).

[Jermo]

http://www.rchobbies.org/lithium_battery_breakthrough.htm

[Pinecone]

Actually C is capacity. So a C is the same as the capacity of your pack. The number before the C is the mulitplier for max amps that the pack can supply.

So a 10C pack can supply amps at 10 times the capacity. For a 650 mAH pack, that means 10 x 650 = 6500 mA = 6.5 amps. A 20C would be 13000 mA or 13 amp capability.

[Maxists The Baddist]

Thanks

[Maxists The Baddist]

Is this correct? Every Li-Po cell is 3.7 volts but that one cell can be made to have any Mah. I'm not asking about a battery pack but the cells in it.

[Pinecone]

Yes.

The 3.7 v is a nominal figure. They function between 3.0 and 4.2 volts (discharged and charged).