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eCigarette Forum => Battery => Topic started by: methos on November 02, 2013, 11:06:30 AM

Title: How low of C rating can you use?
Post by: methos on November 02, 2013, 11:06:30 AM
I was wondering if a 15C lipo is ok to use with a boost board. I've used 20C and 35C so far but space in this mod won't allow me to use a very big size battery.
Title: Re: How low of C rating can you use?
Post by: CraigHB on November 02, 2013, 01:48:03 PM
15C is plenty.  Though, the drain limit in terms of "C" rating depends on cell capacity.  The C stands for charge so a 1000mAh cell with a 10C rating can handle 10 Amps continuous.  The C rating is for continuous drain.  For the intermittent loads we put on an atomizer, it's safe to add 50% to the drain limit.  So, a 1000mAh 10C cell can safely handle 15 Amps intermittently.

If you want to know how low you can go in terms of C rating, it depends on the C rating ~and~ the cell capacity.  For example, I use a pair of 2C cells for one of my mod designs that each have 3000mAh.  Each cell has a max drain of 6 Amps and they're in parallel so that doubles it for 12 Amps.  I can safely go up to 18 Amps on the whole battery with the burst loads of an atomizer.  At a minimum cell voltage of 3.2V, that gives me a max load on the cells of 58 Watts.  The mod will not allow a load on the cells greater than 42 Watts so I'm well within tolerance.

Oh, one other consideration with a booster is supply impedance.  They don't like too much of it.  The higher the drain limit of the battery, the lower the supply impedance.  Though typically it's not a problem unless you're taking a cell right to the edge of what it can handle.  If you don't exceed the continuous drain limit, you'll for sure keep supply impedance low enough for a booster.  The 20C and 35C LiPos actually have much, much lower supply impedance than what is maximal.