Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: aruna1 on November 16, 2010, 08:27:20 PM
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Hi guys;
I'm using NiMH 12V battery packs on my robots.I thought its time to move to LiPo.
problem is I have no idea about LiPo details like what is 20C 25C etc and 2cell-3cell thing.
can someone please post a explanation of battery parameters and how to select LiPos?
Thanks
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[...] what is 20C 25C etc
C is the nominal capacity (in Ah) of the cell/battery. nC is n times C [A] and Cn is C/n (division) [A].
So, for a 2Ah cell, 20C would be 40A, while C20 would be 100mA.
and 2cell-3cell thing.
Oh well, you're kidding, right ???
can someone please post a explanation of battery parameters and how to select LiPos?
I've said it before... You really need to do a bit of googling before asking to get it all served. There are lots of pages dealing with what you want to know and you'll learn much better finding at least the basic info yourself (plus it would convince others that you care about your own projects).
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LiPo stands for "lithium polymer" but for the sake of hobbyist robotics you can consider them Li-Ion batteries (no memory effect, high power to weight ratio) with the added feature of high charge/discharge rates.
As far as the "C" goes, it's shorthand for charge/discharge rate. Lets say you had a battery that had a capacity of 1Ah. If you charged (or discharged) it at 1 amp for 1 hour that would be considered 1C. 2C means you get 2 amps for 30 minutes, 3C means 3 amps for 20 minutes. So for a LiPo battery with a charge rate of 20C, you could get up to 20 amps for 3 minutes. (This is all in an ideal system, in real life you have to take into account voltage curves, inefficiencies, etc.)
As far as selecting a battery is concerned, it's the same as any other part: Calculate what you need then get 150% of that.
[opinion] I think that switching to LiPo batteries for the sake of saying "I've got LiPo batteries" isn't a good idea. If it isn't broken, don't fix it.[/opinion]