Re: [RoboMower] Switching to lithiums for RL500
- On 1/4/2013 3:20 PM, Danny Miller wrote:
> I would strongly caution you against building a large pack like that outI agree with Danny. Your typical 18650 laptop cell is *highly*
> of cobalt-cathode 18650s. That's just dangerous.
combustible. Extensive safety measures need to be taken to prevent them
from ever catching fire, because if they do, it will be spectacular.
Think of them like a box of matches.
The LiFe cells still burn, but it's harder to get them started, and the
resulting fire spreads much slower. Think of them more like a box of
> you need to consider the overall layout and space-efficiency becauseAgain, I agree. The watthours per pound of lithium is about 3 times
> the volumetric density is only moderately better, but the ability to
> utilize the volume is always much less.
better than lead acid, but the watthours per cubic foot is only slightly
more. When I do talks, I have three batteries that graphically
illustrate this: One Hawker lead-acid 12v 60ah, one GM/Ovonic nimh 12v
90ah, and one Thundersky 12v 90ah. All three are the same size. But the
lead-acid weighs 60 lbs, the nimh 40 lbs, and the lithium 22.5 lbs.
When you have a fixed size battery box, you'll wind up with about the
same watthour capacity no matter which battery chemistry you pick.
Results! Why man, I have gotten a lot of results. I know several
thousand things that won't work. -- Thomas A. Edison
Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm