Li Poly?

Hi
Looking for information on Li Poly. Any good websites out there with free
info? I have heard that they give a longer run time than NiCad and NiMh but
do they give the same current out put. For example two identical boat's, one
with NiCad's and the other with Li Poly's, which one would be faster?
Reply to
Birdy Num Num
Loading thread data ...
formatting link
and read the stickies at the top of the batteries forum.
Reply to
The Natural Philosopher
For an equivalent weight of NiCds and LiPos, the LiPos will either run a LOT longer, or give more thrust (higher voltage).
-- Paul McIntosh
Reply to
Paul McIntosh
formatting link

Reply to
Stew
Correct
Total bollocks. The thrust you get is not anything to do directly with the cells, or their voltage.
Asit is teh energy to weight is far better than nickel chemistry, and teh dscharge rates are sufficiently high to allow you to translate that into more duaryion, or more power to weight with sensivble duration.
Nickel still betas LIPO for out and out power to weight, if a minute and a half burn is all you are interested in :-)
The voltage is completely irrelavant in the end, because you can select props, gear ratios and winding strategies to get the best out of almost any voltage.
Reply to
The Natural Philosopher
Check this out
formatting link
run Li-poly, capable of high amperage draws for longer time with out damaging the battery, Read the articles at Battery University and follow the rules for Li-poly and you can't go wrong.
Hope it helps you.
Reply to
Net Report
Not total bollocks. Run the same motor on higher voltage (up to a point) and you will get either larger prop at same RPM or more RPM for the same prop. Either way equals more thrust.
Remember, I am talking about equivalent WEIGHT of battery, not equivalent number of cells or arrangement.
-- Paul McIntosh
Reply to
Paul McIntosh
Exactly, so why has voltage got anything to do with it at all?
If you repalce 8 cells with 2 LIPOS in series, you have LESS voltage.
So by your own admission your own argument doesn't even stand up on your own terms!
*shakes head sadly and goes off to sniff some dope thinners*
Reply to
The Natural Philosopher
Are you serious? Can you comprehend WEIGHT of battery VS number of cells? LiPos have far greater density of power so you can get higher voltage for the same weight.
Lets compare some batteries by weight:
LiPo 2000 pack, 11.1v, 170gm. 30Ah discharge
formatting link
NiMh 1100 pack, 9,6v, 188gm, 10Ah discharge
formatting link
NiCd 2000 subC, 1.2v, 56gm, 25Ah discharge (you get 3 of these for the same weight as the LiPo.
formatting link
Still not convinced? Lets do it by power!
Same LiPo as above. LiPo 2000 pack, 11.1v, 170gm. 30Ah discharge
formatting link
NiMh 1950 pack, 9.6v (lower voltage), 325gm (nearly double the weight), 25Ah discharge (less current available)
formatting link
NiCd 2100 pack 9.6v (less voltage), 468gm (nearly three times the weight), 40Ah discharge (better current available)
formatting link
No matter how you cut it, when you are talking weight, LiPos can supply higher voltages than either NiCd or NiMh for the same Ah capacity. -- Paul McIntosh
Reply to
Paul McIntosh
| Are you serious? Can you comprehend WEIGHT of battery VS number of cells? | LiPos have far greater density of power so you can get higher voltage for | the same weight.
Voltage doesn't really matter. It's power that matters. I'm sure you already know this, but I'll explicitly state it for those who don't realize it.
What you ought to be looking at are four ratios :
capacity/weight power/weight cost/capacity cost/power
(You could think of a few more ratios, like cost/weight, but who really cares about that?)
I mention ratios rather just capacity or just power because you can always double your power or capacity, by doubling the number of batteries, but you're also doubling the weight when you do that.
LiPoly *definately* have the edge over NiMH and NiCd in capacity/weight. This is where they shine.
As for power/weight, I believe they have the edge there as well, though I'm not certain that there aren't some NiCds that can actually dump more power per weight than the best LiPoly cells. It could be the best 90 seconds of your life! :)
As for cost/capacity and cost/power, LiPoly cells seem to be a little more expensive than NiCd and NiMH cells, at least for now. As time goes on, I expect this to change.
So what could LiPoly gain you in your boat?
Assuming you want the same weight in batteries, they can get you either more power, or longer durations, or some combination of the two. Or it could get you the same power, same capacity but less weight (which is less important in a boat than in a plane, but it's still nice.)
Of course, this is all based on the assumption that you make appropiate choices in deciding the correct types of cell, pack arrangement, the right gear ratio and the right props.
Reply to
Doug McLaren

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.