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Old 02-17-2012, 04:31 PM   #83
_cy_ OP
Beastly Adventurer
 
Joined: Sep 2011
Location: Tulsa, Oklahoma
Oddometer: 5,327
Quote:
Originally Posted by 02TAC View Post
Just going off the Lipo batteries I use for my RC stuff, I would not use voltatage reading as an indication of remaining capacity. Lipo batteries, and I am guesing Life too, do not have a linear discharge curve. They tend to deliver a fairly steady voltage and then just drop off drastically.
just got back from a 31 mile bike ride on R80G/S ... in town Friday traffic is the pits...about got hit twice. took a reading when I got back, Shorai 18AH (pb eq) shows 13.23V or right in the middle of lithium iron phosphate's very flat discharge curve. made several stops and Shorai battery performed without a glitch. cranking over strong each and every time with a warm motor in 55 degree weather is child's play for this little Shorai 18AH (pb eq) battery.

note drop from about 13.4v to 12.4v represents about 80% of total capacity. measuring capacity via voltage requires an extremely accurate meter. again.. you don't want to drop voltage below 12.87V (80% DOD). this means 1/2 volt represents 80% of battery's useful capacity.

this is why I'm using a calibrated Fluke 87V for measurements along with temperature and amp draw.
some techniques from the RC transfer across, but not all. due to chemistry and specific motorcycle requirements. RC grade chargers with it's multi-cell balancing capabilities are very much needed. but we will get into that later. Driving a li-po pack HARD and chargers are an area where the RC crowd has the most expertise anywhere on the WWW.

R80G/S outside of Barnstall, OK... according to the sign, birthplace of Clark Gable

_cy_ screwed with this post 02-17-2012 at 04:41 PM
_cy_ is offline   Reply With Quote