Re: Battery Cycle Life/Cost

[Mike Chancey <evtinker@evalbum.com>]

M.C. Appleby wrote:
>You have your trip energy consumption down to a science.   Presuming your
>trips are daily (back to back) - why would you not recharge every two days
>or possibly every three days?  It sounds like even every two days you would
>only be at 50% SOC, but you would have doubled your cycles.

As I understand it, the normal rule of thumb is the shallower the cycle the 
more cycles a battery can deliver.  Basically, a battery that can deliver 
200 cycles at 80% of discharge might deliver twice that number of cycles at 
40% discharge or four of five times that number of  cycles at 20% 
discharge.  The number of cycles goes up exponentially with the drop in 
cycle depth.  Unfortunately, no body know s the exponent.  :^)  (Actually 
it isn't constant there are far too many variables.)

Another reason for the shallow cycles is there are occasional calls for 
additional driving during the day.  If I charge after every leg, then the 
car is 100% charged for the next project as needed.  At work this trips 
come up rarely, may 3 or 4 per year, but at home the extra runs out to the 
grocery store, hardware store, or such is fairly common.  These little 
jaunts are usually no more than 7 or 8 miles.

Thanks,

Mike Chancey,
'88 Civic EV
Kansas City, Missouri
EV List Photo Album at: http://evalbum.com
My Electric Car at: http://www.geocities.com/electric_honda
Mid-America EAA chapter at: http://maeaa.org
Join the EV List at: http://www.madkatz.com/ev/evlist.html