Several threads on bbc forum on lithium batteries, and the guys there are going to lithium batteries. Most are going with the 50 amp for their trolling motors either 24 volt or 36 volt with the 50’s hooked up. 3000-5000 full charges, 5 yr warantee, and a blue tooth program for your phone will show how many amps you have left as your using them, Imjust got a 50 amp Iconic for all my electronics that weighs 14lbs 6 ozs to replace my series 31 that weighs 75 lbs. when my others batteries die, will replace with lithium. One cycle charge of the 3000-5000 is a complete charge. If it only needed charge when at 50% used....that is a half a cycle. So figure how many times you will charge in a year and figure how long the battery will last. Sure they cost. But, I definitely in the next 10 yrs won’t need to get another battery. Read!!!
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http://www.bbcboards.net/showthread.php?t=982657