I just met a fellow who works in directional drilling. He has a problem when his dry cell lithium ion batteries die. It costs him $300,000 when it happens. What he needs to know is when to pull the batteries BEFORE this happens. These Double D cell batteries when connected, hold their 36 volts until the 3.2MJ are used up, then he gets an estimated .2 millivolt instantly. I told him I knew a site that could tell us that for him. SO...here is the question. He starts out with 3.2 MJ...the motor requires 1300 J/H to idle...pulses from his equipment cost 1282J every 6 seconds. How many amp hours does he have before it costs him? When should he pull the batteries for replacement or charge? Is there a formula for this we can give him? My personal interpretation of this equation is to mutiply the J/6 sec into hours and add to the hourly cost. Then divide into the 3.2 MJ for a time allowance. That was not his question though. Any takers?