Battery capacity in Amp-hours is written as C. This notation is most useful when talking about charging/discharging rates.

Note: most deep cycle manufacturer's rate capacity at C/20, due to Peukert effect.

If you have a 200AH battery bank then C = 200AH.

If the manufacturer recommends max charging at C/5 the rate should be at or below 40A (200/5).

If the manufacturer recommends minimum charging at C/10 the rate should be at or above 20A (200/10).

If the manufacturer recommends max discharge (load) be 3C the rate should be at or below 600A (3×200).

If the manufacturer says that Absorption stage is complete when charging current has dropped to C/100 or C/200 then the current to watch for would be 2A (200/100) or 1A (200/200).

For other than C/20 loads¹⁾:

1 Hour = .3 2 Hour = .5 3 hour = .6 4 hour = .65 5 hour = .7 6 hour = .75 8 hour = .8 10 hour = .85 12 hour = .9 16 hour = .95 20 hour = 1 24 hour = 1.05 36 hour = 1.1 72 hour = 1.25 100 hour = 1.30²⁾