# Draw 2 amps from a 75 amp hr trolling battery **URL:** \ **Category:** Factual Questions\ **Created:** [August 4, 2009, 8:13pm UTC](https://boards.straightdope.com/t/draw-2-amps-from-a-75-amp-hr-trolling-battery/505331 "2009-08-04T20:13:07Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![janeslogin](https://avatars.discourse-cdn.com/v4/letter/j/df788c/32.png) [@janeslogin](https://boards.straightdope.com/u/janeslogin)\ **Post date:** [August 4, 2009, 8:13pm UTC](https://boards.straightdope.com/t/draw-2-amps-from-a-75-amp-hr-trolling-battery/505331/1 "2009-08-04T20:13:07Z")
Draw 2 amps from a 75 amp hr trolling battery should last 37.5 hours on paper, I think. How long will it really last? How often can one completely discharge it before ruining it? ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [August 4, 2009, 8:50pm UTC](https://boards.straightdope.com/t/draw-2-amps-from-a-75-amp-hr-trolling-battery/505331/2 "2009-08-04T20:50:40Z")
The rule of thumb is about _half_ that long. Once a lead acid battery, even a deep cycle marine battery, gets over 50% discharged, it becomes increasingly difficult to re-charge. The plates’ll degrade on you more quickly if you make a habit of discharging cmpletely, and that’ll result in you buying a replacement battery more often. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [August 5, 2009, 2:19am UTC](https://boards.straightdope.com/t/draw-2-amps-from-a-75-amp-hr-trolling-battery/505331/3 "2009-08-05T02:19:28Z")
As a first order approximation, the battery should be able to supply 2 amps (continuous) for 37.5 hours. The end time is defined as 1.75 V/cell for lead acid (or 10.5 V for a “12 V” battery). But a number of other factors could make it a longer or shorter time.