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Q. In the article dated December 1996 by Jerry Pucket, he advises that before charging a deep cell battery it should be discharged to a very low point before recharging it. Does this still apply if you have a smart on board charger that monitors the battery automatically? Do I still need to run the battery down before plugging in the charger or can I just plug it in and charge the battery after each time out on the water? I use the battery just to run my trolling motor. If I do need to run the battery down do I need to do this all the time or just the first few times that I charge it.

Thank You,

Mike Tvrdik
Hilton Island Head, SC


A. Mike, thanks for giving us a shout as regards deep cycle battery charging, a subject that continues to mystify. There have been definite advances in both batteries and charging systems in the past 15 years or so and your nudge was a good reason for a bit of updating on our part.

One item is what has become something of a deep-cycle myth – the shallow charge memory dilemma. While that was a factor with some of the first generation ni-cad batteries, and possibly with some early marine batteries, it is no longer a factor with today’s deep-cycle marine batteries.

Assuring that deep-cycle batteries are fully charged with 24 hours of use continues to be the surest way to provide for a long service life and good performance. While most of today’s sources support the use of onboard chargers for deep cycles I continue to have questions when I run across little tidbits such as:

7.8. Avoid opportunity charging.  Size the battery so that there is a minimum of one cycle per day.

That blurb came from an FAQ page on the Marine-Electronics website. The page contains info on this and many other subjects regarding deep-cycle batteries, marine and others such as golf carts. Several of the items I found to be of interest were temperature corrections and lifespan computations based on the average discharge of the normal duty cycle.


What I finally determined to be the most advantageous deep-cycle maintenance habit for my boats (three at one time) was the daily use of a top quality load-bank style battery checker such as the ones available from Snap-On and others. These bacon fryers (they get smokin’ hot in a hurry) place a heavy load on a battery such that you can determine, without a doubt, the overall health of the battery. The checker will also diagnose alternator problems. Surface charge/shallow charge worries are a thing of the past with one of these nifty tools but to get one you’ll need to “charge up” about a hundred bucks.

Thanks again for the “nudge”.

Good fishin’
Jerry Puckett