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Matching the Tool to the Job
By Jerry Puckett

November/December 1996

The Care and Feeding of Deep Cycle Batteries

Batteries can be both mysterious and frustrating, but they only need two things to stay "happy", correct electrolyte levels and proper charging. Low electrolyte levels allow the lead plates to oxidize. Once they do, they have lost at least a portion of their capacity. Capacity that you depend on to feed the assortment of amp gobbling accessories that none of us can seem to do without.

I. Battery Cycle Life

Like a NiCad battery, a deep cycle marine battery must be "trained" in order to do its job at maximum efficiency levels. Let me give you the guaranteed recipe for disappointment. Take anew, fully charged battery and discharge it slightly. Then, put a light charge on it to top it off. Do that several times in a row and you now have a great big battery with nearly no usable power. The battery has been trained to have a shallow charge memory. Weird, but true. For best results a deep cycle battery should be worked hard, discharged heavily and then correctly recharged, fully. Deep cycle charging is almost impossible to do correctly with a manual charger. The battery wants to be charged rapidly at first and then have the balance of the charge load supplied at a successively slower rate. The last bit is only "trickled" in. Unless you "stand over" a charging battery, constantly monitoring both state of charge and charge rate as you follow the directions of a charge rate graph, adjusting the charger's output accordingly, your battery won't be giving you the performance you want by the end of a hard day's fishing. And why is it that batteries can be okay one day and totally worthless a week later, even with correct charging procedures? How can that be? Simple. Correctly charged and maintained batteries do not deteriorate based on age. They, like a NiCad, have only so many "cycle lives" to give. If you look at the cycle life/power curve of a typical deep cycle battery you will see that a new battery can deliver only about 75% of its capacity for the first twenty or so full discharge/recharge cycles. Past that point it should deliver near 100% performance for the next hundred of so cycles, at which point its performance or amp delivery ability begin to slowly taper down to a point where it is producing 50% to 60% of its rated potential. Past that point (approximately 250-350 total cycles, depending on make and model) the battery will simply die, dead. And, it will often happen from one day to the next. These facts bring about several questions. Are you receiving good service from your batteries? If not, something is amiss and you're not receiving fair value for your battery dollar and probably not enjoying the battery performance that you deserve. The solution is not cheap in the short term but will yield better economics and performance in the long run.

II. Battery Charging

First, get a "smart" charger. There are several good models on the market. We prefer the solid state on-board, waterproof models that hard wire into your system and only require a single plug-in to 120V service. The beauty of this system is that you never need to unplug the charger until you're ready to head for the lake. It doesn't matter if it's one day or one year later. The charges automatically taper the charge rate to a mere trickle before shutting themselves off completely. Periodically the charger will "check" the batteries and go to the trickle rate if necessary. Hands off, year-round charge maintenance. I love it, your batteries will too. The only shortcoming that this style charger has concerns its charging capability if the AC service experiences a voltage drop. Let's say you're at a large multi-day tournament, using a parking lot power grid along with a couple hundred other boats. You may not get the power supply your charger requires to put out its rated amp load. Line loss and high demand may result in a low voltage condition at the end of the line, possibly as low as 70-90 volts instead of the 110-120 volts the solid-state unit requires. In some cases the charge output may be near zero, in others only as much as 5 amps per circuit. In either case a heavily discharge battery will not be topped out by morning. Curses! Foiled again! If you generally charge at home this isn't a factor, but if you must deal with the parking lot program there is a cure. Not as handy, also expensive, but effective. At least on charger system (Delco Super Smart) is designed to operate on low voltage, and I assure you that it works. The one I had was portable (but heavy), and had a noisy cooling fan, but would put out 20 amps per circuit if there were any volts available at all. I believe there is now an on-board model available, water resistant but not waterproof like the solid state jobs. If you make a habit of running your electronics and livewells constantly (we always have fish in the livewell, right?) don't forget your cranking battery, particularly if you run one of the new, bad boy, 36 volt trolling motors. Even with today's higher output alternators on the big motor, the trusty cranker needs occasional help. If you're going for an onboard charging system spend an extra couple of bucks and get the three channel model. I spent an interesting day on the Cal Delta paired with a local guy that didn't believe in checking his cranking battery. After the first hour of the day (we were runnin' and gunnin') the cranking battery gave it up, dead. The rest of the day he ROPE started the 150 Merc! I didn't even believe you could do it. Instead of runnin' and gunnin' we were sort of yankin' and crankin'! What a day.

III. Battery Checking

Now that our charging systems are up to snuff, the next thing we need to do is get and use a proper, load-bank style battery tester. I use a Snap-On model that is somewhat pricey ($150), but it works well. No guesswork with this meter, you know absolutely, if your batteries are up to par. The basis of a load bank meter is the ability to "load" the battery. The meter's integral heating coil pulls an extreme load, the coils are hot enough to fry bacon in a matter of seconds. While you're loading the battery you read the meter to monitor the voltage drop. This is the only way to measure the power or staying power of the battery. A battery can show a perfect voltage reading without a load and then fall completely off the scale under load. That battery looks like duck, quacks like a duck and it is a duck. A dead duck. Without a load bank you wouldn't be able to identify the worthless battery in your multi-battery system. So what do we normally do? Usually replace ALL the batteries in a fit of frustration (the good ones, too) because after an hour or so our trolling motor is pooped out. Get a good load bank meter and you'll save money and enjoy the service from your electrical systems that you paid for, and deserve. As bass boaters we are totally dependent on our batteries. The bite can be wide open with all the marbles on the line but you and your shiny new rig are dead in the water without good batteries. Held hostage by $300 worth of batters. Don't let it happen. Equip yourself and your boat with the proper tools for the job.

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