Every fisherman has from one to four deep cycle batteries in their boat. Some fisherman remove them from their boat at the end of the fishing season, some leave them in the boat. Some trickle charge them all winter, some charge them once in a while. Is there a right way or a wrong way to maintain your deep cycle battery? I hope to answer this question, and give you some information that you will find very useful. Unless you are quite wealthy, you will want to take care of your batteries, and they will take care of you for a long time.. Average battery life has become shorter as energy requirements increase. Life span depends on usage; 6 months to 48 months, yet only 30% of all batteries actually reach the predicted life span . Proper maintence, and understanding how you battery works is necessary to achieve this. First lets see just how a deep cycle battery works.

The lead acid battery is made up of plates, lead and lead oxide (various other elements are used to change density, hardness, porosity, etc.) with a 35% sulfuric acid and 65% water solution. This solution is called electrolyte which causes a chemical reaction that produce electrons. When you test a battery with a hydrometer you are measuring the amount of sulfuric acid in the electrolyte. If your reading is low, that means the chemistry that makes electrons is lacking. So where did the sulfur go? It is stuck to the battery plates and when you recharge the battery the sulfur returns to the electrolyte. Deep cycle batteries have thicker plate design and can survive over a hundred discharge cycles.

There are simple steps in testing a deep cycle battery: inspect, recharge, remove surface charge, measure the state-of-charge, load test, and recharge. If you have a non-sealed battery, it is highly recommended that you use a good quality temperature compensated hydrometer; these can be purchased at an auto parts store for between $5 and $20. A hydrometer is a float type device used to determine the state-of-charge by measuring the specific gravity of the electrolyte in each cell. It is a very accurate way of determining a battery’s state-of-charge and its weak or dead cells. To troubleshoot charging or electrical systems or if you have a sealed battery, you will need a digital voltmeter with 0.5% or better accuracy. A digital voltmeter can be purchased at an electronics store like Radio Shack for between $20 and $50. Analog voltmeters are not accurate enough to measure the millivolt differences of a battery’s state-of-charge, or the output of the charging system. The purchase of a battery load tester is optional, these run about $70 at auto parts stores. If you use your electric trolling motor every day, as I do, buy one. A more accurate way of testing the capacity of a lead acid battery is by using a conductance tester.

Ok, so lets visually inspect the battery for obvious problems. Check the electrolyte levels. Is the level below the top of the plates, are the cables corroded , corroded terminal clamps, dirty or wet battery top, loose hold-down clamps, loose cable terminals, or a leaking battery case? If the electrolyte levels are low in non-sealed batteries, allow the battery to cool and add distilled water to the level indicated by the battery manufacturer. If this is not indicated, use ¼ inch below the bottom of the plastic filler tube vent wells. The plates need to be covered at all times. Do not overfill the cells, especially in hot weather, because heat will cause the electrolyte to expand and overflow.

Breakdown of the grid-paste interface occurs when a calcium battery is discharged repeatedly, resulting in battery capacity losses of 40% or more. Additional maintenance expenses are incurred as a result of the battery’s premature failure. The lead antimony battery will withstand repeated charge/discharge cycles and will generally accept charge more readily than a calcium battery. However, the higher charge acceptance of the antimony battery causes increased water consumption and the resultant external corrosion problems associated with the sulfuric acid fumes being carried out for the battery in the evaporation process. If the lead antimony battery is not properly maintained, battery trays and cables will require regular replacement due to corrosion and boil over problems. To achieve longer battery life, the lead antimony battery requires frequent water additions to maintain proper electrolyte levels and the corrosion must be regularly removed from posts, cables, hold-downs, and battery trays.

Thanks to the latest in modern technology, a product called THERMOIL has been developed to reduce, if not completely solve today’s battery problems. Most folks don’t know that just the gases from the battery condensing on metal parts cause most corrosion. As I stated above, Thermoil® is a unique and patented inexpensive battery additive that when added to your new or existing battery will increase battery life, increase shelf life, eliminate corrosion, greatly reduces water consumption, explosion, toxic fumes and will help to keep your battery working under any condition from -50º to 400º Fahrenheit and is Guaranteed 100%. This product is a must for all lawn mower, motorcycle, car, truck, boat, RV, bus, tractor, utility, scrubber, sweeper, golf cart, solar or any other new or used non-sealed lead acid battery. I use Thermoil in every battery I have, and believe me, it works exactly as the manufacture said it would. If you go to their web site you can order it from there, and you will be happy that you did. No more wet tops on your batteries, no more corrosion on the battery posts, and cables, this is a great product, and I know several in the RV industry that recommend it to all there customers because it really works.

Next recharge the battery to 100% state-of-charge.

There are up to four phases of battery charging: bulk, absorption, equalization and float. The bulk stage is where the charger current is constant and the battery voltage increases. You can give the battery whatever current it will accept not to exceed 20% of the ampere-hour rating and this will not cause overheating. The absorption phase is where the charger voltage is constant and current decreases until the battery is fully charged. This normally occurs when the charging current drops off to 1% or less of the ampere-hour capacity of the battery. For example, the ending current for a 100 ampere-hour battery is 1.0 amp or less.

REMOVE THE SURFACE CHARGE

Surface charge is the uneven mixture of sulfuric acid and water within the surface of the plates as a result of charging or discharging. It will make a weak battery appear good or a good battery appear bad. You need to eliminate the surface charge by one of the following methods: Allow the battery to sit for four to twelve hours to allow for the surface charge to dissipate. Apply a load that is 33% of the ampere-hour capacity for five minutes and wait five to ten minutes. With a battery load tester, apply a load of at least one half the battery’s CCA rating for 15 seconds and wait five to ten minutes. Follow the battery and charger manufacturer’s procedures for connecting and disconnecting cables and other steps to minimize the possibility of an explosion or incorrectly charging the battery. You should turn the charger OFF before connecting or disconnecting cables to a battery. Do not wiggle the cable clamps while the battery is recharging, because a spark might occur, and this could cause an explosion. Good ventilation or a fan is recommended to disperse the gasses created by the recharging process. If a battery becomes hot, over 110° F (43.3° C), or violent gassing or spewing of electrolyte occurs, turn the charger off temporarily or reduce the charging rate. This will also prevent “thermal runaway” that can occur with VRLA batteries.

If you are recharging gel cell batteries, a manufacturer’s charging voltages can be very critical. Sometimes, you might need special recharging equipment. In most cases, standard deep cycle chargers used to recharge wet batteries cannot be used to recharge gel cell and AGM batteries because of their charging profiles; using them will shorten battery life or cause “thermal runaway”. Match the charger (or charger’s setting) for the battery type you are recharging or floating.

The best method is to slowly recharge the battery at 70° F (21.1° C) over a 10 to 20 hour period (C/10 to C/20) using an external constant voltage (or tapered current charger) because the acid has more time to penetrate the plates and there is less mechanical stress on the plates. C-rate is a measurement of the charge or discharge of battery overtime. It is expressed as the capacity of the battery divided by the number of hours to recharge or discharge the battery. For example, assume that the ampere-hour capacity of the battery is 220, then it would take 11 hours to recharge or discharge the battery using a C/20 rate. A constant voltage or “automatic” charger applies regulated voltage at approximately 13.8 to 16 volts, based on the manufacturer’s recommendations and temperature. A 10 amp constant voltage charger will cost between $30 and $60 at an auto parts store is suitable for most simple recharging or charging applications. If left unattended, cheap, unregulated trickle or manual battery chargers can overcharge your battery because they can “decompose” the water out of the electrolyte. Avoid using fast, high rate, or boost chargers on any battery that is sulfated or deeply discharged. The electrolyte should never bubble violently while recharging because high currents only create heat and excess explosive gasses. Recharging slowly and keeping your battery well maintained are the best ways to extend the life of your battery. Recharge a deep cycle battery as soon as possible after each use to prevent sulfating. In warmer climates and during the summer, “watering” is required more often. Check the electrolyte levels and add distilled water, if required. Never add electrolyte to a battery that is not fully charged’ just add distilled water and do not overfill. The plates must be covered at all times. High ambient temperatures (above 80%deg; F [26.7° C]) will shorten battery life because it increases positive grid corrosion and growth.

WHAT ARE THE MOST COMMON CAUSES OF PREMATURE BATTERY FAILURES?

Loss of electrolyte due to heat or overcharging. Undercharging. Old age (positive plate shedding) or ”Sludging”. Excessive vibration. Freezing or high temperatures. Using tap water which causes calcium sulfating. Positive grid corrosion or growth due to high temperatures.

HOW CAN I STORE BATTERIES?

When in storage, recharge when the state-of-charge drops to 80% to prevent lead sulfating. Maintaining the correct state-of-charge while in storage, electrolyte levels, tightening loose hold-down clamps and terminals, and removing corrosion is normally the only preventive maintenance required for a deep cycle battery. Avoid “opportunity charging.”

Batteries naturally self-discharge 1% to 15% per month while in storage, and lead sulfating will start occurring when the state-of-charge drops below 80%. If left in a vehicle, disconnecting the negative cable will reduce the level of discharge by eliminating the parasitic load. Cold will slow the self-discharge process down and heat will speed it up. Use the following simple steps to store your batteries:

Physically inspect for damaged cases, remove any corrosion, and clean and dry the battery tops.

Fully recharge the batteries.

Check the electrolyte levels and add distilled water as required, but avoid overfilling.

Store in a cold dry place, but not below 32° F (0° C)

Depending on the ambient temperature and self-discharge rate, periodically test the state-of-charge. When the state-of-charge drops below 80%, recharge the batteries. An alternative would be to connect an automatic voltage regulated, solar panel or “smart trickle” charger to “float” batteries. Based on the manufacturer’s recommendations, use an automatic or smart charger that has been manufactured for this purpose and battery type.

WHAT ARE SOME OF THE MYTHS ABOUT BATTERIES?

Storing a battery on a concrete floor will discharge them. A hundred years ago when battery cases were made of porous materials, such as wood, storing batteries on concrete floors would accelerate their discharge. Modern battery cases, made of polypropylene or hard rubber, which are better sealed, so e xternal leakage, causing discharge, is no longer a problem. However, the top of the battery must be clean and dry. Temperature stratification within large batteries could accelerate the internal “leakage” or self-discharge if the battery is sitting on a cold floor in a warm room.

A battery will not explode.

Recharging a wet lead-acid battery normally produces hydrogen and oxygen gasses. While spark retarding vent caps help prevent battery explosions, they occur when jumping, connecting or disconnecting charger or battery cables, and starting the engine. While not fatal, battery explosions cause thousands of eye and burn injuries each year.

When battery explosions occur when starting an engine, here is the usual sequence of events: One or more cells had a high concentration of hydrogen gas (above 4.1%) because the vent cap was clogged or a defective valve did not release the gas. The electrolyte levels fell below the top of the plates due overcharging, or poor maintenance.

A battery will not lose its charge sitting in storage.

Depending on the type of battery, it has natural self-discharge or internal electrochemical “leakage” at a 1% to 20% rate per month that will cause it to become sulfated and fully discharged over time. Higher temperatures accelerate this process. Batteries stored at 95° F (35° C) will self-discharge twice as fast than one at 75° F (23.9° C).

Maintenance free batteries never require maintenance.

In hot climates, water in the electrolyte is “decomposed” due to the high temperatures and normal charging of a wet maintenance free battery. Water can also be lost due to excessive charging voltage or charging currents. Non-sealed batteries are recommended in hot climates so they can be refilled with distilled water when this occurs.

Pulse chargers.

Using pulse chargers or additives is a very controversial subject. Most battery experts agree that there is no conclusive proof that more expensive pulse charges work any better than constant voltage chargers to remove sulfating.

Batteries last longer in hot climates than in cold ones.

Batteries last approximately two thirds as long in hot climates as cold ones. Heat kills batteries, especially sealed wet lead acid batteries.

Deep cycle batteries have a memory.

Lead acid deep cycle batteries do not have the so called “memory effect” that first generation Ni-Cad batteries have.

HOW LONG WILL A DEEP CYCLE BATTERY LAST ON A SINGLE CHARGE?

Discharging, like charging, depends on a number of factors such as: the initial state-of-charge, depth-of-discharge, age, capacity of the battery, load and temperature. For a fully charged battery at 70° F (21.1° C), the ampere-hour rating divided by the load in amps will provide the estimated life of that cycle. For example, a new, 72-ampere-hour battery with a 10-amp load should last approximately 7.2 hours. As the battery ages, the capacity is reduced. Well, now you know as much as I know about Deep Cycle Batteries. It seems every one has a different way of charging their batteries. Some do it correctly, and many DON’T, and I hope they read this article, as it will help them do it correctly to avoid spending hard earned money needlessly.

If you have any questions on anything in this article you can e-mail me at either RiverRat@Fish-Wisconsin. com or [email protected]. I’d like also to thank my friends at Crestliner Boats, Magic products, Fishtheriver.com, Hummingbird locators, St.Croix Rods, Harriet’s Family Restaurant in Wis.Rapids. Heckels marine, Amherst Marine. Comprop Prop, ISG Jigs, Reeds Sporting Goods, Big Fish Tackle Co., Ipsglass.com, Thermoilbatteries.com and others who have helped me along the way.

This article may not be reproduced without my written permission.