Having the right batteries can make a big …

1 18 TRAILER BOATS MAY 2011BY ALLAN TARVIDM arine 12-volt batteriesare purpose-built, sothe first thing to askyourselfbefore youstart shopping for one is how youplan to use it. Whether the batteryis a flooded-cell, AGM (absorbedglass mat) or a gel design, buying abattery that s not designed for thepurpose you have in mind meansgetting less performance, a shorterservice life or both. It s a waste ofmoney, any way you look at it. With this in mind, let s look ateach category of marine batteriesavailable today to determine whichtype or types will serve as the best cell mates for your the right batteries can make a big differencein how much you enjoy your time on the waterMAY 2011 TRAILER BOATS 19are RC (reserve capacityminutes) and AH (amphours). The RC rating ismore accurate when thebattery is used for highamp-draw devices suchas trolling motors andwindlasses.

2 The AH ratinggives a clearer picture ofhow long a battery cancarry lighter loads, suchas when it is used as ahouse battery to power lights and electronics. The RC rating is the number of minutes that a new, fully-charged 12-volt battery at 80 degrees (F) can carry a 25-ampload and maintain a minimum voltage of volts. The AHrating tells you the number of amps that a new 12-volt batteryat 80 degrees (F) can deliver, multiplied by the number ofhours, without falling below volts. For instance, a 100AH battery can deliver five amps for 20hours because 5 x 20 = 100. The AH figure for most marinedeep-cycle batteries is calculated at a 20-hour discharge rate,and this is important because the amount of amps a batterycan produce is not strictly a linear measurement.

3 The higher the amp draw, the fewer total amps a battery candeliver. A 100AH battery can deliver five amps for 20 hours, butit cannot deliver 25 amps for four hours even though 25 x 4also equals 100. We can see proof of this in our battery chart by comparingthe manufacturer s AH and RC numbers. For example, Trojan sSTARTING BATTERIESU nless you have a small, pull-start outboard, your boat needs abattery to start the engine. The cranking or starting batteries inour comparison chart (page 24-25) are designed expressly forthis purpose, and then act as a sort of buffer while the engine salternator carries the boat s electrical load. A starting battery delivers the sudden burst of starting power,and afterward it takes it easy until it s time to crank the engineagain.

4 The engine s charging system keeps the battery up whileboating, and only a minimum charging is usually needed afteran outing. If you plug in a multibank on-board charger at the end ofthe day, the starting battery s charge status light is usually thefirst to indicate a full charge. The most important rating on a starting battery s label is CA(cranking amps) or MCA (marine cranking amps). Both tell youhow many amps a new, fully-charged battery at 32 degrees (F)can deliver for 30 seconds without falling below volts. Thisnumber is important because it must meet or exceed the requirednumber of cranking amps listed in your engine s owner s manual. If your manual only shows a Cold Cranking Amp (CCA)rating and you are looking at batteries that only show a CA orMCA rating, you can convert one to the other with the simpleformula (MCA x = CCA) or conversely (CCA x = MCA).

5 CCA is the automotive standard and it is calculated using thesame test as CA/MCA, but done at zero degrees (F). The CA/MCAnumber is always higher because batteries are more efficient atthe warmer 32-degree temperature than they are at BATTERIESD esigned to power accessories such as lights, electronics andpumps, the marine deep-cycle batteries in our chart are at theopposite end of the spectrum from starting batteries . Deep cycle describes the ability to be deeply dischargedbefore being recharged. These deep discharge/recharge cyclesare hard on battery plates, making it necessary to design deep-cycle batteries with fewer, but thicker plates than those used instarting batteries . Fact is, starting batteries usually only survive a few deep cycles,while deep-cycle batteries with a suitable MCA or CCA ratingfor your engine can be used as permanent starting batteries .

6 The most important ratings on a deep-cycle battery s labelCrown Battery s deep-cycle Group 27 battery offers170 reserve capacity minutes and 115 amp s 60 Series modelprovides ample starting BOATS MAY 2011of boats. High-powered audio systems areoften best served by a separate deep-cyclebattery TECHNOLOGIESOnce you are sure you ve chosen the righttype of marine battery for your purpose,you are halfway through selecting theright one for your boat. The next step is choosing the type ofbattery technology you want on your for all three purposes are availablein flooded-cell, AGM or gel designs. All three designs will work, but budget,the amount of battery weight your boat canhandle and the amount of maintenanceyou are willing to perform all have a bearingon which technology you BATTERIESF looded-cell batteries are the leastexpensive and often the lightest designfor a given capacity rating.

7 They come infull-maintenance and maintenance-freeversions. The full-maintenance models must becleaned and watered regularly. The topsof their cases collect a caustic residuefrom the normal gassing that occursduring recharging. This gunk can buildup thick enough to pass a low-gradecurrent leak between the posts and roba small amount of battery capacity. Theresidue also can speed corrosion onbattery posts and terminals if they are notcoated with a protective spray or grease. Water is lost from the electrolyte duringSCS150 is rated at 100AH and 150 RCminutes. Since RC minutes are calculatedusing a 25-amp discharge rate, this batterycan only carry that 25-amp load for 150minutes ( hours). If all amp ratingswere truly linear, a 100AH battery couldcarry that 25-amp load for four hours(240 minutes).

8 What all this means is that if you areadding up the small loads that your boat shouse battery will carry, you should choosea battery with an AH rating high enoughto meet your needs. If you are looking forbatteries to run your trolling motor, RCminutes will come closer to showing actualmotor running time than amp BATTERIESSo what ifyou need a battery that canboth crank your engine and run youraccessories? This calls for checking outthe dual-purpose batteries in our batteries have enough plate surfacearea to crank your engine quickly, withbattery plates tough enough to withstandmoderate deep cycling. Dual-purpose batteries came aboutdecades ago when small freshwater fishingboats had room for only one battery to startthe outboard and run the trolling motor.

9 They still meet that need today, but theyalso can start the engine on any boat andpower marine stereo systems or otherentertainment electronics when the engineisn t running. A dual-purpose battery must still meetyour engine s CCA or MCA requirement,and exceed it if you want it to haveenough juice left to crank your engineafter pumping out a few hours ofyourfavorite tunes. Big, tsunami-inducing stereo amplifiersmay not leave you with enough power tostart your engine after entertaining a raftTomorrow s marine batteries willbe lighter, smaller and perhapseven smarter than those we useon our boats today. One company headquarteredin Germany, Torqeedo (815/444-8806; ), isn t waitingfor someone else to lead theway and has introduced lithiummanganese batteries optimizedfor its line of electric outboards.

10 New this year, Torqeedo sPower 26-104 battery uses atechnology more common tocomputers and smart phonesthan to boats. Designed to runTorqeedo s 24- and 48-volt motors,the battery has a nominal voltageof volts and a nominal chargeof 104 amp hours. The battery weighs just 44pounds; an impressive factconsidering it could replace two12-volt, lead-acid batteries thateach weigh more. The batteryhas a built-in managementsystem smart enough to protectit from overcharge, overvoltage,overheating, dangerously deepdischarge, reversed polarityhookup and other potentialproblems. It can be submerged threefeet deep for 30 minutes and stillfunction properly. Torqeedo scharger can raise the battery scharge level from zero to 100percent in eight hours, and whenstored in Deep Sleep mode, thebattery s self discharge rate isan incredibly low (compared tolead-acid batteries ) percentper year.