Should I upgrade to a Gel Battery for my trolling motor?

Should you choose a Gel SLA BatteryGel batteries represent a substantial investment. The BatteryGuy 8G31DTM 12 volt 97 ah Gel Battery, for example, is more than twice the price of the BatteryGuy BG-121000NB 12 volt 100 ah Sealed Lead Acid Battery.

So what are you getting with Gel that justifies the price tag?

The short answer is a battery that can withstand deeper cycles in harsher environments. In this article we’ll let you know where Gel excels so you can decide if it is worth the extra bucks for your trolling needs.

Q1: How deep will you be cycling the battery when trolling?

Charger LED LightEvery time you discharge and recharge your battery is known as a ‘cycle’. The more you discharge before recharging, the deeper the cycle.

The deeper the cycle the more the plates inside a lead acid battery are to buckle.

Small buckling causes pieces of paste to fall off the plates reducing the battery’s ability to recharge. Large buckling, often caused by repetitive small buckling, can cause the battery to short out and die.

Standard lead acid batteries use a glass mat to hold the plates in place (known as Absorbent Glass Matt or AGM for short) but it is not strong enough to prevent buckling or all paste loss. Gel batteries use a semi-solid silicon type material which glues to the plates and helps prevent buckling or paste loss although it cannot eliminate it altogether.

This makes gel batteries much better at deep cycling and gives them a far longer service life as the table below shows.

Depth of Discharge Cycle Life*
8G31DTM Gel Battery BG-121000 AGM SLA Battery
30% 2,000 1,300
50% 1,000 500
100% 450 200
*Cycle Life – the number of times a battery can be discharged and charged before it reaches the end of its life.

As you can see in all conditions a Gel battery will last longer but in very deep cycling conditions its cycle life can be twice that of a standard SLA battery.

You’ll also notice that both types last far, far longer if depth of discharge is kept below 70% so always recharge your trolling battery or batteries immediately after use and keep them fully charged when in storage with a smart charger such as the Genius G7200, regardless of whether they are Gel or AGM.

Q2: In what environment will you be operating the battery?

It is not just discharging and recharging which can cause paste to shed from the plates inside a lead acid battery. Vibrations of sudden jolts and jars have the same effect.

The silicon between the plates in Gel batteries is much better at keeping the plates in shape and the paste in place in these conditions.

This means, generally speaking, that Gel is better for salt water trolling where waves cause constant vibrations and jolts while standard AGM SLA appreciates the calmer environment of freshwater trolling.

However remember to take all aspects into consideration. If your trolling battery is a backup to a diesel or gasoline engine and you need to mount the battery close by, the vibrations of the main engine could also cause damage to internal plates.

Q3: In what temperatures will you be using the battery?

Trolling in the cold
In colder environments Gel batteries offer more power for longer than AGM Sealed Lead Acid batteries

All Lead Acid batteries are at their best when the temperature is around 77 degrees Fahrenheit (25 degrees Centigrade). The colder it gets the worse they perform and the slower they are to recharge.

A standard lead acid battery will operate down to -4 degrees Fahrenheit (-20 degrees Centigrade), perhaps a bit beyond, while Gel batteries will work even at 76 degrees Fahrenheit (-60 degrees Centigrade) although they won’t give their best performance!

If you are trolling in open waters out of season and your battery is mounted in an uninsulated area of your vessel you would be well advised to invest in Gel .

Even if you don’t expect temperatures to drop close to or below 32 Fahrenheit ( 0 Celsius) a Gel battery will give you longer lasting performance in each trip and recharge more efficiently afterwards.

Q4: Is Size and Weight important?

All other things being equal there is not much in it when it comes to size and weight as the comparison below demonstrates.

8G31DTM Gel Battery BG-121000 AGM SLA Battery
Weight 68.6 lbs (31kg) 62.2 lbs (28.2kg)
Dimensions (in) L: 12.93, W: 6.74, H: 9.33 L: 13.00, W: 6.74, H: 8.66
Dimensions (mm) L: 329, W: 171, H: 237 L: 330, W: 171, H: 220


The BG-121000 AGM SLA Battery is a solid choice for most trolling needs especially if heavy discharging is avoided. If it can’t be, or if the environment you troll in is harsh, the 8G31DTM Gel represents a much better investment.

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