Maintenance Free or Gelled Electrolyte Batteries

So-called new no maintenance batteries with a marine label are not that much different than automotive no-maintenance batteries except the price. The reference to Gelled (Prevailer) has caused confusion. The gel only serves to hold the battery electrolyte captive and in deep cycle service it results in lower capacity than their rating. Batteries made with this construction are usually acid starved without sufficient electrolyte to activate the plates. The result is low capacity size for size.

By sealing the battery, there is no practical way of determining the battery's condition if the battery can't be checked with a hydrometer, the boat owner could be starting a cruise with low batteries; in an emergency it could result in battery failure just when the battery power is needed most.

The buyer of a Gelled type battery should be cautioned that the voltage setting of the regulator may have to be changed. The Prevailer has a 14.1 maximum volt limitation. Most alternators are preset at 14.2 to 14.5 volts and must be reduced in order to protect Gelled electrolyte batteries. Some distributors of Gelled type batteries have suppressed the fact that the ship's charging system may require an expensive modification to accommodate this type battery.

Most so-called sealed batteries are assembled in gray propylene cases - similar to most automotive batteries. Rolls uses only black rubber containers on all series 400, including the smaller size marine Batteries. White propylene cases are used only on our 3rd line series.

Promoters of these types of batteries are highly sales motivated. They fail to put the boat owner on notice that, in the event of improper voltage regulator setting, the battery could dry out and, if so, there would be no way to replace the water allowing the battery to continue to function.

They refer to cranking power. They have no more than the average maintenance free automotive battery, which depends on a multiple of thin plates - the thinner the plates, the shorter the battery life, and the less able to stand abuse and overcharging.

The maintenance-free automotive batteries normally have plates as thin as .0500 thick, with low density porous active material (oxide) which does not lend itself to deep cycling or overcharging. It does have one advantage: it uses less lead and is a cheaper way to make a battery.

With low capacity characteristics inherent in Gelled electrolyte batteries, their claims of faster recharge ability exist partly because there is less capacity to return to the battery. These claims are immeasurable because the only state of charge measurement is surface voltage which is not an accurate indicator for calcium lead alloy batteries. Because Gelled batteries are acid starved they have less capacity and also less problems with sulfation.

The positive plates in a lead acid battery are the limiting factor in life expectancy in deep cycling marine service. The so-called new sealed battery has very fragile thin plates no different than common automotive batteries.

Gelled batteries, such as the Prevailer battery, costs approximately 40% more than Rolls Marine Series 400 and 100% more than American made automotive batteries. They use a cheap polypropylene case compared to rubber and they are clearly designed for float operation and a periodic deep cycling. Periodic deep cycle normally is not suitable or will not qualify as a deep cycle battery. Most automotive batteries qualify for periodic deep cycle service.

The above is only a brief comparison to reflect the fact that there is little, if any difference, except the higher price, with the average North American car battery.