A primer on ATV batteries

What you need to know about powering up your ATV

Story by Gary L. Gustafson, Dec. 15, 2006

As with many electrical technologies, the relationship between the battery and charging system is a little fuzzy in the minds of many consumers. And truth be told, even service technicians sometimes have a hard time separating the two. The battery and charging system are directly related, but each actually has its own purpose. The charging system on an ATV needs to support all of the high duty-cycle (frequent, long-term) electrical loads and keep the battery charged as well.

Examples of high duty-cycle loads are: cooling fans, headlights, and accessories such as sprayers that draw a lot of power and are on for long periods. The battery alone cannot support high duty-cycle loads because in most cases an ATV battery’s energy storage capacity (measured in amp-hours) is actually pretty low. Batteries with low amp-hour capacities are used on ATVs to reduce weight, for easier packaging and to reduce cost. If the loads on the electrical system exceed the charging system capacity, even a large battery will go dead sooner or later. The battery is meant to handle low duty-cycle, high current electrical demands like starting the engine and winching. In other words, the battery on most ATVs is built to deliver a lot of ‘juice’ for a short time. Batteries also stabilize the voltage on the DC power bus, helping all components to operate without malfunctioning.

A battery is most properly viewed as being an energy storage tank that needs to be topped off on a daily basis. In most cases, the ATV charging system will perform this operation, but in some instances the operator must take responsibility for charging the battery. When in doubt, use a battery maintainer or tender when you park your quad, and leave it on until the battery is re-charged.

The terms ‘gel cell,’ ‘sealed’ and ‘maintenance-free’ are often used when comparing battery types. The fact is there are two basic types of battery technology in use on ATVs today—conventional (also known as flooded) and AGM—short for absorbed glass mat. All other terminologies are simply different ways to describe these battery types. Conventional battery technology is just that. It has been around for many, many years. AGM batteries are a little newer. They were pioneered on Honda powersports vehicles in the early 1980s (with an expensive learning curve) but have since become by far the prevailing battery technology on motorcycles, ATVs, snowmobiles and personal watercraft. The innovative ‘spiral’ cell batteries from Hawker and now Johnson Controls are just a different way to implement an AGM battery.

AGM Battery Design
Characteristic: Conventional AGM
Other common names: Flooded Sealed, Gel Cell*, VRLA, Maintenance-Free, Recombinant
Specific Gravity of Electrolyte (at 77F): 1.265 1.310
At-rest fully-charged voltage (no loads)**: 12.6-12.8 12.8-13.1
Filler cap type: Removable Permanently installed
Typical Housing Colors: Natural, White Black, Grey
Needs distilled water refills?: Yes No
Use bulk acid to activate?: Yes No. Use pre-measured electrolyte container.
Can be installed at an angle or on it’s side?: Never Sometimes (if activated properly)
Has a vent hose?: Yes (On ATVs, not autos) No
*There is a separate Gel-cell design, but it is not used on any ATVs
**After 24 hours at rest to allow “surface charge” to dissipate.
Source: Yuasa Corp.

Almost 100% of the time, when people talk about sealed, gel-cell or maintenance-free batteries from any manufacturer on a powersports vehicle, they are actually talking about AGM technology. Absorbed glass mat refers to the battery’s design in which all of the electrolyte (acid) is absorbed into fiberglass-pads that are pressed between the positive and negative plates. There is no loose acid in a properly-activated AGM battery. Conventional batteries must have extra acid above all of the negative and positive plates. Dry plate surfaces become damaged and that is one reason why conventional batteries must be topped off with distilled water as needed. AGM batteries are not vented to atmosphere so they do not dry out with normal use. One thing that should be noted is that while the basic technology is the same regardless of manufacturer, there are varying levels of quality between brands. The familiar names in lead-acid batteries do have a longer track record of quality than many of the newcomers do.

AGM batteries have several advantages over conventional batteries, such as having a much higher cranking capacity for the same weight. They do not need to have distilled water added, ever. They can be installed at an angle—but only if they have been perfectly activated. They generally have a higher amp-hour rating for the same weight than a conventional battery will. Lastly, they do not have a vent hose to deal with because vapors are contained and re-combined into the electrolyte as part of the design.

The disadvantages of an AGM battery are that they are very sensitive to how well they are initially activated, they cost more, and the misnomer ‘maintenance-free’ often misleads people to think they do not need to be concerned with charging them. An AGM battery needs to be kept properly charged every bit as much as a flooded battery does, and they require more complex equipment to both activate and charge them.

Initial activation of new batteries

Here’s a tip for the next time you buy an ATV. Tell the dealer that before you take ownership you want the new battery to be trickle charged for at least 8 to 10 hours at between 1 and 3 amps (depending on battery size) on a charger designed specifically for powersports vehicle batteries—not a car battery charger. If the dealer makes comments such as “The quad can charge the battery. Just take it out for a drive when you get it home,” or “The battery is charged when you pour new acid into it,” or “We use a rapid-charger, it’ll only take an hour and the battery will be ready,” tell the dealer you are not satisfied with his answer and insist on a proper trickle charge on a ‘smart’ charger before the battery is ever put into service.

Tests indicate that a battery can lose substantial capacity, permanently, if it is not properly activated. You will miss that capacity if you ever have to start your ATV on a cold day to plow snow or when you are winching your way across a long swamp. Time must be allowed for the electrolyte to soak into the fiberglass matting thoroughly before a charging voltage is applied. In addition, both proper voltage and current must be administered for the battery to be properly activated. That is why a smart or programmable charger designed for AGM batteries must be utilized for the initial charge. Recommended models include the Christie chargers that have been mandated to Honda’s dealers and Tecmate units used by some Yamaha dealerships. These chargers have all been developed specifically for AGM battery technologies. They will charge the battery at the right current and voltage if they are utilized correctly by the technician who is doing the set-up. Low-current battery tenders, typically in the 900 mA range, are not adequate for the initial activation of the battery. They are fine for maintaining the battery once it is in service.

The best dealerships constantly anticipate which batteries are going to be installed in their ATVs and keep a supply of batteries charging at all times. AGM batteries that are put on a smart trickle charger can be charged for months, as needed, with no damage to them. An advantage of the Christie and Tecmate chargers is that they have a desulfating feature that really works. A battery that has discharged and sulfated can usually be brought back to at least 90% of its original capacity after it has been put on a desulfating charge cycle.

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