Using a Battery Tender on Your Generator

What a battery tender is

A battery tender, sometimes called a battery maintainer, is a low-rate charging device that connects to a generator's starter battery and keeps it at a maintained charge. It stays connected while the generator sits, rather than bringing a completely dead battery back to full charge in a short session. The maker's manual is the place to find the exact connection steps and the conditions the tender is meant for.

A battery tender differs from a conventional battery charger in how it is used. A charger is usually connected for a limited session to bring a battery up, and then removed. A tender is meant to remain connected over a long period, watching the charge level and keeping it in a narrow band. That difference matters for a generator that sits between seasons.

A battery tender is a separate purchase from the generator. The listing for the generator states whether electric start is included, and electric start is the feature that points to a starter battery. If you see electric start on a listing, the generator uses a battery; if the listing shows recoil start only, there may be no battery at all. For a comparison of the two starting systems, see how electric start and recoil start compare.

Why a stored battery loses charge

A lead-acid battery slowly loses its charge on its own when the generator is not running. A generator stored between storm seasons, or a camping generator stored between trips, can sit for months. During that time the battery can drop to a low level, and a low battery may not have enough power to turn the starter motor when you need it.

The rate at which a battery loses charge depends on the battery and the storage temperature, and the maker's manual is the only source for what your model does. The manual's storage section states how long the battery can sit before it needs attention, and whether the manual calls for a maintainer.

The generator maintenance checklist describes the storage steps the maker intends, and the hour meter is how you track usage between checks. The manual's storage section is the authority for how long the battery can sit before it needs attention.

What sulfation is

Sulfation is the term for lead sulfate crystals that form on the plates of a lead-acid battery when it is left at a low charge for a long time. The longer the battery sits low, the more the crystals build up, and the harder it becomes for the battery to hold a charge. Sulfation is a property of the battery chemistry, not a feature of any particular generator.

A battery that is kept near full charge does not develop sulfation the way a deeply discharged battery does. The way to address sulfation, as the maker's manual describes it, is to keep the battery charged while the generator is stored. A battery tender does that by maintaining the charge level instead of letting the battery drop.

The related article on battery charging and maintenance covers the general steps in more detail, and the battery charger type article explains the difference between charging and maintaining.

How the manual describes battery care

The maker's manual is where the battery care schedule lives. It describes how to locate the battery, how to connect a maintainer, and when to check the charge. The manual also states whether the starter battery is included with the generator or is a separate item, and it names the charging method the generator expects.

This article is not a substitute for the manual. The model-specific details, such as the battery location and the connection order, come from the maker's documentation. The maker's page is the place to confirm the specifics for your model, and the listing shows whether the battery is stated as included.

Reading a listing for the battery

On a generator listing, the words that point to a battery are electric start and remote start. A generator with electric start has a starter battery, and some listings state the battery as an included item in the bullet list. A listing that does not state the battery may still include one, and the maker's page is the place to confirm.

Recoil start is the alternative way to start a generator. A recoil-start generator is started by pulling a cord, and it may not have a starter battery. If you are shopping for a camping set or a small inverter set, the best camping generators guide looks at listings by stated features, and the inverter generator guide compares inverter sets that often carry electric start.

Battery tenders as a separate purchase

A battery tender is bought separately from the generator, so it is not part of the generator's listed details. When you compare generators, the question for a battery tender is whether the generator has a starter battery at all. If it does, the tender keeps that battery maintained during storage; if it does not, a tender is not needed.

The portable generator guide covers open-frame and inverter portables by stated details, and the whole house generator guide is where standby units are compared. The dual fuel generator guide compares listings that state two fuels, and those generators may or may not carry electric start.

What to pick for your situation

Questions

What is a battery tender?

A battery tender, also called a battery maintainer, is a low-rate charger that stays connected to a generator's starter battery and keeps it at a maintained charge during storage.

Does every generator need a battery tender?

Only a generator with a starter battery needs one. Electric-start generators have a starter battery; recoil-start generators may not.

Is a battery tender the same as a battery charger?

A battery charger brings a battery back to full charge, while a battery tender is designed to stay connected and maintain the charge level. The manual describes which device to use for storage.

Where do I connect a battery tender?

The battery tender connects to the battery terminals. The maker's manual shows the battery location and the correct connection points.

How long can a battery tender stay connected?

The manual describes the storage period and how long the maintainer can remain connected. The hour meter and the battery check schedule are in the manual.

What is sulfation?

Sulfation is lead sulfate crystals that form on a lead-acid battery's plates when it sits at a low charge for a long time. The maker's manual describes keeping the battery charged as the way to address it.