What Is a Battery Equalize Mode?

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A battery equalize mode is a controlled, higher-voltage charging stage that some charge controllers can run for a limited time. It is meant for battery types that tolerate it, and it is not a general boost setting for weak batteries. The Victron Energy SUN Inverter manual we opened describes equalization as a feature that is disabled by default, must be started on purpose, and can damage a battery that is not suitable for it. Read the battery maker’s instructions before you enable it.

Quick answer

Equalize is a deliberate, time-limited charge stage with a higher voltage than normal charging.
On the Victron SUN Inverter, the manual says it is disabled by default and can be started manually with a START NOW button.
The manual says to use it only during the absorption and float stages, and only when there is enough sunlight.
Check the battery manufacturer first. The manual warns that equalization can damage a battery that is not suitable for it.

What equalize mode does

Most solar charge controllers move a battery through stages. The bulk stage pushes current into the battery. The absorption stage holds a regulated voltage while the current tapers. The float stage keeps the battery topped up at a lower voltage. Equalize sits on top of that cycle as an extra stage. According to the configuration section of the SUN Inverter manual, during the equalization stage “the charge voltage increases up to the set equalization voltage.” That sentence is the core of the feature: the controller raises the voltage above its normal target for a while, then returns to normal charging.

The manual does not give a numeric equalization voltage. It says the value is set in the controller, so the number depends on the settings you choose and on the battery. Do not copy a voltage from a forum or a generic chart into the controller. Use the figure your battery manufacturer gives.

When the controller allows it

The same configuration section sets out the timing rules we could find in the manual. A manual equalization can be started by pressing the START NOW button. The manual says to use that option only during the absorption and float charge stages, and only when there is sufficient sunlight. A manual equalization lasts one hour, and it can be stopped at any time with the Stop Equalize command. Automatic equalization works differently and depends on the battery preset and the stop mode chosen in the settings. The manual does not give a single automatic schedule for every setup, so read the settings screen for your exact unit.

The sunlight condition matters. A controller that begins equalization on a weak or fading sun may not hold the stage in a stable way. For that reason the manual ties manual equalization to good sunlight rather than leaving it open to any time of day.

Why the warning matters

The manual is direct on the risk. It states that “equalization can cause damage to the battery if the battery is not suitable for an equalization charge.” It also tells the installer to “always check with the battery manufacturer prior to enabling equalization.” The same section says the battery preset does not support equalization for lithium batteries. If your battery is lithium, equalize should not be enabled on the controller, and the preset list is the first place to confirm that.

Two points follow from the warning. First, equalize is not a repair tool. A weak battery may need a proper inspection, a load check, or replacement, and a higher charge voltage can make a damaged battery worse. Second, the controller does not know your battery’s history. It applies the settings you give it. A wrong battery type in the preset is a common cause of trouble.

Before you enable equalize

Confirm the battery type. Read the label or the maker’s data sheet, not the case shape or the brand.
Read the battery maker’s charging instructions. The SUN Inverter safety section says to consult the battery maker’s manual for charging, recharging and disposal of the battery. Follow that document for the battery in front of you.
Set the battery preset before anything else. A preset that does not match the battery is the first thing to fix if the system behaves oddly.
Check the voltage with a multimeter. A reading at the battery terminals shows where the battery stands before you start a charge stage. Our guide to testing a battery charger with a multimeter covers the basic readings. Take readings with the meter set for DC volts, and keep the probes away from moving parts and from anything that could short the terminals.
Disconnect the battery before maintenance. The safety section says to disconnect the battery before carrying out maintenance or servicing. Treat any work on the wiring the same way.

How equalize differs from absorption and float

Absorption and float are the normal stages that keep a battery in working order every day. Absorption holds a higher regulated voltage until the current drops to a low level. Float holds a lower voltage so the battery stays full without heavy gassing or overcharge. Equalize is different in purpose and duration. It is occasional, it is time-limited, and it runs at a voltage above the normal absorption target. In the SUN Inverter manual, the one-hour manual run is a bounded window, not a permanent setting.

Because equalize is occasional, it does not replace a regular charging profile. A system that never reaches full charge will not be fixed by equalize alone. The manual’s wording about absorption and float implies that the controller must already be in those stages before a manual equalization is useful. Check your charge history before you assume equalize will help.

Where a multimeter fits

A multimeter does not run an equalize stage, and it cannot tell you whether a battery is suitable for one. What it does is give you the voltage picture before and after a charge cycle. Take a reading with the system at rest, then again during charging, and compare the values against the battery maker’s figures. If you are checking a solar setup more broadly, our guide to multimeters for solar panels explains which meter features matter for panel and controller work. Keep the meter rated for the circuit you are measuring, and never measure voltage on a live mains circuit with a meter that is not rated for it.

How we chose

This explainer covers one feature: equalize mode as described in a single Victron product manual. We opened four pages of the SUN Inverter manual on 2026-10-27: the configuration section, the safety instructions section (dated 2022 in the page title), the technical specifications section and the general description section. We counted each page as its own source, as the sourcing rule for this site allows. We left out retailer pages, community threads and forum posts, because they do not meet the source rule for this site. We did not add a general chemistry lecture with numbers that the sources do not state.

What we could not verify

The equalization voltage value. The manual says it is set in the controller and does not give a number.
The automatic equalization interval and the exact timing of automatic runs. The manual refers to the battery preset and stop mode without a fixed schedule on the pages we opened.
Which battery chemistries beyond lithium the preset list supports. The pages we opened name only lithium as unsupported.
How equalize behaves on a controller other than the SUN Inverter. Settings and wording vary between Victron models.

FAQ

Is equalize the same as a normal charge?

No. A normal charge follows the absorption and float stages. Equalize runs at a higher voltage for a limited time and is started on purpose. The SUN Inverter configuration section describes it as a separate stage.

Is equalize disabled by default?

The configuration section says expert mode is set to disabled by default, and the equalization settings are listed under expert mode. Check your own unit’s settings before assuming it is off.

Can I use equalize on a lithium battery?

The manual says the battery preset does not support an equalization charge for lithium batteries. Do not enable it for a lithium battery.

How long does a manual equalize run last?

The manual states that a manual equalization stage lasts one hour and can be stopped at any time with the Stop Equalize command.

Do I need a multimeter to use equalize mode?

The manual does not require one for the controller settings. A multimeter is still a useful way to check battery voltage before and after a charge cycle.

Bottom line

Turn on equalize only when the battery manufacturer allows it, the preset matches the battery, and the controller is in absorption or float with enough sunlight. If any of those checks is missing, leave equalize off.

Sources

Victron Energy, SUN Inverter Manual, “4. Configuration” (equalization charge section). https://www.victronenergy.com/media/pg/Sun_Inverter/en/configuration.html . Opened 2026-10-27.
Victron Energy, SUN Inverter Manual, “1. Safety instructions” (dated 2022 in the page title). https://www.victronenergy.com/media/pg/Sun_Inverter/en/safety-instructions.html . Opened 2026-10-27.
Victron Energy, SUN Inverter Manual, “6. Technical specifications”. https://www.victronenergy.com/media/pg/Sun_Inverter/en/technical-specifications.html . Opened 2026-10-27.