Victron Battery Balancer: How It Works and Where It Fits

The Victron Battery Balancer solves a quiet problem in 24V and 48V lead-acid banks. When you wire 12V batteries in series, one battery with slightly higher internal leakage slowly drifts to a lower state of charge. Victron’s manual warns that this imbalance can substantially shorten the bank’s service life. The balancer is a small box that keeps the batteries matched. Here’s how it works and what the specs say.

Victron Battery Balancer: Specs

Spec	Battery Balancer
Input voltage	Up to 18V per battery, 36V total
Turn-on voltage	27.3V (±1%)
Turn-off voltage	26.6V (±1%)
Deviation to start balancing	50 mV
Max balancing current	0.7A (deviation over 100 mV)
Alarm trigger / reset	200 mV / 140 mV
Alarm relay	Normally open, 60V / 1A
Protection	IP22
Size / weight	100 x 113 x 47 mm / 0.4 kg

Source: Victron Battery Balancer product page and manual.

How the Victron Battery Balancer Works

Once a 24V bank’s charge voltage rises above 27.3V, the balancer switches on and compares the two series batteries. Victron says it draws up to 0.7A from the battery with the higher voltage. That current difference during charging lets both batteries reach the same state of charge.

Green LED: on (battery voltage above 27.3V)
Red LED: alarm, when the deviation exceeds 0.2V. It stays on until the deviation falls below 0.14V.
Alarm relay: closes when the red LED comes on, so you can trigger a remote alarm.

48V Banks and Parallel Strings

Victron says several balancers can be paralleled, and a 48V bank needs three balancers, one across each pair of 12V batteries. It also works on several parallel strings of series-connected batteries.

For more insight, Victron suggests the BMV-702’s midpoint monitoring, which displays the deviation in volts or percent and can trigger an alarm.

Who It’s For

24V and 48V AGM, GEL or flooded banks built from 12V batteries.
Off-grid and marine systems where a lead-acid bank is expected to last years.

Who Doesn’t Need It

Victron lithium batteries. Victron’s LiFePO4 batteries are balanced at cell level by their own system. The balancer is designed around lead-acid voltages, with a 27.3V turn-on level.
Single 12V systems. There’s nothing to balance.

Good to Know Before You Buy

Works only during charging, above 27.3V.
Slow. 0.7A won’t fix a badly mismatched or damaged battery.
IP22, so mount it somewhere dry.

Victron lists every Battery Balancer variant, with datasheets, on its official product page.

Worked Example: Two 12V Batteries in a 24V Bank

Two 12V 200Ah AGM batteries are wired in series for 24V. Battery A has slightly higher self-discharge than Battery B. After weeks of cycling, during charging Battery A sits at 13.6V and Battery B at 13.8V, a 200mV deviation.

The bank reaches 27.3V while charging, and the balancer switches on.
The deviation is over 100mV, so it draws its maximum 0.7A from Battery B, the one with the higher voltage.
Battery A now receives slightly more charge current than Battery B, so it catches up.
Once the deviation falls below 50mV, balancing stops.
At 200mV the red LED and alarm relay activate, and they reset once the deviation drops below 140mV.

Example values based on the manual’s thresholds.

Worked Example: How Much Correction 0.7A Gives

If the bank spends about 3 hours a day above 27.3V during absorption, the balancer can shift up to about 2.1Ah per day between the batteries (0.7A × 3h, estimate). That’s plenty to keep up with normal small differences in self-discharge, but it can’t recover a battery that’s tens of amp-hours behind. In that case, charge the low battery separately with a 12V charger, then let the balancer maintain them.

Wiring a 24V Bank

Connect the balancer’s three wires: the negative to the bank negative, the midpoint wire to the connection between the two batteries, and the positive to the bank positive.
Fuse the wires as shown in the manual.
Optional: wire the alarm relay (60V/1A) to a buzzer, a light or a GX device digital input.
Charge the bank and check the green LED lights above 27.3V.

Wiring a 48V Bank

For four 12V batteries in series, use three balancers. Each one connects across a pair of adjacent batteries, so together they cover every midpoint: between batteries 1–2, 2–3 and 3–4. Victron’s manual shows the exact layout.

Parallel Strings

With two or more parallel strings of series batteries, connect the midpoints of the strings together and use one balancer per midpoint, or follow the manual’s diagram for your layout. This keeps every battery in the bank evened out.

Monitoring the Midpoint

A SmartShunt or BMV-712’s auxiliary input can show the midpoint deviation in VictronConnect and on a GX device, with an alarm threshold you set. Watching it alongside the balancer’s LEDs tells you whether the bank is staying even over months.

Good Habits for a Long-Lasting Bank

Build each series string from identical batteries of the same age and batch.
Use equal-length interconnecting cables.
Charge fully on a regular basis; lead-acid batteries last longer when they reach 100% often.
Check terminals for tightness and cleanliness a couple of times a year.

FAQ

How many Victron Battery Balancers do I need for 48V?

Three, according to Victron.

When does the balancer turn on?

When the bank voltage rises above 27.3V. It turns off below 26.6V.

Does it drain the battery?

Victron lists a small current draw when off. It only balances while charging.

Can I use it on a 12V bank of parallel batteries?

No. Parallel 12V batteries share the same voltage, so there’s no series midpoint to balance.

Does the balancer work on AGM and gel batteries?

Yes. Victron designed it for lead-acid banks, including AGM, gel and flooded.

Can I add a balancer to an older bank?

Yes, but if one battery is already well behind, recharge it separately first. The balancer is best at keeping a healthy bank matched.

Sources: Victron Battery Balancer product page and Battery Balancer manual (PDF), victronenergy.com, accessed Oct 2026.