# Motobatt MB3U · Motorcycle battery 12V 3.8Ah 50A

![Motobatt MB3U · Motorcycle battery 12V 3.8Ah 50A](https://bateriasonline.es/3138-home_default/motobatt-mb3u.jpg)

> Motobatt MB3U: 3.8 Ah motorcycle battery, 50 A (EN), 98×56×110 mm, AGM. Compare sizes and equivalents; 14-day returns.

**Category:** [Motorcycle batteries](https://bateriasonline.es/en/motorcycle-batteries) → [Motobatt](https://bateriasonline.es/en/motobatt-batteries)

- **Canonical URL**: https://bateriasonline.es/en/motobatt-mb3u
- **Language**: en
- **Brand**: Motobatt
- **Reference**: BOL-MOTOBATT-MB3U
- **MPN**: MB3U
- **Price**: 362,31 € (VAT incl., Spain)
- **Last updated**: 2026-10-27

## Technical specifications

| Feature | Value |
|---|---|
| Brand | Motobatt |
| Range | MOTOBATT QUADFLEX |
| Application | Motorcycles |
| Technology | AGM |
| Voltage | 12 V |
| Capacity | 3.8 Ah (C10) |
| Cold cranking amps (EN) | 50 A |
| Length | 98 mm |
| Width | 56 mm |
| Height | 110 mm |
| Weight | 1.34 kg |

## Quick description

Motobatt MB3U: motorcycle battery (AGM) with 12 V, 3.8 Ah and 50 A cold cranking current, measuring 98 × 56 × 110 mm.

## Description

## Who the Motobatt MB3U is for

The Motobatt MB3U is a motorcycle starter battery: compact, vibration-resistant and with just the right power to turn the starter motor and feed the electronics. It handles frame vibration and idle periods better than an adapted car battery.
At 3.8 Ah it is a small battery, typical of 50 to 125 cc scooters and light motorcycles. The MB3U belongs to the Motobatt MOTOBATT QUADFLEX range. [See all Motobatt batteries](https://bateriasonline.es/en/motobatt-batteries)

## Motobatt MB3U codes and part numbers

The MB3U is listed under these codes on labels, in garages and in catalogues:

| Commercial reference | MB3U |
|---|---|
| Not to be confused with | Motobatt MB5U (7 Ah, 90 A), Motobatt MB7U (6.5 Ah, 100 A), Motobatt MB9U (11 Ah, 140 A) |

## Equivalents and alternatives to the Motobatt MB3U

No other reference in the catalogue fully matches the dimensions and polarity of the MB3U; you will find the closest ones among our [motorcycle batteries](https://bateriasonline.es/en/motorcycle-batteries).

## Motobatt MB3U vs mb2.5u and MT4R

What sets the MB3U apart from its neighbours in the Motobatt range:

| Model | Capacity | Cold cranking (EN) | Dimensions (mm) | Weight |
|---|---|---|---|---|
| Motobatt MB3U (this one) | 3.8 Ah | 50 A | 98 × 56 × 110 | 1.34 kg |
| Motobatt mb2.5u | 2.5 Ah | – | 80 × 70 × 105 | 1.18 kg |
| Motobatt MT4R | 2.5 Ah | 45 A | 114 × 49 × 86 | 1.15 kg |

- Motobatt mb2.5u: 1.30 Ah less, a different case (80 × 70 × 105 mm).
- Motobatt MT4R: 1.30 Ah less, 5 A less cranking power, a different case (114 × 49 × 86 mm).

## What to look at before buying the MB3U

- Length, width and height of the MB3U: 98 × 56 × 110 mm.
- Your current battery should say about 3.8 Ah; a little more is also fine.
- Check the EN amps on your battery: if it says 50 A or less, the MB3U covers your engine.

## Frequently asked questions about the Motobatt MB3U

### Motobatt MB3U or mb2.5u?

Compared with the MB3U, the Motobatt mb2.5u has 1.30 Ah less. With 3.8 Ah, the MB3U runs longer between charges than the mb2.5u (2.5 Ah). Mind the space: the mb2.5u measures 80 × 70 × 105 mm.

### How much does the Motobatt MB3U weigh?

The MB3U weighs 1.34 kg. For reference, the Motobatt mb2.5u (2.5 Ah) weighs 1.18 kg.

### Does the Motobatt MB3U come charged and ready to fit?

Sealed AGM and gel batteries leave the factory charged and ready. Conventional ones with a separate acid pack are activated when filled and should be charged before fitting.

## Inside the MB3U: AGM technology

The MB3U is AGM: the electrolyte is absorbed in glass fibre mats, so it is sealed and spill-proof. It withstands many more cycles than a conventional lead battery, at the cost of being more sensitive to overcharging.

## Keep comparing: alternatives to the MB3U

- [All motorcycle batteries](https://bateriasonline.es/en/motorcycle-batteries)
- [The whole Motobatt range](https://bateriasonline.es/en/motobatt-batteries)

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*bateriasonline.es — Batteries and accessories · 2026-11-10*