# Optima RTU-3.7 · Car battery 12V 44Ah 730A

![Optima RTU-3.7 · Car battery 12V 44Ah 730A](https://bateriasonline.es/3870-home_default/optima-rtu-3-7.jpg)

> Optima RTU-3.7 (ETN 822255000): 44 Ah car battery, 730 A (EN), 237×172×197 mm, positive terminal on the left. Equivalent to Optima RTS-3.7.

**Category:** [Car batteries](https://bateriasonline.es/en/car-batteries) → [Optima](https://bateriasonline.es/en/optima-batteries)

- **Canonical URL**: https://bateriasonline.es/en/optima-rtu-3-7
- **Language**: en
- **Brand**: Optima
- **Reference**: BOL-OPTIMA-RTU-3.7
- **EAN**: 4016987113561
- **MPN**: RTU-3.7
- **Price**: 183,28 € (VAT incl., Spain)
- **Last updated**: 2026-10-27

## Technical specifications

| Feature | Value |
|---|---|
| Brand | Optima |
| Range | OPTIMA RED TOP |
| Application | Cars |
| Technology | Spiral AGM |
| Voltage | 12 V |
| Capacity | 44 Ah |
| Cold cranking amps (EN) | 730 A |
| Length | 237 mm |
| Width | 172 mm |
| Height | 197 mm |
| Weight | 15.7 kg |
| Polarity | Positive terminal on the left |
| Terminal type | 1 & 21 |
| ETN code | 822255000 |

## Quick description

The Optima RTU-3.7 (ETN 822 255 000, also written 822255000) is a car battery (spiral AGM) with 12 V, 44 Ah and 730 A cold cranking current, measuring 237 × 172 × 197 mm, with the positive terminal on the left. Need the positive terminal on the right? The same battery is the Optima RTR-3.7.

## Description

## The Optima RTU-3.7 at a glance

The Optima RTU-3.7 is a starter battery for cars without Start-Stop: it delivers the current the starter motor needs and then powers lights, control units and audio with the engine off. If your car has no Start-Stop and had a 44 Ah battery, the RTU-3.7 is a direct replacement.
At 44 Ah it is a small size: the usual choice for petrol superminis and city cars with little equipment. The RTU-3.7 belongs to the Optima OPTIMA RED TOP range. [More Optima batteries](https://bateriasonline.es/en/optima-batteries)

## Optima RTU-3.7 codes and part numbers

The RTU-3.7 is listed under these codes on labels, in garages and in catalogues:

| Commercial reference | RTU-3.7 |
|---|---|
| ETN code | 822255000 (also 822 255 000) |
| EAN | 4016987113561 |
| Case size according to Optima | 75/25 (BCI) |
| Base hold-down | B1 |
| Terminal type | 1 & 21 |
| Also known as | Optima 822255000 · Optima 822 255 000 |
| Not to be confused with | Optima RTR-3.7 (44 Ah, 730 A, positive terminal on the right) |

## Optima RTU-3.7 vs RTC-4.2, RTR-3.7 and RTS-4.2: differences

How the RTU-3.7 compares with Optima batteries of similar size and capacity:

| Model | Capacity | Cold cranking (EN) | Dimensions (mm) | Positive | Weight |
|---|---|---|---|---|---|
| Optima RTU-3.7 (this one) | 44 Ah | 730 A | 237 × 172 × 197 | left | 15.7 kg |
| Optima RTC-4.2 | 50 Ah | 815 A | 254 × 175 × 200 | – | 18.5 kg |
| Optima RTR-3.7 | 44 Ah | 730 A | 237 × 172 × 197 | right | 15.6 kg |
| Optima RTS-4.2 | 50 Ah | 815 A | 254 × 175 × 200 | left | 18 kg |

- Optima RTC-4.2: 6 Ah more, 85 A more cranking power, a different case (254 × 175 × 200 mm).
- Optima RTR-3.7: identical to the RTU-3.7 except for the positive terminal, which is on the other side (positive terminal on the right).
- Optima RTS-4.2: 6 Ah more, 85 A more cranking power, a different case (254 × 175 × 200 mm).

## Equivalents and alternatives to the Optima RTU-3.7

As the RTU-3.7 is an AGM battery, we only list other AGM batteries with its dimensions and polarity: neither an EFB nor a conventional battery can replace it.

| Model | Technology | Capacity | Cold cranking (EN) | Dimensions (mm) |
|---|---|---|---|---|
| Optima RTS-3.7 | Spiral AGM | 44 Ah | 730 A | 237 × 172 × 197 |

## Inside the RTU-3.7: spiral AGM technology

The RTU-3.7 is a spiral-cell AGM battery. Perfect for 4x4s, marine use and vehicles with lots of electronics.

## Check this before ordering the Optima RTU-3.7

- The RTU-3.7 is AGM: it replaces an AGM or an EFB of the same size. You can swap an EFB for an AGM, but not an AGM for an EFB.
- The RTU-3.7 delivers 730 A cold cranking (EN standard); do not go below what your original battery states.
- With 44 Ah, the RTU-3.7 replaces an original battery of that capacity or slightly less.
- With the terminals facing you, the positive terminal of the RTU-3.7 is on the left.
- Measure the space: the RTU-3.7 takes up 237 × 172 × 197 mm.

## Frequently asked questions about the Optima RTU-3.7

### Optima RTU-3.7 or RTC-4.2?

Compared with the RTU-3.7, the Optima RTC-4.2 has 6 Ah more and 85 A more cranking power. If your current battery says 815 A or more, choose the RTC-4.2; if it says 730 A or less, the RTU-3.7 is enough. Mind the space: the RTC-4.2 measures 254 × 175 × 200 mm.

### What is the difference between the Optima RTU-3.7 and the RTR-3.7?

They are the same battery with the terminals swapped: positive terminal on the left on the RTU-3.7, positive terminal on the right on the RTR-3.7. Look at your current battery with the terminals facing you and pick the one that matches. That is why their ETNs only differ in the middle group: 822 255 000 for the RTU-3.7 and 835 255 000 for the RTR-3.7.

### What is the ETN code of the Optima RTU-3.7?

822255000, also written 822 255 000. The ETN (European Type Number) is printed on the label and used in parts catalogues.

### Can the Optima RTU-3.7 be used in a car with Start-Stop?

Yes. As an AGM battery, the RTU-3.7 handles automatic engine stop and brake energy recovery, and it can replace an EFB of the same size.

### How much does the Optima RTU-3.7 weigh?

The RTU-3.7 weighs 15.7 kg. For reference, the Optima RTC-4.2 (50 Ah) weighs 18.5 kg.

### Which battery is equivalent to the Optima RTU-3.7?

Only other AGM batteries with its dimensions and polarity: Optima RTS-3.7. Neither an EFB nor a conventional battery replaces the RTU-3.7.

### Which charger does the Optima RTU-3.7 need?

A charger with an AGM mode. If the battery has dropped below 10.5 V some chargers will not recognise it: use one with a recovery mode or one specific to spiral AGM.

## Keep comparing: alternatives to the RTU-3.7

- [More car batteries](https://bateriasonline.es/en/car-batteries)
- [More Optima models](https://bateriasonline.es/en/optima-batteries)
- [Long WPX14-BS](https://bateriasonline.es/en/long-wpx14-bs) · 12 Ah, 151×88×147.5 mm

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