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

![Optima RTR-3.7 · Car battery 12V 44Ah 730A](https://bateriasonline.es/3855-home_default/optima-rtr-3-7.jpg)

> Optima RTR-3.7 (ETN 835255000): 44 Ah car battery, 730 A (EN), 237×172×197 mm, positive terminal on the right, spiral AGM.

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

- **Canonical URL**: https://bateriasonline.es/en/optima-rtr-3-7
- **Language**: en
- **Brand**: Optima
- **Reference**: BOL-OPTIMA-RTR-3.7
- **EAN**: 4016987113578
- **MPN**: RTR-3.7
- **Price**: 187,78 € (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 | 15.6 kg |
| Polarity | Positive terminal on the right |
| ETN code | 835255000 |

## Quick description

Optima RTR-3.7 (ETN 835 255 000, also written 835255000): 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 right. If yours has the positive terminal on the left, you need the Optima RTS-3.7.

## Description

## The Optima RTR-3.7 at a glance

The Optima RTR-3.7 is made for petrol and diesel cars without automatic engine stop. If your car has no Start-Stop and had a 44 Ah battery, the RTR-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 RTR-3.7 belongs to the Optima OPTIMA RED TOP range. [More Optima batteries](https://bateriasonline.es/en/optima-batteries)

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

What sets the RTR-3.7 apart from its neighbours in the Optima range:

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

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

## Optima RTR-3.7 codes and part numbers

Shops, garages and catalogues identify the RTR-3.7 with these codes:

| Commercial reference | RTR-3.7 |
|---|---|
| ETN code | 835255000 (also 835 255 000) |
| EAN | 4016987113578 |
| Case size according to Optima | 35 (BCI) |
| Base hold-down | B3 |
| Also known as | Optima 835255000 · Optima 835 255 000 |
| Not to be confused with | Optima RTS-3.7 (44 Ah, 730 A, positive terminal on the left), Optima RTU-3.7 (44 Ah, 730 A, positive terminal on the left), Optima YTR-3.7 (48 Ah, 660 A) |

## Equivalents and alternatives to the Optima RTR-3.7

No other reference in the catalogue fully matches the dimensions and polarity of the RTR-3.7; you will find the closest ones among our [car batteries](https://bateriasonline.es/en/car-batteries).

## Before ordering the RTR-3.7, check this

- The RTR-3.7 needs 237 × 172 × 197 mm of space: measure it with the hold-down clamp in place.
- The RTR-3.7 has the positive terminal on the right: compare it with your current battery.
- Capacity of the RTR-3.7: 44 Ah; the same as your current battery or slightly more is fine.
- Check the EN amps on your battery: if it says 730 A or less, the RTR-3.7 covers your engine.
- The RTR-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.

## Inside the RTR-3.7: spiral AGM technology

Inside, the RTR-3.7 rolls its plates into cylindrical cells (spiral AGM). It is the basis of OPTIMA batteries.

## Frequently asked questions about the Optima RTR-3.7

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

Compared with the RTR-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 RTR-3.7 is enough. Mind the space: the RTC-4.2 measures 254 × 175 × 200 mm.

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

They are the same battery with the terminals swapped: positive terminal on the right on the RTR-3.7, positive terminal on the left on the RTS-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: 835 255 000 for the RTR-3.7 and 820 255 000 for the RTS-3.7.

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

835255000, also written 835 255 000. The ETN (European Type Number) is printed on the label and used in parts catalogues.

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

Yes. As an AGM battery, the RTR-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 RTR-3.7 weigh?

The RTR-3.7 weighs 15.6 kg. For reference, the Optima RTC-4.2 (50 Ah) weighs 18.5 kg.

## More batteries to compare with the RTR-3.7

- [Other car batteries](https://bateriasonline.es/en/car-batteries)
- [Full Optima catalogue](https://bateriasonline.es/en/optima-batteries)
- [Exide EK013](https://bateriasonline.es/en/exide-ek013) · 1.2 Ah, 18 A, 97×43×58 mm
- [Long WPX14-BS](https://bateriasonline.es/en/long-wpx14-bs) · 12 Ah, 151×88×147.5 mm

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