Optima RTS-3.7 Red Top · Car battery 44Ah 730A AGM

Yes: the RTS-3.7 from Optima uses AGM (Absorbent Glass Mat) technology, a sealed lead-acid battery whose electrolyte soaks a glass-fibre mat. It is the technology required by cars with advanced Start-Stop and regenerative braking. It withstands more cycles than a conventional battery and copes better with heat.

Yes. It is a AGM battery of 44 Ah, designed for vehicles with Start-Stop. AGM batteries support advanced Start-Stop and regenerative braking thanks to their higher cycle count. Basic Start-Stop: EFB. Start-Stop with regenerative braking: AGM, which withstands more cycles. Check the handbook for the technology the car manufacturer requires. Once fitted it is ready to go; registering it via OBD, advisable on most modern models, lets the alternator charge with the optimum profile.

For the detail, read our guide to replacing the car battery and, if in doubt, the owner's handbook or a main dealer. With a 10 mm spanner, swapping in the Optima RTS-3.7 takes 15 to 30 minutes on most cars; if the battery sits in the boot or under a seat, allow up to twice as long. What matters most is the terminal order: removing, negative (−) before positive (+); refitting, positive (+) before negative (−). In between, with the engine off and the key out, release the clamp and fit the new battery the same way round as the original, positive on the left (polarity).

Estimated lifespan of the Optima RTS-3.7: 5 to 8 years in mild-climate car use with Start-Stop. Treat it as an approximate guide, as every case is different. It can vary considerably with usage (short or long journeys), temperature, the condition of the alternator and charging system, power drawn with the engine off and maintenance, plus the car itself and Start-Stop. Cold demands more at every start and intense heat evaporates the electrolyte.

The Optima RTS-3.7 takes up 237×172×197 mm (length, width and height, terminals included), with a B1 hold-down. Before buying, measure the space in your car: one extra millimetre can stop the hold-down clamp from closing.

The RTS-3.7 has the positive on the left: that is its polarity. Face the battery with its terminals nearest you and see which side the positive post (+, red ring) is on. A change of polarity from the original means longer cables or a reconfigured system and can cause a short circuit: check it before ordering.

Three codes identify this Optima: MPN RTS-3.7, ETN 8202550008882 (short form 820 255 000, the European parts-catalogue identifier) and EAN-13 4016987113554. It belongs to the OPTIMA RED TOP range. Use them when asking for a quote or comparing prices.

Not sure? Try your number plate in the finder (DGT/DVLA/KBA detect model and engine) or the "Compatible vehicles" tab, checked by our technical team; if your car is not there, send us make, model, engine and year on WhatsApp and we will reply during business hours (Mon–Fri 10:00–13:30 and 16:30–18:00 (Spanish time, CET)). The car manufacturer's specifications always take priority over our tables. The compatibility list for the RTS-3.7 runs to 39 verified vehicle versions.

A direct equivalent needs what this RTS-3.7 offers: 237×172×197 mm, positive on the left, the same Ah and CCA and AGM technology. The "Equivalents" section of this page gathers the recommended options with equivalent performance; remember that in Start-Stop cars an EFB should not be replaced with a conventional battery.

Same case and same technology as the RTS-3.7: an alternative by size, not an official equivalent. Compared with the RTS-3.7 it has the same Ah and cranking power. It costs 3,50 € less. If the polarity matches and your car had a similar capacity, it works as a replacement; if in doubt, ask us with your model.

Cold cranking current (EN) of the Optima RTS-3.7: 730 A. The absorbent glass-fibre mat of an AGM retains the electrolyte, so it cannot leak and withstands considerably more cycles than a conventional battery. For regenerative braking systems such as BMW EfficientDynamics, Mercedes Eco, Audi MHEV, Land Rover ECO or Volvo i-Stop, AGM is the recommendation; it also copes better than an EFB with tilting, vibration and extreme temperatures.

It is not strictly necessary on most cars, because the alternator detects the change and adapts the charge. The advisable step is to register it via OBD: the charging profile is optimum from the first minute and the battery lasts longer, especially on brands with sophisticated BMS (BMW, Mercedes, Audi, Volvo, Land Rover). Any garage with an OBD scanner can do it in a few minutes. If you prefer to do it yourself: VCDS / Carista (VAG), Bimmercode (BMW) or iCarsoft. If you do not register the RTS-3.7, it will keep starting fine while the alternator adjusts the profile over a few days.