If your scooter struggles to start in the morning, the starter turns slowly or the dashboard cuts out when you press the button, the most likely cause is a worn-out battery. The Yuasa STR9-BS is the 12V 8Ah battery of the Yuasa Scooter Series, the same product family also designated YTX9-BS: same dimensions, same capacity and same polarity, ready to replace the original battery of many scooters and light motorcycles.

How it is built

It is a VRLA battery with AGM technology, lead-calcium (Cast Ca/Ca), fully sealed. This means no caps to open, no topping up with distilled water and no acid leakage: it fits without special precautions and only needs an occasional charge if the scooter stands idle for long periods. The declared cranking current is 135 A (EN), a value designed to ensure a quick start even in cold weather, and the capacity is 8 Ah at 10 hours (8.4 Ah at 20 hours).

Size and polarity: what to check

The dimensions are 150 x 87 x 105 mm (length x width x height) and the positive terminal is on the left (SX) when looking at the battery from the terminal side. Before buying, compare these three details with the battery fitted: type code, dimensions and terminal position. The battery compartment is often tight, and a battery with reversed polarity cannot be connected without straining the cables.

STR9-BS or YTX9-BS: what is the difference?

STR9-BS is the code under which Yuasa lists the battery in the Scooter Series, while YTX9-BS is the code of the YTX series. The declared values match: 12V, 8Ah, 135 A, 150 x 87 x 105 mm. If you find the code YTX9-BS in the manual or on the original battery, this is the equivalent battery.

When to replace it

A scooter battery typically lasts a few years, but age is not the only factor: short frequent trips, long idle periods, intense cold and a charging system that is not fully efficient wear it out faster. Slow starting, lights dimming when you press the button and the need to recharge it often are typical signs of a battery to change. If the battery is new but starting is still difficult, have the voltage regulator and alternator checked too.

Fitting tips

Switch the scooter off and remove the key. Disconnect the negative terminal first, then the positive; fit the new battery in the reverse order, connecting the negative last, and tighten the terminals firmly without forcing them. Always respect the polarity and check that the battery is held firmly in its compartment. The old battery must be handed in to a collection point or to the retailer: never throw it away with ordinary waste.

Which scooters it fits

The table below gathers the scooter models this battery is specified for, according to the manufacturer's catalogue data: open the table and look up the brand, model and year of your scooter.

The table lists the scooter models for the YTX9-BS/STR9-BS code; the same battery is also specified for some motorcycles and quads. Always check the code, dimensions and polarity of the original battery, or send us your vehicle's model and year: we will confirm compatibility.

Technical data sheet

• Brand: Yuasa, Scooter Series
• Voltage: 12 V
• Capacity: 8 Ah (10 h) / 8.4 Ah (20 h)
• Cold cranking current (CCA, EN): 135 A
• Dimensions: 150 x 87 x 105 mm (L x W x H)
• Polarity: positive on the left
• Technology: VRLA AGM, lead-calcium (Cast Ca/Ca), sealed and maintenance-free
• Mounting angle: moderate
• Equivalent code: YTX9-BS