Motorcycle Battery Codes Explained (YTX, YTZ, YB)
Reviewed by CrankDex editorial
A code like YTX14-BS looks cryptic, but it's really just a compact description of a battery's size, terminal layout, and type. Once you can read it, picking a replacement gets a lot simpler.
Motorcycle, ATV, UTV, and scooter batteries are almost always labeled with a short alphanumeric code rather than a simple size like a car battery's group number. That code follows a standard naming pattern used across most Japanese and Japanese-style (JIS) battery manufacturers, and once you understand the pieces, it tells you nearly everything you need to know before buying a replacement.
Why the code matters more than the voltage
Almost every powersports battery is 12 volts, so voltage alone doesn't tell you much. What actually determines whether a battery works in your bike is its physical size, its terminal position, and its capacity class. The code bundles all three into one string, which is why matching the code, rather than just the voltage, is what makes a battery a true fit for the tray, the cables, and the charging system it was designed around.
Reading the prefix: YTX, YTZ, and YB
The letters at the front group batteries into families with a shared case style. The YTX family is one of the most common sealed AGM lines, used across a wide range of street bikes, cruisers, and ATVs. The YTZ family is generally a newer, more compact, high-performance AGM design, often used on sport bikes and other machines where a lighter, higher cranking-power battery in a smaller case is useful. Plain YB codes, without an X or Z, are typically the older conventional (flooded, non-sealed) design; these can ship with a separate acid pack and, on some models, may need occasional water top-ups over their life, unlike sealed AGM types.
The number in the middle
The number that follows the prefix (like the "14" in YTX14-BS) generally relates to the battery's case size and capacity class within that family. As a rough rule, a higher number in the same family tends to mean a larger case and more capacity, but this is a relative comparison within a product line, not an exact, universal scale you can use to compare across different prefixes. The safest approach is always to match the full code from your original battery or your owner's manual, not just the number.
The -BS suffix
BS stands for "Bottle Supplied." A battery with this suffix ships dry, without electrolyte inside, along with a sealed acid pack. You activate it once by filling it with that acid according to the included instructions, and after a short rest period it becomes a sealed, maintenance-free AGM battery for the rest of its life. Some batteries are sold already factory-filled and sealed, in which case they're ready to install with no activation step.
What about lithium?
Most lithium (LiFePO4) drop-in replacements are manufactured and labeled under the same codes as the AGM batteries they replace, so a lithium version of a YTX14-BS is still sold as a YTX14-BS-equivalent and fits the same tray. The code is really describing the case and terminal footprint the industry standardized on; the chemistry inside can vary while the code, and the fit, stays consistent.
How to use this when shopping
The fastest, most reliable way to buy a replacement is to find the code printed on your old battery's case, or look up your specific make, model, and year, and match that exact code. If the label is worn away, cross-referencing your bike's model is usually more reliable than guessing from the old battery's rough dimensions.
Frequently asked
What does the -BS mean on a motorcycle battery?
BS stands for 'Bottle Supplied.' It means the battery ships dry, without electrolyte, along with a separate acid pack. You fill it once, let it sit briefly, and it becomes a sealed, maintenance-free AGM battery. A code without -BS is often sold already filled and sealed at the factory.
Is YTX the same as YTZ or YB?
No, they're different families under the same general JIS-style naming system. YTX and YTZ codes are typically sealed AGM designs, with YTZ generally used on higher-performance, more compact high-output batteries. Plain YB codes are usually the older conventional (flooded) design, which can ship with acid you add and sometimes need occasional water top-ups.
Can I use a battery with a different code than the original?
Not reliably. The code encodes the physical case dimensions, the terminal layout, and the capacity class the manufacturer designed the tray and charging system around. A different code may not physically fit the tray or may have terminals in the wrong place, even if the voltage looks similar. Matching the code is the safest way to guarantee fitment.
Do lithium motorcycle batteries use the same codes?
Yes. Most lithium (LiFePO4) drop-in replacements are built and sold under the same case-size codes as their AGM counterparts, such as YTX14-BS, so they fit the same tray and terminal layout. The chemistry inside is different, but the code is still how you match the size.
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