In short
- Measure length, width and height; include the terminals in the height measurement.
- With the label facing you and the terminals at the top, note which side the + is on.
- A replacement can be slightly smaller (use foam to pack it out), but it must never be larger in any dimension.
- Check the terminal type and, if it is a conventional battery, which side the vent is on.
A battery part number identifies its family, but three things determine whether it will fit your motorcycle: its dimensions, polarity and terminals. If all three match the original, the replacement will fit, the cables will reach and everything will connect properly.
You’ll need a tape measure or, ideally, callipers, and either the battery removed from the motorcycle or the battery compartment in view.
The three dimensions
- Length: the longest side of the battery, viewed from the label side.
- Width: from the front face to the back (the depth).
- Height: from the base to the highest point, including the terminals. This measurement causes the most problems: the battery fits, but the cover or seat won’t close, or a terminal touches a metal part.
Write down all three measurements in millimetres, in this order: length × width × height. This is the same order used on product pages, for example 150 × 87 × 105 mm.
Never larger
The replacement can be a few millimetres smaller: fill the gap with a foam block so it doesn’t move around. It must not be larger in any of the three dimensions. Manufacturers specify dimensions with a tolerance of around ±1.6 mm, so two batteries with the same battery part number may differ by one or two millimetres.
If you don’t have the old battery, measure the compartment: the free space in the battery tray and the height up to the cover or seat. These three measurements will let you rule out any batteries that won’t fit.
Polarity: which side is the positive terminal on?
Position the battery with the label facing you and the terminals at the top, along the edge nearest you. Check which side the positive terminal is on (+; it usually has a red cover):
- Positive terminal on the left: the usual layout for YTX and YTZ batteries without an “L” (YTX9-BS, YTX14-BS, YTZ10S...).
- Positive terminal on the right: the layout for battery part numbers with an L (YTX7L-BS, YTX20L-BS, YB12AL-A2...).
This is the most common mistake when buying a replacement: the YTX14-BS and YTX14L-BS are exactly the same size, but their terminals are on opposite sides. With the wrong one, the cables won’t reach or, if you force them, they’ll be connected the wrong way round and could blow fuses or damage the voltage regulator / rectifier or ECU.
Check with a photo
Before removing the old battery, take a photo of how the cables are connected. If you’re unsure when fitting the replacement, the photo will show you what to do: the red cable goes to the positive terminal.
Terminal type
- Tab terminal with bolt: a plate with a hole, a bolt and a square nut. This is common on AGM batteries (YTX, YTZ, YT).
- Side terminal: a small tab with a horizontal hole. Many small conventional batteries use this type (YB, 12N).
- Tapered post: like the type used in a car. Found on some larger batteries for quad bikes, personal watercraft (PWC) or lawn mowers.
As well as the type, check the position: two batteries with the same case can have their terminals in different places. If you’re switching battery type (for example, from a conventional battery to an AGM), compare the terminal positions with those on the original.
The vent (conventional batteries only)
Conventional flooded batteries (YB, 12N) have a vent tube that releases gases. Check which side it exits from: the tube must run away from the chain and below the swingarm. AGM batteries don’t have a vent, so if you switch to an AGM, the motorcycle’s vent tube is left disconnected.
Once you have the dimensions, find the battery part number
With the length, width, height, polarity and terminal type, you can look through the battery part number pages: each one includes a scaled drawing and the dimensions. If you’re choosing between two, the rule is simple: the same polarity, the same terminal type and no dimensions larger than the original. For the rest of the process, see our guide to choosing a motorcycle battery.
Satkit battery
OUTDO UTX14-BS
12 V, 12 Ah battery with 200 A cold cranking amps, compatible with the YTX14-BS. Factory-activated and charged, ready to fit. Positive terminal on the left.
Where to buyfrom €36.54
Prices incl. VAT checked on 7 October 2026; they may change.
OUTDO UTX7A-BS
12 V, 7 Ah motorcycle battery with 105 A CCA, a direct YTX7A-BS replacement. Factory-activated and charged, ready to fit. Positive terminal on the left.
Where to buyfrom €20.28
Prices incl. VAT checked on 7 October 2026; they may change.
Sources
- Yuasa, technical manual for motorcycle and recreational vehicle batteries (in English)
- Shorai, LFX lithium battery manual (in English)
