Method & sourcing
Where every cell size and key fob answer on this site comes from, and how we check it.
Which sources count
We start from the people who made the thing: the carmaker’s owner’s manual for a key fob, and the battery maker’s datasheet or cross-reference for a cell. Other sources sit below those, in this order:
- Owner manual
- First choice for which cell a key fob takes.
- Battery maker datasheet
- First choice for a cell’s size, voltage, chemistry and equivalents.
- Battery maker lookup tool
- Used alongside the first-hand sources, cited on the row it supports.
- Regulator
- Used alongside the first-hand sources, cited on the row it supports.
- Safety organization
- Used alongside the first-hand sources, cited on the row it supports.
- Retailer
- Shown only as “According to …”, never as a plain fact.
- Key shop
- Shown only as “According to …”, never as a plain fact.
How each value is checked
For every value we keep a copy of the source page or PDF, the sentence that states the value, and the PDF page it sits on. Before the site is rebuilt, a script opens each saved copy and looks for that sentence on that page; if it isn’t there word for word, the build stops. Each row on the site links to the source and shows the date we checked it.
Panasonic’s key fob finder returns its answer as a product picture. For those rows we check that the result title names the vehicle and that the picture shown is the cell listed, and we give the finder entry so you can repeat the lookup.
When sources disagree
If two sources give different answers for the same key or the same cell, we show both, each with its own link, in a box marked “Sources disagree”. We don’t pick one for you. The owner’s manual for your car’s exact model year is the one to trust.
What “equivalent” means here
A cell is called an equivalent only when a battery maker lists it as one. Two cells whose datasheets give the same diameter and height (within 0.05 mm) are shown as the same size, which is not the same thing: chemistry, voltage and capacity can still differ. Each comparison gets one of these labels:
- Listed as equivalent by a battery maker
- Same size, different chemistry — not listed as equivalent
- Same size on the datasheets — not listed as equivalent by a maker
- Different size
- Not enough published data to compare
What we couldn’t find
We only list a key fob when a public source names the cell. For Honda and Toyota, the full owner’s manuals sit behind an owner sign-in or an interactive lookup we couldn’t read, and the public excerpts we could open don’t name the battery, so those makes aren’t listed yet. Model years with no public answer are named at the bottom of each make’s page.
What we don’t do
- We don’t sell batteries and have no shop or affiliate links.
- We don’t copy replacement instructions; each row points to the manual page that has them.
- We don’t guess a value that no source states.
Spotted a mistake? Email the address in the footer with the page and the source, and we’ll recheck it.