It depends on the exact model, since the Lenovo Flex name covers 11-inch through 16-inch convertibles built from 2013 to today. A modern Flex 5 (14IAU7) commonly uses a 3-cell 52.5Wh pack such as the L21L3PE0 or 5B11F38042, while a Flex 3 (11IGL05) often uses a smaller 36.4Wh battery like the 5B11B36314. Because capacity ranges from about 36Wh to 52Wh and higher across the line, check your model number before ordering. Replacement packs here run from $34.99 to $69.99.

Match the exact model number printed on the sticker on the bottom of your laptop, for example Flex 5-14ARE05 or 14IAU7. The Lenovo Flex line varies across 11-inch, 14-inch, and 16-inch sizes and multiple production years, so the series name alone is not enough. Once you have that full model code, you can confirm the right part number, such as L21L3PE0 for a newer 52.5Wh Flex 5 or 5B11B36314 for a 36.4Wh Flex 3. Matching the model avoids a pack that fits physically but is wired differently.

Replacement batteries for the Lenovo Flex run from $34.99 to $69.99. Smaller-capacity packs for the Flex 3 (around 36Wh to 42Wh) tend to sit toward the lower end, while higher-capacity 3-cell packs near 52.5Wh for the Flex 5, like the L21L3PE0, fall toward the upper end. The price tracks capacity and the specific part number your model uses, so confirm your exact model number to land on the correct option.

No, not across the line. The Lenovo Flex family covers 11-inch, 14-inch, and 16-inch convertibles with capacities from about 36Wh to over 52Wh, and the packs differ in size, connector, and part number. For example, a Flex 3 (11IGL05) uses a 36.4Wh 5B11B36314, while a Flex 5 (14IAU7) uses a 52.5Wh L21L3PE0, and these are not swappable. Always match your exact model number rather than assuming any Flex battery will work.

Capacity and cell layout are the main differences. The IdeaPad Flex 3 and 3i target budget and education buyers with smaller packs around 36Wh to 42Wh, such as the 5B11B36314. The IdeaPad Flex 5 and 5i are the mainstream 14-inch and 16-inch models, commonly using 3-cell lithium-polymer packs near 52.5Wh like the L21L3PE0 or 5B11F38042. The IdeaPad Flex 6 is an older intermediate 14-inch series. All are internal batteries reached through the bottom cover.

Two reliable places. First, flip the laptop over and read the model number on the bottom sticker, for example Flex 5-14ARE05, then match it to the correct pack. Second, if you open the bottom cover, the battery itself is usually printed with its part number, such as L21L3PE0, 5B11F38042, or L17M3PB1. Either route confirms the exact battery, which matters because Flex capacities range from about 36Wh to over 52Wh depending on the model and year.

Yes, most owners can. Modern Lenovo Flex models use internal lithium-polymer batteries, so you remove the bottom case to access the pack rather than releasing an external latch. You will typically unscrew the bottom panel, disconnect the battery cable, unfasten the pack (for example a 3-cell 52.5Wh L21L3PE0 in a Flex 5), and reverse the steps with the new one. Work with the laptop powered off and use the correct screwdriver to avoid stripping the small bottom-case screws.

Watch for runtime dropping far below normal, the laptop shutting off suddenly even when it shows charge, or the system staying powered only when plugged in. You may also see the battery stuck at a fixed percentage or reporting a much lower full-charge capacity than its rated value (for example well under the 52.5Wh of an L21L3PE0 pack). If you notice the bottom case no longer sitting flat, stop using the battery and replace it. Packs here range from $34.99 to $69.99.