Quick answer

The Promaster LI-40/42B is a replacement lithium-ion pack for Olympus cameras that use the LI-40B or LI-42B cell, and it is built to meet or exceed the original manufacturer's specifications. If your camera's battery door or manual lists LI-40B or LI-42B, this pack is the correct fit. Buy it as a spare or a low-cost replacement rather than as an upgrade, and charge it in the camera or in a charger designed for that cell type.

Which Olympus cameras take an LI-40B or LI-42B?

The LI-40B and LI-42B share the same physical and electrical format, so a camera that accepts one accepts the other. Olympus used this cell across its compact Stylus and Tough lines and in several entry-level mirrorless bodies, which is why the same part number shows up in so many manuals.

The reliable check is your own gear, not a web list: open the battery compartment and read the label on the pack you already own. If it says LI-40B or LI-42B, the Promaster LI-40/42B is the matching replacement. If it says LI-50B, LI-90B, or BLN-1, it is a different format and will not fit.

  • Look for LI-40B or LI-42B printed on the existing pack.
  • Check the camera manual's specification page under 'Battery'.
  • Do not force a pack that needs pressure to seat — the latch should click with light thumb pressure.

Is a third-party pack safe for my camera?

A replacement pack is safe when it matches the cell format and the camera's charging circuit. ProMaster states its replacement batteries are manufactured to meet or exceed the equipment manufacturer's specifications, which is the standard you want: same voltage, same contact layout, same protection expectations.

What you give up versus an OEM pack is mostly certainty about long-term cycle life and any proprietary communication the camera may use for battery-level reporting. Some bodies show remaining charge accurately with third-party cells; others show a coarser estimate. That is a reporting quirk, not a safety issue.

How should I charge an LI-42B pack?

Charge it the way the camera was designed to be charged. Most cameras in this family charge the pack in-body over USB or through a dedicated AC adapter, and that is the simplest path because the camera manages the cutoff voltage.

If you prefer an external charger, use one rated for the LI-40B/LI-42B format. A charger built for a different cell can under- or over-charge, and an unregulated bargain charger is the usual cause of swollen packs. Either way, charge at room temperature and unplug once the indicator shows full.

  • Charge before first use — new packs often ship at a partial storage charge.
  • Avoid charging in a hot car or in direct sun; heat is what shortens lithium-ion life.
  • For storage longer than a month, leave the pack around half charge rather than full or empty.

How many shots should I expect, and when do I replace it?

Runtime depends on your body, whether you use flash, and how much you review images on the rear screen, so treat any single number with suspicion. The practical signal is change over time: when a pack that used to cover a full outing now dies halfway through the same kind of shooting, it is done.

Two packs are more useful than one big pack. Keep a charged spare in your bag and swap at the first low-battery warning rather than waiting for shutdown, which protects you from missing a shot and avoids deep discharges that age the cell.

Do other power accessories in this category apply to me?

Only if you shoot with different gear. The Westcott FJ Pro AC/DC Battery & Power Adapter is built for FJ800 and FJ400 II strobes, not for compact Olympus cameras — it solves a studio lighting problem, not a camera battery problem. If you are shopping for a camera pack, stay with the LI-40/42B format and ignore the strobe accessories.

LI-40/42B quick answers

Will it fit if my manual says LI-42B but the battery says LI-40B?

Yes. The two designations describe the same cell format, so either label points to the same replacement pack. Match the format, not the exact suffix.

Can I leave it charging overnight?

In-camera charging stops at full, so overnight is generally fine — but an unregulated external charger is not. Use a charger rated for this cell and unplug when the light says full. In-camera charging is the safer default.

Should I buy one spare or two?

Two packs cover a full day of mixed shooting with margin and cost little more than one OEM pack. Rotate them so both age evenly. Two packs, swapped at the first warning.

How do I know the pack is failing rather than the camera?

If a second, known-good pack also drains fast, the camera or charger is the suspect. If only one pack misbehaves, replace that pack. Swap packs to isolate the problem.

Product facts