As mentioned in a previous post, I’ve been mulling over battery options — partially because OEM batteries are fairly expensive, and partially because some 3rd party options have potentially attractive additional features.

I’d gotten busy with regular life activities, and almost forgotten about my promise to do some testing, when I ran across this interesting video on YouTube. In the video, a Finnish gent tests an OEM BLH-1 battery and some 3rd-party replacements for it, using an OM-D E-M1 camera. I liked his approach, with a few provisos — namely, that I think using the internal intervalometer was causing him some of his issues (camera stops recording before the battery is fully discharged, residual charge level varies from battery to battery).

So I made a few changes to his approach in an attempt to get somewhat more deterministic results on my E-M1. Here’s what I did:

• Rather than using the in-camera intervalometer, I used an external unit to trigger the camera every 2 seconds.
• The camera was set to manual focus / manual exposure / silent (electronic) shutter (1/25 sec). No camera time lapse / interval functionality was involved.
• The camera was set to take a single photo every time the intervalometer triggered, saving images in RAW format, to two high-speed 256 GB SD cards.
• FWIW, I did my testing in my basement, at an ambient temperature around 66° F / 19° C.

My setup was pretty plain: stick the camera on a tripod and take endless photos of some “stuff” against a wall with constant overhead lighting. I wanted to avoid any uncontrolled variables, so having a static scene with unchanging lighting was important (otherwise the image files could get larger / smaller, impacting the image save time & effort).

For each test run, I started with a fully charged (via an OM System BCX-1 charger) battery, and let things run until the battery was fully depleted.

The numbers

My first surprise from the testing was that I got a lot more exposures than expected from every battery — about 10 times the “rated” capacity — likely because the camera didn’t have to focus, or check exposure, or move a mechanical shutter around. And of course, I wasn’t “chimping” either, and that nice LCD display can eat some watts! No matter, I wasn’t looking for real-world results, just consistent and repeatable comparison data on relative battery capabilities.

OEM battery (BLX-1)

• Rated for 2280 mAh / 17 Wh, costs $100
• 6191 exposures

ProMaster non-USB battery

• Rated for 2250 mAh / 16.2 Wh, costs $60
• 4999 exposures

ProMaster USB-C battery

• Rated for 2250 mAh / 16.2 Wh, costs $80
• 5291 exposures (avg. of 2 batteries)

If you assume that the OM System BLX-1 lives up to its quoted specs (2280 mAh, 17 Wh), then both of the ProMastery battery models should result in just a slightly lower number of exposures (2250 mAh is only 1.3% below 2280 mAh, 16.2 Wh is about 5% below 17 Wh). So something around 6000 exposures, rather than the measured values in the neighborhood of 5000. It’s a good thing that the ProMaster batteries are cheaper than the OEM ones, because they test at 15% – 20% below the BLX-1 in actual capabilities.

Conclusions:

Bearing in mind (again) that you won’t get anywhere near 5000 exposures from one of these batteries in a realistic situation, here’s how these batteries compare in terms of capacity for price (using Feb., 2023 online prices in the U.S.):

• BLX-1 — 62 exposures / dollar
• ProMaster non-USB battery — 83 exposures / dollar
• ProMaster USB-C battery — 66 exposures / dollar

Given those numbers, I’d say that the ProMaster batteries are a reasonable value for the money. But they have measurably lower capacity than do the OEM batteries, so you’ll need to buy / carry extras for days when you’ll be doing a lot of shooting. And of course, the batteries with built-in USB-C charging can really come in handy in certain situations (i.e., when you need to charge one using a USB battery pack while you’re out & about).

Admittedly, I haven’t torture-tested the ProMaster batteries yet, so we’ll have to see how well they hold up over time, and out in real-world weather.

Other observations:

While I was running these tests, I thought I should take the opportunity to see how accurate the OM-1’s indication of battery charge was. Since one image should consume as much power as the next, one would ideally expect to see the battery charge percentage drop from 100% to 0% in a linear way. But that’s not what I saw:

• The display over-estimates battery charge when it’s nearly fully charged.
• The display under-estimates battery charge when it’s running low.

Here’s a plot of discharge over time for my two ProMaster USB-C batteries (the blue line with dots show data for a run with one battery that I “baby-sat,” and so has fairly regular data points; the small crosses are data for a run using the other battery and which I only supervised toward the end; the green line shows what a truly linear output would display):

The non-linearity is relatively slight, so likely won’t cause anybody issues in real life, but you can see it when you know what to look for. If nothing else, it’s nice to know that when the battery is getting close to fully drained, you’ve actually got *just a bit* more power available to you. Also, note that the camera’s display doesn’t give you any numeric estimate of charge once it gets below 10% — you just get a flashing orange outline of a battery shape.