When the folks at OM System (formerly Olympus Imaging) released their new flagship camera, the OM-1, it came with its own new high-capacity battery — the BLX-1. As is usually the case with new battery designs, supply was tight at first. But pandemic supply chain issues (and maybe other problems) have helped keep supply tight since then, and prices for BLX-1 batteries have only gone up in the meantime.

So what’s an OM-1-loving / cost-conscious photographer to do? Plenty of 3rd-party batteries are available on various websites, with varying price, performance, reliability, and safety. I’ve seen good results from ProMaster accessories in the past, so I thought I’d give their batteries a try, particularly since they’ve recently introduced BLX-1 “equivalents” with a twist — built-in USB charging. What follows is a “first impressions” view of the situation (more details will follow in a later post).

Visual overview

Let’s start visually. Here’s a bottom view of three batteries that I’ll be comparing — an OM System BLX-1, a ProMaster replacement, and a ProMaster battery with built-in charging. If you were curious, I purchased all of them — no vendor-provided stuff here.

They all look pretty similar, with the exception that in the tiny print both ProMaster batteries quote a capacity of 2,250 mAh / 16.2 Wh, compared to the OEM battery’s 2,280 mAh / 17 Wh. I’m not surprised that the model with USB-C charging has a lower capacity (you have to give up *something* to make room for the charge circuitry); I am, though, a little surprised that even the ProMaster non-USB-C model also has the lower nominal capacity (admittedly it’s only a 4.7% drop, but still…).

The contact-end view of the three batteries — no surprises here.

Top view of the three batteries — the only substantial difference here is the USB-C battery’s charging port and charging indicator LED.

The nagging bit

But wait — there’s more! That is, there’s also an instruction card included with the USB-C battery (here’s where things get really interesting for geeks like me):

Two things stood out for me on this little card:

1. ProMaster actually identified the included cable as being charge-only (no data lines). It’s not a life-or-death thing, but I wish every gadget that included a cable was so forthcoming, it’d save folks a lot of aggravation when they use the cable for other things.
2. The first note on the back of the card should be more-highly-emphasized, it’s safety-critical. But read on…

Like (probably) quite a few people, I now travel with AC adapters and USB batteries that can provide power at a number of voltages and currents (see, for example, this previous discussion). Normally, some negotiation takes place between source (AC adapter / battery) and customer (camera, etc.) to pick the voltage and current that maximizes power flow. My reading of ProMaster’s note is that the built-in USB-C circuitry in their battery can’t take part in this negotiation, and so accepts whatever power the source provides — but with the potential for serious problems if that power takes an undesired form.

This struck me as an unfortunate approach, so I used the ProMaster contact form, and received a prompt reply from them on the subject:

I hope that your new USB battery is working well for you! As far as the voltage and charging goes, it is not recommended for use with USB plugs that are above the recommended voltage. It does feature an overcharge protection and it is unlikely that anything disastrous will occur if used with a plug that is not recommended. To ensure a long life and use of your new battery, I would make sure you utilize a charger within the recommended voltage.

Having spent much of my career implementing fault management logic in complex systems, I’ve got… thoughts… on this.

There’s a big difference between nominal control and emergency protections. Think of it like driving — the driver’s attention (and a correctly operating vehicle) keep the vehicle from running headlong into a tree. But in case something goes wrong, the vehicle occupants have seat belts and airbags and other safety equipment — this gear won’t guarantee crash survival, but it dramatically tilts the odds in favor of the humans. Still, the car manufacturer isn’t going to recommend that drivers head straight to the nearest tree, just for fun. The safety equipment is very good, but it’s no guarantee.

I see the ProMaster response in the same light — the built-in overcharge protection is there to protect against failures elsewhere, not to routinely control charging of the battery by a multi-voltage source. So the battery with built-in USB-C charging gives you convenience (you can charge the battery outside the camera without the clutter of a dedicated charger), but brings its own inconvenience (you need to make sure you’ve brought along a USB adapter and / or battery that only provides 5V power and only at between 0.5 and 3 Amps). You’ll need to read the tiny print on your charging gear very carefully.

The batteries in-use

With that unpleasantness out of the way, how well do the ProMaster batteries work? Well, in short — they work in-camera just the same as an OEM battery (full battery info is displayed), charge in-camera just like an OEM battery, and charge in the external OM System charger just like an OEM battery. The new USB-C battery charged without any problems using the supplied cable and an old iPhone charger I had rattling around (5V / 1A for the win!). I’ll update this post if I experience any issues in long-term use, but for now it’s so far / so good.

As for the convenience aspect of the new batteries, at worst, you’re swapping out a (fairly bulky and expensive) OEM battery charger for a small USB adapter that you likely already have cluttering up a drawer — not a bad trade, particularly when you’re traveling.

Just remember to carefully check the power source when you’re charging one of the USB-C batteries out of the camera. I’ve reminded my future self to do this by (crudely) marking the battery with a paint pen.

Coming up next

I plan on doing some quantified testing of the actual performance of the ProMaster batteries (number of shots you can take with each) vs. the OEM battery.

Update (20 Feb., 2023)

I’ve done my testing, and it’s all written up in a follow-up post.