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Sig BDX and Leica RF freeze test

catorres1

Private
Full Member
Minuteman
Nov 24, 2013
318
234
On another thread, the question came up this morning about some RF's not working well in freezing conditions, and there was some question around how the BDX system would work under freezing conditions, particularly in terms of communication and also being able to see the dots. Some had heard that the brightness faded, so the holds could not be seen clearly when used below freezing. We have used our Leicas and our Sig BDX stuff (3k RF and Sierra 3) in sub freezing temps without issue, and we don't keep them near our bodies, so they are very cold, but never sub 0 for very long, so I wanted to see what would happen.

This was sort of an off the cuff conversation this morning, but I had some time so did a quick and dirty test, it's certainly not conclusive but hopefully it's helpful. As we don't have anything like freezing temps just now where I am, I tossed them in my deep freeze that runs between -8F and -13F.



I put a Sierra 3, my 3kBDX, and my Leica 2800 in there and left them for 3 hours. I then took them out and tested to see if the electronics responded, and in the case of the BDX stuff, if they communicated and worked.



The problem was that because they were so cold and today's temps were in the 60's and rainy, the glass, including that over the laser, immediately froze over with frost. So not only could I not see what I was aiming at, the laser could not fire through the emitter window.



I tried wiping it off, but the units were so cold that they froze up again almost immediately. Eventually, I was able to get my son to help so we could wipe it off and immediately range in the short window before they refroze. Long story short, both the Leica and the 3k BDX ranged fine.



As for the scope, it connected to the 3k as it should. However, I noted the dots were somewhat dim, but quickly realized that this was due to frost over the eyepiece. Once I wiped it clean, for the few seconds it was frost free, it was as bright as always.



So in short, in at least this limited testing, they all worked just fine, we had no problems.

My guess, and it's only a guess, is that folks having problems might be spending a lot more time in the super cold than just 3 hours, and in that case, the batteries are getting too cold to function properly, lithium or not. I have seen this happen with my Kestrel, where it 'loses' most of it's battery, but it returns once things warm up.

I have an extra Sierra 3, so I might just take it and leave it in the deep freeze for a day or two and see what happens to the battery, but at least from this little test, a few hours in sub zero temps doesn't appear effect anything, providing your glass is not covered by ice or other precipitation.
 
Cool, awesome testing. It's also possible users are taking partly used batteries into the cold as well, making them even weaker before they even get cold. I know guys that when hunting in very cold temps will use new batteries daily, or at least keep new batteries with them while hunting in a warm pocket etc. Lithiums seem to do the best in the cold, perhaps some are not using lithiums as well. There's also the fact that especially for coin cell batteries, places like Amazon are filled with counterfeit junk batteries in Energizer/Duracell looking packaging. Considering how many people order stuff from Amazon I bet there's a lot of substandard 2032 batteries out there in use.

It would be an interesting study to see how long it takes for a scope's internals to reach outside temp, seems like 3 hours should be enough. You're day test should flesh that out.

I kind of started this rabbit hole, so it's good to see it seems some products are doing very well below freezing. Here's some of the threads that spurred my question where it seemed like there were a lot of users having problems in the cold, and even a couple posts where they had tested quite a bit of gear at various temps.

 
Those are interesting articles, particularly the one on Rokslide. Think I'm gonna have to try and freeze up my batteries and see what happens. It does seem that might be the issue based on those articles.
 
I did hear back from Sig's optical division today. Their answer is a bit tongue and cheek, but fair. They stated that they test their scopes including the electronics using -20C to +20C cold/hot cycles. However, they also stated that lithium batteries are known not to work well in the cold and while they can guarantee the scope's electronics to work at -20C they can't guarantee lithium batteries will. So my guess is they are testing with a bench power supply, not batteries.

So if you are in a lab, with a bench power supply, guaranteed to be good to at least -20C. If you live in the real world and use lithium batteries, all bets are off :)
 
What if the batteries used some of their own energy to keep the compartment above freezing 🤯
 
My guess would be you'd deplete the tiny lithium battery extremely quickly, even if the battery compartment was well sealed. We used to build hvac containers for a wide variety of interesting sensors for everywhere from death valley to the arctic circle, and even very well insulated if it's really cold you need a ton of power to heat to say 0C and there's nothing well insulated about a rifle scope. Now if the battery compartment was super well insulated, you had a very efficient heating element that would only maintain the bare minimum temp you needed for proper battery performance, and you used a second lithium battery to run the heater, and the first to run the scope, it might work pretty well, but I've yet to see a consumer electronic device that took it's cold use that seriously.

My guess would be the best bet, since there's no way to keep a rifle scope in your jacket or pocket like you can with a rangefinder, kestrel etc. would be to use a hand warmer on the scope wherever the battery compartment is. The only downside is most handwarmers if left out in the open air burn nice and warm, but much shorter than their listed times. Used in conjunction with say a neoprene scope cover it might do pretty well, but at some point condensation is going to start being a problem. It's one of the biggest problems using heated optics or sensors with optics, if you need to keep the electronics package warm, you have to ensure you isolate the optics enough that the temp delta's don't fog stuff up. If you had unlimited resources I suppose one could say have the battery remote in the stock with lots more room for a heating element and more battery, you would just have to mill the action/mount/etc. to ensure the wires were all secured.

Really even -20C, the coldest temp they are testing to is only -4F, which is cold, but I grew up in ND, and have hunted well below that. I've seen colder temps in NV/UT/CO hunting and doing field work in winter at high elevation.