Backscatter HF-1 Strobe battery compartment flood

[Dave_Hicks]

TLDR; The strobe lives and seems to be working normally after cleaning it up.

 

Yesterday I was doing my second dive of the day when one of my HF-1 strobes made a little tiny pop and stopped working. The green indicator light was off and turning it off and on again did nothing. I was at about 80-85 feet at the time. I turned it off, folded it away, and used the remaining strobe for the rest of the dive.

 

I had set up my camera and strobes on Friday night, and they headed out early Saturday morning for two shore dives about a 90-minute drive away. The conditions were not great, and I didn't take many photos maybe 50. I lightly rinsed the camera and strobes at the dive site and then soaked it in the sink once I got home. I had another pair of boat dives planned Sunday morning, also a 90 minute drive. Since I had not taken many photos I decided to leave the entire rig, camera and strobes alone and dive it again without opening or charging anything. I did a few test shots and packed it in the car. The first dive all worked normally and during the second dive both strobes worked until the Pop.

 

After I got home, I soaked and dried the entire rig and then went to see what was going on with the dead strobe. Had the batteries died suddenly, was the strobe broken? It didn't seem likely to me that it might had flooded. As such, I was a bit surprised to see moisture and a little black goo in the battery compartment. It made another little pop when opened, releasing pressure. There was NOT a lot of water in it. It was not fully flooded, just a bit wet. The batteries and strobes electrical contact showed some black goo and corrosion on the positive terminal at the bottom of the compartment. I dumped out the batteries as set them aside wrapped in paper towels. (they went to a can outside the house) I took the strobe and rinsed it repeatedly under the sink and scrubbed the battery compartment with a toothbrush. My handy electric blower dried it out quickly. I wrapped some sandpaper on the end of a chopstick and cleaned up the corroded Pos+ terminal at the bottom of the compartment.

 

I went to the manual and confirmed my recollection that the battery compartment is sealed from the rest of the strobe. The manual says "maybe" the strobe will survive a flood, and that unless it starts acting erratically you can keep on using it. After allowing it to continue to dry overnight, I loaded fresh batteries this morning and the strobe seems to be working correctly 100%. I'll dive it in a few days to confirm further, but the good news is that it seems to live up to the sealed compartment promise of the manual.

 

I really don't know what caused the flood. I am very meticulous in cleaning and lightly lubricating the orings and sealing surfaces with tribolube with each battery change. There was no hair or debris in the seal when I opened it. No cracks in the case or cap that I can detect. I removed the orings and cleaned the cap and groves carefully with a toothbrush and lint free laboratory wipe. The orings seem to be in good shape so I cleaned those too and put them in spares. I swapped in the spare set of orings that Backscatter provided with the HF-1 on both strobes. 

 

I didn't take any photos of the flood, but it was not very dramatic in any case. Just a touch of goo and corrosion. It just goes to show that every strobe or o-ring sealed device is never 100% foolproof and the best we can do is take care. Have a spare on hand if you can't afford to be down a strobe on a big trip. I have a couple of big trips coming up in April and May, so I'll be bringing at least 1 spare strobe and a few extra batteries!

[Chris Ross]

Sorry to hear about the flood, but good the strobe appeared to survive.  I can see a maybe 3 possible leak sources, the general integrity of the cap,  the pressure relief valve in the cap and the o-rings themselves.

 

This strobe has an additional o-ring sometimes called a sand seal that the strobe cap contacts when installed.  I have one of these on my INON torch and my experience is there is no water entry past that o-ring, so that I don't get sand/grit on the o-rings and there are never any water droplets.  My INON Z240 strobes always have water drops on the o-rings in contrast.  Did you happen to check for water droplets on your o-rings?

 

For the other two entry points, I'm wondering if it might be worthwhile to get a new cap as a precaution? 

[Dave_Hicks]

We'll see what happens when I dive it again this week. There is usually some water under the cap, but I don't know if the orings are wet. Perhaps the first one is, but I could not say for sure. 

 

I know there is an overpressure valve, I assume that is the metal disk as the center of the cap. It would be interesting to know how to test that independently.

[Barmaglot]

On 4/7/2025 at 10:55 PM, Dave_Hicks said:

moisture and a little black goo in the battery compartment

Are you sure it was water intrusion from the outside? I've had batteries leak electrolyte inside my strobe - granted, those were NiMH AAs, but Li-Ion cells can do it as well.

[Tom Kline]

Your story reminds me of one from a few months ago involving Retra. Diving on more than one day without opening and re-sealing. What can happen? One can only speculate. I have done multiple dives many times without changing batteries in my strobes within a day but not with a time gap of an overnight. I have for the camera housing (two days diving (as well as stream shooting) without recharging or removing cards).

Edited Wednesday at 06:24 AM by Tom Kline

[Architeuthis]

Maybe it is worth to take the strobe  UW, for the first dive after the leak, without batteries and some paper towels inside...

(In case the leak is via the pressure relieve valve, it will be almost impossible to detect this by inspection)

[Dave_Hicks]

7 hours ago, Tom Kline said:

Your story reminds me of one from a few months ago involving Retra. Diving on more than one day without opening and re-sealing. What can happen? One can only speculate. I have done multiple dives many times without changing batteries in my strobes within a day but not with a time gap of an overnight. I have for the camera housing (two days diving (as well as stream shooting) without recharging or removing cards).

Yes, i thought about that. Could a build up of pressure in the compartment cause the issue? Perhaps only if the batteries were the root cause and not an external flood.

[Dave_Hicks]

7 hours ago, Architeuthis said:

Maybe it is worth to take the strobe  UW, for the first dive after the leak, without batteries and some paper towels inside...

(In case the leak is via the pressure relieve valve, it will be almost impossible to detect this by inspection)

Probably a good idea.

[MatthewSullivan]

it is interesting how relatively frequently it seems that strobe floods occur when they have remained sealed for X amount of time after diving, and then diving again. The only strobes I've ever flooded happened this way and I recall several other accounts both here and on we**ixel that were in the same vein

[Dave_Hicks]

4 minutes ago, MatthewSullivan said:

it is interesting how relatively frequently it seems that strobe floods occur when they have remained sealed for X amount of time after diving, and then diving again. The only strobes I've ever flooded happened this way and I recall several other accounts both here and on we**ixel that were in the same vein

I guess we need to add "burp your strobe" to the best practices of Underwater Photography. 🙂 🫧

[Klaus]

I got seawater into an old Sea&sea strobe once - never touched any of those Orings before. It was after a few dives, sort of half-way during the vacation. I think the Orings that sealed the strobe itself were simply showing their age. (For an HF1 that is simply impossible at this point, though- too recent.) But when I finally did take it apart, I couldn‘t find any obvious source of the leak. 

 

For the record: The batteries had stayed dry, since the compartment is sealed… 

[Tom Kline]

I did not want to speculate above but one possibility is gas expansion in the battery compartment pushing the o-ring in the wrong direction. BTW when I take a pressure reading of my housing using the Backscatter model housing sucker part (there is a gauge on it), the vacuum reading tends be lower (!) after use in local water (local mean water temp measured by a graduate student is 5°C). Housing is still cold; it takes hours to warm up at room temp.

Edited Wednesday at 08:59 PM by Tom Kline

[Chris Ross]

3 hours ago, Tom Kline said:

I did not want to speculate above but one possibility is gas expansion in the battery compartment pushing the o-ring in the wrong direction. BTW when I take a pressure reading of my housing using the Backscatter model housing sucker part (there is a gauge on it), the vacuum reading tends be lower (!) after use in local water (local mean water temp measured by a graduate student is 5°C). Housing is still cold; it takes hours to warm up at room temp.

 

Whether or not an o-ring can withstand reverse pressure depends upon the design of the o-ring groove.  A surface o-ring like used in Ikelite and the Nauticam housings  with removable backs cannot as they rely upon the external pressure pushing the housing back into contact with the o-ring.  A piston o-ring such as INON caps or the HF-1 should be fine

 

Lubrication can also be an issue on clamshell and piston style o-rings.  The o-ring needs to be able to slide back and forth in its groove to press up against the sealing surfaces and form the seal.  If the o-ring hangs up up it might prevent the seal from forming.  I note with my Z-240 strobes I apply a very thin layer of  lube to the cap inside surface and it screws on very easily.  When I come to remove the the cap it is often quite tight, like as if the lubricant has washed away.  If you had internal pressure the o-ring would need to move.  Internal pressure is relative - you could have higher internal pressure from taking your strobe to a higher altitude.  Having said that I often leave the batteries in for extended periods after a dive particularly if I only do one dive.   So far I've been fine.