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cheap chinese video light review

Discussion in 'Strobes & Lighting' started by vovanx, Feb 18, 2019.

  1. Graeme Fraser

    Graeme Fraser Tech Instructor

    # of Dives: 1,000 - 2,499
    Location: Narnia
    932
    1,627
    Hi Andy

    As a complete novice with only amateur aspirations, I'm interested in your opinion on some of the cheapy video lights. Is the following eBay offering the type you refer to in your post?

    QH27 80M Underwater Diving Flashlight 3 Color Light Waterproof Aluminium Alloy 6933834539542 | eBay

    I appreciate that at this price I could end up with a dud, but maybe worth a punt if others have had reasonable success.

    Thanks. G
     
  2. TravisD

    TravisD Assistant Instructor

    # of Dives: 200 - 499
    Location: Westminster, MD
    700
    116
    Since I just ordered a couple of these... might as well ask now - what's the mod? Just bridge the switch contacts?
     
  3. AdamSa

    AdamSa Registered

    # of Dives: 500 - 999
    Location: Malta
    53
    33
    The switches are meant to just provide a pulse to the PCB when pressed, so bridging the switches will not get the job done. What you need to do is locate the wires that drive the LEDs, cut/desolder those from the PCB, and solder those to a connection on the PCB which connects directly to the battery voltage. These are easy to locate using a multi-meter and looking for the connections where the battery makes direct contact. This effectively eliminates the LED driver and logic circuit. With this mod I have now done 100+ dives down to 115m - no issues so far.

    Another option (I have only tested it on land so far), is to remove the switch, fit in a small (normally open) reed switch, and seal it all in with epoxy. Moving a magnet close to the reed switch should actuate the reed and simulate a button press as with the old switches. Only problem is how/where to mount/carry the magnets conveniently.
     
    TravisD and Addison Snyder like this.
  4. TravisD

    TravisD Assistant Instructor

    # of Dives: 200 - 499
    Location: Westminster, MD
    700
    116
    Thanks! Does this introduce any safety or other issues, such as low-voltage cutoff to protect the batteries?
     
  5. AdamSa

    AdamSa Registered

    # of Dives: 500 - 999
    Location: Malta
    53
    33
    The batteries have their own built in protection circuit. Although if i'm completely honest i'm not sure if there are any concerns i should be aware of. I also don't use these torches as life support equipment, they are purely for video work - so if they fail, no real issue. All I can say is that i have not have had any issues thus far!
     
  6. Addison Snyder

    Addison Snyder Contributor

    # of Dives: 200 - 499
    Location: Gainesville, FL
    216
    135
    It should be mentioned that for most of us, our batteries don't have that protective circuit built-in. They are A) generally less common (in my experience), B) more expensive, C) drain faster in storage, and D) have (obviously) more limited useful capacity. Before assuming they won't be damaged when the light runs down, check your batteries when using the simple circuits like this (or in other cheap chinese lights, most of them I've seen don't shut-off automatically).

    On a sidenote, these are cheap solid (unprotected) batteries. I've bought two batches of and they work really well. Especially when compared to anything bundled with a light that I've gotten (usually the cheapest batteries manufacturers can get their hands on). On a rare occasion when I accidentally overdrew one of them (left a light on for a day), I was able to put 3500 mAh into them. Normally I try to limit that to 2000 or so, but obviously they can discharge a lot more than that.
    US $2.82 25% OFF|Hot liitokala 100% New Original NCR18650B 3.7 v 3400 mah 18650 Lithium Rechargeable Battery For Flashlight batteries (NO PCB)|li-ion battery|battery for flashlightbatterie 3400mah - AliExpress
     
  7. AdamSa

    AdamSa Registered

    # of Dives: 500 - 999
    Location: Malta
    53
    33
    Fair point. I know that mine have the circuit just because you can see the round PCB if you peel the battery wrapper. I have no idea whether the circuit cuts off or not to be honest... but with that being said, I don't know if the original torch circuit had a cutoff either. The lights typically dim and turn off if you keep them on, but this could just be the forward voltage of the LEDs being higher than the battery voltage rather than the circuit cutting off.
     
  8. AdamSa

    AdamSa Registered

    # of Dives: 500 - 999
    Location: Malta
    53
    33
    After giving this some more thought, the forward voltage of a white LED (>~3.2V) will always be higher than the "safe" voltage of a 18650 lithium ion battery(>~3V). As such, in theory at least, if you drive the LEDs directly, the batteries should be unable to drain to a dangerous level. You will always have a small amount of leakage current, but unless you turn the torch on and forget it for a very long time, you should be ok.
     
  9. greeniguana

    greeniguana Contributor

    554
    568
    Using an unprotected cell in a small one cell light is probably OK, but I don't think it's worth the risk sticking 2 or 4 of them together in a light, especially a sketchy cheap Chinese light. ....

    The protection circuit also guards against damage caused by cheap Chinese chargers with poorly designed voltage regulators.
     
    grantctobin likes this.
  10. Addison Snyder

    Addison Snyder Contributor

    # of Dives: 200 - 499
    Location: Gainesville, FL
    216
    135
    US $8.3 40% OFF|LiitoKala Lii PD4 Lii S6 Lii500s battery Charger for 18650 26650 21700 18350 AA AAA 3.7V/3.2V/1.2V/ lithium NiMH battery|Chargers| - AliExpress
    Got one of these, works really well. I don't trust chargers without a voltage display.

    The one battery I had in a backup light that was left on for about 48 hours. Pulled out of my pocket (above surface pre-dive check :thumb:), confirmed it was on, with a dim glow coming from the single LED (one of those common 1000ish lumen ones). Turned it off and left it. Later in the day I turn it on again and (maybe because of temperature or something) it turned on, dim but present. When I charged the battery, got a fairly crazy amount of oomph into it. I think the initial (at least for a few seconds) voltage was 2.2v or something. In hindsight, I wish I recorded those numbers.
     

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