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Dive Light Battery Lifetime

Discussion in 'Lights' started by vinsanity, Jul 26, 2021.

  1. vinsanity

    vinsanity ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 50 - 99
    Location: Portland, Oregon
    105
    51
    What kind of battery life can one expect out of a quality dive light's Li-Ion batteries? Most of my cell phone batteries have been worthless after 2-3 years, while my Tesla is claiming 10 years.

    I'm considering buying a used primary light. Found a LM 15-32 for $900, some Big Blue options out there too, but that's a VERY different proposition if the batteries are in good condition vs need to be replaced soon. They are big $$$$.

    Trying figure out how to recognize a good vs bad deal on a used light.

    Sorry for what is kinda an impossible question to answer, but any guidance would be appreciated.
     
  2. tbone1004

    tbone1004 Technical Instructor ScubaBoard Supporter

    # of Dives: I'm a Fish!
    Location: Greenville, South Carolina, United States
    18,776
    11,284
    do NOT buy a big blue canister light, they do not sell them any more for a reason and it has to do with the fact that they are wildly unsafe.

    now, into how and why batteries fail. This is very high level, not all-inclusive, so fairly general.
    Batteries fail when they are mistreated in terms of charging *too fast, too high voltage, deep discharge, too hot, etc*, and then obviously by number of charge cycles which is reduced by the mistreatment. Also included is the rate of charge and discharge that the batteries see with a dive light being around 0.5C-full discharge in 2 hours, where your Tesla is probably 0.2C, lower is better on both sides.

    Your cell phone is designed to be disposable, does not have active cooling, is mistreated from heat during rapid charging, and suffers all sorts of deep discharges, but more importantly it isn't really designed to be used for that long anyway since the technology is deemed obsolete.
    Your Tesla has all sorts of protection built into it to control temperature during charging and discharging and also has all sorts of protections built into how low it will discharge and how high it will charge.

    Dive lights are much less complicated, especially the older ones. Several have very sophisticated BMS systems in them like the UWLD from @Bobby and others do not, like Big Blue. The ones with better BMS systems will generally speaking last longer than those that do not. I have UWLD's that are about 7 years old now and they are still performing at about 90% of what they were rated at when new. I would not hesitate with a 3-5yr old UWLD, but I would from most other companies unless you are saving more than enough that you can replace the battery and still be ahead of the game.
     
    lexvil, vinsanity and grantctobin like this.
  3. vinsanity

    vinsanity ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 50 - 99
    Location: Portland, Oregon
    105
    51
    Thanks! Great info.

    Do you know if the Light Monkey 15-32W VF has a sophisticated BMS?

    Thanks for the heads up on Big Blue. I was considering a new Big Blue VTL8000P-MAX. I assume the safety issues they had do not apply to this?
     
  4. tbone1004

    tbone1004 Technical Instructor ScubaBoard Supporter

    # of Dives: I'm a Fish!
    Location: Greenville, South Carolina, United States
    18,776
    11,284
    unsure on the BMS, but that is not a light I would recommend buying, it has not proven reliable over the last few years.

    The BB is not a primary light I would look at, too big and heavy for primary usage...
     
  5. halocline

    halocline Contributor

    9,055
    3,495
    If that light is in good condition, that's a good price. I would ask how many charge cycles are on it, and ask about how it was stored. If the seller says he stored it partially discharged, that's an indication that he took care of it. If he says he stored it completely charged that's not as good for the battery life. I would guess you can expect a few hundred charge cycles before any significant loss of burn time.

    Light Monkey has decent customer service, and you could ask them about the light if you can get the serial number. They were helpful to me when I bought a used one several years ago.

    I personally will never buy another primary light without demoing it first. Lights really do look different; the color, beam tightness, spill, hot spot, they all vary from light to light. You're going to be looking at this light for a long time.
     
  6. Bobby

    Bobby Contributor

    # of Dives: I just don't log dives
    Location: Charleston, SC
    529
    421
    I have UWLD customers with battery canisters that are over 10 years old and still have over 90% of the original burn time. Very active UWLD divers seem to get 5-7 years out of their batteries. My biggest dealer has demo lights that go out nearly every day and they get a little over 2 years from their batteries. There is also a live aboard company that has our video lights on their fleet, those go out every day and often multiple charge cycles per day, they get just over a year. I also have a few customers that charge their battery after every dive (usually not needed) and top them up every month and before every dive. They need new batteries sooner because LiION will wear out faster with this type of usage. Not trying to confuse the issue however, as tbone said, there are a number of factors that affect battery life.

    Your best option is to see if the manufacturer, of a light that you're considering, can do a burn test with a data tracker so that you will know where you stand with a particular used battery. I charge for this service as it is time consuming and takes my time away from building lights, however it is not expensive (from me and IMHO). I charge $85.00 USD which includes return shipping within the continental US and you get a pdf print out of the burn test.
     
    tbone1004 likes this.

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