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Teric Feature Request

Discussion in 'Shearwater Research' started by Cleavitt, Sep 30, 2019.

Would you use the "max charge %" setting described below on the Teric if it were an option?

  1. Yep

    6 vote(s)
    37.5%
  2. Nope

    10 vote(s)
    62.5%
  1. Cleavitt

    Cleavitt Nassau Grouper

    # of Dives: 500 - 999
    Location: Central Florida
    120
    28
    28
    Due to the non-user replaceable battery in the Teric, I only charge it to around 70 to 80% before most dives. This should extend the life of the battery considerably, but it's kind of lame to have to constantly check on the charge state while it's charging so that I can stop at the right time. If it's possible via firmware to control the charge cycle it would be nice if there was a "max charge %" option in the settings. Options for 70, 75, 80, 85, 90, 95, and 100% would be nice. That would allow users to leave it on the charger and still charge to a more conservative level.

    Poll included to determine if anyone else would find this useful.
     
    scrane likes this.
  2. Jay

    Jay Need to dive more!

    # of Dives: 100 - 199
    Location: Melbourne, OZ.
    800
    400
    63
    I don't think that will make any difference to the battery's longevity. Reasons: I had extensive discussions with SW re various battery factors, and for longevity, what will adversely affect the battery are extreme temperatures, and running it below critical (including not recharging it every few months).

    This thread has some battery info: The Teric's Battery Performance.
     
  3. Cleavitt

    Cleavitt Nassau Grouper

    # of Dives: 500 - 999
    Location: Central Florida
    120
    28
    28
    The charge level (both high and low) has an impact on all lithium ion batteries. Keeping a lithium battery between 80% charge and 30% discharge will roughly quadruple it's useful life vs a 100% to 20% charge/discharge profile. For example, Tesla has a similar "max charge level" setting on their cars. They suggest charging to somewhere in the 80 to 90% range on a regular basis and 100% only for long trips.

    Manufacturers don't mention this for a few reasons...

    1) In devices with removable batteries or designs that often get replaced before the battery ages (like phones) it doesn't really matter.

    2) In more expensive systems, manufacturers sometimes build in a buffer so that "100% charged" is actually more like 85%. This is mostly done in very large battery systems in applications that need to last for decades, but sometimes smaller devices will do this if long life is a priority. My Makita cordless tool batteries work this way (80% max charge or 4 volts per cell) which makes sense considering how many charge cycles they might see each day on a job site. This does not seem to be the case with the Teric though. The SW Cloud software graph shows the battery is charged to 4.2+ volts which is fully charged.

    3) If the design spec of the battery is 500 cycles from 100% down to 20%, then technically charging to 100% isn't "hurting the battery" since it should last 500'ish cycles under those conditions. It would be working as intended and the user would get the battery replaced at the manufacturers intended interval. On the other hand excessive heat or discharging to near 0% regularly would be outside the "normal" conditions and that could result in less than the manufacturers "normal" 500 cycles. However, that doesn't mean that we can't extend the batteries intended life even further than "normal" by limiting the max charge level and getting more like 2000 cycles from 80% down to 30%.

    I'm finding that even after a very long day of diving I'm only using about 40% of the battery at most. Therefore, from a battery health perspective, 80% down to 40% and back is better than 100% down to 60% and back. It could be the difference between having to get the battery replaced once or twice over the life of the Teric vs not needing a battery replacement at all.
     
    RainPilot and VE7DAC like this.
  4. SquareJ

    SquareJ Angel Fish

    # of Dives: 200 - 499
    Location: Dallas
    11
    2
    3
    I defer to SW for the actual value of limiting total charge, if it extends battery life then I am all for it. And for all we know 100% on the screen is in reality an 80% charge on the battery already.
     
  5. Cleavitt

    Cleavitt Nassau Grouper

    # of Dives: 500 - 999
    Location: Central Florida
    120
    28
    28
    I agree, but that doesn’t seem to be the case. The SW cloud software shows that at 100% charge the battery voltage is 4.2 or even 4.3 volts. That is fully charged for li-ion battery cells. A voltage of 4.0 is about 80% which is what the software shows when I limit charging to around that level. So I believe the displayed battery level is actual battery level with no hidden buffer.

    Having said that, I too would defer to SW if they have other thoughts.
     
  6. Jay

    Jay Need to dive more!

    # of Dives: 100 - 199
    Location: Melbourne, OZ.
    800
    400
    63
    When the Teric is 'off' it's not really off, the battery diminishes around 1%/day when 'off'.

    The time (~couple/few days) between 100% and 98% (the next displayed level) is relevant to the points you make, but I suspect that either any damaging effect would be next to nothing or SW doesn't make 100% really 100%.

    SW are pretty good responding to these technical points, and if it's something they've not considered they are good at rectifying that too.
     
  7. Cleavitt

    Cleavitt Nassau Grouper

    # of Dives: 500 - 999
    Location: Central Florida
    120
    28
    28
    Here is an article that explains the effects of different charge/discharge profiles with lithium ion batteries...

    How to Prolong Lithium-based Batteries - Battery University

    Figure 4 and the following quote from the article sum things up pretty well if you don't feel like absorbing all the nerdage in the article...

    "Lithium-ion suffers from stress when exposed to heat, so does keeping a cell at a high charge voltage. A battery dwelling above 30°C (86°F) is considered elevated temperature and for most Li-ion a voltage above 4.10V/cell is deemed as high voltage. Exposing the battery to high temperature and dwelling in a full state-of-charge for an extended time can be more stressful than cycling. Table 3 demonstrates capacity loss as a function of temperature and SoC."

    Below is a screenshot from Shearwater Cloud showing the battery voltage on a dive where I started with a full 100% charge. It shows the battery voltage of 4.3. Again, I'm not saying there is anything "wrong" with fully charging the battery and I'm not saying SW hasn't considered this in their design. They clearly have since they have given estimates about how often they expect the battery to need replacement. I'm just saying that there seems to be an opportunity to extend the battery life even further than the design baseline and possibly avoid ever having to send your Teric in for battery replacement entirely. Teric Battery Voltage.jpg
     

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