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Thread: Opus BT - C3100 "secret voltages" work pretty much as expected

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    Default Opus BT - C3100 "secret voltages" work pretty much as expected

    I verified last night that the internal "4.2/4.35/3.7" slide switch functions as expected by changing the termination point of a charge. I don't have any 4.35v cells but I have some 4.30v (Samsung ICR18650-28A and LG LGABC21865) that I watched and pulled at 4.3v. The latter took about 150mAh additional charge current above where they were at 4.2v. I also used the 3.7v setting to take several cells to storage voltage. One quirk is that any battery above about 4.15v or so will be detected as "Full" when inserted and you have to take it down to about 4.09v or so before it will start charging (but it will terminate at 4.35 instead of 4.2v).

    Mike


  2. #2
    Flashaholic* ChrisGarrett's Avatar
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    Default Re: Opus BT - C3100 "secret voltages" work pretty much as expected

    I drilled a hole in my 3400, in the bottom of the case, right over the switch, so I don't have to muck with it. I just use a toothpick to slide it around.

    Chris
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    Default Re: Opus BT - C3100 "secret voltages" work pretty much as expected

    Quote Originally Posted by ChrisGarrett View Post
    I drilled a hole in my 3400, in the bottom of the case, right over the switch, so I don't have to muck with it. I just use a toothpick to slide it around.

    Chris
    Yes they convienetly put the switch above a flat spot mid-way between the vents on that side (and a circuit board mounting screws on either side. There are also mold marks where a screw post would have gone on the back cover right over these screws. It looks like it was a design feature which ended up on the cutting room floor at some point.

    I'll probably do the same thing but smaller and square out the hole with my nibbler.

    Mike

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    Default Re: Opus BT - C3100 "secret voltages" work pretty much as expected

    Interesting Mike about the "full" when the 4.35v cells are above a certain voltage. I have noticed that when topping some off ready for next day use............Just using a sanyo now to get it dropped down in V and try out the 4.35 setting again. I kind of just used the vp2 up stairs for the 4.35v cells............this will save me a journey. I did wonder why it stopped working

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    Default Re: Opus BT - C3100 "secret voltages" work pretty much as expected

    WOW that did not take long with a quad 219bt, down to 3.63v and now on charge with the 4.35v setting. No full showing

    Good stuff!!!! will see now and hopefully terminate at 4.35v..........

  6. #6

    Default Re: Opus BT - C3100 "secret voltages" work pretty much as expected

    It gets even better. The when set to 3.7v all modes that charge stop at 3.7v as do all modes that discharge! Clearly it was meant to be a storage mode.

    This was a coincidence. See my reply a couple posts down. The discharge run just happened to (thermal?) abort at 3.7v.

    Mike
    Last edited by Arizona_Mike; 04-19-2017 at 12:12 PM.

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    Default Re: Opus BT - C3100 "secret voltages" work pretty much as expected

    ^^^ Are you sure about discharges stopping at 3.7V? I presumed the 3.7V setting was for LiFePO4 (not storage), so it would discharge much lower than 3.7V.

    Update: according to this post, the discharge termination voltage (2.8V) is the same for both the 4.2V and 3.7V charge termination setting. So unless something has changed, this seems to imply that the 3.7V setting is indeed designed for LiFeP04.
    Last edited by Gauss163; 04-19-2017 at 09:19 AM.

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    Flashaholic* ChrisGarrett's Avatar
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    Default Re: Opus BT - C3100 "secret voltages" work pretty much as expected

    The switch in my BT-3400 v. 2.2 is marked 4.20v, 4.35v and 3.7v. I just assume that it's for those three chemistries/voltages and works as one expects, but I don't own any LiFePO4 cells to confirm the discharge points.

    For 4.35v and 4.20v, my Opus discharges down to 2.80 volts and then back up to 4.35v and 4.20v, respectively, as one would expect.

    Chris
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    Default Re: Opus BT - C3100 "secret voltages" work pretty much as expected

    Too add, the charger terminated at 4.35v as expected. Cool finding though as i thought it was a 1 charge wonder(well 3 or 4 to be exact). If the 4.35v cell is near or over 4.2v , then it does show full. I simply use the cell more before topping back up to 4.35v if using the opus. Happy with that

  10. #10

    Default Re: Opus BT - C3100 "secret voltages" work pretty much as expected

    Quote Originally Posted by Gauss163 View Post
    ^^^ Are you sure about discharges stopping at 3.7V? I presumed the 3.7V setting was for LiFePO4 (not storage), so it would discharge much lower than 3.7V.

    Update: according to this post, the discharge termination voltage (2.8V) is the same for both the 4.2V and 3.7V charge termination setting. So unless something has changed, this seems to imply that the 3.7V setting is indeed designed for LiFeP04.
    I've been trying to get a whole bunch of laptop pulls down to 3.7 for cold storage. I had a batch of 2600s stop all between 3.68v and 3.71v when doing a 1A (0.38C) discharge, but it turned out to be a coincidence. The next batch stopped around 3.78 and I noticed no capacity displayed just current at 0. Then I had a batch of 4.3v 2800s that went all the way down to 2.8 (and displayed capacity). I tried 4 more of the 2600s @700mA (0.25A) and there was not interruption and they went all the way down to 2.8v at the lower current. They were stopping because they were aborting, not end-pointing.

    Mike

  11. #11

    Default Re: Opus BT - C3100 "secret voltages" work pretty much as expected

    Quote Originally Posted by ChrisGarrett View Post
    The switch in my BT-3400 v. 2.2 is marked 4.20v, 4.35v and 3.7v. I just assume that it's for those three chemistries/voltages and works as one expects, but I don't own any LiFePO4 cells to confirm the discharge points.

    For 4.35v and 4.20v, my Opus discharges down to 2.80 volts and then back up to 4.35v and 4.20v, respectively, as one would expect.

    Chris
    3.7 is a little high for most LiMPO4, even single cell. Straight LiFePO4 is usually rated 3.65+/-0.03. LiFePO4 is much more tolorant of overvolting due to super lown internal resistance. I'd be more concerned about if the charge profile and termination current is correct for the other chemistry. I think it is designed as a storage charge as explicitly stated for other chargers.

    Mike

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    Flashaholic* ChrisGarrett's Avatar
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    Default Re: Opus BT - C3100 "secret voltages" work pretty much as expected

    Quote Originally Posted by Arizona_Mike View Post
    3.7 is a little high for most LiMPO4, even single cell. Straight LiFePO4 is usually rated 3.65+/-0.03. LiFePO4 is much more tolorant of overvolting due to super lown internal resistance. I'd be more concerned about if the charge profile and termination current is correct for the other chemistry. I think it is designed as a storage charge as explicitly stated for other chargers.

    Mike
    That 3.7v number is just a label and as we see from unit to unit, these chargers are all over the map when it comes to hard numbers.

    First question is, why put that switch there and cover it up?

    Secondly, the 4.35 label and the 4.20 label target specific voltages that we commonly encounter, so why not include the third 3.6v-3.7v (3.0v/3.2) voltage?

    We have 3 voltages and they seem to address that with the switch. Xtar doesn't use their 3.2v setting for storage, or market it that way. They make no mention of it in fact. The end result is more happenstance than a dedicated storage feature IMO, but that's just speculation on my part.

    What is the margin of error with that 3.7v number you're getting? 10% tolerance?

    I'm not trying to argue, just pointing out some contrarian observations.

    I've got four 25Rs here that have been discharged down and I'm going to put them on charge with the 3.7v setting and see what I see, as I've not toyed with 'storage settings', but for doing in manually in my lights.

    Chris

    ETA:

    My four 25Rs terminated at 3.7v and then settled on the charger to 3.69v after a few minutes, on the 3.7v setting, so that perhaps might be a bit high for LiFePO4, so I don't know what's up?
    Last edited by ChrisGarrett; 04-19-2017 at 02:38 PM.
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    Default Re: Opus BT - C3100 "secret voltages" work pretty much as expected

    Opus is currently considering an updated version of the 3400 which will have an external voltage switch so the back doesn't have to be removed plus it will charge NiZn batterys.
    SkyRC MC3000, Opus BT-C3400 3.1, La Crosse BC 9009, Saitek SmartCharger. Utorch UT01, UT02. Convoy C8, M2, S2+, 502b. Triton M30. Hugsby XP1 and XP2.

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