How to best minimize the "coming out of regulation" issue?- Mtbr.com
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  1. #1
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    How to best minimize the "coming out of regulation" issue?

    I have the Yinding (Gemini Duo Clone) light on order, and have a feeling I am going to love both the weight, output and customizability of optics. I race a 24hour solo every year and have been very happy with my Magicshine 808E as a helmet light except for the weight (when worn from around 7pm to 6am..).


    The thing I'm not sure I am going to love is the issue where it comes out of regulation when battery voltage falls below the sum of Vf + cable/etc voltage drops. I see reviewers noting this occurs at about 6.3-6.4V at the light head, but suppose once the cabling and battery protection circuit is included, we are talking 6.6V or higher(?). I am not saying I will hate it, but would like to mitigate it as much as makes sense.


    Some ideas I have thought of, in order of increasing difficulty/inconvenience:


    1) Beef up wires from driver to emitter board:
    I believe that was one of the recommendations from experienced users in the original-yinding thread, to minimize voltage drop.


    2) High-voltage 4.3V (LiHV) battery cells:
    I understand for example Sanyo UR18650ZT 2800mAh cells will offer higher voltage throughout most of the discharge cycle than many traditional cells, even when charged to 4.2V (I have a link to a post on BLF but not sure if links to other forums are permitted..). They are also very cost effective at $10 a pair from fasttech. Are there other cells I should be considering as well?


    3) Lengthen lamp cable so an extension cable isn't needed:
    (I carry the battery in a jersey pocket). Use thick 20/22 AWG cable. Experiences? Use RTV to seal entry point into body?


    4) Build an external boost converter?:
    A compact 4amp DCDC boost converter is less than $2 on ebay. Could go in an extension cable. Input down to 3V, output adjustable. Most efficient if input is close to output voltage. If efficiency is decent, power loss should be arrund 2W so not a huge concern. Not sure what happens if the output voltage is set to, say 7V, and input voltage is higher? Could equip it with a switch and a battery voltage indicator. Anyone build something like this?


    5) Converting to 3S battery:
    Not sure if the driver supports it. Also, do not want to do this as I don't have chargers with pit-crew friendly ease of use for it. Also, 3S1P would give me probably less runtime than 2S2P and 3S2P with 18650 cells will be heavier than I'd like. Not super interested in LiPoly wither, seeing as I carry these packs in my jersey pocket.


    6) Building a custom 1S LED driver (drive LED's in parallel):
    Yeah... sounds like a lot of work.. But if anyone has already started on a project like this, I would love to hear about it.


    I'm mostly thinking 1-3, possibly 4. Would love to hear what others have done.

  2. #2
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    IMO the best bang for the buck would be to make sure the cable between the battery and light is no less than 22 AWG (or metric equivalent) and preferably 18 to 20 AWG without any unneeded connectors. Better cells for the battery are right there too.

    IMO, it's really no big deal on most lights when they start to drop out of regulation. They just start to dim gradually. Some folks like this as a "warning" system that it is time to swap batteries.
    GoPro adapters for bike lights http://www.pacifier.com/~kevinb/index.html

  3. #3
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    The noted loss of regulation is using standard packs. It has to do with the voltage getting to the head. when voltage at the head reads in that area so VF becomes higher than supplied voltage the driver goes "direct drive". Good, bad, crap cells, length of cables etc, none of that changes the voltage at which the head comes out of regulation. its a constant.

    How to lengthen the time is as Vanc said, to reduce the voltage drop (voltage loss due to resistance) between the pack and the driver.

    step 1, 22AWG is enough, 20awg at the short of a wire matters almost nothing we just do it cause we can. Has no effect on driver coming out of regulation though, its purely a slight output boost (no visable, but measurable)

    high voltage cells are good, but be in a better position with panasonic 3400mah because you need run time. So though your cells maintain a higher voltage, they are still going to run out much faster. if your running on medium your loosing a good 30 mins run time on a 2s1p pack (so hour or more on 2s2p). Run time trumps the slightly higher voltage as youll still drop out of regulation alot sooner than normal 4.2v 3400mah panasonics cells.

    Your going to have to run a longer cable, yinding stock cable and battery cable is too short to run to pocket on a jersey. Those that get buy with it have it in a hydropack. Easy fix, use 18AWG wire and if really ambitious, use a RC Deans connector (ultra low resistance) and have it close to the pack with all the wire length attached to the head (having connector flopping around in the wind it can eventually work loose)

    KEEP RTV AWAY FROM THESE THINGS. The fumes can cause corrosion to the driver circuits, any exposed copper corrosion is accelerated 100x. there is silicone that is electronics safe. USE THAT.

    No driver doesnt support anything but 8.4v packs.

    With any light, it comes down to those factors. Voltage sag from pack to light head, quality of the cells, all translate to run time. If your running a protected pack then you have little to worry about. a 2s2p panasonic 3400mah (6800mah total) running the yinding on mostly medium your looking at 6-7 hours run time. High about half that before loss of regulation, and you have a little bit of time still before cells start getting low enough to risk damage to them. 6V at the head with light on medium is about limit of safe voltage under load. And thats when the dimming REALLY becomes noticeable, to me anyway.

    BTW your referring to loose cells, you do understand those require a case for them which youll have to source yourself. Not much for options out there. Just so your aware. Be easier to just buy pre-assembled packs. And batteries are NOT the place to be overly cheap. Look for deals, not the cheapest you can find. Your purpose, you need reliable equipment, light head will get you there, but batteries are the critical point.

    So simply go bigger wire, get a couple good panasonic packs and go. Simple and done. Depending on your pit stop spacing and what you have ready there, dont NEED pansonics. Samsung 3000mah celled, sanyo 2600 celled (5200 mah) packs. Best way to judge: 1000mah capacity means 1amp of draw per hour. Yinding medium is that. High is 2.0A iirc, so 2000mah means yinding on high for 1 hr. multiple that buy time between pit stops or how ever long you want to go between pack changes (always round down though so you have extra battery power for emergencies, so if your pack is 6800mah, plan it out as if you only have 6000mah)

  4. #4
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    Thank you for taking the time to write such a detailed answer. I plan on building a spot welder and rebuild by old magicshine packs, reusing those protection circuits and rubber shell. My aim is to run the light at high. Medium would be less light than the Magicshine 808E which takes 1.3A from battery (10.35W).

    On the topic of cells, your input is highly valued. It prompted me to look in detail at the excellent cell tests at lygte-info.dk. Lots of data there, and the best cell will obviously very much require on the specific use.

    From what I could find, the light comes out of regulation at about 6.3V. With even just a small amount of voltage drop over cables and protection circuit, cells will need to stay above 3.2V (or 3.3V?) each to avoid going out of regulation. Also, assumint the review I read is correct and the light takes about 1.6A we are looking at 0.8A per cell in a 2S2P pack and should be looking at the 1A discharge curves. Also, since this light uses a buck converter, the metric we are interested in is not mAh, but rather energy consumed from the battery in Wh.

    Below is the energy provided at 1A discharge down to 3.2V for the the following cells:

    LG 18650 E1 3200mAh [email protected] : 11.2 Wh ($13.27 a pair at FastTech)
    Test of LG 18650 E1 3200mAh (Green)
    LG 18650 MH1 3200mAh [email protected] : 10.9 Wh ($14.40 a pair at FastTech)
    Test of LG 18650 MH1 3200mAh (Cyan)
    Panasonic NCR18650B 3400mAh [email protected] : 10.7 Wh ($12.96 a pair at FastTech)
    Test of Panasonic NCR18650B 3400mAh (Green)
    LG 18650 D1 3000mAh [email protected] : 10.6 Wh ($12.23 a pair at FastTech)
    Test of LG 18650 D1 3000mAh (Pink)
    Sanyo UR18650ZTA 3000mAh [email protected] : 10.3 Wh ($13.26 a pair at Fast Tech)
    Test of Sanyo UR18650ZTA 3000mAh (Magenta)
    Sanyo UR18650ZT 2800mAh [email protected] : 9.2 Wh ($10.23 a pair at FastTech)
    Test of Sanyo UR18650ZT 2800mAh (Orange)

    In case we look at the 2A discharge curves for a 2S1P pack, the panasonic climbs down and the gap to the LG E1 cell widens (still looking at down to 3.2V):

    LG 18650 E1 3200mAh [email protected] : 10.7 Wh
    LG 18650 MH1 3200mAh [email protected] : 10.3 Wh
    LG 18650 D1 3000mAh [email protected] : 10.3 Wh
    Panasonic NCR18650B 3400mAh [email protected] : 9.8 Wh
    Sanyo UR18650ZTA 3000mAh [email protected] : 9.8 Wh
    Sanyo UR18650ZT 2800mAh [email protected] : 8.8 Wh

    Looking at 3.3V instead of 3.2V would also widen the advantage for the LG cells.

    I'm glad I looked into it further - those Sanyo cells don't look as good as what I had gathered from a BLF forum post (turns out that was compared to Panasonic NCR18650A 3100mAh).

    Well, the complications of choosing the optimal cell do not stop there. At the race, I have been using my Magicshine 1.8A chargers. I measured the open voltage on these and found one is 8.46V and the other 8.60V. So my chargers are already (somewhat / definitely) geared for higher voltage cells. So a question arises, how much capacity is lost if that nice LG E1 cell is charged to only 4.23V?

    Well, the graphs at lygte-info do tell us that after discharging at very low current to 4.2V, about 0.8Wh is given up. So, when charging to 4.23V, probably 0.5Wh given the expected slope of the curve. That means it would be a dead run against a correctly-charger Panasonic 3400. Also, the LG cells would not get worn out on the out-of-spec 8.60V charger, as will be the case for the Panasonics.

    A point I hadn't thought about is I will need to check my existing protection circuits for max charge voltage. Well, in any case they have been working with those two magicshine chargers and I presume without tripping the safety circuit. Need to check again but I know at least one of the protection circuits went up to 8.65V before it cut in when testing a charger that came with a "Bright-Eyes" light from Amazon (I later found that charger has a resting voltage of 10.6V!).

    So, I see two directions:
    - Go with LG 18650 E1 3200mAh cells. Potentially a handful of % better, worst case same performance as Panasonic 3400. No concerns with overcharging with my existing chargers. Will cost $0.31 more per cell.
    - Go with Panasonic NCR18650B 3400mAh. Will provide a bit longer out-of-regulation runtime. Need at least one new charger (to replace my 8.60V one).

    Not much difference either performance or cost wise. But the nerd in me is leaning towards the LG direction. Not because you pointed at the Panasonics, at least I don't think that is why.

    Lastly, thanks for the tip about not using plain RTV from the tools drawer. Makes a lot of sense. I won't ask how you know :-)

  5. #5
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    I still think ur way over thinking the matter lol. But our "inner nerd" causes that problem sometimes.

    Remember one key point, voltage sag is a good thing to a point. It prolongs battery life. This is because the cells are actually not discharged as deep as it appears they are at the light head (something some people forget about, cell voltage is going to be higher under load than what's making it to the driver in these instances).

    I dont know alot about high voltage cells yet (just starting to dig into that) but make sure that actual safe discharge voltage isn't higher as well, end up wearing your cells out way faster if this is the case.

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