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Thread: Solar charging 14500 Li-Ion batteries. Best option?

  1. #1
    Unenlightened
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    Default Solar charging 14500 Li-Ion batteries. Best option?

    I have a 12v 30w solar panel. I don't mind charging one 14500 cell at a time if I have to since this is for camping where you have plenty of time for such things. If such a device that can accept solar power already exists, please let me know, but my search efforts are exhausted for naught. I thought about just connecting my xtar charger straight to the panel since it accepts 12v at 2 amps but the concern of over voltage and lack of power made me rethink. isn't there some sort of cheap regulator or something that doesn't steal all my power?

  2. #2
    Flashaholic
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    Default Re: Solar charging 14500 Li-Ion batteries. Best option?

    How about using the panel to charge a powerbank, then charging your cells off that?

  3. #3
    Flashaholic* Timothybil's Avatar
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    Default Re: Solar charging 14500 Li-Ion batteries. Best option?

    Quote Originally Posted by Scourie View Post
    How about using the panel to charge a powerbank, then charging your cells off that?
    Does your solar panel have the option of outputting at USB levels? If it does, there are several very good chargers like the Xtar VC4 that run off of USB ports. If I remember correctly, the Nitecore I4 charger has a 12v input so that is an option. But I don't know how it would behave with a varying input voltage.
    Does your solar panel have a regulator to output the 12v, or does it really put out like 18v and depend on a charge controller to do the regulation?
    Remember, Two is One, and One is None!.

  4. #4
    *Flashaholic* ChrisGarrett's Avatar
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    Default Re: Solar charging 14500 Li-Ion batteries. Best option?

    Quote Originally Posted by Squig View Post
    I have a 12v 30w solar panel. I don't mind charging one 14500 cell at a time if I have to since this is for camping where you have plenty of time for such things. If such a device that can accept solar power already exists, please let me know, but my search efforts are exhausted for naught. I thought about just connecting my xtar charger straight to the panel since it accepts 12v at 2 amps but the concern of over voltage and lack of power made me rethink. isn't there some sort of cheap regulator or something that doesn't steal all my power?
    With anything over 20w, you really need a 12v digital charge controller, like my Morningstar SS-10-L, that charges/powers a battery and/or a 12vdc load.

    I have an older Xtar WP2 II 12vdc charger that does 500mA and 1A, so that works with my 12v solar panels (2x30w). Personally, I'd look for a Anker PowerPort 21w USB folder and something like an Xtar Hummingbird XP-1 NiMH/li-ion single bay charger for <$10 and go that route. It doesn't accept anything larger than an AA/14500, but it has two rates of 250mA and 500mA, so it's good for the smaller cells.

    Chris
    Convoy: S2, S2+, M1, M2, Fenix: P1D, PD32, HL30, ET: D25C Ti, SF: 6P, ZL: SC-600, Klarus: P2A, Jetbeam: BA-20, Icon: Rogue 1, L3: L10, Xeno: E03, ShiningBeam: I-Mini, Olight: i3s, SWM: D40A, M11R, V11R, Maglite: 6Ds, MMs, Solitaires, LaCrosse BC-700, Maha C-9000, XTAR VP2, MP1S, XP1, MC1+, WP2 II, NiteCore i4, v2.

  5. #5
    Flashaholic
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    Default Re: Solar charging 14500 Li-Ion batteries. Best option?

    Chris has it right. For camping purposes, a smaller Morningstar 4.5a Sunguard controller would do fine with your 30 watt panel, especially because it is all sealed and potted. No adjustments.

    Grab a small agm, like 5 to 7ah size as your intermediary load to charge, and at the same time use a 12v li-ion charger attached to that.

    Like most controllers, attach the battery to the controller first, and the panel last. This allows the controller to get it's brain together first. If you attach the panel first, and the battery last, many controllers not knowing the difference between a dead 0 volt battery, and one that is missing entirely as you put the system together may either refuse to charge, or go into a float-only safe mode. So batt first, panel last. And of course attach your li-ion charger to the agm battery once that's all together.

    Now you have a stable source of power for the charger. When clouds or other obstructions pass over the panel, the li-ion charger doesn't know any difference.

    If the 14500's are LiFeP04 chemistry (3.2v nominal, not the 3.6v nominal of other types), a smaller setup like a folding panel with a 5v usb output to a SunJack AA/lifepo4 charger works too. BUT, you have to babysit the charger, since any obstruction to direct sunlight may make the charger reset, and in some cases stop charging altogether and error-out, requiring a reinsertion of the batteries. Make note of the beveled side of the micro-usb jack - it's not too apparent and if you push it in the wrong way, you can damage the jack. On mine, the smaller beveled side of the jack is facing down.

    I charge 14500 lifepo4's as a goof this way. Not a serious setup, but it works. And, the low 300ma output per cell (if you're lucky) is just too slow for most AA nimh, but I guess if you have no other option ....
    Last edited by IonicBond; 11-01-2018 at 01:13 PM.

  6. #6
    *Flashaholic* ChrisGarrett's Avatar
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    Default Re: Solar charging 14500 Li-Ion batteries. Best option?

    Quote Originally Posted by IonicBond View Post
    Chris has it right.
    I've learned a lot from you over my stay here, so keep it up and thanks!

    Chris
    Convoy: S2, S2+, M1, M2, Fenix: P1D, PD32, HL30, ET: D25C Ti, SF: 6P, ZL: SC-600, Klarus: P2A, Jetbeam: BA-20, Icon: Rogue 1, L3: L10, Xeno: E03, ShiningBeam: I-Mini, Olight: i3s, SWM: D40A, M11R, V11R, Maglite: 6Ds, MMs, Solitaires, LaCrosse BC-700, Maha C-9000, XTAR VP2, MP1S, XP1, MC1+, WP2 II, NiteCore i4, v2.

  7. #7
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    Default Re: Solar charging 14500 Li-Ion batteries. Best option?

    Thanks - I learned most of my li-ion stuff from CPF'ers, so we're even!

    Just to be complete without turning it into a lead-acid thread - with the Morningstar Sunguard, it run a very conservative absorb voltage of 14.1v, which is ok for a sealed gel, but not really for a sealed agm. To do agm right, it needs to see 14.4 to 14.7v absorb.

    So in this case the small sealed AGM with the Sunguard is kind of sacrificial. It won't last as long as it would on the SunSaver with it's voltage jumpers. "Sealed", on the Sunsaver is also conservative, designed for gel, and not agm. If the longest life is desired for a true agm, then remove the jumper on the Sunsaver, and run with the "flooded" voltage, which is about 14.4v.

    So just a tip for lurkers not to blindly use the silk-screen jumpers without checking the actual voltages used first, and use what is actually appropriate.

    The other tip is that despite how fast we may want to charge lead-acid, it takes 8-16 hours of float to *truly* recharge that last 1 percent of an agm. There is no way to hurry that up for most people. A luxury we don't have with most solar setups since the sun doesn't stay up that long. So be sure to give the batt plenty of float time, even though it may be a ridiculously low amount of current compared to overall panel output. Hard to do in a daily cyclic-discharge scenario, but just try your best.

    It's really funny how too long a time spent getting that last 1 percent of li-ion recharged to full is actually detrimental, whereas with lead-acid agm's, it is beneficial to give the batt a long period of float charge to get that last 1 percent in - otherwise you walk it down in capacity from sulfation over the long run.

    I always found that difference fascinating.
    Last edited by IonicBond; 11-12-2018 at 03:04 PM.

  8. #8
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    Default Re: Solar charging 14500 Li-Ion batteries. Best option?

    Quote Originally Posted by IonicBond View Post
    [...] It's really funny how too long a time spent getting that last 1 percent of li-ion recharged to full is actually detrimental, whereas with lead-acid agm's, it is beneficial to give the batt a long period of float charge to get that last 1 percent in - otherwise you walk it down in capacity from sulfation over the long run. I always found that difference fascinating.
    There are many radical differences due to the very different chemistries. Another major difference is that you don't gain much using shallow cycles for lead-acid, but for Li-ion you can get 10x or more equivalent full cycles (or lifetime total Ah), e.g. see this post for some graphs.

  9. #9
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    Default Re: Solar charging 14500 Li-Ion batteries. Best option?

    Quote Originally Posted by IonicBond View Post
    [...] It's really funny how too long a time spent getting that last 1 percent of li-ion recharged to full is actually detrimental, whereas with lead-acid agm's, it is beneficial to give the batt a long period of float charge to get that last 1 percent in - otherwise you walk it down in capacity from sulfation over the long run. I always found that difference fascinating.
    There are many radical differences due to the very different chemistries. Another major difference is that you don't gain much using shallow cycles for lead-acid, but for Li-ion you can get 10x or more equivalent full cycles (or total lifetime Ah), e.g. see this post for some graphs (see esp, the dramatic Wohler curves at the end of that post).

  10. #10
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    Default Re: Solar charging 14500 Li-Ion batteries. Best option?

    As a total goof, I'm going to try a LiitoKala charger with a 5v usb input and see how that goes. Supposedly handles the typical fold-out portable panels. For nimh, 3.2v and 3.6v nominal li-ion chemistries too.

    We'll see how well that goes when I walk in front of the panel.

    Yep - shallow cycling is bad for lead-acid too. Unless one draws at least 5 - 10 percent of the capacity, the natural sulfation process during discharge is not spread out evenly and hot-spots develop.

    Nice charts - the takeaway from that is to center your usage for best longevity, rather than keep cells full and shallow cycle from 100%.

    The problem for me was that with total over the board care of my huge LiFep04's, I outlived the cycle-life. That is, after about 8 years, they aged faster than I could cycle them.

  11. #11
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    Default Re: Solar charging 14500 Li-Ion batteries. Best option?

    Quote Originally Posted by IonicBond View Post
    [...] Yep - shallow cycling is bad for lead-acid too. Unless one draws at least 5 - 10 percent of the capacity, the natural sulfation process during discharge is not spread out evenly and hot-spots develop [...]
    The linked graphs show that shallower cycles do improve total lifetime Ah for the lead-acid batteries tested there, but the gains are very small: max 20% (vs. 420% for Li-ion, and up to 1700% in the 2nd study).

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