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rob_g's avatar
rob_g
Explorer
Apr 26, 2015

Charging lithium batteries with solar

I've got lithium camera batteries and a lithium jump starter battery pack. All charge via 12v auto circuits, i.e. they have their own chargers, they aren't bare batteries. They all work up to at least 13.8v, which is what is going into my house or vehicle batteries via the alternator.

My question is how to charge them with a 27W, 18v max solar panel. It puts out 18v at best. If I attach a Morningstar Sunguard solar controller, it can't sense anything at the end, hence it doesn't go on. I have tricked it by attaching a 12.7v battery and then disconnecting it, but that's obviously not a good solution. Once on, it runs at 13.8.

I also have a DC power converter; it will take the voltage and output 12.25 to 12.5v. This works too, but I'm wondering if it would be better to get something that could output a bit higher voltage, like 13.8. I've noticed when using house power to charge these batteries all of them cut out at some point, so I assume the overcharge protection is working on all of them. I can get bare buck converters on eBay for about $10 complete with LEDs for voltage.

Does this make sense? Will I blow up?

Rob
  • MrWizard's avatar
    MrWizard
    Moderator
    Apr 27, 2015
    I don't understand your aversion to using your existing lithium chargers, which are designed to charge the devices involved

    Plus your solar controller won't work because it does NOT sense a Battery attached

    I wish you luck in your experiments with the voltage booster
    But in the end I think you are going to fry those small lithium batteries, I hope the you do not damage the devices
    Lithium are current and heat sensitive, ever see a swollen cell phone battery, one that spent too many hours on charge, or been charged with the wrong charger
    Go on you tube and check it out, lithium battery fires
    With your surplus of POWER, the solar can handle using the appropriate chargers, no need for all this tinkering, except to satisfy your desire to do so, that is ok, as long as you are willing to accept the loss of these devices as the price paid for you curiosity
  • rob_g's avatar
    rob_g
    Explorer
    Apr 27, 2015
    Those converters look like the ticket. My existing one isn't adjustable except in about 3v steps, and maxes at 12.5. Like to get it a bit higher. But it did work fine. The charger only pulls 400ma at 13.8v; and lower amperage at down around 12.2v (150ish), then none a bit below that. They've got those CC/CV converters with the LEDs on Amazon for $15 shipped. Nice.
  • rob_g's avatar
    rob_g
    Explorer
    Apr 27, 2015
    I KNOW I can run these off existing 12v batteries, and I appreciate efforts to help, but the question, as yet unanswered, is specifically about using solar directly with existing lithium chargers to lithium batteries. So: panel>controller>charger, or panel>buck converter>charger?

    Since I asked, I've discovered very very few controllers will do this, since almost all small ones are battery chargers. Although there are tons that have circuitry to do USB power, 1 or 2.1A at 5v. I assume that those are basically voltage converters with appropriate limits on USB power to the standard specs of USB 1.1 and 2 (haven't seen 3.1 yet, which is higher amperage I believe, and could be useful for us). So I am know thinking I'll just use the buck converter like this one, which seems to provide the same utility, but at a different voltage: http://www.amazon.com/Switching-Regulator-Converter-Adjustable-Stabilizers/dp/B00BYTEHQO/ref=sr_1_2?ie=UTF8&qid=1430085381&sr=8-2&keywords=12v+buck+converter
  • red31's avatar
    red31
    Explorer
    Apr 27, 2015
    kaydeejay wrote:
    That's a lead/acid battery. Where does this fit in the picture?


    Why does the type of battery to power the controller matter?

    panel - controller - 12v batt - cig lighter plug - individual 12v chargers
  • kaydeejay's avatar
    kaydeejay
    Explorer
    Apr 27, 2015
    red31 wrote:
    How about using a same 12v battery

    http://www.homedepot.com/p/Mighty-Mule-12-Volt-Battery-for-Automatic-Gate-Opener-FM150/100016474
    That's a lead/acid battery. Where does this fit in the picture?

    OP - Lithium batteries are very particular as to how they are charged (Think Boeing 787 fires!) so using any charger other than the specified unit is looking for trouble.
    If this works on 12V, then the suggestion to maintain your chassis batteries with the solar unit and use those batteries to provide power to the Lithium charger is probably the best.
  • RoyB's avatar
    RoyB
    Explorer II
    Apr 26, 2015
    X2 on using a small INVERTER for all of your must have chargers and things. I use my 600WATT PURE SINE WAVE Inverter and route a 120VAC Extension Cord to my home entertainment area and my bedroom night stand area. This provides me 120VAC PSW for all of my emergency items I need to have powered up at all times.

    Roy Ken

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