Gutted USB Power Packs Run Your TV

With a computer in every pocket, being tethered to large mains-powered appliances is a bit passe. No longer must you be trapped before the boob tube when you can easily watch YouTube on your phone. But you might be jonesing for the big screen experience in the middle of a power outage, in which case learning to build a simple battery bank built from cheap cell-phone power packs might be a good life skill to practice.

Looking more for proof of concept than long-term off-grid usability from his battery bank, [Stephen] cobbled together a quick battery bank from 18650 lithium ion batteries and a small 300W inverter. All the hardware was had on the cheap from an outfit called Cd-r King, a Phillipines-based discount gadgetorium we’d like to see in the states. He got a handful of USB power packs and harvested the single 18650 battery from each, whipped up a quick battery holder from 1/2″ PVC pipe and some bolts to connect the inverter. With four batteries in series he was able to run a flat-screen TV with ease, as well as a large floor fan – say, is that a Mooltipass on [Stephen]’s shelf in the background? And what’s nice about the gutted USB power packs is that they can still be used to recharge the batteries.

As [Stephen] admits, this is a simple project and there’s plenty of room to experiment. More batteries in parallel for longer run times is an obvious first step. He might get some ideas from this laptop battery bank project, or even step up to Tesla Li-ion battery hacking – although we doubt Cd-r King will be of much help with the latter.

30 thoughts on “Gutted USB Power Packs Run Your TV

  1. This is good, but it seems a little pointless using an Inverter to convert the dc battery to ac, just to have the tv’s power brick convert it back to dc again.

    If you match the battery voltage to the TV’s power brick output voltage, you could do away with two power converters, an increase in around %30 efficincy (rough guess)

    1. Yep. and I believe that TV is the typical 18V type so it would have been trivial to make a power supply for it. I found that a lot of devices are actually quite tolerant of voltage swings. for example my panasonic toughbook runs and charges just fine from 19V to 15V into it’s power jack.

    2. If the TV has an external PSU, it normally gets one voltage and you could do what you are saying. But if it is internal, chances are that it generates multiple voltages at the same time. So it would be more difficult to do it.

  2. You can get new, quality 18650’s consistently if you’re willing to pay about $9/ea. Or you can get cheap 18650’s on Ebay, but you’ll be lucky if it has even 50% of the stated capacity. Some are just old and worn-out batteries, that are relabelled. Others were found to actually contain a much smaller battery inside, with the extra weight provided by filling in the space with flour.

    So where do cheap consumer goods that contain 18650’s, like the power packs in this project, fall on the price/quality scale?

    1. I bought Sanyo 2600mAh from eBay few times, and it costs half that price, 4pack for around 18 dolars. I test them with 1A discharge current and they are all in 5% of the specified capacity. Of course, you can buy MumboJumboFirePowerUltra 10000mAh for $2 each, but you’ll be lucky if you measure 1000mAh with those.

  3. Another option is just to string enough cells in series to reach the cut in voltage of the power supply. About 40 v DC is enough to get my cell phone charger running well. Be sure its a switching power supply, otherwise you will cook your “iron heart” supply.

    1. Or you can use $0.99 portable charger that accepts 18650 cell, it has circuitry for charging and protecting battery and for converting 3.0-4.2V into 5V. All inside nice aluminium casing. Adding cells to meet your mains charger cut-off voltage just requires more cells and you end up with switching converter anyways.

    2. Just to correct myself (insert mention of edit button here), my power-bank example is for your mobile charging case, for the TV powering your idea seems OK since those mobile phone charging banks can’t provide enough voltage and current for TV powering, and 18650 cells can.

  4. Average operating voltage of an 18650 is 4V. 4 in series is 16V.
    If the 18650 is 2200 mA/H, 35W/16V=2,2A = 1C.
    @50W the discharge is 3,2A => 1,4C.
    Well below the recommended max working current.
    This hack made me think…wow.. I wouldn’t have believed this is a safe hack. But is is.
    (Actually, without monitoring your battery voltage, this is a good way to kill them)

  5. It isn’t uncommon for single 18650 vape-devices to run around 60-70w – so ~40w for the TV is perfectly reasonable for 4 18650s in series. If you got more than 3 at a time in parallel it’s entirely possible to run around 200w off of 3 18650s.

    1. It seems to me that the ~40w of power the device stated is drastically wrong. Firstly this is a modified sine inverter and as such the efficiencies are horrendous! It could be as high as 40% off due to PF issues. Secondly, that ‘watt-meter’ looks like a cheapy and as such probably doesn’t take into account the changes in voltage (not to mention it probably assumes it’s pure sine) and as such the calculations for power consumption cannot be trusted even for ball-park figures.

      Any Vape devices i have seen seem to run at around 35w max, but seeing as a 5s cell can power a 600w+ power drill I have no doubt that these cells can handle it just fine.

      1. Not really apples to apples here, as 18650 only refers to the size of the cell and says nothing about the chemistry. “Lithium-Ion” is a blanket term that covers multiple chemistries, including lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese cobalt oxide, lithium iron phosphate, lithium titanate, lithium nickel cobalt aluminum oxide, and so on. They all have different specific energies and charge/discharge rates (and some have different voltages, such as the iron phosphate and titanate).

        I would expect that the batteries in a portable cell phone charger are not designed for high discharge currents like the ones used in vaporizers and power drills (usually lithium manganese oxide), so what he’s doing here is probably not a good idea.

  6. So a guy runs an inverter from a 12-16v power supply. Where is the hack? As far as I can see this is devices doing EXACTLY what they were designed to do. The batteris aren’t even in the inverter! Sorry but *YAWN*

  7. the tv has an external power supply putting out i think 16 volts so it may be possible to connect directly just cut the plug off the tv power supply or use universal power plug it is just a barrel plug like laptops use.

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