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I want to power one particular device that feeds of 12V (5W) electricity.

However this device is intended to be highly portable and as such, I am quite tight on space, which means 12V accumulators are too big for this purpose. Also they are in fact, way too durable (and quite costly).

The power source must be rechargeable, so that I can take advantage of my charger. It is enough if it lats at least 1 hour and I cannot afford more than 10$ for it.

What would be the most cost-effective, small, disposable 12VDC power source that lasts at least 1 hour on a 5W power consumption?


As a side note, I already have x4 LG HG2, they are hi-drain (20A) and quite durable (3000mAh). Maybe I can use some boost converter to make 12V out of it. It may last 4 times less (decrease to about 6A), but that would still be very long-lasting I think.

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  • \$\begingroup\$ \$5\:\text{W}\$ for an hour is \$18\:\text{kJ}\$. A single AA alkaline battery has about \$10\:\text{kJ}\$ in it. So your problem and its solution should reasonably be expected to also fit your budget. In short, "it's doable." \$\endgroup\$ – jonk Jul 4 '18 at 4:09
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You need a 5W 12V load supplied for at least 1h or 5Wh

Each “holy grail” LG battery has V=3.6V nom. with a 1C dropout of 3.0V @3Ah or 3.3Vavg*3Ah=10Wh which will support a 2h load with a DC-DC boost converter with 90~95% efficiency from TI WebBench designs or off-the-web purchase.

You will also need a matched charger and undervoltage protection (UVP) on the boost regulator.

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  • \$\begingroup\$ What do you mean matched charger on the boost regulator? \$\endgroup\$ – Edenia Jul 4 '18 at 4:17
  • \$\begingroup\$ Also I think the UVP will use some of the energy too. Also isn't it better if I search for a BMS \$\endgroup\$ – Edenia Jul 4 '18 at 4:25
  • \$\begingroup\$ Yes a matched charger or BMS , UVP could be 1uA can also be part of BMS \$\endgroup\$ – Sunnyskyguy EE75 Jul 4 '18 at 5:58
  • \$\begingroup\$ I ended up giving 3 batteries for spot welding, I will use 3S BMS, they all have UVP. 3 batteries is much better than just one, because the looses are much smaller. Also I found a very good and cheap DC-DC converter with 95% effectiveness to fulfill the voltage. \$\endgroup\$ – Edenia Jul 6 '18 at 14:42
  • \$\begingroup\$ I am still unsure whether to connect the batteries in parallel or in series. \$\endgroup\$ – Edenia Jul 6 '18 at 14:49

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