Wave Reserve Power Bank

Details

A power bank that prints the number you can use next to the number that goes on the box, and shows the working between them. The mAh figure on a power bank is the most durable piece of misdirection in consumer electronics, and what makes it work is that it is not a lie. A 20,000 mAh bank really does contain 20,000 mAh of cells, at 3.7 V. Your phone charges at 5 V. Milliamp-hours are a charge, not an energy, and they only compare at one voltage, so 20,000 mAh at 3.7 V is at most 14,800 mAh at 5 V before anything else happens. That is 26 percent gone to arithmetic alone. The boost converter then takes about 11 percent more. The honest unit is the watt-hour, which is what aviation regulators use and what no shelf edge in India prints. The arithmetic is on the case and on this page, twice, once per size.

• 10,000 mAh at 3.7 V is 37.0 Wh. Delivered 32.9 Wh at 5 V, measured at a 2 A draw, which is 6,580 mAh at 5 V, or 66 percent of the printed number. Check it: 0.74 x 0.89 = 0.66
• 20,000 mAh at 3.7 V is 74.0 Wh. Delivered 65.5 Wh at 5 V, measured at a 3 A draw, which is 13,100 mAh at 5 V, or 66 percent again
• Where the loss goes, both sizes: 26 percent to the voltage step from 3.7 V to 5 V, which is arithmetic and not inefficiency, and 11 percent to boost conversion, which is measured
• In real phone charges: a 5,000 mAh 3.87 V phone holds 19.35 Wh and charges at about 93 percent, so a full charge draws 20.8 Wh. The 10,000 gives 1.6 charges. The 20,000 gives 3.1. Not two and not four
• Cells: INR21700 lithium-ion, 5,000 mAh each at 3.7 V nominal. Two in parallel for the 10,000, four for the 20,000, so the pack figures follow from the cell count
• Output: 65 W maximum on the 10,000, 100 W on the 20,000. The 100 W needs a 5 A e-marked cable; with a 3 A cable it gives 60 W, which is correct behaviour
• Ports: two USB-C and one USB-A, all usable together, with pass-through so it charges itself and a device at once
• Input: 45 W on the 10,000, empty to full in about 1 hour 25 minutes. 65 W on the 20,000, about 1 hour 50 minutes
• Display: an OLED reading watt-hours remaining and live watts in and out. Not four bars, and not a percentage of a number that was never true
• Both sizes are under the 100 Wh cabin baggage limit, and the Wh figure is printed on the case where airline staff look for it
• Six Torx T6 screws, cell pack on a connector, no adhesive. Cell pack Rs 890 on the 10,000 and Rs 1,490 on the 20,000, and old packs come back to any Shuunnya LifeStore for recycling
• Protection: over-charge, over-discharge, over-current, short circuit, cell balancing and an over-temperature cutout at 65 degrees C
• The price ladder follows the cells. Rs 2,490 for 37 Wh is Rs 67 per watt-hour; Rs 3,990 for 74 Wh is Rs 54. Capacity doubles and the price rises 60 percent, because the shell, board and display do not double
• There is no Shuunnya service-centre network. A warranty claim means posting the bank to us, with no turnaround time promised