High-Capacity Solar Power Bank with Foldable Solar Panels

Around four for a typical phone, sometimes three for a large one. No power bank delivers its full rated capacity to a device, because converting from the internal cell voltage to USB loses some along the way. Four is a realistic figure rather than an optimistic one.

Longer than you would like, and this is the honest part. Panels this size produce a few watts in perfect conditions, so refilling 20,000mAh from empty by sun alone is a matter of days, not hours. Charge it from the mains before you leave. Use the panels to slow the drain while you are out, which they do well in Tanzanian sun.

Unfolded, flat, facing straight up at the sun, with nothing shading any part of them. Shade on one panel drags down the whole set, so a strap shadow or a rucksack corner costs more output than you would expect. On the roof of a vehicle or the top of a tent works well.

The panels yes, the battery no. Heat is what ages a lithium cell fastest, and a black power bank in direct Tanzanian sun gets very hot. Put the panels in the sun and keep the body itself in shade if you can manage it.

Carry-on only, never in checked baggage, which is the rule for every lithium power bank. At 20,000mAh it is roughly 74Wh, comfortably under the 100Wh limit airlines allow without special permission. Keep it where you can reach it.

The remaining charge in the pack. It is a useful feature at this price, because the four-dot indicators on cheaper banks tell you almost nothing between full and empty.

Store it around half charged if you are not using it for months, never flat, because a lithium cell left empty for a long time loses capacity permanently. Top it up every couple of months. Keep the ports free of sand and dust, and fold the panels closed when it is packed so the surfaces do not get scratched.