a solar-powered battery for the survivalist

I am not the “prepper” type. For the past 15 years, I have lived in large cities and rarely stray into the wilderness. The idea of going too far away from mobile phone coverage, let alone a stable electricity supply, does not seem like a relaxing holiday.

So when I was sent a large, high-capacity battery pack and accompanying solar panel to review, I was not quite sure what to do with it. There is clearly demand for something like the River “mobile power station”, as its Chinese manufacturer EcoFlow describes it; the company raised more than $1m in a crowdfunding campaign earlier this year and the device is now sold in big-box retailers including Home Depot, Camping World and Amazon. Competitors such as Anker’s Powerhouse and Goal Zero’s Yeti show there is a growing market for a clean alternative to petrol-powered portable generators.

A couple of things finally got me plugging in the River. One was moving from San Francisco to the less foggy climes of southern California, where the sun shines consistently enough to fill up the capacious 412Wh battery using the solar panel. The other was that living on the West Coast, the prospect of nuclear attack or violent populist uprisings suddenly seem somewhat less remote than our existing concerns of earthquake and drought. Watch too much American television news or Twitter these days, and California dreamin’ can feel nightmarish. It is almost enough to consider joining the “survivalists”, who are stockpiling supplies for the apocalypse — whatever form it might take.

Perhaps this is why Silicon Valley companies are so keen on solar power. The Googleplex has long had a solar array, while Facebook spent millions of dollars installing panels on the roof of its new Frank Gehry-designed HQ. Apple could take its entire headquarters off the grid and barely miss a beat. Apple Park, the iPhone maker’s new “spaceship” campus, is completely powered by renewables, including a huge 17MW of rooftop solar.

At about $600 each, it is hard to make a cost-saving argument for the purchase, even if the environmental benefits are sound

It is not just big tech companies that are trying to live off-grid, even in built-up areas. Here in LA, Rob Rhinehart, the chief executive of meal-substitute drink Soylent, wired up a solar panel to a lead-acid car battery in his apartment a couple of years ago. Because he drinks Soylent so often, he was able to do away with his fridge and other high-energy kitchen equipment. He used the battery to power a mini-PC, his smartphone, some LED lights and a pocket projector for watching movies.

I have not gone quite as far as Mr Rhinehart (who also ordered custom-made clothing from China then gave it away instead of using a washing machine). Nonetheless, thanks to the River, I have powered my MacBook, iPhone and iPad entirely from the sun for almost a whole working week. The River comes equipped with an array of USB ports and AC plug sockets, and with 300W of continuous output, it is powerful enough to charge several devices at once. An LCD display gives a real-time estimate of how much charge remains in the battery and how long it can keep supplying whatever devices are plugged into it at the time.

The wattage is enough to charge a dozen smartphones or a laptop between five and nine times, according to the manufacturer. River can also power a miniature fridge, drones, loudspeaker or projector for hours — ideal for preppers who need to survey the post-apocalyptic landscape from the air while keeping their beers cold, or who want multimedia raves held deep in the woods. However, it does not have enough wattage to fuel electrical heating devices, such as drip-coffee makers or hairdryers.

The foot-long battery is sturdy, with an integrated carrying handle, but at 5kg it is more suited for car camping than backpacking.

Eli Harris, co-founder and chief executive of EcoFlow, says River was intended to fill the sizeable gap between a Tesla Powerwall, which can charge an electric car, and the pocketable powerpacks that keep our smartphones topped up. While the battery cell technology is by this point pretty much a commodity, EcoFlow claims its expertise — drawn from several employees’ time at DJI, the drone maker — is in the software and circuitry that regulates the energy flow. For instance, it turns itself off when a device is fully charged or if the battery overheats. EcoFlow says River can keep almost all of its charge for up to a year, although I have not had it long enough to test that claim.

While the River is versatile, powerful and portable, I found that it takes quite a while to charge up using the panel — even in sunny LA, it took several days, not the 10-15 hours that EcoFlow advertises. That might be because I was not moving the panels around to the optimal angle for the sun every hour, but I am not sure that is a reasonable request for most people. That means it takes a little too long to top up between charges. To truly take my electronics off-grid, I would probably need two batteries, one to charge while the other is in use. At about $600 each, it is hard to make a cost-saving argument for the purchase, even if the environmental benefits are sound.

Before the River launched, Mr Harris experimented with targeting ads to hundreds of different groups of people on Facebook. The device was most popular with RV owners looking for an alternative to smelly, noisy, gas-powered generators. But coming in second were fans of zombie drama The Walking Dead, “people who are afraid of the apocalypse, who want this as a back-up power source,” he says.