iPAQ EFX Solar Charger: Portable Solar Power in the Pocket PC Era

By the middle of the 2000s, an HP iPAQ wasn't just a calendar and a contacts list — it was doing email on the road, running turn-by-turn GPS navigation, holding documents for a business trip, and, for a growing number of owners, connecting over Wi-Fi. All of that came at a cost the batteries of the era weren't really built to absorb. A day of real use could leave a Pocket PC dead well before an outlet was anywhere nearby, and that gap is exactly the space a small UK-made accessory called the EFX Solar Charger tried to fill.

What Was the EFX Solar Charger?

The EFX Solar Charger — branded within its own product line as the Solar:EFX — was a pocketable photovoltaic charger sold by EFX, a UK company, in the mid-2000s. Mobility Today reviewed it under the headline "EFX Solar Charger Power-On-The-GO!", and the surviving archived copy is the clearest record of what the device was: a small panel, built into a rugged case, converting light into electricity and storing it in an internal battery, with a USB port used to charge phones, PDAs, and other gadgets through device-specific adapter cables. It wasn't marketed as an iPAQ-only accessory — it was a general-purpose personal solar charger that happened to work well for iPAQ owners willing to track down the right cable.

The iPAQ Era and the Battery Problem

HP's iPAQ line was one of the dominant Pocket PC families of the early-to-mid 2000s, and by the time models like the hx and rx series arrived, they'd taken on far more responsibility than the original Palm-style organizers ever carried. Color touchscreens, Bluetooth, Wi-Fi radios, and GPS receivers all drew real power, and none of that hardware was designed with multi-day battery life as the priority. The practical result, widely discussed among Pocket PC owners at the time, was that heavy use away from a charger could drain a device well before the day was over. Spare batteries, car chargers, and AC adapters were the standard answers. A charger that ran on ambient sunlight instead was a genuinely different kind of answer, and that's the niche EFX's product aimed at.

Mobility Today's 2005 Review

The review was written by a Mobility Today contributor identified only as "Jack," and it's worth being upfront about how the surviving copy was recovered: the Wayback Machine holds archived snapshots of pages one, two, and three of what was originally a four-page review, captured between November 2005 and early 2006. The concluding fourth page — where Jack presumably delivered a final verdict — was never crawled and doesn't survive anywhere accessible. Everything below drawn from "the review" reflects those first three pages only.

A couple of contextual details are worth noting. Reader comments on the archived page go back to January 2005, months before the November 2005 "posted" date at the top of the review, and in one comment Jack confirms the piece was a rerun — a reader asked "Didn't you review this product once before, Jack?" and Jack replied that Mobility Today had "had a request to run it again." By the time the Wayback Machine captured it in late November 2005, the page had already logged over 56,000 pageviews and seven reader comments, a meaningful amount of ongoing interest for an obscure accessory review.

Jack's framing for wanting the charger is relatable: he described spending time outdoors — walking trails in Maine, reading by the shore while listening to music over HP's Bluetooth headphones — far from an outlet and not always near his car either. A car charger had been his fallback, but it didn't cover the situations he found himself in most.

Inside the Solar:EFX: Panel, Battery, and Case

The review gives a genuinely specific physical description of the unit, unusual enough for a product this obscure that it's worth repeating closely rather than paraphrasing loosely. The charger measured 123mm x 128mm x 15mm — small enough, in Jack's words, to fit in a coat pocket — and used a blue polycrystalline solar panel set into a case built from graphite-finish anodized aluminum combined with injection-molded ABS plastic. EFX's own marketing, as relayed in the review, claimed it packed the largest area of polycrystalline solar cells of any pocketable solar charger available at the time — a manufacturer claim reported in the review, not something this article can independently verify. A stand on the back folded out so the panel could be tilted toward the sun rather than left at a fixed angle.

Critically, the charger did not power a connected device directly from the panel. The panel fed an internal battery — the review describes the electricity being "stored in batteries within the SolarEFX" — and that battery is what actually delivered power to a connected phone or PDA through the USB port. Panel output was rated at 200 milliamps at 6 volts, the regulated USB output was 5 volts at 500 milliamps, and the internal battery was rated for roughly 1,000 recharge cycles. That battery kept trickle-charging any time the panel was exposed to light, sunlight or otherwise, per the review.

How It Connected to an iPAQ

The charger's own port was USB, but that's only half the story — a mid-2000s iPAQ didn't take USB power directly, and most PDAs of the era used their own proprietary charging connectors. EFX's answer was a fixed, non-selectable USB output paired with separate "connectivity packs" — device-specific adapter cables bridging that output to whatever plug a given phone or PDA needed. Jack used a BoxWave retractable cable to connect his iPAQ, and a compatible adapter to charge a cell phone; he noted he didn't have an adapter for his Bluetooth headphones. The comment thread shows this created real friction for some buyers — one reader asked whether the charger would work with an iPAQ rx3115 and whether a compatibility list existed, and Jack's answer was that there was no selectable output, only whatever connector matched the cable you had. That's a genuinely different model from today's USB-C world, where one cable covers nearly every device — in 2005, matching charger to connector was an active, sometimes frustrating part of ownership.

Charging Performance: What the Review Found

Jack ran several informal tests rather than a single lab measurement, and the numbers he reported are worth repeating directly, with the caveat that this is one reviewer's field testing, not controlled lab data. Starting from an iPAQ at 89% battery, a full charge came quickly. In a more deliberate test starting from 48%, the iPAQ reached 70% after 40 minutes, 75% after 60 minutes, and 88% after 120 minutes — Jack attributed the fast early gains partly to the charger's own internal battery, still holding a charge at the start of that test. In a separate run, after leaving the Solar:EFX in direct sunlight for several hours to fully top up its internal battery, then connecting a drained iPAQ, a full charge came in under twenty minutes. He reported repeating these tests multiple times with broadly consistent results.

The pattern held across attempts: an initial burst of relatively fast charging, powered largely by whatever charge the internal battery already held, followed by a slower rate once that reserve was depleted and the charger was running on live panel output alone. Jack's own daily-use summary was that his iPAQ typically used up 25 to 30 percent of its battery per sitting, and topping that back up with the EFX charger was realistic given reasonable sunlight.

Direct Sun vs Weaker Light

Jack was explicit that his testing happened during a period of the year with relatively weak sunlight, and he flagged that as a likely drag on both charging speed and overall efficiency — with the clear implication that stronger, more direct sun would perform better. That tracks with how photovoltaic charging works in general: a solar panel's output scales with the intensity and directness of the light hitting it, so a device charging in full midday sun will always outperform one charging under clouds or indoor lighting. The review doesn't provide controlled side-by-side numbers for direct sun versus overcast conditions, so treat this as a directional finding from real-world testing rather than a precise performance chart.

Travel, Camping, and Emergency Use

Jack framed the appeal in practical terms: as long as there was sun, he felt confident he could keep his iPAQ charged without carrying spare batteries, which he noted could get expensive, or relying entirely on an AC or car charger he might not always have access to. That framing — a lightweight, sun-powered backup that doesn't depend on an outlet — is exactly why gear built around this idea has long shown up in outdoor and preparedness contexts, and this review is a documented example. A preparedness document called "The G.O.O.D. Backpack (Get Out of Dodge)," a bug-out-bag packing guide circulated online, lists a "Brunton SolarPort or similar photovoltaic charger" as recommended gear for keeping a cell phone and GPS running, and directly points readers to this same Mobility Today review as a reference alongside it. That's a real, verifiable citation — it confirms the review was still being treated as a useful reference on portable solar charging well after its original publication, in a completely different context than the Pocket PC review scene it came from.

Who Was EFX?

EFX operated as a UK-based retailer and product brand, reachable at the time through sales@efx.co.uk according to Jack's replies in the comments. Beyond that, the surviving material doesn't spell out much about its broader catalog — whether "EFX" was primarily a manufacturer, an importer, or a gadget retailer putting its name on a range of products isn't settled clearly here. What's confirmed is narrower: EFX sold the Solar:EFX charger, corresponded with customers by email, and was, per one commenter, responsive and pleasant to deal with.

EFX Solar Charger vs Other Charging Options

The comparison that matters most historically isn't really EFX versus Brunton — it's the proprietary connector versus what came later. Every option on that list except the modern USB charger depended on matching the right physical plug to the right device, and accessory makers like EFX had to maintain a whole family of adapter cables just to stay useful across a fragmented market. USB-C's rise as a near-universal standard didn't just make charging more convenient — it eliminated an entire category of friction a device like the Solar:EFX had to work around directly.

Why It Appealed to Mobile-Computing Enthusiasts

Part of the draw was pure novelty — generating usable power out of sunlight, with no cable back to a building, still had a bit of a gadget-magic quality in 2005. Part of it was practical: business travelers, hikers, and early GPS-navigation users all had real reasons to want power independent of infrastructure. And part of it was the personality of the iPAQ community itself, which skewed toward tinkerers comfortable hunting down obscure accessories and testing whether an adapter cable would actually deliver power at the right voltage — exactly the audience a cable-dependent charger like the Solar:EFX was built for.

What Couldn't Be Confirmed

A few things the surviving review does not confirm are worth listing plainly, so as not to overstate what's actually recoverable here. It doesn't state which specific iPAQ model Jack used for testing — device names elsewhere on the archived page belong to unrelated sidebar items, not his test unit, and a reader's mention of an iPAQ 2750 refers to that reader's own device, not Jack's. It doesn't give a retail price for the charger or the connectivity packs. And because the fourth page never got crawled by the Wayback Machine, Jack's final conclusions and any rating simply aren't available — what's above is the substance of his testing, not a recovered verdict.

Using an Original EFX Charger Today

A genuine EFX Solar Charger surviving in a drawer somewhere is, at this point, a piece of mid-2000s mobile computing history rather than a usable power accessory. The internal battery — rated for roughly 1,000 recharge cycles even when new — has almost certainly degraded well past useful capacity after two decades, and if it's a lithium-based cell, a long-dormant, unmaintained battery is a safety concern as much as a performance one. The proprietary adapter cables it depended on are hard to source today, and even a functioning unit has nothing modern to plug into — there's no current iPAQ, and phones and PDAs from that generation are largely retired. Treat a surviving unit as a historical curiosity, not a working charger.

Collecting and Preserving a Surviving Unit

For anyone who has one, a few basic checks are worth doing before assuming it's safe or usable. Inspect the solar panel for cracking, delamination, or heavy discoloration, since prolonged UV and heat exposure can degrade photovoltaic cells even without physical damage. Check the USB port and the adjustable stand for corrosion or wear. And if the internal battery is a lithium chemistry and the unit has sat unused for years, look carefully — without applying pressure — for any swelling in the case, a sign of a degraded cell and a real safety flag, not just a cosmetic one. If a swollen cell is suspected, treat it as a case for professional battery disposal, not casual repair.

FAQ

What was the EFX Solar Charger?

A pocketable photovoltaic charger sold by the UK company EFX in the mid-2000s, marketed under the Solar:EFX name. It used a solar panel to charge an internal battery, then delivered power to phones and PDAs through a USB port paired with device-specific adapter cables.

Could it charge an HP iPAQ?

Yes — Mobility Today's reviewer used it to charge his iPAQ via a BoxWave retractable USB adapter cable, and reported multiple successful charging tests. The exact iPAQ model he tested isn't confirmed in the surviving review.

How did solar charging work for Pocket PCs?

The EFX charger's panel didn't power a connected device directly — it charged an internal battery, rated for about 1,000 recharge cycles, which then supplied power to the device through a regulated 5-volt, 500-milliamp USB output.

How long did it take to charge an iPAQ?

In the review's testing, results varied by starting battery level and available sunlight: a phone going from 48% to 70% took about 40 minutes, reaching 88% by two hours, while a fully sun-charged unit brought a drained iPAQ to full in under 20 minutes. These are single-reviewer field results, not lab-controlled benchmarks.

Did it work without direct sunlight?

The reviewer noted his tests were conducted during a period of relatively weak seasonal sunlight and suggested this slowed charging, implying stronger direct sun would perform better — but the review doesn't provide precise numbers comparing direct sun to overcast or indoor light specifically.

Which iPAQ models were compatible?

No official compatibility list survives in the recovered review. The charger had a fixed, non-selectable USB output, and compatibility in practice depended on sourcing the correct adapter cable for a given device rather than the charger supporting specific iPAQ models by design.

Was it useful for camping or emergencies?

The reviewer framed it that way, and a preparedness packing guide called "The G.O.O.D. Backpack" independently lists a photovoltaic charger alongside a direct link to this review as recommended emergency gear for keeping a phone and GPS charged, which is a real, confirmed citation.

How does it compare with modern solar chargers?

The core difference is the connector, not the solar technology. The EFX charger needed a matching proprietary adapter cable for every device type, while modern solar chargers with USB-A or USB-C output work across nearly any current device without that adapter-hunting problem.

Can an original EFX charger still be used today?

Not practically. A battery rated for around 1,000 cycles has almost certainly degraded badly after two decades, aging lithium cells can pose a safety risk if swollen, the specific adapter cables are hard to find, and there's no current device it was originally designed to charge. It's best treated as a historical piece rather than a working charger.

What survives of Mobility Today's EFX Solar Charger review is incomplete — three of four pages, no price, no confirmed test-unit model, no final verdict — but what did survive is unusually concrete for a fifteen-plus-year-old accessory review: real dimensions, real output figures, a real battery architecture, and real field-testing numbers from a reviewer clearly trying to solve a problem plenty of iPAQ owners had. It's a small reminder of how much friction the proprietary-connector era added to keeping a device charged, and how much of it quietly disappeared once USB, and eventually USB-C, became the default rather than the exception.