BLUETTI PV120D 120W folding solar panel – good, but (off-grid review) - Cybershack

The BLUETTI PV120D 120W folding solar panel is good, but as anyone who understands solar will tell you, it has practical limitations.

Those include a clear view of the sky, the right panel pitch for the area, east-west orientation, and what happens during rain, clouds, or snow. The short answer is that solar charging is a bonus when it works.

The ideal placement is sun-facing (east to west) with a clear, unobstructed sky view at the optimum pitch (panel angle is basically your latitude below).

If you are camping, you might find such a space, but it is increasingly hard to find in suburbia. Placing them flat on the ground substantially reduces the power output (see tests later).

The four panels are serially connected. This means the wattage output is only as much as the lowest wattage produced by any panel.

The other issue is that solar efficiency depends on the time and the length of the day. The example below (using Viridian 405W solar panels with DC/AC Enphase microinverters) shows typical generation patterns over a day.

On a good day (left), solar power (Blue) starts at sunup and continues to build until around noon, then slowly reduces. The 10kW battery (Green) charges in 2-3 hours. On a bad day (right) solar generation is minimal, and you use grid power (or a car charger) to top up the battery.

The same principles apply to portable panels, except that you can shift them and alter the pitches to get maximum charging.

This is not meant to diminish the BLUETTI PV120D 120W folding solar panel because it is as good as it gets. It is a well-designed, well-made folding panel that can top up portable power stations when the sun shines and grid power is unavailable.

BLUETTI have 120, 200, 350 and 420W folding panels up to 2675 x 975mm x 14kg. They all share the same efficiency, so you should buy the biggest panel to match the power station’s DC input charge.

We use Fail (below expectations), Pass (meets expectations) and Exceed (surpasses expectations or is the class leader) against many of the items below. We occasionally give a Pass(able) rating that is not as good as it should be and a Pass ‘+’ rating to show it is good but does not quite make it to Exceed. You can click on most images for an enlargement.

The four-fold panel is reasonably portable at 500 x 500 x 45mm x 5.36kg (folded) and 500 x 1760mm (unfolded). It produces 24.6V/4.87A/120W wired in serial (30W per panel).

The panels have adjustable 15-45° pitch struts, an integrated carry handle, and a zippered bag for MC4 cable storage. They are ETFE laminated (Ethylene tetrafluoroethylene has high corrosion resistance and strength over a wide temperature range), are IP67 water resistant, and have a 12-month warranty.

We tested on the BLUETTI Handsfree 2 backpack (review here), which has a built-in MPPT (maximum power point tracker – a DC to DC converter that optimises the match between the PV panels and the power bank battery). This allows a solar panel to plug directly into the two-pin XT60 DC input socket. You can use any compatible solar panel from 12-45V DC at up to 8.2A for a maximum of 350W input.

Solar panels (in this case, 4 x 30W) only generate the lowest volts/amps panel’s output. For example, when correctly sited east to west and angled, the panels produced 108W at noon (that is fair for a 120W panel under ideal conditions), but the moment one had a shadow on one corner, it reduced to <10W when laid flat, reduced to 91W.

The moral is that you need to find an open sky, orient it east to west and use the correct angle.

If we could have maintained 108W output, the charge would be 512W/108 = 4.74 hours plus some system overhead, so let’s say approx. 6 hours.

BLUETTI advertises 2 hours using 350W (700W), which gives a 73.14% charge efficiency, on par with quality solar panels.

Folding solar panels are a real benefit for campers, especially if they are used optimally to maximise solar production.

Over several tests, we could not reach the theoretical maximum nor sustain output without occasional alignment improvement.

Note: This is not the older PV120 design.

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