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Hands-on Gear Review

Instapark Mercury 4S Review


Solar Charger

  • Currently 3.0/5
Overall avg rating 3.0 of 5 based on 2 reviews. Most recent review: May 29, 2015
Price:   $33 List
Pros:  Light, inexpensive, simple, internal battery
Cons:  Our panel stopped working well after 4 months, no cigarette lighter adapter: only charges USB devices
Manufacturer:   Instapark
Review by: Chris McNamara ⋅ Founder and Editor-in-Chief, OutdoorGearLab ⋅ December 15, 2014  
If you need a small panel that is inexpensive, will charge your phone/tablet AND has an internal battery, this is a good deal. It performed nearly as well as is its sibling and Editors' Choice winner the Instapark Mercury 10 and yet was half the price. The Mercury 10 produces over twice the power and can charge two devices at once. The Mercury 10 is better if you don't mind a little extra weight.

After about 3 months, the 4S panel stopped working that well. It would not hold much of a charge and when plugged in, it stopped charging the iPhone short of a full charge… even in direct sun. Other user reviews have reported similar problems. For this reason, we need to test a few more of these devices before we can recommend it. In the meantime, if you are looking for a good budget and compact solar charger, we recommend going with the Anker 14W Foldable Dual Port Solar Panel. But the 4S has the advantage of an internal battery and it can be easily clipped to your backpack while hiking. For the Mercury 10, we generally recommend getting an extra external battery, which further raises the weight and cost.

Got a laptop or larger device to charge? Read our full Portable Solar Review to see the more powerful options.

RELATED: Our complete review of solar chargers

  • Photos
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OutdoorGearLab Editors' Hands-on Review

A folding solar panel with an integrated battery, the Mercury 4S is a decent panel for a decent price.

Performance Comparison

Instapark Mercury 4S
Credit: Instapark

Output Power

4 W is not a mighty number but it is plenty to charge any laptop or smartphone we threw at it. At 800 mA, this panel charges a phone or tablet about as fast as any other panel we tested. Only a few other panels charged at 1000 mA or higher. In addition, the internal battery means you don't have to worry about a passing cloud interrupting the charge. This panel gives you peace of mind because you don't have to constantly monitor it to make sure it is charging.


There is no real storage with this panel. You can fold your charging cable into the panel…but it seems to always slide back out. we recommend bringing an extra soft sunglasses case to hold your charging cables.

Ease of Use

This is about the easiest panel to use if you are just charging one USB device. You just need your USB charging cord for whatever you are charging.

There are grommets at the edges of the panel for clipping to trees, tiny carabiners or string. This makes it very easy to orient the panel for optimal sun exposure. However, the grommets are quite small so you likely need to purchase some extra string and create loops to really be able to attach the panel to much.

The panel folds into itself, which make it very compact. However, it also makes it a little hard to lay perfectly flat. Not a big deal, but something to point out as it can take a little wrestling to get the panel to face perfectly perpendicular to the sun.


The 4S lacks adapters and you can't add them later. There is no CLA capability or way to charge a laptop or device that does not have a USB cable. Certain devices, such as some camera battery chargers, are not easily charged from this panel. This is really a panel for charging smartphones and tablets. Other panels with a wider variety of adapters will be better for charging camera batteries, motorcycle batteries, laptops and a wider variety of devices.


This panel is not light overall. However it is light per watt. All the other panels nearly as powerful were almost double the weight. Another way to look at it is that this is by far the lightest panel that can charge two devices at once.
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Instapark Mercury 4S on the back of a 98 Honda SuperHawk. Ride all day, charge all night.
Credit: Chris McNamara


Anyway you look at it, the Mercury 4S is an amazing value. Overall it is one of the least expensive panels, and it is by far the least expensive per watt. It is also by far the least expensive panel that can charge two devices at once.

Best Application

This panel is ideal for groups with two to four people that all want to keep their smartphones and tablets charged. It is also ideal for a single person that has a "mobile office" with a tablet and smartphone that will be in heavy use in the field. We highly recommend combining this panel with an inexpensive external battery so that you can charge the battery and a device at once.


If you want a charger with an integrated battery and are on a budget and don't want to spring for the Poweradd Apollo 2, then this is the panel to get. Your dollar won't go any further for a small and light device that charges your tablet or phone.

Other Versions

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Instapark Mercury 10
  • Cost - $63
  • Editors' Choice Award Winner!
  • Lightweight and inexpensive
  • Charges two devices at once
  • 10 watt output
  • Pair with a battery for reliable, constant power

Chris McNamara

OutdoorGearLab Member Reviews

Most recent review: May 29, 2015
Summary of All Ratings

OutdoorGearLab Editors' Rating:   
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Average Customer Rating:     (0.0)
Rating Distribution
1 Total Ratings
5 star: 0%  (0)
4 star: 0%  (0)
3 star: 100%  (1)
2 star: 0%  (0)
1 star: 0%  (0)
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May 29, 2015 - 03:12pm
Bargainhunter · Climber
Ok, after owning this product for 2 years now, I had finally had the internal battery fail, which is a common complaint. I suspect the problem has to do with heat. Since lithium ion batteries don't do well in high (100F+) temps, integrating the battery into the solar charger's case exposes them to the same high temps that's bathing the photovoltaic panels in sunlight. Not a good design idea.

I unscrewed the little screws and opened the case and removed the 3.7V 2000mAh internal battery (by cutting the positive and negative electrode tabs). This lightened the whole unit by 1.2 ounces. There are no replacement batteries available from Instapark (yes, I contacted them), so I bought a small lightweight (2.5oz) Instapark 3000mAh 3.7 volt lithium ion waterproof cylindrical external battery (see the website) for $8 on Amazon and just plugged it into the solar charger's USB port. It appears to charge without problem. I plan to buy a longer (maybe 3 feet) USB to micro USB cable so I can put the eternal battery in the shade while the panel is in the sun. I'll report back if I run into any problems.

It's recommended to not simultaneously charge the external battery while charging the phone off the battery, as it shortens the external battery's life. It is possible that simultaneously charging the panel's internal battery while charging the phone could have been an additional cause of shortening the life of the internal battery.
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Instapark Mercury 4s
Credit: Instapark
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