MetFut/Latimeria M30000 Solar USB Power Bank Teardown and Review

Introduction

I’ve only disassembled a handful of power banks so I am still learning about them. But when MetFut reached out to me about reviewing their M30000 power bank, I wasn’t initially enthusiastic as they were implying that I should participate in some sort of Amazon review shenanigan. But they agreed to send me a review unit directly so I accepted. When I saw the price of $17, I was really curious about the level of quality you can get for so little money.

Full disclosure: While this is not a sponsored post, the product showcased was provided at no cost for evaluation purposes. Products received in this capacity are destined for teardowns, future device interoperability testing, giveaways, trades for other items to test, and/or charitable donations. (MetFut/Latimeria are brands owned by Shenzhenshi Xianboshi Keji Youxian Gongsi, based in Shenzen, China.)

Advertised specs

• 33800 mAh (misleading – more on this later)
• LED flashlight
• solar panel with suction cup
• IPX7 shockproof/dustproof/waterproof
• 11.3 ounces (320 grams)

Unboxing & Physical Characteristics

The packaging was a simple brown cardboard box. Inside, the power bank was wrapped in a thin white plastic baggy. Included was a 10cm USB -> microUSB charging cable, dual suction-cup clip, mini carabiner clip, user manual, and a “please don’t return it” card that seems to be universal in low-end products on Amazon. The power bank itself has an outer black textured hard plastic shell with a blue silicone/rubber insert. Different variations have different color silicone inserts but are otherwise identical.

Weight of the power bank was 215 grams with exterior dimensions of ~139mm x 75mm x 19mm.

suction cups clipped on

green LED indicates solar charging

rear panel

Flashlight/torch is bright enough

Silicone cover for ports

215 grams – at 150Wh per kg, estimate

Usability and Performance

Charging the power bank

The solar charging feature is SLOW – as advertised it does 5V @ 0.15amps or 750mW. So in order to charge from 0 – 100% would take ~40 hours under ideal conditions. Without direct sunlight, it could take much longer. MetFut does mention in the documentation that the solar feature is not intended to do full charging but just to top-off the battery. Given the solar panel adds very little weight, I guess its a nice-to-have feature, but not really necessary. Charging via USB is a more reasonable 3-6 hours depending on the style of USB charger you use. This seems typical for pocket sized power-banks.

When charging from solar the LEDs illuminate green and seem to indicate the brightness of the light hitting the solar panel. But when charging from USB they illuminate blue and indicate the available capacity. I’m not sure why they bothered with this. I guess the green LEDs provide some assurance that the solar charging is actually working and Green = environmentally-consicious I guess?

Charging phones

I was able to charge two phones at the same time with each receiving ~4.6W. The documentation says that one port can do 2.1 amps but I was only able to get a max of 1.2 amps. The combined output on two ports simultaneously was about 2.1 amps though. Having all three USB ports in use simultaneously seemed to work OK, but “passthrough” charging didn’t seem to work which wasn’t surprising. For high-end battery packs, when you plug into AC/Mains, not only does it charge the battery but also splits away some power to charge the USB devices at the same time. This ZMI unit I reviewed last year has that feature.

Note: my regular USB power meter was malfunctioning so I needed to use my USB-C power meter with adapters so the voltages are probably reading about 0.1v low compared to a direct connection. I will re-test when I receive my new tester in the mail.

All three cables in use

Other

The Amazon detail page states IPX7 waterproof rating which means immersion in at least 1cm of water for 30 minutes shouldn’t cause any undesired effects. Based on the construction, I would not trust this claim. Very little effort was needed to pull the blue silicone cover insert from the main plastic body revealing glimpses of the inner components. And the part that seals up the USB ports was quite loose-fitting. Water splashes would be OK but not I would not trust immersion.

The built-in flashlight/torch feature is rather handy and well-executed on this device. It is bright enough to help you find your keys in a purse or look for items in the trunk of your car. The “SOS” flashing feature is just a gimmick and unlikely to be useful.

The belt clip is thin plastic and I reckon it would snap off with use. Likewise, the included suction cup and carabiner accessories are not inspiring – I didn’t use them though so can’t comment on their actual effectiveness.

Teardown

The construction was simple with two black plastic half-shells fastened together. After popping 4x silicone screw covers off, I unscrewed 4x Philips (+) #0 screws and loosened 6 integrated plastic clips. After separating the two halves, the blue silicone seal fell off easily. Inside, there were three main components:

• 107mm x 61mm solar panel hot glued in place
• charge controller PCB marked XHD-2592H
• 12mm x 60mm x 90mm Li-Po cell rated for 8000mAh @ 3.7V (29.6Wh) with a chevron-shaped logo and factory code “NV”.

Analysis

Overall, the construction is mediocre with hard plastics and hot glue used for the assembly. It uses a no-name charging controller with no markings on the two integrated circuits. Although the Li-Po cell has a design voltage of 3.7V and 8000mAh rating (29.6Wh capacity), after charging overnight, the battery voltage reached 4.1V leading to a real-world capacity of 34.5Wh. This is typical in low-end power banks as overcharging provides a higher capacity at the expense of a reduced number of charge cycles before the battery dies.

Misleading capacity?

The Amazon detail page specifies 33800mAh and 5 volts. But this voltage is the output of the USB port not the battery internal charge voltage. Actual charge voltages can vary between 3.7-4.3V depending on how aggressive the charge controller is. And that voltage is stepped up to 5V with a boost-converter circuit. Reporting mAh (milli-amp hours) is only relevant if the battery charge voltage is also reported. With both of these figures you can compare capacities across different battery brands. Without both, you cannot compare since different vendors could be using a different voltages. If the charge voltage is not specified, I assume 4V. If we take the vendor at their word, then 338000mAh multiplied by 4 volts is ~135Wh (Watt hours) which is well beyond the typical 100Wh limit allowed for airline travel. Also, battery packs of this capacity typically weigh ~800 grams – not ~200 grams.

What we see inside is an 8000mAh Li-Po cell – clearly not a 338000mAh cell. If this cell is charged to 4.225V it would actually have a capacity of 33800mWh. Had the vendor advertised it this way, their claim would have been ~12% higher than the actual 34500mWh capacity rather than ~290% higher.

Its plausible the vendor just made a mistake – but after looking at dozens of eBay and Amazon detail pages for competing products, its clear that mAh claims are all over the place. Some vendors seem to be substituting mAh instead of mWh but others seem to just pull a number out of thin air. My recommendation is that whenever you buy a battery pack, just divide whatever rating is advertised by 4 and you’ll probably be close to the actual rating.

Based on these findings I asked the vendor to correct the page – if they do, I will post an update here.

Manufacturer info

I was able to find the actual manufacturer of these power banks on Alibaba and they are charging ~$5 USD. China->USA shipping and Amazon Prime fulfillment probably adds ~$5/unit, so at $16.99-19.99 retail, profit is limited to $7-10 per unit. Amazingly, the Alibaba listing mis-advertises the capacity as 20000mAh. So somehow we got from an 8000mAh -> 20000mAh -> M30000 model name -> advertised rating of 33800mAh. Amazing!

Conclusion

For under $20 USD ($16.99 on sale), you can’t really expect much from a portable power bank. And the MetFut M30000 meets that expectation. It uses uninspiring materials and assembly methods. But with its simplicity, it ends up being fairly rugged. I tossed mine around the workshop and hit the concrete floor multiple times and the plastic didn’t shatter and the solar panel stayed in place. The blue silicone doesn’t make the best seal so I wouldn’t trust the waterproof claims, but it should be good enough for the occasional spill or splash. The flashlight is handy and bright enough for casual uses. The carabiner and suction cup are not items I would rely on and are just “filler” accessories. And the solar panel is more of a gimmick than anything else since it charges so slowly.

Would I recommend this product for daily use? Probably not. For battery packs, I prefer spending more for something that is higher quality. But if you just want to have something cheap to toss in a vehicle glovebox for occasional use, I think this would be OK. If you know of any reputable power bank brands that advertise *real* mWh or Wh ratings instead of fake mAh numbers, please let me know. Even highly regarded brands seem to screw this up.