There is no way this has 12,000 mAh of capacity. I have not tried it to start a car yet, but I wanted it to charge my laptop. Works to give my Acer laptop a little charge. My Dell gives me a warning pop-up, but allows it to charge. This charger only had enough capacity to charge my tiny 4870mAh laptop by about 40%. When the charger had 14% charge remaining, it took less than 2 hours to fully charge back to 100% at 1Amp/15V. So, being generous, I'd say it only has a maximum of 3,000 mAh of stored power, or 25% of its stated capacity. Given its size and its claim to be a 12,000 mAh charger, this should have much much greater capacity, and should take closer to 8 hours to charge at 1A/15V. I was hoping it would be better than the scam no name Li-Ion batteries coming from China, but it is actually even worse. It took my a few months to find the right adapters for my laptops, so I wasn't able to test it earlier. I was also surprised that it did not have adapters for Acer or Dell laptops. Overall, I am very very disappointed with this product because the stated capacity is completely different from actual capacity. I wish I could just swap out the batteries with good ones, since the rest of the unit seems to be fine.

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