Here’s my report on this “6800” mAhr battery. It cost me $26 shipped.
When I received the battery, direct from China, I was also suspicious of its capacity. Not from its size, but from its weight. I realize Li-ion batteries are light for their capacity, but this thing is only 206 grams (7.25 oz). Nevertheless, on with the test.
I charged the battery fully, and it had a no-load voltage of 12.7 V. I connected it to a Sound Devices 722, connected a couple of condenser mics (actually a Nevaton MC404 stereo mic). The loaded voltage dropped to 12.4 V, and during record there was 0.7 A flowing. I let the 722 record until it shut down, which took 4:32. Let’s call it 4:30. (At shutdown, the battery was at about 9 V; it’s not good for a 12V Li-ion battery to be discharged that far.)
So that means my sample of this battery is:
4.5 hours x 0.7 A = 3.15 Ahr = 3150 mAhr
I really ran this battery down to get to 3150 mAhr, so in use I’d rate it to be no more than 3000 mAhr. That is 3000 / 6800 = 44% of its rated capacity, which is pretty bad.
There is more bad news. When I used the included wall wart battery charger to charge my now deeply discharged batter, the charger blew up! The outside plastic case of the charger was deformed from overheating. I took the charger apart and the plastic case power transistor (without a heatsink) had split into pieces. Obviously, the charger busted a gut trying to recharge the very dead batter.
I sent an email to the seller, explaining that the charger had blow up the second time I charged the battery, and he said he is shipping a new battery and charger. I have no doubt I’ll get it. When it comes I’ll take the charger apart and add a heatsink, run it outside its case, and maybe use a fan when charging.
I can find a use for this battery, but would I buy one again? Nope.