Neewer is a lower cost photo and video accessory provider and I've used several of their products before. I happen to own a couple items that can use the Sony NF-P battery standard for power: an LED light panel and a monitor. Since I normally power these off of AC power and a power cable, respectively, I was not interested in the higher cost NF-P options, as I'm rarely in a location without power outlets. But when I saw this four pack and charger, and taking into account my generally positive past experience with Neewer products, I figured it was time to get some batteries just in case I find myself in a place without convenient power.The kit includes a quad charger, AC power supply, and four 6600mAh batteries. At 7.4v, each battery should have approximately 48 Wh of power. To test this, I charged all four batteries up to full capacity and put them on my light panel at 100%. I’ve measured that AC power draws 76.6W from the outlet with this light, so two batteries should theoretically give me about 75 minutes of power [(48 Wh + 48 Wh)/76.6 W]. Keeping in mind that voltage drops as the batteries lose power and my light will shut off below a certain voltage, real life power delivery will give me a bit less than the theoretical 75 minutes.I ran two tests, with the light dying at 65 and 69 minutes, which is pretty close to the theoretical maximum run time. In fact, when I first put the batteries on, the light told me it had an estimated run time of 52 minutes, so they lasted longer than the light anticipated. I’m pleased with the amount of run time I get out of the light with the batteries and will help in those situations where an outlet for AC power is just not convenient or available. Since my aforementioned monitor (which I did not test the runtime on with these) draws a maximum of 13W (and likely less most of the time), I anticipate getting at least 4 hours out of each battery when used to power it.When it comes to charging, the charger is fairly basic, with a maximum 3.5amps of charging power. It can deliver maximum power (or nearly) with 1 or 2 batteries, drawing approximately 20W per battery. Once you add a third, that power is split in half between slots 1+2 and 3+4, with approximately 9W per battery when charging three or four of them. In a perfectly efficient system, adding 9Wh of power to the battery every hour, that means a 48Wh battery could charge in 5 hours and 20 minutes. In practice, since there are inefficiencies in battery charging, slots 1 and 2 charged in almost exactly 6 hours, while slots 3 and 4 took about 6 hours and 15 minutes. That’s about what I’d expect. When charging only two batteries from completely dead, I clocked about 3 hours and 40 minutes, a bit slower than I would have expected considering the initially measured power draw. I should have measured the power draw as they neared fully charged, as that might explain the time difference, as most charges start to taper off charging speeds as batteries near capacity, since this helps with the lifespan of the battery.At the end of the day, these will fulfill the purpose I got them for: offering me flexibility in powering some devices that I normally power other ways. At the list price of $160 for the set, however, I think these have some stiff competition from others that are offering faster charging speeds, batteries with higher (claimed) capacity, and batteries with power level indicators built in. Some even offer charging the battery directly with a USB-C cable, allowing you to use far smaller USB bricks instead of the larger type of charger this uses.