Bests & Worsts Reviews from Amazon

I have used solar panels for my amateur radio hobby for many years and more recently to recharge drone batteries out in the field. But doing it that way requires to carry a large solar panel, then the heavy battery, a charge controller, an inverter and all of the wires needed for all that. Along comes this Yeti 400 Lithium. Suddenly I had visions of what I could be doing better/faster. It's the size of a small lunchbox. Grab the handle and go; there's your charge controller, battery and inverter; complete with exceptionally informative display. Add solar panel and you have a complete power solution for the great outdoors; or indoors during power outages. Details: The lithium battery can be routinely discharged deeply without much damage to it, unlike with lead acid batteries where deep discharge seriously impacts its life span. It is also relatively lightweight, I measured it as 17 pounds plus or minus a pound or two. In other words you get more of the 400 watt-hours of useful power. The sine wave inverter is high quality. If the photo uploads work you'll see a photo from a Fluke scopemeter. It looks as perfect as any sine wave I've seen and measures 118.2 volts RMS, right on the money. That's with a fully charged battery; depending on its regulation it might keep that during discharge but I'll test that once I get the battery down a bit. It will NOT power up a Calumet 750 watt-second studio flash. The big capacitor in the flash looks like a short circuit to the Yeti so it just beeps at me. That's a big disappointment but not entirely surprising. I've ordered high power, low ohm resistors from Amazon and am going to make an inline resistor box to control that inrush current. (UPDATE: It works but the resistors get hot. Need heatsink). Lithium batteries have a substantial, nearly linear voltage drop as you consume power. It starts out at 12.3 volts but at 50 percent remaining capacity the 12 volt is now 11 volt. Lithium batteries have surge current capability vastly superior to lead acid batteries and with much less fluctuation in voltage just because of current draw (in technical terms: Lower internal battery resistance) . I couple it with Boulder 30 solar panels of which I have three. They are rated 30 watts (each) and as you probably know actually getting that much is a scientific feat. They daisy chain one into the next and the last plugs into the Yeti 400. The Yeti 400 can take up to 10 amps in its charge port. When it comes to charging you think of amps, not watts. A Boulder 30 puts out 2 amps. The specification is that only 4 Boulder 30's can be daisy chained, giving you 8 amps. The battery is 40 amp-hours so do the math: 8 into 40 if the battery is flat dead (which you should avoid) but that's 5 hours. Three Boulder 30's will go from zero to full in 7 hours or less. I was surprised to get 24 watts (on a slightly hazy day) charging which is nearly the rated power of the solar panel. That's rather unusual and relates to the Boulder series lower open-circuit voltage which stems from fewer actual solar cells. Less waste in other words. The photo of charging at 14 watts was early morning with hazy sunlight, single Boulder 30, so not that strong. UPDATE (14 Aug 2017): Best inverter regulation I've seen. At 55 percent battery, the inverter provides 117.9 volts AC RMS into a load of 50 watts. The battery itself, at 55 percent remaining, measures 10.96 volts unloaded and 10.91 volts providing 50 watts into a load. That's remarkably low internal resistance in a battery.