Mark, thanks very much for your review of the LightSaver Max. We’ve been working with Powerfilm for over 15 years now, and they are always excellent. We will forward your review to their marketing team. I’d like to respond to a few of your comments in order to clarify a few points for readers. Powerfilm made some very specific design choices for this product. First, the output limit of the battery is the determining factor in how much power the unit can deliver. The 5A limit for a Lithium Polymer battery pack of this size is very generous, and for safety reasons, this limit is set. If you noted that the unit heated-up at 4A, this is an indication of stress on the battery. 3A is more typical for small LiPO batteries (ie 2C rate). Note that Powerfilm has had this LightSaver Max off the market for almost 2 years now as they are in the process of upgrading the battery. We are keen to see the results. Your comment regarding the nature of the solar module itself is unfortunately incorrect. Powerfilm’s technology is Amorphous thin-film, not Polycrystalline. Powerfilm’s amorphous cell technology is deposited on a flexible poly substrate that allows it to be extremely lightweight and flexible. Hence it can be wrapped around the LightSaver Max’s battery for easy transport. This thinfilm cell technology is less efficient than standard monocrystalline solar cells (less than half as efficient), but this only means that the same solar panel area would provide 20W peak if it was monocrystalline instead of amorphous. But, such is the trade-off for extreme portability. While only 50% as efficient, amorphous is more sensitive. This is why thin film is what gets used in solar calculators that work indoors. Thin film will reach threshold voltage and start producing useable power earlier in the day, and later in the afternoon than crystalline. Hence, a 10W amorphous solar panel can generate more useable energy over the course of an entire day than a 10W crystalline panel will (but it will be twice as large, and not as long-lived chemically). When we outfit Parks Canada research teams with pack-in/pack-out solar equipment, it is almost always Powerfilm thin film. Lightweight & effective are the main power system design concerns. Your last comment regarding the charge indicator is well taken. The LEDs approximate battery state-of-charge in 20% intervals. When the unit is exposed to light, it will indicate the level it is charging at. For example, if the battery is showing 3 LEDs, it is somewhere between 60% & 80% full. Roll-out the panel, and it may start flashing the second LED to indicate that it is charging the 40-60% range. This may only be for a short period of time, but it is somewhat misleading. I see this behaviour on many battery packs. If you would like a more powerful version of the LightSaver Max, this can be built using their standard rollable solar modules and a LiFePO4 battery pack. Single panels are available up to 60W in this weatherproof format, and a good battery match would be 20Ah. Not as portable as the LightSaver of course, but much higher output capability (for comparison: 20Ah, 12V LFP battery can deliver up to 40A). Cheers!
