A bit late, I know, but...

The charger is fine for juicing up my cell phone (Samsung Core Prime), for several cycles, but the real issue is the slowness of the PV cells to get the charge back into the batteries again. There are four lights that show level of charge, and, while in Queensland recently (one of the sunniest places in Australia), I left the pack to recharge for almost an entire day, and it only moved the lights from one to two in that time -- I had pretty well exhausted the battery pack before this).

One thing that does slow down PV cells is heat and while leaving the pack out in the sun is what has to happen, the trade-off is that on hot days, the efficiency level goes down. It does seem to continue recharging in lower-light conditions, however. Even with full sun power, I suspect it would take three or four days to bring the batteries back to full charge.

Conversely, plugging the charger pack into my computer had the pack up to full charge in several hours.

I will keep using the pack to recharge my phone while riding in extended events such as randonnees, but I will rely more on connection to the mains with a USB adapter or to my computer than sunlight to restore power to it.