well yes, with the usual warning.
first to clarify your speaking of li-ion as the rechargable.
the protection is not designed to be the charge curcuit, its desgned to be the protection, the charger itself should still stop at the peak voltage.
It is preferable that when it gets close to the end of charge, the charge slows down a bit.
solar charges faster if there is a wider voltage differential, like say a 6V max cell set to charge a 4.25v max battery. with a higer voltage differential more amps flow. this is true of anything, but was more important with solar.
you could potentially put one of many types of voltage cutoffs or li-ion charge chip thing on the solar side, basically doubling up the protection, or giveing the "charger" a "proper" charge curcuit, then use the protection for the protection that it is (for the battery).
now with that said, i have put a protection curcuit on the end of a 6V max solar pannel, and use it to charge unprotected and protected li-ion batteries.
to achieve the ramp down in power, preffered for the proper charging of a li-ion, a person could use a 5V set of cells, or pannel thing, the normal type of diodes that have a .5-.7 volt drop, on a protected battery, and have an almost totally proper safe setup. There would be little power moving when the 4.3V point was reached.
IF the solar charge is slow small pannel thing, then the need to ramp down at the end of charge is much less nessisary, as the charge rate is already low.
with your usual solar stuff used in outdoor lighting , the charge rate is very low for the long time it can have sun. and consumption of that charge is 1-3 5mm leds that light up about 1 foot
ni-mhy or ni-cd is a better choice when size, weight, and self discharge are not issues, like on landscape or pond lighting stuff. and with the slow charge, and constant discharge/recharge ni-mhy would really love to perform this task and it should give many more cycles if you use good batteries.
with solar when the sun is clouded, and the pannel puts out little power, the voltage does not sag much, it is the current or rate of charge that sags most when there is not direct sun.
Because of winter, and clouds and shadows, and angle of sun, and all the stuff that has solar working poorly. a setup that had Vast backup capacity, and large solar pannel, charging strongly, would be important if you MUST have it working Every single night. like 3-5 times the juice needed to operate the light.
so lets take an example of a simple single high powered led, running at 500ma including inefficency of any curcuit. you want it to run for 14-16 hours max , after a 6-8 hours of sun (winter).
so you already need 1500ma, if you dont use solar Tracking, you lose about 40% sooo lets start with 2500ma pannel. ok now for 3 days it rains and is cloudy, now you need about 3500ma pannel.
3.5A x 6V = 21 watts , no problem just 2 square feet of pannel.
now we need to make it through the 3 days, with it still operating for the 14-16 hours a night. 8000ma of battery capacity per night, or 24amps of backup. soo we just need about 10 18650 type li-ions. or 4 big fat li-poly batteries.
with a 3500ma max output pannel, you will need about 3 of the 18650 batteries minimum , just so the charge rate is ok for them.
basically either think BIG with the solar pannel, have some good backup capacity, or just have the thing die (cutoff) after 3 hours of operation each night, and not light up on cloudy winter nights, or Best, turn it on for the 20 minutes your going to actually use it, and turn it off when done. or motion sencors.
Solar teaches more about being effecient, than it teaches about alternative energy, conservation is then learned
sombody check my math.
