Remote Living > Lighting
another NiCad to LiFePO4 conversion
(1/1)
dnix71:
I have two led shed lights bought from Home Depot several years ago. They use a 3 cell AA nicad pack to power 5 leds. The battery pack is identical to the one used in many older cordless phones.
The original plastic rocker on/off switch on both failed after a few weeks. Since I knew it to be a defective design, instead of returning the lights, I went to Radio Shack and bought 2 proper metal toggle switches and fixed both.
The shed lights are solar charged from a small thin-film panel that has a 10 foot cable for remote mounting. Fully charged when new the lights would run for at least 4 hours
The one in my bathroom worked well for a while and then on cell on the outside of the pack went bad. I replaced the bad cell. Today I noticed a second cell was getting weak and decided to try a LiFePO4 cell instead of tearing the pack apart again.
It works. The AA sized 3.2v LiFePO4 cell was put in a AA holder and the original pigtail connector cut and soldered to the new cell holder.
The second pic is a closeup of the circuit that drives the leds. The diffuser was removed so you could see the leds clearly.
vtpeaknik:
Is this "AA sized 3.2v LiFePO4 cell" a standard (?) 14500 (or 14505) cell? Does it have a built-in circuit to prevent overcharge? I wonder how well it will work in cold conditions. My outdoor solar LED motion-sensing light worked OK for a year or two but then stopped working most of the time in the winter, when I actually need it. Perhaps I should put a Lithium cell in it like you did.
dnix71:
The cells I use are plain cells. They are physically an exact match for a common AA cell. Rechargeable outdoor led lights use lipo cells now. Just take the light apart and you may find it uses something Radio Shack sells. I can get these cells at Radio Shack, but they don't sell chargers. That's not a problem if you are just replacing a cell in an outdoor solar light.
vtpeaknik:
Well if the solar panel is in a sunny spot it may over-charge the battery, and Lithium batteries are famous for fireworks. I was even worried about the NiCad battery overcharging, so put the panel of my motion sensing light in a location where it gets limited sunshine. That turned out to be not enough light in the winter, perhaps.
Any easy way to add a simple "charge controller" of some sort to this? E.g., a zener diode of about 3.6V in parallel with the battery? (If there is such a zener diode available.)
Harold in CR:
From my very recent search for the Radio Shack cells, they are no longer available ???. Not in the Solar application anyway. ?
I had to go to Hong Kong and buy a pair of 700MHR 14500's. Got them in less than 10 days to Florida. Now, to get them sent down with other goodies, in the next 3-4 days.
Navigation
[0] Message Index
Go to full version