- Fri Nov 20, 2015 7:43 pm
Hi, I've looked at Li-x batteries with regard to solar charging & it's a bit of a minefield. These batteries don’t easily lend themselves to charging from solar (where the full charge my not be completed, not enough sunlight) or when they are being discharged during charging.
I came to the conclusion that if space isn’t an issue, use 8 NiCd & a 12V solar panel.
buck stepdown (buck / boost to max potential)->
charge regulator ->
Discharge limiter ->
Buck stepdown ->
This doesn’t benefit from the latest technology, but should work. As we are looking at 500 charges from a Li-x battery if you nurse it, as opposed to 1000 from NiCd which are far more tolerant to low or incomplete charge cycles.
The other complication is that Li-x charge at about 4.2V, which is above the recommended supply for an ESP. Whilst an ESP can be powered (not recommended) from 4.2V if you do the current consumption increases & defeats the point. That means you will need a voltage regulator, unfortunately most have a +1V dropout, which means that you start voltage is 3.2V (4.2 - 1.0 + 3.2V) & will drop from there, as it’s reported that the ESP will operate with voltages as low as 2.7V this sort of works.
I have a project running at the moment & rather than using a voltage regulator I’ve used a 0.7V drop diode in series with the supply, this delivers 4.2 – 0.7 = 3.3V -> 3.7 – 0.7 = 3.0V, which is about the bottom limit for Li-x under light loads (yes 3.0v if your discharging at C10, but we are not) and if you sleep this has implications.
Anyway just my thoughts, Li-x great for aircraft and cars if you want 15 minutes of max power and 2 to 4 hours of controlled charging. NiCd use and abuse then bin and replace.