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Useful article! There's one thing you didn't consider: Charging temperature. Lithium charging temps are typically 0 degrees Centigrade. Any lower could damage t
by SlowBro 9y ago
Useful article! There's one thing you didn't consider: Charging temperature. Lithium charging temps are typically 0 degrees Centigrade. Any lower could damage the cells. NiCd is a bit better and there are some low temp NiMh but for the ultimate go with lead acid. They are not small but there are cells the size of a D battery.
- retSava 9y agoThanks! You are correct, the li-poly I've looked at specify basically the same operating temperatures, discharge: -20 to +60 deg C charge: 0 to +40 deg C Exactly, the energy density is much less with lead acid, and they also have poor low-temperature discharge performance. I wonder at what level a very insulated and slightly heated (if temp < 0) li-poly would be better? I see there is still room for improvement in the system model we've used in the article :) Stay tuned for the sequel! We plan on doing one on indoor-solar powered devices too :)
- SlowBro 9y agoSince charge time occurs during the middle of the day when both ambient temperatures are higher, and sunlight is warming the enclosure, and since charging slightly warms cells, and since electronics also warm cells, you have a better chance of reaching the minimum low charge temperature. Maybe add some aerogel insulation? Also, active heating could work; requires a larger panel though. This solar-powered Pi project integrates a battery heater: https://hackaday.io/project/13260-lifepo4weredsolar1 https://hackaday.io/project/13260-lifepo4weredsolar1