- Mon Sep 04, 2017 5:56 am
#69725
The whole point of supercapacitors is their ability to discharge large amounts of current very quickly. In your own terminology, the cap has a huge garden hose coming out of it. Like infinitely large. Please don't derail this thread by making surprising claims that capacitors cannot charge or discharge current at the same rate as batteries, because it's just not true. Caps are much, much faster. We're talking orders of magnitude faster. A cap can be charged at 100A if you want to - it acts as a short circuit until it is charged. If you take the 120F I'm talking about and charge it up completely, and then short the terminals with a piece of wire, the plastic insulation on the wire MELTS. Sounds like more than 200 mA to you?
If I charge the cap fully and then connect it to the ESP8266 (through a buck step-down) it will run for a long, long time with no problems. What I'm talking about is the voltage on the cap as it charges. Caps are not like batteries, there is a linear correlation between their voltage and their carge - unlike a battery, which is more of a constant voltage source. So when the cap charges, the voltage "slowly rises" from 0V to 3.3V, which is what the power circuitry on the ESP8266 cannot deal with. That's the problem we're trying to address here.
It's just for buffering, the main power is the solar panel. But the panel charges the cap, which causes the cap voltage to rise slowly up from 0V, which causes the problem with the logic level on the ESP8266.
philbowles wrote:a) "Tiny" ESP8266 can draw over 200mA when sending
The whole point of supercapacitors is their ability to discharge large amounts of current very quickly. In your own terminology, the cap has a huge garden hose coming out of it. Like infinitely large. Please don't derail this thread by making surprising claims that capacitors cannot charge or discharge current at the same rate as batteries, because it's just not true. Caps are much, much faster. We're talking orders of magnitude faster. A cap can be charged at 100A if you want to - it acts as a short circuit until it is charged. If you take the 120F I'm talking about and charge it up completely, and then short the terminals with a piece of wire, the plastic insulation on the wire MELTS. Sounds like more than 200 mA to you?
If I charge the cap fully and then connect it to the ESP8266 (through a buck step-down) it will run for a long, long time with no problems. What I'm talking about is the voltage on the cap as it charges. Caps are not like batteries, there is a linear correlation between their voltage and their carge - unlike a battery, which is more of a constant voltage source. So when the cap charges, the voltage "slowly rises" from 0V to 3.3V, which is what the power circuitry on the ESP8266 cannot deal with. That's the problem we're trying to address here.
philbowles wrote:"If a battery can supply an ESP8266 with power, then so can a super capacitor" are you sure? For how long?
It's just for buffering, the main power is the solar panel. But the panel charges the cap, which causes the cap voltage to rise slowly up from 0V, which causes the problem with the logic level on the ESP8266.
