How can I stabilize the voltage to be 5V from range of 4-7V? Also what is a good homemade way to measure maximum current that the panels are capable of?
How can I stabilize the voltage to be 5V from range of 4-7V? Also what is a good homemade way to measure maximum current that the panels are capable of?
Maximum current is with a short circuit. put your VOM in current measurement position to measure AMPS and see what you get.
Your 7V measurement is "open circuit" voltage. You will not have open circuit with your battery charger. Measure the resistance of the input to your charger and put a resistor close to that value across the output of your solar panels and then measure the voltage.
Paul_KD7HB:
Maximum current is with a short circuit. put your VOM in current measurement position to measure AMPS and see what you get.
Your 7V measurement is "open circuit" voltage. You will not have open circuit with your battery charger. Measure the resistance of the input to your charger and put a resistor close to that value across the output of your solar panels and then measure the voltage.
Paul
So making voltage divider? The post under yours is also adding zener. I'd like to understand how it would work.
I have not yet bought battery charger. I'm thinking about buying pre made battery bank, it will be less hassle and it already got battery and charging circuit.
ok, after getting some time to do more research I've checked the specs of the chargers ICs and the common one is TP4056 which has –0.3 – 8V rating, if It would be greater than 8V, I think that I'd use DC-DC step down converter
The photo shows 20,000mAh on the back of the unit which is also probably nonsense, but
not quite so stupidly out.
Power bank capacities are already a bit of a scam since it based on the nominal capacity of the battery cells inside, not the amount of charge it can deliver to another battery. The "charging ability" needs to be derated by maybe 50% to cover the conversion loss.
This isn't just an online problem though. I bought a "10,000 mAh" battery bank from Microcenter. When I cracked it open, the LiPo had 8000 mAh stamped on it. A small lie, but still a lie.
For some reason, battery sellers on Amazon and ebay are horribly and blatantly fraudulent to a much larger degree than I've seen with other electronics products on there. I don't understand why.
Jiggy-Ninja:
For some reason, battery sellers on Amazon and ebay are horribly and blatantly fraudulent to a much larger degree than I've seen with other electronics products on there. I don't understand why.
Not just battery sellers.
I just received a bunch of 6watt downlights from China.
Cracked one open, and found 3watt worth of smd LEDs inside.
The 'transformer' that came with it delivered 265mA with a Vf of 9.75volt to the LEDs.
That works out to 9.75*0.265= 2.58watt.
More than a 50% lie.
Stupid tactics, because if I had known they were <=3watt I would have ordered the (more expensive) larger ones.
Leo..
Because they know that 99.95% of the general public has no concept of "mAh", they just look for the biggest number for the lowest price.
Like the 6 HP air compressors that ran on 120VAC that the "home improvement" stores used to sell, the only data on the motor was "120 volts", the 6 HP came from the 35 Amps the 1 HP motor drew when starting.