Greetings all, this is my first post here.
I'm been learning electronics for years now and would like to work up towards being confident in power generation, regulation and storage. At present i'm working on what would seem to be a really simple project but i've encountered some niggles which I hope I can resolve after posting here lol. Basically the system is just a 10w 18v multicrystaline solar panel with a battery pack and a dc dc converter integrated so that I can have power on the move. At present its very basic and I simply have the output from the solar panel outputting directly to a 9.6v 1000mAh nicad battery pack via a 2N4001 diode. The dc dc output converter is strapped directly to the battery terminals after the diode.
Some of the devices I use are sensitive to undervoltage and would prefer no volts to low volts. Without resorting to LM IC modules what is a simple voltage trigger circuit? Ive tried using a 12v zener diode in reverse so that if the volts are over 12v the 2N3906 PNP transistor's base is saturated letting the main 12v pass to next stage but for some reason it just stays stuck on and the volts seemed to level out at 7v. This is on the output of the dc dc on the final stage. Ive also noticed that the dc dc outputs wrong volts (always lower not higher) when amps and volts jump around and down lots as clouds cover sun.
Really id like some better batteries to act as a larger buffer incase the sun goes in. Now at the moment ive been using nicad but to be honest they are not really the best solution and can suffer from erratic discharges and other issues. I wondered about lithium ion but then they can explode so then I thought perhaps lithium phosphate for safety. But if I buy protected cells can I trust the overdischarge and overcharge circuits? Should I have a separate charge protection circuit? If the batteries have protection PCB could I not just have the cells hooked up like the nicads? Or I wondered if perhaps I could use some of the LM324 quad op amps I have lying around to rig a comparator circuit to monitor the voltage and switch charger on and off. Im not sure how I can have the charger integrated on a system that is linked to the solar output and charging and discharging randomly as use fluxuates. Other systems ive seen seem to disconnect the source and drain to check battery voltage using a microcontroller. I have an arduino which im also learning to use if anyone thinks perhaps that is the way to go. As for the capacity of the cells im thinking 3.7v 2400mAh 18650 seems he most common place,I saw some real nice Headway 10000mAh 3.2v 38120 cells which would seem to have great capacity but I cant find anywhere other than alibaba to buy them in quantities less than 100x. I figure having four 18650's in series so that I get 14.4v with 18v solar panel to charge. Or I could have a dc dc buck converter to take any solar output and step it down to the exact charge voltage of four cells half series half parallel (8.4v) to give better overhead with solar input. I also wondered about setting the charge system to only charge batteries 80% based on max charge volts to avoid complicated circuitry and excessive battery wear. Anyhoo that's where im up to at the moment.
Thoughts appreciated, kind thanks.
I'm been learning electronics for years now and would like to work up towards being confident in power generation, regulation and storage. At present i'm working on what would seem to be a really simple project but i've encountered some niggles which I hope I can resolve after posting here lol. Basically the system is just a 10w 18v multicrystaline solar panel with a battery pack and a dc dc converter integrated so that I can have power on the move. At present its very basic and I simply have the output from the solar panel outputting directly to a 9.6v 1000mAh nicad battery pack via a 2N4001 diode. The dc dc output converter is strapped directly to the battery terminals after the diode.
Some of the devices I use are sensitive to undervoltage and would prefer no volts to low volts. Without resorting to LM IC modules what is a simple voltage trigger circuit? Ive tried using a 12v zener diode in reverse so that if the volts are over 12v the 2N3906 PNP transistor's base is saturated letting the main 12v pass to next stage but for some reason it just stays stuck on and the volts seemed to level out at 7v. This is on the output of the dc dc on the final stage. Ive also noticed that the dc dc outputs wrong volts (always lower not higher) when amps and volts jump around and down lots as clouds cover sun.
Really id like some better batteries to act as a larger buffer incase the sun goes in. Now at the moment ive been using nicad but to be honest they are not really the best solution and can suffer from erratic discharges and other issues. I wondered about lithium ion but then they can explode so then I thought perhaps lithium phosphate for safety. But if I buy protected cells can I trust the overdischarge and overcharge circuits? Should I have a separate charge protection circuit? If the batteries have protection PCB could I not just have the cells hooked up like the nicads? Or I wondered if perhaps I could use some of the LM324 quad op amps I have lying around to rig a comparator circuit to monitor the voltage and switch charger on and off. Im not sure how I can have the charger integrated on a system that is linked to the solar output and charging and discharging randomly as use fluxuates. Other systems ive seen seem to disconnect the source and drain to check battery voltage using a microcontroller. I have an arduino which im also learning to use if anyone thinks perhaps that is the way to go. As for the capacity of the cells im thinking 3.7v 2400mAh 18650 seems he most common place,I saw some real nice Headway 10000mAh 3.2v 38120 cells which would seem to have great capacity but I cant find anywhere other than alibaba to buy them in quantities less than 100x. I figure having four 18650's in series so that I get 14.4v with 18v solar panel to charge. Or I could have a dc dc buck converter to take any solar output and step it down to the exact charge voltage of four cells half series half parallel (8.4v) to give better overhead with solar input. I also wondered about setting the charge system to only charge batteries 80% based on max charge volts to avoid complicated circuitry and excessive battery wear. Anyhoo that's where im up to at the moment.
Thoughts appreciated, kind thanks.