For my project I am hoping to have my Arduino and hardware running off a 12v 100ah leisure battery, which I am going to keep charged with a 20w solar panel. I have been told a couple of times that I "should" be able to wire the panel to the battery as the system will prevent the battery from being overcharged and I wont need a charging unit.
I'm a bit of a noob when it comes to electronics so am unsure of what diode I need to place across the panel.
Do I need one for the amps of the battery or the output of the panel??
I already have 1N4001 and 1N4742 if either of those are suitable.
For low power solar systems, you can put a diode in series with the positive lead from the panel to the battery, to keep the battery from discharging during the night. However, it is possible that the panel could cook the battery if you are not using it, so be skeptical of the advice you are getting.
A 20W panel might provide 6-8 Ah per day, which is not much. It will only keep the battery topped up, and only if you use the system lightly.
The OP is a Noob. Speak English. He wouldn't know a shunt regulator from any other kind of regulator. I think you should spell out what that means to him. I could do it but it was your comment. 2n3055+shunt+regulator
Do I need one for the amps of the battery or the output of the panel?
What's the most current the panel can output at any given moment under ideal conditions ?
IainStott:
I have been told a couple of times that I "should" be able to wire the panel to the battery as the system will prevent the battery from being overcharged and I wont need a charging unit.
I've heard this called the "3% rule" for lead acid batteries. So for a 100aH battery you can charge it at 3A continuously without damaging the battery.
Yeah it's a legit rule, but with the price of charge controllers being so low (~$10) and giving you undervoltage lockout, etc. I'd still buy the charge controller.
Cheers for all the input guys. I will be buying a charging unit at some point as I reckon my mum will want to additions to the system over time, but for the time being if I can get away with a diode for a month or so it gives me a bit of head room.
When I was in elementary school corporal punishment was still legal but only reserved for disciplinary cases. There was no punishment for poor academic performance or student apathy. I was always being repremanded for staring out of the window (day dreaming) during lectures but they were never able to pin any thing on me because when they called on students who were NOT staring out the window and couldn't get the correct answer to the question after 3 or 4 incorrect answers from students they would call on me.
I would just give them a blank stare and ask "What was the question ?" to which the whole class would laugh. The teacher would repeat the question and without hesitating I would give the correct answer. She would stare at me in amazement and say, "Why, that's correct Robert. Very good." Then when the recess bell rang I would run out the door and ten guys would chase me around the playground until they caught me and then they would kick my ass. I really knew how to win friends and influence people... One day the teacher asks me why I am always out of breath when I come back from recess and I told her we were playing a game ..."tag. your it...." They could never figure out how I always knew the answer. I never told them that my mother dragged me (literally) out of bed at 4 am to do my homework. If I didn't get out of bed she would throw cold water on me. I had to read all my homework before school every day. If I didn't eat my vegetables I had to drink two raw eggs and a tablespoon of Cod Liver Oil. I hated spinach so it was always a "raw egg day" if my mother served cooked spinach. Yeah, my childhood was fun.
raschemmel:
.. One day the teacher asks me why I am always out of breath when I come back from recess and I told her we were playing a game ..."tag. your it...." They could never figure out how I always knew the answer. I never told
Yes i had several kickings from being a swot/clever dick.
If you were not good at rugby/thumping people , rough time, and cold showers from the PE master, who also happened to be my form tutor.
My question is about this forum though.
Newcomers often come here with pre conceived ideas from instructables.
They cannot be shaken from what they have seen and sometimes will not respond to simple questions for some reason.
I do not know how to address this.
My posting style is probably not the best and i do not know how to address this.
You "could" use a zener as a voltage regulator and then a diode as a feedback current regulator...but a zener from Farnell rated 15V @ 20W is a decent £14. Already more than the cheap 10A (120W ish) solar panel charge controllers that have more features and protection.
(good guess though:correct)