Battery Charger Circuit - Page 1
Forum section: electronics / projects

author: david476
author_rank: Newbie
timestamp: February 07, 2015, 07:08:12 am
content: Hi, just started watching Dave and thought this would be a good place to ask a question! I just made a simple solar powered battery trickle charge circuit (solar panel, batteries, diode) and was wondering about an easy auto cut off for the circuit. Voltage measured on the battery side of the diode appears to be the current battery voltage so there should be a way! Could you throttle the solar panel voltage as well? Thanks for any help!P.S. I'm not new to electricity and components in general, but using specific ones and designing a circuit is fairly new to me.

author: oldway
author_rank: Super Contributor
timestamp: February 07, 2015, 09:26:04 am
content: A very easy solution is to use a 14V 5W zener diode in parallel with the battery (with the right polarity ! ) to limit the max. trickle voltage to 14V so not to damage the battery by overcharge.

author: Seekonk
author_rank: Super Contributor
timestamp: February 07, 2015, 09:54:45 am
content: You didn't indicate the size of your solar panel or battery voltage. That determines the method to use.

author: david476
author_rank: Newbie
timestamp: February 07, 2015, 07:44:26 pm
content: I'm using a 4.5V, 1.5W Radio shack solar panel and two 1.2v AA rechargeables in series.

author: lapm
author_rank: Frequent Contributor
timestamp: February 07, 2015, 09:56:04 pm
content: Personally i would make switching power supply to charge those batteries.. Sometimes you need to lower voltage coming from solarpanels and sometimes you might want ti raise it...Batteries often dont like overcharge or overvoltage... Hence even if simple circuit works for now it will most likely have serious effect on lifetime of those batteries.

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 08, 2015, 06:38:18 am
content: A solar panel that low power is unlikely to damage those batteries.

author: Rerouter
author_rank: Super Contributor
timestamp: February 08, 2015, 10:29:30 am
content: My solar pump project is just a voltage regulator set a little less than float voltage, using the solar panel voltage to control the enable pin of the regulator, so far it has been running strong with no issues,for you, after the diode have a mosfet and comparator (with some hysteresis, which is a single resistor), when you exceed the float charge, comparator switches, fet opens and it stops charging,

author: MrAl
author_rank: Super Contributor
timestamp: February 08, 2015, 03:35:06 pm
content: Hi,You really have to specify the battery chemistry and voltage.For NiMH you do it one way, for lead acid anther way, for Li-ion another way.

author: david476
author_rank: Newbie
timestamp: February 23, 2015, 05:31:49 pm
content: I looked into zener diodes and they look like a good idea, just a few questions. Why did you suggest 14v diode, charging two AAs wouldn't I want something like a 2.5V one (data sheets show 1.4V on full charge)? Could I use it to power something like a normally closed MOSFET? The original tutorial I was following said it was bad to put current into the solar cell. Again, basically a beginner to electronics so please excuse stupid mistakes!

author: david476
author_rank: Newbie
timestamp: March 01, 2015, 06:51:34 am
content: Bump. I don't know very much so I need the help. Thanks!