charge battery with solar panel - Page 1
Forum section: electronics / beginners

author: knarf.be
author_rank: Contributor
timestamp: March 11, 2013, 07:39:25 pm
content: Hi,I want to charge a 6v lead battery with a solar panel.Specs solar panel:5w (Voltage drops to 4v)Voltage max in sun 9.5vVoltage in shade 8-9vBattery specs:4 Ah6vLead sealedWhat is the best option to charge the battery? I want a system with a verh low voltage drop, and im using a ge diode to protect the solar panel.Currently I'm planning to use a lm7807 low drop and diode, vin is 7.5 and higher, vout is 6.6v.Anyone other ideas? Please let me know

author: SeanB
author_rank: Super Contributor
timestamp: March 11, 2013, 09:10:16 pm
content: 1A Shottky diode in series with the panel and connect across the battery. 5W panel will not overcharge the battery, it does not put out enough to drive the battery to the point where it will generate gas. It would be better to use a second panel in parallel to increase the current though, the panel is just too small to get any useful power out of it.

author: commerou
author_rank: Contributor
timestamp: March 12, 2013, 08:27:54 am
content: HiI want to charge a 12v lead acid battery with a 12v 13w solar panel, do I require any kind of circuit or could I just hook it straight up?

author: knarf.be
author_rank: Contributor
timestamp: March 12, 2013, 12:10:19 pm
content: Quote from: commerou on March 12, 2013, 08:27:54 amYou always need a diode, and thanks to seanb, I know now it has to be a Shottky.But for 12v you better use a cheap off the shelf charger. (These aren't available for 6v) Just look on ebay.As far as I know it will destroy your battery without a descent charging circuit.

author: Kevin.D
author_rank: Frequent Contributor
timestamp: March 12, 2013, 12:43:38 pm
content: Quote from: commerou on March 12, 2013, 08:27:54 amDepends on the capacity of the lead acid battery .But for a car battery size (~60Ah) you can usually leave upto 10 Watt's max size panel on permanently without a regulator , but for 13 Watt panel I would use a regulator if it's conected permantley to prevent overcharging

author: SeanB
author_rank: Super Contributor
timestamp: March 12, 2013, 06:46:08 pm
content: With a car battery ( especially as you can check water level) the 13W panel is ok, it will keep the battery close to full charge and will only need checking every month for water level.

author: ivan747
author_rank: Super Contributor
timestamp: March 12, 2013, 11:50:06 pm
content: Just a tip. Diodes have a smaller voltage drop at higher temperatures, so don't heatsink them more than necessary! In fact, you may even want to place the diodes in the sun to heat them up. And don't use a 1A diode for a 1A solar panel. Why? Because it is operating at its maximum rating. Its lifespan will be shorter and it is more likely to fail. Also the voltage drop will probably be higher.

author: ZOMGVTEK
author_rank: Contributor
timestamp: March 13, 2013, 12:17:49 am
content: A car battery won't mind a 10W trickle during daylight hours. Lots of panels, especially smaller ones, have diodes built in, so that might be unnecessary. Just something to be aware of. You run into this a lot more with cheap 12V panels, since they typically have battery charging in mind.

author: knarf.be
author_rank: Contributor
timestamp: March 14, 2013, 05:14:54 pm
content: It may be possible to charge it with 9v without problems, but I think it wil lower the battery life.For now I've got a simple lm317K and a few resitors, and it seems to work fine, but there is a voltage drop of 1.5V. And if i have to use a si shottiky, there will be to much voltage drop.I attached some photo's of the circuit, using a 5W 10 Ohm resistor as battery replacement.

author: commerou
author_rank: Contributor
timestamp: March 14, 2013, 06:33:12 pm
content: Thanks for all the replies, as mentioned by ZOMGVTEK the solarpanel is made to the purpose of charging batteries from caravans, but mine would'nt charge anything, I guess I'll have to check all swithes and wires again.