Lithium Battery Upgrade Solar Outdoor Light with Overcharge Protection

Old 10-13-17, 09:39 PM
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Lithium Battery Upgrade Solar Outdoor Light with Overcharge Protection

I want to buy a few outdoor light kits that use a solar panel (and batteries). I came across a video where someone showed some of these units are being shipped with NiCad batteries. Also, there is no overcharge protection within the circuitry so the batteries are not lasting as long as they could which is probably why some people are having problems with them lasting.

A guy online upgraded from the NiCad pack (6v nominal) to two 186500 Li-Ions ( 7.2v nominal). A person responded to that by stating he would need a Lithium Battery 18650 Charger Protection Board (which is shown below). Another poster said to use a buck converter to lower the voltage coming from the solar panel.

The buck converter and the Charge Protection Board are both inexpensive and seem like an easy upgrade.

Can anyone confirm this upgrade would likely work? If using a buck converter what would be a good ideal voltage to lower it to? Would the Charge Protection Board work and be a better solution?

This was an old post and no one ever confirmed this to be a viable solution. Thanks for any feedback.

Charge Protection Board
Main function:
Over charging protection, over discharge protection, short circuit protection, over current protection function.

Technical parameter:
Overcharge Detection Voltage: 4.25-4.35Vą0.05V
Over Discharge Detection Voltage: 2.5-3.0Vą0.05V
Maximum Working Current: 5A
Transient Current: 7A
Quiescent Current: less than 5uA
Internal Resistance: <300mΩ
Short circuit protection: can be protected, need to recharge recovery.
Effective Life: >50,000 hours
Operating Temperature: -40-50℃
Size: 38x 8x2.5mm

Adjustable Buck Converter Step Down Module Power Supply 1.23V-30V
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Old 10-14-17, 05:40 AM
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NiCd work quite well and generally provide a couple years service. When you think that that is 700-1'000 charge discharge cycles then the stock lights perform pretty well. So, I would not do your project in an attempt to improve the light but it could be fun if you want to do it just for the sake of a project.

If you attempt this project I would do some reading and learn how to charge lithium cells. There is a reason NiCd cells are used in inexpensive solar devices. They are easy to charge. They handle abusive dumb charging and they are safe. Converting to lithiums will require you to be on your A game as far as charging.

One of the first issues that comes to mind with your plan is it sounds like you intend to charge the 18650's in series and do it with simple voltage limiting. Have you checked the output of the solar panel? How much amperage can it produce, which leads me to wonder if it will provide more or less than a 1c charge rate?
Old 10-14-17, 10:00 AM
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I've been rethinking this.

I'm concerned about the batteries because it seems this is where the complaints come it. Not everyone has a complaint but those who do blame it on the batteries.

Instead of lithium batteries I was thinking about buying a 12ma 6v battery lead acid (SLA) battery like the pictured. They have them for under $20.00. I could run all my lights from that. This way I could ditch the solar panels and just trickle charge the battery on occasion. I would also be able to keep the large battery indoors such as the garage at better temperature and away from freezing and very warm temperatures.

I probably would just use the lights with the supplied batteries until one fails. The battery packs are close to $15 so if/when it's time I would buy the large battery.

I don't have specs on the solar panels yet. I'm thinking 18g thermostat wire would be enough to run power from the larger battery to each solar light I don't know though for sure. The included battery packs are appr. 6v 900mAh.

I also don't know if the panels that come with the lights would be enough to charge the large battery but I don't really want to spend too much time if the larger battery works well.

I know I'm getting ahead of myself but it would be nice to have one central battery. Once it was set up I may not have to worry about a battery for 5-10 years and changing it would be from one central location.

I've included pics of the batteries that may come with the lights. It's hard to say which ones would come with it because so many companies make these but the batteries are different.

Any thoughts on this? Thanks.
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