I need help building a 1.3V solar charger from garden light cells?


I need some help with building a solar charger...I don´t know much about electronics, maybe one of you has the patience to answer a few questions?

The device I want to charge has a label that says 1.3V=2W (there is 1 rechargeable Nickel-Cadmium battery inside), the wall charger is labeled 1.3V=1500 mA...

I have 2 solar cells from garden lights, they both were used to charge two 1.2V batteries with 600 mAh (in series). That´s all I know about them, I have no way of measuring the output...

My questions:

1. How many Volts (at least) does it take to charge that device?
2. How many Volts can the battery take without getting damaged?
3. How many Volts do I usually get from those garden light cells? If they charge 2 batteries (1.2V) in series it should be 2.4V, right?
4. If 2.4 Volts is too much for the device, how do I limit it?

I would like to build the charger without buying a multimeter and the parts will be salvaged from other stuff...I hope...

I know those are a lot of noob questions but I would really appreciate your help!

yamata452 years ago
Hi Fypsigon

I'll give you my best shot at an answer. The two pieces of into you'll have to find out is:
1. What is the rating on the NiCa battery? probably 1.2V at around 600/1200 mAh
2. What Voltage and Amperage will the solar cells output?

From my experience with Garden Solar Cells, they put out about 2.4V at 47-50 mA each. So you are right about that. If they are wired in series, they put out 2.4V at 40-50 mA, which means it would take about 12 hours to charge the 600 mAh battery fully. It would then output 600 mA for 1 hour, or 100 mA for 6 hours, as you convert.

I'm confused about your "Device" and the "Wall Charger". Are they the same device? 1.3V at 2W is about 1500 mA or 1.5A. Do you want to power the device itself, or are you hoping to recharge the battery through the device? Depending on what you want to do, the answer changes.

Hope this helps!

Fypsigon (author)  yamata452 years ago
Thanks for the answer so far!

The "device" is an electric razor with 1 NiCa battery inside (that´s all I can see, I would have to break the thing open to see the rating)
The label that says 1.3V=2W is on the outside of the electric razor...

I want to charge that battery with the 2 solar cells...