Solar panel question.

[steve99]

Hello,

i am usin a small 5v 40mA solar panel that will be left in the sun all day to charge a battery. I am having difficulties in choosing a correct battery for the solar panel and have a few questions which i am unclear about.

First off can i can use rechargable lithium (phone batteries) Ni-mh, Ni-cd etc? Secondly if the battery is only 300mAh and there is full sunlight will it cause the battery to overflow and blow? Lastly what voltage battery should i for a 5v siolar panel? Is 3.6v ok?

Thanks.

 

[mister_rf]

At only 40mA and max 5V you will charge in single day for a period of 10h-12h sun exposure something up to 400-500mAh capacity . Of course nowadays 500mAh is obsolete but using a larger capacity doesn’t help too much.
If we consider some losses in the charger circuit and usually an typical element Ni-MH fully charged at 1.45V you can use maximum 3 elements to produce 4.35V or a single Li-Ion cell (maximum charged at 4.1-4.2V). The type of the battery is related to the charger used for.

 

[siongboon]

You can't connect a panel to battery directly.
At least put a diode in between from the direction solar to battery.

For the type of battery you mention, a charger circuit is recommended.
Some sort of voltage regulation.

 

[Audioguru]

Your little solar panel will produce 5V at 50mA only if it is noon and it is in the Sahara desert with it pointing straight up at the sun.
Its output might be only 30ma at noon where you are. From 7AM to noon the average current might be 10mA. The same for 2PM to 7PM.
So it might have an output of only 150mAh per sunny day.

The lithium battery might catch on fire if it is over-charged.