Hi guys,

I am trying to measure the actual harvested energy from the solar panel and get the relationship between the energy (or power) and the time. Also, I want to measure the actual energy consumption (real-time) in the waspmote.

Do I need an external device to do it, such as current-voltage logger? If yes, should I connect it to the solar panel or directly to the battery? Which pin is for the charge circuit and which is for the power supply? Can you give me some guides how to complete these two tasks?

Thanks.

Mike

Hi Mike2012,

you may monitor the battery charge level and have a reference of the balance in energy consumed and gathered, but that won't give you an accurate measurement.

You will need a current sensor to monitor both the current harvested from the solar panel and the current from (or into) the battery. You may use a non invasive sensor (a DC current clamp) or an invasive sensor, such as an integrated circuit sensor, that will be cheaper but will need of an electronic adaptation stage.

Regards.

Thanks for the quick reply. I have a few more questions.

1) Do you mean the output voltage level of solar panel is always equal to the battery voltage so we can read batter level to get the voltage reading?
2) If I want to add the ammeter, should I cut the battery cable to insert it or cut the solar panel cable to insert it?
3) Here, can I separately measure the current harvested from the solar panel and the current from the battery?
4) I know that solar panel itself cannot power the sensor node. Then, during sunny, daylight
hours, will the solar panel charges the battery and also powers the sensor nodes? Or the battery is charged by the solar panel and also power the sensor node at the same time?
5) I found that solar panel cannot charge the battery to reach 100% level. The battery level reach 95% at noon and then cannot go up even though there is sun insulation during afternoon. Is it normal? Can you let me know why?

Thanks.

Hi Mike2012,

1) No, what I meant to say was that a rough way to measure the energy balance is to monitor the battery voltage, which is a function of the battery charge, and though it is a very inaccurate method it may be a first approach that requires no hardware modifications.
2) There are non-invasive current clamps to measure the current through a wire, they may be bulkier and more expensive than other systems but you wouldn't have to cut the wire.
3) You can, but you will need two devices, one for one of the solar panel wires and another for the battery. Monitoring both currents, if you subtract the first one to the second one you will have the mote consumption.
4) The solar panel only charges the battery, the current to power the circuit is sourced from the battery.
5) It is normal, owed to the way the charge monitor was implemented (not all the batteries have the same exact voltage when fully charged) and the balance between the current consumed to power the circuit and the minimum charge current of the battery, dependent of its charge.

Regards.