MPPT - but with low voltage input (max 7V) and low power transfer ( ~3W max)

Using Arduino Project Guidance
1

Hi,

for my Arduinos I want "Free Energy" :slight_smile:

I bought two solar panels rated 6V 500mA 3Watt (15cmx16cm each).
When directly pointed to the sun its 7.1V open circuit and 450mA short circuit.

To optimize power transfer I want an MPPT...BUT
I googled a lot and found a lot of MPPT schematics out there....
with bulky cooling devices, BIG MosFETs, XXX-Amp fuses and such.

I need an MPPT design for just 3Watts for each of the panels to
(for example) just charge one LiPO cell.

May be I used the wrong keywords (I am no native speaker) or
"this thing" is named differently when applied to lower Watts.

What can I use for this purpose?

Thank you very much for any help in advance!
Best regards,
mcc

2

Something like this, with the LT3652.

Leo..

3

Hi Wawa,

thank you for your reply! :slight_smile:

Yeah! That's /nearly/ ideal.

The only "BUT" is: Minimum input voltage is 6V. My Solar Cell is rated
6V 500mA...so if the sun does not directly hit the surface of the
panel I will get less than 6V. So in most cases...

But anything like this with -say- 3.5V minimum voltage would
be "That's it!"

Any idea?

Cheers!
Meino

4

The principle to make an MPPT is the same whether the voltage is low or high.

You need to monitor the panel current and voltage and adjust the load to maximize the product of the two.

To use the Sunny Buddy you could meet the 6V minimum by wiring the two panels in series. The voltage produced by a solar panel does not depend strongly on the illumination, but the current does.

5

The chip is a buck converter.
High voltage/low current is converted in low voltage/high current.
If the two panels in series produce 10volt/300mA, you could get ~600mA into your single cell battery.
Leo..

6

An MPPT is usually not useful for very small power levels, as the best that you can achieve is about a 30% improvement.
Its cheaper to simply add another Solar Cell.
And you will need a suitable battery.

7

You need some sort of charger chip for a LiPo battery anyway, so why not pick one that can do MPPT as well.
Downside is that those chips are expensive.
Leo..

8

You may also want to document yourself about "low power Arduino". When not in use a Pro Mini can be put in sleep mode to consume down to few microamps, or tens of microamps.
For most sensing/communication projects a 500mA should be sufficient.
What else, besides Arduino, do you want to power, what is your power budget?