E = 1/2 C V^2

10x 2.7V 500F capacitors
35 x 60mm
500F:
-> E(14V) = 36 kJ
-> E(10V) = 25 kJ
-> E(14-10V) = 11 kJ




16 x 27 mm


12V x 20A = 240 W
say a 4 second tug
that's 1 kJ
E = 1/2 C (Vf^2 - Vi^2)
C = 2 E / (Vf^2 - Vi^2) = `2 * 1k / (14^2-10^2)` = 20 F
So we're talking super-cap range

A 9ah battery is like $22

https://www.digikey.com/en/products/detail/abracon-llc/AHCR-S04R0SA227Q/23018981
$7.20
220F - max storage is 1.76 kJ

https://www.digikey.com/en/products/detail/abracon-llc/AHCR-S04R0SA127Q/23018999
$5.17
100F - max storage is .80 kJ

oh but these all have peak currents of like 10A
and what do you do after dark
and on and on

just put a damn battery on it and move on to the next problem



PWM vs MPPT chargers
- MPPT are up to 30% more efficient, especially in lower light
- PWM are simpler
- Both need a microcontroller I guess


https://www.instructables.com/DIY-1kW-MPPT-Solar-Charge-Controller/
https://github.com/opensolarproject/OSPController/wiki
https://www.arduined.eu/arduino-solar-charge-controller/
https://hackaday.io/project/159708-arduino-pwm-solar-charge-controller
http://www.andrewwhyman.com/blog/electronics/arduino-pwm-charge-controller/
https://web.archive.org/web/20161023034412/http://256.uk/?page_id=23
![[MPPTschematic.jpg]]

https://www.solorb.com/elect/solarcirc/scc3/index.html


how to drive an IRF4905 - should be able to replace BC337 with 2N3904 (but how are those BJTs not a short?)
https://forum.arduino.cc/t/automotive-pwm-control-of-p-channel-mosfet-irf4905-as-high-side-switch/434372/93
![[a5f9f8ce1c919c81156c09ffb5a3e5eed443ef58.gif]]


https://www.instructables.com/ARDUINO-SOLAR-CHARGE-CONTROLLER-Version-20/


https://github.com/gameinstance/switcharger

![[getnt29x2jjg7gb9.png]]