### Author Topic: Making every photon count?  (Read 2237 times)

0 Members and 1 Guest are viewing this topic.

#### jwhitmore

• Regular Contributor
• Posts: 155
• Country:
• Software head strays into the Hardware.
##### Making every photon count?
« on: November 05, 2016, 02:55:38 am »
Still learning stuff, mainly from youtube videos and looking at other people solutions but I have a question about making the most out of the photons.

In an ideal world every photon would add stored energy to the batteries, but it appears that if you're charging 12V batteries you're not going to store anything until the voltage from a solar panel reaches a value above 12v. Maybe it's not worth chasing after the energy of a 9V solar panel as you'd have to add fancy electronics and charge pumps or something. Maybe you could charge a different battery technology at a lower voltage which would require the intelligence of a micro-controller which might burn up more energy then you'd generate so there's no point chasing after that energy.

Yes perhaps many more youtube videos are required. I have bought a few books but none I was happy with, basically they had a list of things to plug together which didn't help my understanding of the subject.

#### Kleinstein

• Super Contributor
• Posts: 14155
• Country:
##### Re: Making every photon count?
« Reply #1 on: November 05, 2016, 09:05:21 am »
If the open circuit voltage on an solar panel drops a lot, like from > 12 V to below 9 V, there is only very little power (e.g less than 0.1 % of rated power) left to be used. So usual it is not worth the effort. The more important point is to have good efficiency when you have a reasonable amount of light (e.g. 20%-90% of rated).

The usual way to get high efficiency in charging a battery from a solar panel is using a panel with a somewhat higher voltage (e.g. 18-25 V for a 12 V battery, that is actually more like 14 V when full) and have a step down converter, that keeps the solar panel at its maximum power point.

#### jwhitmore

• Regular Contributor
• Posts: 155
• Country:
• Software head strays into the Hardware.
##### Re: Making every photon count?
« Reply #2 on: November 05, 2016, 12:29:15 pm »
Thanks a million for that response, you've answered my question and saved me a load of thought ;-) thanks again

Smf