diy solar

diy solar

September mourn...

If his data posted here is right he should be seeing a much higher voltage on the battery's terminals with such a light load given the power taken out of the battery so he has two problems to solve.

1) needs a larger solar panel or more than one due to latitude and weather
2) has a capacity problem with the battery, it's defective or the ratings are false
 
What is the reasoning behind using a buck converter? I cannot get my head around this and suspect it is limiting more than 1 or 2 watts. Something is no adding up besides your battery capacity (which should run for several days without ANY charging).
600wh / 6w = 100h. (4 days)
Ok, maybe this is in line with expectations/graph.

I just pleaded against using regular buck converters. Real MPPT controllers are buck converters with a variable operation point.
But IMHO for small single panel operation, they do not really offer an advantage, since they are usually built for > 10A operation, where 200mA quiescent current for their own consumption does not matter.

My experience is that, under 100W, most of the 18V panels are designed to have their optimum close to the 14V anyway.
So a dumb PWM controller will do at least as well.
I have chosen an adjustable power point converter adjusted to run at its best under cloudy weather and it does not drain my battery 18hours a day for nothing, since it needs only 3mA quiescent current.
 
If his data posted here is right he should be seeing a much higher voltage on the battery's terminals with such a light load given the power taken out of the battery so he has two problems to solve.
1) needs a larger solar panel or more than one due to latitude and weather
2) has a capacity problem with the battery, it's defective or the ratings are false

OK. It was a test at home anyway. I wanted to find a solution for an unattended off-grid measuring station.
1) Going for bigger solar panels is problematic, it increases the risk of theft /vandalism and all the mechanical stuff around the overall solution gets more expensive.
2) The battery has probably not really the 100Ah it was sold for. :-(
3) I must tweak my design to further reduce power, where I can.
 
Do you need to use a router that uses 6W? The dlink dwr-116 I mentioned had a long term use of about 2.5W (overall setup was assumed to use 10W as a design principle even though it fell way under that in practice), with things connected to the 100Mbit/sec ethernet ports, and including a 3G mobile data dongle. The use of a sync switched buck regulator instead of a cheaper diode switched design made the conversion of battery voltage to regulated 5V for the dlink more efficient too.

Do you have any ethernet wiring connected? It may be feasible to limit your port speed to 100Mbit/sec rather than letting it autosense if it has gigabit ports, that will save you a little power if you are hypermiling-watting.

There is also thinking entirely outside the box too. I'm not sure how you are getting the readings out of your measuring equipment but if you are using a separate SBC with serial IO it may even be possible to have the router itself do that if you can run one of the open-sourcey router OSes on it like openwrt, ddwrt etc.
 
Do you need to use a router that uses 6W?
No, the current router is just a test-load for evaluation.
The final config will be with a GSM network. Currently my battery monitoring and the measurement stuff runs on an ESP8266 microcontroller + a Raspberry Pi using~ 400-600mA @ 5V. = roughly 2,5W. But that must then really run 24/365 off grid.
 
Is the ESP is talking to the RPi over wifi? Would it be practical to do that with serial comms instead? That might let you remove the wifi router completely and let the RPi itself handle the internet communications if you are using a usb stick for mobile data instead of just a SIM card in the router.
 
Is the ESP is talking to the RPi over wifi? Would it be practical to do that with serial comms instead? That might let you remove the wifi router completely and let the RPi itself handle the internet communications if you are using a usb stick for mobile data instead of just a SIM card in the router.
That is EXACTLY my current concern.
The ESP is directly communicating to a distant storage server over Internet. I plan to get Internet over a SIM 800 module.
LoRa Radio instead would be MUCH better, but it would violate the maximum 1% sending allowance per second. :(

I hope to be able to get rid of the Pi which is currently just a gateway, or at least to run it on premises.
But we are drifting off the solar topic...
 
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