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diy solar

September mourn...

rin67630

Solar Enthusiast
Joined
Apr 29, 2020
Messages
1,066
Location
Nort-Rhine-Westphlia Germany
Just for your info, my experience with a 100W solar panel and 100Ah 12V lead battery.
That just runs an internet router drawing no more than 6W.
I bought a new battery on Sept 3.
After 5 days of cloudy weather since Sept. 26., I am close to a dead battery.
September.jpg
 
Are you powering the router directly with 12V, or are you inverting it?
 
Just for your info, my experience with a 100W solar panel and 100Ah 12V lead battery.
That just runs an internet router drawing no more than 6W.
I bought a new battery on Sept 3.
After 5 days of cloudy weather since Sept. 26., I am close to a dead battery.

I am sorry about this but isn't it somewhat to be expected? A 12V 100Ah lead-acid battery can store approx. 600 Watthours (assuming 50% DoD). Powering a 6W router for five consecutive days requires 6W * 5 * 24h = 720 Wh. This means that at least a 120 Wh charge needs to be supplied by the panels during this period to assist the battery.

I think that if you wish the system to deliver sustained power to your router for cloudy periods of similar length, you either have to upgrade to a larger capacity lead-acid battery or change to a LiFePo battery system with the same nominal capacity but a higher DOD.
 
Are you charging your battery direct from solar panel or using a secret SCC?

This is an excellent question, and I do wish I could read the chart provided; however, I have to believe that charting data is coming from a fancy SCC... :)
 
I had a wifi router up a hill running off a 100W panel and <scratch head> 50Ah (?) worth of 12V battery with a PWM (gasp) controller. In the years that it was in operation it never ran out of juice even with several days of heavy cloud (tropical coast, Queensland Australia). The only real limiter was trees which had to be cut back a couple of times. A similar setup was at another location but with a small dumb MPPT controller.

The weather must have been truly diabolical to keep the output of a 100W panel so low that it couldn't keep up with the demands of the router.
 
My thinking is there's an inverter involved, and his 6W is actually > 6W.
 
Yes, that would certainly explain it. My memory was wrong, it was 14Ah of battery.

Details:
1 x 100W panel
2 x 7Ah 12V SLA batteries
1 x cheap PWM charger
1 x dlink DWR-116 wifi router with USB stick for mobile data
1 x buck regulator, sync switching for better efficiency to take 12V to 5V for the router
Located at lat 21 south.

It's possible @rin67630 's setup is at a latitude that gives poor sun hours in the first place I guess. No monitor of the setup I did was ever done beyond 'is it working?' so it's also possible it did get close to the point of falling off a cliff but it never actually did.
 
I am sorry about this but isn't it somewhat to be expected? A 12V 100Ah lead-acid battery can store approx. 600 Watthours (assuming 50% DoD). Powering a 6W router for five consecutive days requires 6W * 5 * 24h = 720 Wh. This means that at least a 120 Wh charge needs to be supplied by the panels during this period to assist the battery.

I think that if you wish the system to deliver sustained power to your router for cloudy periods of similar length, you either have to upgrade to a larger capacity lead-acid battery or change to a LiFePo battery system with the same nominal capacity but a higher DOD.

I know. I just wanted to let everybody know, that at 51° latitude, a 100W panel reveals unable to balance a 6w permanent load even in september.
 
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Are you charging your battery direct from solar panel or using a secret SCC?
I have made several tests with different solar controllers. Currently I have a "pseudo-MPPT" SCC in operation, operating a buck converter with an adjustable operation point. That was the best compromise between efficiency and low quiescent current.
Under cloudy weather conditions (where it matters) and for that panel size, the MPPTs were not really better than PWM modules, most of them even worse, since they swallow too much power for themselves.
 
You must have had attrocious weather to not get any watts out of the panel to leave you in the situation where your battery was done after approx 5 days, that or some critical piece of information is not being told that is already limiting your power production. Even in heavy cloud I'd expect to get 1/10th of the panel's rating out of it. My own experience is that a 100W panel is quite sufficient to hold up a wifi router in my area and it can be cloudy here for weeks.

Care to provide any details of what went on?
 
You must have had attrocious weather to not get any watts out of the panel to leave you in the situation where your battery was done after approx 5 days, that or some critical piece of information is not being told that is already limiting your power production. Even in heavy cloud I'd expect to get 1/10th of the panel's rating out of it. My own experience is that a 100W panel is quite sufficient to hold up a wifi router in my area and it can be cloudy here for weeks.

Care to provide any details of what went on?
Have a look at the better chart below. The blue power line (with the axis on the right) is the power balance from/to the battery. One needs at least ~6W from the panel to become positive.

Here is my ongoing monitoring for the last 24h.
Thinger ongoing monitoring
 
Your battery voltage was making it to absorption until the 25th/26th. The discharge cycling voltage up until there says the battery was being charged fully up to that date, assuming points prior to this date are being fully charged which looking at the absorption stage I'm saying it was. From 26th to 30th saw battery voltage drop to 12V with approx 0.5A load and despite being greatly reduced some power is still coming in from the panel. 12V with that sort of load suggests SOC 20%. I'd be looking at the health of the battery personally, that doesn't add up otherwise.

I do see you are at 51 degrees, so that's certainly going to knock your production around but even so, the graph doesn't sit well with me compared to battery capacity really. If you have something else that will paint a different picture I'm all ears.
 
I am also close to thinking that the advertised battery capacity they sold a month ago to me was badly exaggerated.

I am recording long time the daily Ah and the battery voltage (measured at 4h after a night of discharging at ~0,5 A)
If I take a look at the last 10 days, where it began tho have a continuous negative balance, the total Ah discharged was only 31Ah and i am already far below 12V, discharging at C/200!

2020-09-21T22:00:01.377Z
2.13​
12.72​
2020-09-22T22:00:01.623Z
1.79​
12.72​
2020-09-23T22:00:00.971Z
-0.13​
12.70​
2020-09-24T22:00:01.108Z
1.54​
12.60​
2020-09-25T22:00:01.767Z
0.14​
12.69​
2020-09-26T22:00:01.755Z
-5.86​
12.59​
2020-09-27T22:00:01.513Z
-4.11​
12.47​
2020-09-28T22:00:01.526Z
-8.45​
12.41​
2020-09-29T22:00:00.792Z
-9.56​
12.26​
2020-09-30T22:00:01.818Z
-1.31​
12.07​
2020-10-01T22:00:01.151Z
-7.11​
12.04​
2020-10-02T22:00:01.873Z
-4.15​
11.87​
Sum
-35.09​
is that the regular behaviour of an 100Ah lead-acid solar battery?
 
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I have made several tests with different solar controllers. Currently I have a "pseudo-MPPT" SCC in operation, operating a buck converter with an adjustable operation point. That was the best compromise between efficiency and low quiescent current.
Under cloudy weather conditions (where it matters) and for that panel size, the MPPTs were not really better than PWM modules, most of them even worse, since they swallow too much power for themselves.
What is your watt output from your psedo controller during good sun? I have something similar I made and It is lackluster to say the least. Not to say that yours couldn't be way better than mine but I was surprised how poorly my buck converter did from the solar panels compared to powering with a power supply set to same voltage and amps panel was supposed to produce.
 
I got 65W peaks in bright sun, which is OK for my latitude, but mainly it throttled down due to the max battery voltage reached.
Now that my battery is discharged, I could surely get the full 65 watts for longer, if I only had sun for a couple of hours...
:-(

Regular buck converters are not doing well. They usually tend to stall the solar panel, you need those, where you can at least trim the operation point.
I use that one: https://www.aliexpress.com/item/4000147421854.html
OK they just pretend to be MPPT, in fact they are AMPP (adjustable).
But full MPPT are not doing much better for that panel size, and usually swallow around 1-2 W for themselves.
 
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.
 
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