Artlav
New member
- Joined
- Oct 18, 2018
- Messages
- 27
It all started 4 years ago, when i was on an Ebay spree (this happens sometimes...) and bought some cute solar cells.
As luck would have it, these turned out to be genuine Maxeon Sunpower cells, pretty much top of the line.
[img=640x480]
After some looking around, i managed to find a place to get them professionally soldered and laminated and ended up with a pair of solar panels.
[img=640x480]
And there the luck ran out - the panels added up to about 9 V max power point, and were neither here nor there.
Eventually they went into the attic and haven't seen the light of day for years.
A year later i slowly started accumulating 18650 cells, mostly from used laptop batteries.
I always wanted to make a big battery based power system, a KWh of storage at least, and often salivated over industry sized batteries, but so far sanity always prevailed.
As the cells accumulated, i started to wonder how to sort them and figure out their state and capacity.
A regular li-ion charger i had kept giving random values, so eventually i just gave up and made my own battery exercise unit.
[img=640x480]
It was fairly simple - a linear constant current source to charge the cells at 1A, a big resistor to discharge them, multiply by 4, add a microcontroller to monitor and record everything to a microsd card.
It would cycle the cells 4 times automatically, over the course of a day or so, charge them up to 50% and beep.
With this i went through the whole collection and managed to get them characterized, with a charge performance, estimated ESR and precise capacity.
[img=640x320]
The results weren't that good - about half the cells were dead, with capacity under 500mAh. The rest were evenly distributed across the 1000-2000mAh range.
I used the best of the crop to make phone powerbanks and stuff, but by and large they sat in a box unused for a few years.
Eventually i had a lapse of sanity and bought a couple of large LiFePO4 cells on Ebay.
[img=640x853]
On a quick check they looked fine, but i had no real use for them... So they sat in a box for some time.
Fast forward to present days.
Having recently moved, i've been unloading all the crap i accumulated from my previous garage sale and ebay sprees.
I recently made a bunch of autonomous cameras, and one of them sat on the second floor of the garden house, staring out of the window.
It was powered by an extension cord running all over the place, and people kept forgetting to plug it in.
So one day i figured out i can solve this problem and unload a bunch of junk at the same time - slap the solar panels onto the roof, add batteries, power the cameras from that.
Easy, right?
I started composing the system and testing things.
[img=640x667]https://i.imgur.com/GHpEj6Y.jpg[/img]
Rather quickly it became obvious that i've been had with the LiFePO4 cells - they barely held any charge and instead of 40Ah they were more like 4Ah.
While contemplating the fragility of human planning, i noticed the box of 18650 cells.
Cells that were sorted and characterized years ago, and added up to quite a noticeable volume.
So i took the best of them, made a 2s6p pack totalling 10Ah, built everything up and tried it out.
[img=640x1055]https://i.imgur.com/IJgt8Zp.jpg[/img]
It worked quite well, even if a bit underpowered - the panels put out 40W, and with only 70 Wh of storage it wasn't a good match.
But now it was time to get serious.
First, instead of duct taping the panels to the roof, how about a proper frame.
[img=640x1138]https://i.imgur.com/4r9y4wu.jpg[/img]
Then, instead of a bunch of spaghetti, how about a proper cutting board.
[img=640x718]https://i.imgur.com/HoJEj45.jpg[/img]
16 more cells were added, from the middle of the list.
That's another 10 Ah, bringing the total to 120Wh.
Also in frame an MPP controller/charger, a reverse protection diode, a low voltage cut-out and a step-up converter with a fuse.
This all went onto a wall, neatly mounted this time.
[img=640x1137]https://i.imgur.com/07cbKj6.jpg[/img]
All this thing powers is a couple of cameras and a 4G/Wifi converter. It can also dual-power a few LED lights around the house.
Maximum power output of 60W, as limited by the step up converter.
Not the scale you folks are used to, but it is power and it is on a wall.
Since then i had a couple of additions.
First, i found 12 more cells. These appear to have been bought new and are protected flashlight types.
No idea where they came from, but they added another 12Ah to the system.
So the total is 32 Ah or 230Wh and 40 cells in 2s20p configuration.
[img=640x1138]https://i.imgur.com/9QkNXB7.jpg[/img]
I also added an innovative monitoring system consisting of a spare camera with an LED taped to it, pointed at the instruments.
[img=640x1138]https://i.imgur.com/PceOB6V.jpg[/img]
This lets me see how things are going at any time.
I might make some sort of an ESP based board to actually track everything later, but i'm too lazy at the moment to do it.
Odds are i'll be expanding the system over the years.
But for now, that's all folks.
As luck would have it, these turned out to be genuine Maxeon Sunpower cells, pretty much top of the line.
[img=640x480]
After some looking around, i managed to find a place to get them professionally soldered and laminated and ended up with a pair of solar panels.
[img=640x480]
And there the luck ran out - the panels added up to about 9 V max power point, and were neither here nor there.
Eventually they went into the attic and haven't seen the light of day for years.
A year later i slowly started accumulating 18650 cells, mostly from used laptop batteries.
I always wanted to make a big battery based power system, a KWh of storage at least, and often salivated over industry sized batteries, but so far sanity always prevailed.
As the cells accumulated, i started to wonder how to sort them and figure out their state and capacity.
A regular li-ion charger i had kept giving random values, so eventually i just gave up and made my own battery exercise unit.
[img=640x480]
It was fairly simple - a linear constant current source to charge the cells at 1A, a big resistor to discharge them, multiply by 4, add a microcontroller to monitor and record everything to a microsd card.
It would cycle the cells 4 times automatically, over the course of a day or so, charge them up to 50% and beep.
With this i went through the whole collection and managed to get them characterized, with a charge performance, estimated ESR and precise capacity.
[img=640x320]
The results weren't that good - about half the cells were dead, with capacity under 500mAh. The rest were evenly distributed across the 1000-2000mAh range.
I used the best of the crop to make phone powerbanks and stuff, but by and large they sat in a box unused for a few years.
Eventually i had a lapse of sanity and bought a couple of large LiFePO4 cells on Ebay.
[img=640x853]
On a quick check they looked fine, but i had no real use for them... So they sat in a box for some time.
Fast forward to present days.
Having recently moved, i've been unloading all the crap i accumulated from my previous garage sale and ebay sprees.
I recently made a bunch of autonomous cameras, and one of them sat on the second floor of the garden house, staring out of the window.
It was powered by an extension cord running all over the place, and people kept forgetting to plug it in.
So one day i figured out i can solve this problem and unload a bunch of junk at the same time - slap the solar panels onto the roof, add batteries, power the cameras from that.
Easy, right?
I started composing the system and testing things.
[img=640x667]https://i.imgur.com/GHpEj6Y.jpg[/img]
Rather quickly it became obvious that i've been had with the LiFePO4 cells - they barely held any charge and instead of 40Ah they were more like 4Ah.
While contemplating the fragility of human planning, i noticed the box of 18650 cells.
Cells that were sorted and characterized years ago, and added up to quite a noticeable volume.
So i took the best of them, made a 2s6p pack totalling 10Ah, built everything up and tried it out.
[img=640x1055]https://i.imgur.com/IJgt8Zp.jpg[/img]
It worked quite well, even if a bit underpowered - the panels put out 40W, and with only 70 Wh of storage it wasn't a good match.
But now it was time to get serious.
First, instead of duct taping the panels to the roof, how about a proper frame.
[img=640x1138]https://i.imgur.com/4r9y4wu.jpg[/img]
Then, instead of a bunch of spaghetti, how about a proper cutting board.
[img=640x718]https://i.imgur.com/HoJEj45.jpg[/img]
16 more cells were added, from the middle of the list.
That's another 10 Ah, bringing the total to 120Wh.
Also in frame an MPP controller/charger, a reverse protection diode, a low voltage cut-out and a step-up converter with a fuse.
This all went onto a wall, neatly mounted this time.
[img=640x1137]https://i.imgur.com/07cbKj6.jpg[/img]
All this thing powers is a couple of cameras and a 4G/Wifi converter. It can also dual-power a few LED lights around the house.
Maximum power output of 60W, as limited by the step up converter.
Not the scale you folks are used to, but it is power and it is on a wall.
Since then i had a couple of additions.
First, i found 12 more cells. These appear to have been bought new and are protected flashlight types.
No idea where they came from, but they added another 12Ah to the system.
So the total is 32 Ah or 230Wh and 40 cells in 2s20p configuration.
[img=640x1138]https://i.imgur.com/9QkNXB7.jpg[/img]
I also added an innovative monitoring system consisting of a spare camera with an LED taped to it, pointed at the instruments.
[img=640x1138]https://i.imgur.com/PceOB6V.jpg[/img]
This lets me see how things are going at any time.
I might make some sort of an ESP based board to actually track everything later, but i'm too lazy at the moment to do it.
Odds are i'll be expanding the system over the years.
But for now, that's all folks.
