John in CR
100 TW
I finally obtained cells/panels that make sense to finally build some solar panels for charging my ebikes anywhere. The concept is to end up with series strings that I can fold up and deploy when parked. Each string will be low current with the cells exceeding pack voltage by a sufficient margin so the cells deliver full current. Then each string or parallel group of strings will have a very simple and efficient HVC to protect the pack from over charging. The HVC unit will have a range of adjustment, so I can stagger the cutoff voltages if I use a large array to emulate CC/CV charging.
I typically use 500-1000wh/day on my bikes, so our pretty reliable 5-6 hours of good sun typically through lunchtime should make a solar solution simple. The sun is more powerful here so close to the equator at our 1km of elevation. Ask LFP how badly we got burned before 9am helping me fix a water leak. 8) . When we go to the beach a big array will get double duty as a power source and sun shade, and no need to ration anyone for their beach rides due to fixed battery limitations. Low tide riding on a shallow sloping beach with fine sand that packs hard is a truly unique experience in peaceful fun that I highly recommend.
The panel modules I found are 18V nominal with an open circuit voltage of about 21V, and rated current of about 0.3A . 5 in series should work great for the 82-83V cutoff I use for all my packs. Then I just connect strings in parallel for the charge power I want. The cells are monocrystalline PVs with a claimed efficiency of 16%. With the border around the cells and protective layers between the sun and the cells, they work out to just over 11% efficiency based on total surface area at rated output. Maybe I'll get lucky and my location and elevation net higher than rated output at peak time of day.
In addition to an easy to add up voltage for no losses stepping up to pack voltage, and no expensive charge controller, what makes these modules to me seem perfect is their construction. They're 135mm X 330mm X 2.4mm . The modules are composite sandwich with a layer of PET as the front surface, followed by EVA, the cells themselves, and again EVA. Then to add rigidity and strength the back is a fiberglass board like a PCB. Front and back are flat and smooth with the metal to solder the electrical connections on the back. The edges seem like they need sealing to make them truly waterproof, but I'll just include the edges in whatever I use to seal the electrical connections. They're quite rigid, so the physical structure I need to come up with should be simple.
I'm exited to start kicking the electric company out of the equation for my transportation needs. It won't be saving like the $2k-3k/yr I stopped giving to the oil company, but an extension cord connecting to the sun that easily folds up to put in a backpack will be sweet.
John
Here's a couple of pics
I typically use 500-1000wh/day on my bikes, so our pretty reliable 5-6 hours of good sun typically through lunchtime should make a solar solution simple. The sun is more powerful here so close to the equator at our 1km of elevation. Ask LFP how badly we got burned before 9am helping me fix a water leak. 8) . When we go to the beach a big array will get double duty as a power source and sun shade, and no need to ration anyone for their beach rides due to fixed battery limitations. Low tide riding on a shallow sloping beach with fine sand that packs hard is a truly unique experience in peaceful fun that I highly recommend.
The panel modules I found are 18V nominal with an open circuit voltage of about 21V, and rated current of about 0.3A . 5 in series should work great for the 82-83V cutoff I use for all my packs. Then I just connect strings in parallel for the charge power I want. The cells are monocrystalline PVs with a claimed efficiency of 16%. With the border around the cells and protective layers between the sun and the cells, they work out to just over 11% efficiency based on total surface area at rated output. Maybe I'll get lucky and my location and elevation net higher than rated output at peak time of day.
In addition to an easy to add up voltage for no losses stepping up to pack voltage, and no expensive charge controller, what makes these modules to me seem perfect is their construction. They're 135mm X 330mm X 2.4mm . The modules are composite sandwich with a layer of PET as the front surface, followed by EVA, the cells themselves, and again EVA. Then to add rigidity and strength the back is a fiberglass board like a PCB. Front and back are flat and smooth with the metal to solder the electrical connections on the back. The edges seem like they need sealing to make them truly waterproof, but I'll just include the edges in whatever I use to seal the electrical connections. They're quite rigid, so the physical structure I need to come up with should be simple.
I'm exited to start kicking the electric company out of the equation for my transportation needs. It won't be saving like the $2k-3k/yr I stopped giving to the oil company, but an extension cord connecting to the sun that easily folds up to put in a backpack will be sweet.
John
Here's a couple of pics