I'll start with an apology as I'm sure threads like this could get annoying. I've tried to educate myself as well as I can, and will present what my assumptions are, but still have some confusion with my project and would like clarification.
Basically I'm doing what I'm sure many have done before, and making a battery boosted solar charger for smartphones etc. I'm aiming for a 5V, 2A output and have some questions about what best to use circuitry wise.
The most basic of questions is whether to go for a higher voltage battery (7.4V) and step down, or lower voltage (3.7V) and step up. I'm leaning towards higher as from what I understand it should be less straining on the battery as less current will be drawn, and the circuitry involved is slightly more efficient.
Second is what to use as a controller. My understanding is MPPT is the most optimum, but at this size not enough to make a noticeable difference for the increase in complexity, which means I should be looking at a linear charge controller? In all honesty there's more of these than I know how to differentiate between, but the ones from microchip or linear look hopeful, any particular recommendations? The panels I'll be using are fairly open at the moment, but will likely be along the lines of 3, 6V 2W panels wired in series (which I think eliminates the microchip options due to input voltage). Will the voltage difference between source and battery lead to problems/inefficiencies or should I be ok? N.B. due to the conditions this might be used in (hot cars etc) is something with the option for a thermal sensor a wise idea?
Lastly is how to integrate the load (in this case the USB out for the phone). I'm after what I imagine is the fairly standard concept of the panel powering the charger when possible (or as much of it as it physically can) whilst being boosted by the battery when needed, and then when their is excess/no load, the panel charging the battery, basically so at the output I always get as close to 5V, 2A as possible, with as little drain on the battery until it's dead. I know to an extent this will sort of take care of itself if wired in parallel, but I've read of various downsides of this, with a couple of solutions involving p-channel MOSFETs. Is the solution of bypassing the charge controller to the load via a single p-channel suitable or is a more complex solution necessary/better. I assume a voltage limiter before the load would in this case need to be capable or stepping the full solar panel output down to 5V.
Thanks in advance for any help you can give to any of the above questions. I hope they're not to inane, I've tried my best but am a bit nervous of going ahead without clarification.
Basically I'm doing what I'm sure many have done before, and making a battery boosted solar charger for smartphones etc. I'm aiming for a 5V, 2A output and have some questions about what best to use circuitry wise.
The most basic of questions is whether to go for a higher voltage battery (7.4V) and step down, or lower voltage (3.7V) and step up. I'm leaning towards higher as from what I understand it should be less straining on the battery as less current will be drawn, and the circuitry involved is slightly more efficient.
Second is what to use as a controller. My understanding is MPPT is the most optimum, but at this size not enough to make a noticeable difference for the increase in complexity, which means I should be looking at a linear charge controller? In all honesty there's more of these than I know how to differentiate between, but the ones from microchip or linear look hopeful, any particular recommendations? The panels I'll be using are fairly open at the moment, but will likely be along the lines of 3, 6V 2W panels wired in series (which I think eliminates the microchip options due to input voltage). Will the voltage difference between source and battery lead to problems/inefficiencies or should I be ok? N.B. due to the conditions this might be used in (hot cars etc) is something with the option for a thermal sensor a wise idea?
Lastly is how to integrate the load (in this case the USB out for the phone). I'm after what I imagine is the fairly standard concept of the panel powering the charger when possible (or as much of it as it physically can) whilst being boosted by the battery when needed, and then when their is excess/no load, the panel charging the battery, basically so at the output I always get as close to 5V, 2A as possible, with as little drain on the battery until it's dead. I know to an extent this will sort of take care of itself if wired in parallel, but I've read of various downsides of this, with a couple of solutions involving p-channel MOSFETs. Is the solution of bypassing the charge controller to the load via a single p-channel suitable or is a more complex solution necessary/better. I assume a voltage limiter before the load would in this case need to be capable or stepping the full solar panel output down to 5V.
Thanks in advance for any help you can give to any of the above questions. I hope they're not to inane, I've tried my best but am a bit nervous of going ahead without clarification.
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