Small off grid solar usb charging station system.

[AllOuT]

Your fact is Tom Foolery. Assuming you had a 100 watt panel, enough to generate 8 amps of charge current would destroy a 7.5 AH battery in a week. You charge batteries at C/10 rate, not 1C. 8 amps into a 7.5 AH battery is greater than 1C charge rate. With 8 amps of charge current requires a 80 AH battery.

What I meant was the current, would the battery be compatible with the 12v 8A charge controller 13,9V charging voltage, but the system I'm looking at is a 100 w panel that's rated at 2,81A and the battery is AGM 32ah 12v rated at a max charging current of 7.5A, Capacity at hr10 (c10) 30ah (3.0A, 1.75V). Would that still kill the 32ah battery? Or is this fine?

[AllOuT]

Why on earth would you use solar for this? You would be throwing away money. Do you like throwing money away?

You can do what you want easily and the really good thing is it will work better, and you can power a lot more things other than charging cell phones. It is so simple a 10-year old can make it.

Battery Charger > 12 volt Battery > 12 Volt USB Hub Charger

The beauty of it is you could oversize and buy say a 15 amp battery charger to charge a 12 volt 150 AH battery. That would be enough to charge. That would be enough to charge roughly 150 cell phones over periods of weeks/months without power. However add an Inverter and you can watch TV and have a few lights. It would cost less than your plan.

Now if you want to limit it to just cell phones and tablets, all you need is a Wall Wart 2-amp 12 volt charger, a smaller 12 volt 10 to 15 AH battery, and your 12 volt USB Hub Charger. It would still run circles around your idea and cost 1/4 of what you want to do. Enough to charge 10 to 15 cell phones over a period of a few days without power.

Okay, cheaper sounds good, but is it renewable without grid power present? What would charge the battery charger so it could charge the system? A 150 ah battery would cost as much as a 100w mono 36v solar panel, 12v 32ah agm battery, 300w inverter, and a charge controller (330 dollars, not including shipping) I don't understand that, but I'm willing to make the system as cheap as possible. I don't understand, using a wall wart? My intention for this system is to be off-grid, reusable weekly, for as long as the battery lives. How would I connect a usb hub directly to a 12 volt battery?
Thanks for the input, looking forward to your answer.

[Sunking]

Would the fact that I'd only use the system weekly, change the solar panel size? Since I don't need it to charge the battery that quickly? What amperage of a charge controller would I need? I've found a 8A charge controller, I would assume it would work for the battery, if the battery is rated at 7.5A max current?

Your fact is Tom Foolery. Assuming you had a 100 watt panel, enough to generate 8 amps of charge current would destroy a 7.5 AH battery in a week. You charge batteries at C/10 rate, not 1C. 8 amps into a 7.5 AH battery is greater than 1C charge rate. With 8 amps of charge current requires a 80 AH battery.

[Sunking]

Why on earth would you use solar for this? You would be throwing away money. Do you like throwing money away?

You can do what you want easily and the really good thing is it will work better, and you can power a lot more things other than charging cell phones. It is so simple a 10-year old can make it.

Battery Charger > 12 volt Battery > 12 Volt USB Hub Charger

The beauty of it is you could oversize and buy say a 15 amp battery charger to charge a 12 volt 150 AH battery. That would be enough to charge. That would be enough to charge roughly 150 cell phones over periods of weeks/months without power. However add an Inverter and you can watch TV and have a few lights. It would cost less than your plan.

Now if you want to limit it to just cell phones and tablets, all you need is a Wall Wart 2-amp 12 volt charger, a smaller 12 volt 10 to 15 AH battery, and your 12 volt USB Hub Charger. It would still run circles around your idea and cost 1/4 of what you want to do. Enough to charge 10 to 15 cell phones over a period of a few days without power.

[AllOuT]

An inverter is required, if you have loads that need 120VAC If you can get by with 12V dc loads, or simply only using the USB output of the controller, you don't need an inverter

Would the fact that I'd only use the system weekly, change the solar panel size? Since I don't need it to charge the battery that quickly? What amperage of a charge controller would I need? I've found a 8A charge controller, I would assume it would work for the battery, if the battery is rated at 7.5A max current?

[Mike90250]

An inverter is required, if you have loads that need 120VAC If you can get by with 12V dc loads, or simply only using the USB output of the controller, you don't need an inverter

[AllOuT]

What is your load:
30x5 = 150wh
or
30x12= 360wh

Your 12V battery needs to be 2x the size of your load.

360Wh @ 12V = 30ah. 60A is a battery found in a small car. A cheap 12V 80ah marine battery is about your only choice, or spend 2x as much for a lawn tractor battery at 60ah, depends what you can get in your area.

To charge that, you need a 100 - 150V pv panel, with a Voltage Max Power of about 18V Vmp=18V, Voc=21V

My load would be 150wh, then I assume a 32ah would do just fine? I've found a AGM deep cycle solar battery for 100 dollars, The panel necessary would be 100 - 150 watt? Would an inverter be required for the system?

[Mike90250]

What is your load:
30x5 = 150wh
or
30x12= 360wh

Your 12V battery needs to be 2x the size of your load.

360Wh @ 12V = 30ah. 60A is a battery found in a small car. A cheap 12V 80ah marine battery is about your only choice, or spend 2x as much for a lawn tractor battery at 60ah, depends what you can get in your area.

To charge that, you need a 100 - 150V pv panel, with a Voltage Max Power of about 18V Vmp=18V, Voc=21V

[AllOuT]

You need to come up with a few more numbers. Calculating power requirements in Watt Hours is a more universal way than other convoluted methods.

30000 mah = 30Ah @ __what voltage 5V, 12V ?___
30x5 = 150wh
30x12= 360wh Big difference. Most charge controllers require a 12V battery to power their internals. so that battery has to be accounted for also.

Doing this under $250 is going to be rough

Hi, I assume the charge controller would be 12V, but I would use the power only through the 40w usb charger which changes the voltage to 5V only, I am not sure on how that would change the required system size, that was one of my original questions, we can ignore the budget and just look at the most cost-effective way, I suppose that would be best.

[Mike90250]

You need to come up with a few more numbers. Calculating power requirements in Watt Hours is a more universal way than other convoluted methods.

30000 mah = 30Ah @ __what voltage 5V, 12V ?___
30x5 = 150wh
30x12= 360wh Big difference. Most charge controllers require a 12V battery to power their internals. so that battery has to be accounted for also.

Doing this under $250 is going to be rough

[AllOuT]

Hello, tried to make sense of what I need myself, but I cant seem understand how big of a solar panel I need, battery size, or if I can actually use solar for this purpose.

I want to make an off-grid USB charging station with a solar panel, preferably with one panel, I have 6 devices that have a total battery capacity of 30000 mah (2500 mah to spare), are there charge controllers that have at least 4 USB ports in them? I would assume if I would charge my load from the controller directly, I wouldn't need an inverter? Otherwise the charging station is a 40w load, I would assume it's more the more devices you charge. I have no clue of how long these devices would charge, I know the USB charger is rated at 5v/2.4A

The purpose of this system would be in a grid-down situation, I wouldn't use this daily, but assuming once the grid is down, I would use the system once every 5th or 6th day, I don't mind keeping the system up, but I'd prefer maintenance-free batteries. I have 4.8 sun hours where I live.

My question is, what's the most cost-effective way to make this system, does the fact that I would only use the system for USB charging change the battery capacity or panel size? Is solar even a choice if I would use this system weekly, not daily? Note: I am on a tight budget (I'm a student), I would like to spend no more than 250$ for the whole system (except the load).

Sorry if there's dumb questions, I'm pretty new to solar, and batteries and such.

I appreciate all answers, and thank you for your time.