iceblu3710
Member level 3
Hello everyone!
I just bought a tablet for work and found out it only charges via a 12V, 18W wallwart. This is annoying but its a fantastic device. I currently use an ElCheapo deal extreme solar charger for my phone at work and want a single device I can put on my dash and charge all of my equipment.
I will use an atmega to control my design and my idea is this:
- 24V 4.5W solar panel is the charging source
- 18650 batteries to store the charge
- 5V @ 1A USB output (For my phone/mp3)
- 12V @ 1.5A output
- My tablet has a 1530mAh, 11.3W battery in it, I am assuming its running at 7.4V as reviews say it starts charging at >8V. When the device is plugged in dead the wallwart draws ~12W and when its on and topping up the battery it only draws around 7W. (Acer Iconia A100 1530 mAh, 11.3Wh Li-Polymer battery pack (BAT-711))
- Need to be able to charge the 18650's while charging devices (maybe not the tablet at least)
I plan on making a DC/DC Buck-Boost converter and getting the 5V @ 1A shouldn't be a problem but the 1.5A @12V might be a challenge. If its not hard on the tablets battery I might change it to 8V @ 750mA so it will still charge in 2hrs.
The #1 challenge I am confused with right now is how to actually charge the 18650's. All of the charger IC's I see out there are single cell only. I will need to run 3 in series and 3 in parallel to get a good capacity. (11.1V @ 5000mAh, would take >13hrs to charge but would be on the dash all day and I only charge 3-4 times a week)
The charger idea I came up with was have FETs on each +/- of the 18650's so my micro can switch them onto a charger IC one at a time and then when you plug something in they switch to a series/parallel combo then back to where it left off charging when your done. While this is not overly difficult if I needed to charge my phone and tablet on the same day I would half to wait until the charger charged...
Any ideas?? Thanks!
I just bought a tablet for work and found out it only charges via a 12V, 18W wallwart. This is annoying but its a fantastic device. I currently use an ElCheapo deal extreme solar charger for my phone at work and want a single device I can put on my dash and charge all of my equipment.
I will use an atmega to control my design and my idea is this:
- 24V 4.5W solar panel is the charging source
- 18650 batteries to store the charge
- 5V @ 1A USB output (For my phone/mp3)
- 12V @ 1.5A output
- My tablet has a 1530mAh, 11.3W battery in it, I am assuming its running at 7.4V as reviews say it starts charging at >8V. When the device is plugged in dead the wallwart draws ~12W and when its on and topping up the battery it only draws around 7W. (Acer Iconia A100 1530 mAh, 11.3Wh Li-Polymer battery pack (BAT-711))
- Need to be able to charge the 18650's while charging devices (maybe not the tablet at least)
I plan on making a DC/DC Buck-Boost converter and getting the 5V @ 1A shouldn't be a problem but the 1.5A @12V might be a challenge. If its not hard on the tablets battery I might change it to 8V @ 750mA so it will still charge in 2hrs.
The #1 challenge I am confused with right now is how to actually charge the 18650's. All of the charger IC's I see out there are single cell only. I will need to run 3 in series and 3 in parallel to get a good capacity. (11.1V @ 5000mAh, would take >13hrs to charge but would be on the dash all day and I only charge 3-4 times a week)
The charger idea I came up with was have FETs on each +/- of the 18650's so my micro can switch them onto a charger IC one at a time and then when you plug something in they switch to a series/parallel combo then back to where it left off charging when your done. While this is not overly difficult if I needed to charge my phone and tablet on the same day I would half to wait until the charger charged...
Any ideas?? Thanks!