Solar/Battery iPad Charger? Moderators: adafruit_support_bill, adafruit

[marcflood]

I have a project I am working on with my son but I am a little confused on the components I need to purchase if this can be done.

We would like to build a device that will charge an iPad at its full charge rate of 12 watts/2.1 amps. We would like to have it powered by a rechargeable battery. Additionally we would like to utilize a solar panel. If the iPad is plugged into the USB port of the device it would draw power from either the solar panel or battery pack. However, I understand that if the solar panel is connected the iPad would not charge at the full rate and I am okay with that.

Can this be done and if so what parts do we need to purchase?

Best I can tell, this can be done with the following parts:
USB / DC / Solar Lithium Ion/Polymer charger
6V Solar Panel
Lithium Ion or Polymer battery
MintyBoost Kit

However, I do not think the MintyBoost kit will supply enough power to charge the iPad at the full rate. Would it be possible use the same parts above but instead of connecting the MintyBoost to the USB / DC / Solar Lithium Ion/Polymer charger, could I instead connect a PowerBoost 1000 Basic to the USB / DC / Solar Lithium Ion/Polymer charger?

[adafruit_support_bill]

The MintyBoost will max out at about 500mA. The PowerBoost 1000 is a better choice. It can deliver 2A from a 3.7v LiPo source.

The only catch here is that the PowerBoost doesn't like input voltages higher than 5.5v. If the charger is operating in load-sharing mode, you could potentially see as much as 6v at the input. This will typically drop a bit under load. But a 5.v zener diode across the inputs to the powerBoost would give you some protection against brief periods of overvoltage.

[safeness]

Would the powerboost 1000 output 2A with lipo batteries in its stock configuration or would the voltages on D+/D- need to change?

[adafruit_support_bill]

Would the powerboost 1000 output 2A with lipo batteries

Yes, but only if your batteries are capable of sourcing 3-4A.

[safeness]

I bought the 2500mAh one here. I figured the battery could do it, but it was more a question of the iPad charging at 2A.

[adafruit_support_bill]

I bought the 2500mAh one here. I figured the battery could do it

That cell will not do it. The recommended discharge current is 1/2C or 1.2A: https://www.adafruit.com/datasheets/785 ... _sheet.pdf

The 4400mAh pack would do it. It has a max continuous discharge rating of 1C or 4.4A http://www.adafruit.com/datasheets/18650%204400mAh.pdf

[safeness]

Ah ok, thanks. I put the 6600mAh one on my Christmas list, so I'll keep my fingers crossed:)

[safeness]

When I plug the iPad in to the powerboost 1000, it registers as a 1A charger as seen in iBatteryInfoPro2 (requires JB.) From what I found here http://www.voltaicsystems.com/blog/choosing-usb-pin-voltages-for-iphones-and-ipads/ it sounds like the voltages on the data pins need to be swapped for iOS to see it as a 2A charger.

I haven't tested this yet since I don't have a suitable battery, but I'll post back when I try it. Probably the easiest way to do this is by cutting the D+/D- traces and crossing them with jumper wire.

[adafruit_support_bill]

it sounds like the voltages on the data pins need to be swapped for iOS to see it as a 2A charger.

We haven't personally reverse-engineered the iPad charging interface. Let us know if swapping the data pin voltages works.

[safeness]

It works! I ended up just swapping R9 and R11 and now it sees it as a 2A charger. The input voltage sags and the low battery light comes on, but eventually goes away after a while during the 2 times I tried it so far. Should I just add another 10uF or so capacitor in parallel with the one that's already there?

[adafruit_support_bill]

I don't think 10uF would help all that much. But it doesn't hurt to try.

[josuan75]

i bought two of these for my raspberrypi and they are working perfect! but when i connect a ios device, it wont detect the charge, :( i thought it would, i will try safeness solution.