I am doing an arduino project that requires wireless charging. I am trying to get all the parts on Amazon because I have giftcards to burn so I had to go with a more complicated but I feel safer than a hack solution.

I have an Arduino Fio that has a built in LiPo USB Charging circuit.

My plan is to use a Galaxy S3 Wireless charging base transmitting to a Galaxy S3 Wireless receiver which I will solder a USB dongle onto and plug into the Arduino Fio (The USB port on the Arduino fio is ONLY for battery charging so this should work)

To keep things consistent I am going to buy a Galaxy S3 3.7v 2100mAh battery to power this device.


So my question is the battery appears to have 4 contacts on it. From research I am assuming that 2 of the contacts are for reading the battery temp and other stats. If I am using the Arduino Fio's lipo charging circuit do I need to connect these other 2 terminals on the battery or can I just use the + and -

This is the battery http://www.amazon.com/gp/product/B0089VO7OM/ref=ox_sc_act_title_2?ie=UTF8&psc=1&smid=A2DE8N3Z0PUB32

To keep it consistant I plan on using this wireless charger http://www.amazon.com/gp/product/B00B7LPA42/ref=ox_sc_act_title_7?ie=UTF8&psc=1&smid=A2L77EE7U53NWQ

With this receiver http://www.amazon.com/gp/product/B00BCC2B1Q/ref=ox_sc_act_title_6?ie=UTF8&psc=1&smid=A2L77EE7U53NWQ

Arduino Fio http://www.amazon.com/gp/product/B005K0O1PA/ref=ox_sc_act_title_8?ie=UTF8&psc=1&smid=A1LHQ5G6ONPXVT

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    \$\begingroup\$ Your best bet is probably going to be to buy a extra battery, and take it apart. \$\endgroup\$ Sep 18, 2013 at 3:50
  • \$\begingroup\$ @ConnorWolf well i am getting an extra battery just encase this plan falls through. My idea though was to keep all parts consistant with what is known to work together to prevent explosions. \$\endgroup\$ Sep 18, 2013 at 12:53

1 Answer 1


You can in practice ignore the other pins. The battery will just charge if a suitable voltage and current is applied. One of the pins be connected by a thermistor to another pin, possibly ground. This is to indicate over-temperature. That's not much of a problem unless it's in an enclosed case and you're trying to charge it very quickly.

The wireless charger side of the plan I'm less sure about; it looks like you're supposed to attach it directly to the battery. I'm also unclear about how you plan to hold all this together and make contact with the battery. Note that you MUST NOT solder the battery terminals directly.

  • \$\begingroup\$ Thanks for the clear response. My plan is to take the leads from the wireless charging receiver and solder them to a USB dongle. The Arduino Fio has a USB port that is intended for charging batteries only. The battery itself will plug into the two pins next to the USB made specifically for the battery. I am assuming if I pump the proper voltage in, nature will handle the rest. (hopfully not with an explosion) \$\endgroup\$ Sep 18, 2013 at 12:41
  • \$\begingroup\$ The battery will have two gold surface contacts, not a plug, giving you a problem in connecting it to those pins on the Fio. The charging reciever may output 4.2V if it's intended to charge batteries, in which case it won't supply the 5V that the USB is expecting. \$\endgroup\$
    – pjc50
    Sep 18, 2013 at 13:07
  • \$\begingroup\$ yes I agree the flat terminals on the battery are an engineering challenge that I have considered. I don't think it's an impossible challenge though so I disregarded it for now. As the for charging, the Wireless charging reciever says that it outputs 5v and if I am reading right the arduino fio is expecting 4.7v in. I am looking at page 1 on the datasheet dlnmh9ip6v2uc.cloudfront.net/datasheets/Components/General%20IC/… \$\endgroup\$ Sep 18, 2013 at 13:15

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