Induction charging

User avatar
zebedeesknees
Posts: 114
Joined: Mon Jul 12, 2010 5:15 pm

Induction charging

Postby zebedeesknees » Thu Jan 05, 2017 8:30 pm

Successful charging of an on-board LiPo battery can be done this way:-
InductionTxRx02.jpg

jasp
Posts: 126
Joined: Thu Dec 04, 2008 9:24 am

Re: Induction charging

Postby jasp » Thu Jan 05, 2017 10:39 pm

That looks very interesting.
Could we have some details, please?
Jim P

User avatar
zebedeesknees
Posts: 114
Joined: Mon Jul 12, 2010 5:15 pm

Re: Induction charging

Postby zebedeesknees » Thu Jan 05, 2017 11:47 pm

There are a lot of details.. off the top of my head right now.. I searched 'induction charger' on eBay and the like, and found pairs with small enough coils to fit beween the rails, and small pcbs. The one in the picture is the transmitter coil and circuit board, to which I soldered a Bridge rectifier and a piece of stripboard to which is soldered a couple of lengths of 26swg p.b. wire, acting as a sprung connection to the rails. A 10v supply DC of either polarity, or 11.5v AC will give the optimum transmission strength.

The receiver pcb is about half the width, and provides a peak of 750mA at 5v DC, but maybe wouldn't last that long at that rate. The battery I am using here limits it's charge rate to around 160mA, so divide that into the mAh rate of your battery and that's how long it will take to charge. Roughly!

User avatar
kelly
Posts: 385
Joined: Mon May 30, 2016 1:59 pm

Re: Induction charging

Postby kelly » Fri Jan 06, 2017 2:13 am

Nice work :) an interesting solution.

You could probably do similar for wireless handsets around the layout, putting the receivers in the cradles? lots of possibilities there.
DEMU UPDate Editor
DEMU
Photos on Flickr

User avatar
Paul Townsend
Posts: 859
Joined: Mon Sep 14, 2009 6:09 pm

Re: Induction charging

Postby Paul Townsend » Fri Jan 06, 2017 6:10 am

This technique is going to be widely used but needs attention to detail:
My mobile phone was not designed for this but a third party addon was bought and worked well for 6 months.
Then the phone packed up with battery fail. The phone dealer told me this was common due to overcharging not being protected via the induction charger.

nigelcliffe
Posts: 605
Joined: Mon Jul 21, 2008 8:31 am

Re: Induction charging

Postby nigelcliffe » Fri Jan 06, 2017 9:41 am

Paul Townsend wrote:This technique is going to be widely used but needs attention to detail:
My mobile phone was not designed for this but a third party addon was bought and worked well for 6 months.
Then the phone packed up with battery fail. The phone dealer told me this was common due to overcharging not being protected via the induction charger.


Hmm.... I suspect a phone dealer wanting to blame the third party product.
Which phone ? Most phones have the battery protection circuitry in the phone/battery combination and the chargers supplied by the maker are very dumb.


- Nigel ( was involved in mobile phone design and development some years back )

User avatar
Paul Townsend
Posts: 859
Joined: Mon Sep 14, 2009 6:09 pm

Re: Induction charging

Postby Paul Townsend » Fri Jan 06, 2017 2:36 pm

nigelcliffe wrote:
Paul Townsend wrote:This technique is going to be widely used but needs attention to detail:
My mobile phone was not designed for this but a third party addon was bought and worked well for 6 months.
Then the phone packed up with battery fail. The phone dealer told me this was common due to overcharging not being protected via the induction charger.


Hmm.... I suspect a phone dealer wanting to blame the third party product.
Which phone ? Most phones have the battery protection circuitry in the phone/battery combination and the chargers supplied by the maker are very dumb.


- Nigel ( was involved in mobile phone design and development some years back )

Samsung Galaxy S4
I think this was the last of the Galaxies before Samsung added "QI" i.e inbuilt inductive charging.

User avatar
zebedeesknees
Posts: 114
Joined: Mon Jul 12, 2010 5:15 pm

Re: Induction charging

Postby zebedeesknees » Fri Jan 06, 2017 3:28 pm

On LiPo batteries.. The ones on eBay, Gearbest, etc., made in China for quadcopters and drones have a very small internal pcb which controls the charge and discharge rates. A single cell has a nominal 3.7v, and is quickly destroyed if the voltage on the bare cell is pushed to over 4.2v, or discharged below 3v. I have recovered one that went down to 2.8 though, so there is some small tolerance there.

They have some really good properties, and some very bad ones. A not so good one is that they don't weigh much for their volume. Also not so good is that they will not charge properly in series. So if you want to join 3 in series to get around 12 volts, they will have to be separated and charged individually.

On the other hand, they put out a constant current until the control circuit switches off. No slowing down as the battery drains, like we're used to with NiCd or Nimh. In fact, that is one of the great dangers with 'bare' cells. If shorted, they will dump a massive amount of current in a short while, and if not contained, swell up, and give off a noxious fume which may be flammable. Whatever shorted it will get very hot very quickly too, glowing white if it is a wire. I found out...

Being positive again, the control circuit allows the battery to be recharged at 5v DC from a variety of sources, induction, regulator, USB, and prevents overcharge again by switching off at 4.2v. That controller has only two wires, so current flow in and out does not need to be switched externally.

Of course, most of us are using 12v motors exclusively, so one LiPo cell doesn't sound much use.. But - recently a booster pcb became available from China, small, and at a very good price. The circuit is labelled icsa004a, the chip on it is MT3608. From a DC supply as low as 2volts, the output is adjustable up to 24v, and can deliver up to 2 amps into the load.


Return to “Control Concepts”

Who is online

Users browsing this forum: No registered users and 2 guests