Inductive charging (wireless) for eboard? Is this possible?

Yeah, wanted to answer to this:

Practicallity reasons…

  • No need to carry around wires
  • Leave the wires on the ground
  • Could be developed as a standalone product

If I dont come up with a wireless solution, I might as well try to figure out to make a removable battery or at least a battery contact which is more ‘‘smooth’’ / easier to connect.

Your answer in short: no cable Instead, you have a big plate on a ground / wall. Congrats.

DO IT.

hah, you actually seem pissed off that someone tries to come up with such a solution… :smiley:

Im not sure why do you concentrate so much on the efficiency! We use a lot of in-efficient things around us… and besides ‘‘baking’’ some electronics (if the heat is really a problem) what bad can happen?

Im not pissed off. I try to explain the problems it introduces so you dont have to waste your time doing something pointless. But if you want, do it. At least you will learn something new once you finish it or give it up due to many problems.

If charging a board slowly is possible by simply putting it somewhere, and it will balance all the cells, seems an obvious plus.
Even if efficiency isn’t that good I wouldn’t mind as I don’t count the pennies when charging and the heat could be isolated as said.

So far I came up with the numbers = 10-18% and it was a somewhat diy version of these wireless power transmission circuits…

So, taking 18% efficiency, that would mean instead of putting in 200w of power, we would need 1000w … Ok, at 10% it is a bit worse… but still - dont you know in how many other ways ppl waste energy? :smiley:

@Hummie at least you are with me on this one… :smiley:

The reason for inductive (wireless) charging, would be to leave the board for the night… even if it takes more than 5hours to charge (if the charge rate is slow)… then you would have a charged board next morning without the hassle of plugging in wires, removing them, turning off devices etc…

I dont promise I will build anything in the coming month or so… but if this topic is ‘‘feasible’’ enough I might go and talk with some more ppl who know more about inductiion, electromagnetic fields, transformers and other stuff…

I just see this as an opportunity to make something that has not been seen before :slight_smile:

Ok, latest find:

http://powerbyproxi.com/wp-content/uploads/2012/09/PP150-P012-Datasheet-v1.8-15-mm.pdf


It is bulky, I know, but I think it is made this way to withstand the mechanical shocks and other stuff in the environment it was designed for (forestry for example)…

Maximum distance seems to be 10mm without loosing voltage, still might work ok, if the pad and the receiver box is constructed in a right manner.

I wrote them a message, enquiring about 40mm optimum power transmission distance and capability of 100-200w output, will see if they are nice enough to reply and give out some more details!

~83% efficiency does not sound bad… 10mm distance is a bit too little, should find out how good it works for about 40-100mm.

I like your idea but wouldn’t you just use a BMS and feed the power wirelessly to the BMS which will take care of the balancing for you?

Although, when using a BMS you lose all the extra cables and have just one, similar to a laptop charger lead… won’t that be sufficient for you as you won’t have power + balance cables any more?

Yes, some type of bms circuit would be totally needed to charge effectively the battierys.

I might move onto a bms solution but for now I either have to stick with my current setup or make up how to make the connectors more convenient or the battery removable…

This is just an idea of the concept… If I come up with something that is reasonably affordable and doable, I will also post it here…

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I liked no bms and instead a “receiver” on each battery cell. Each would take the voltage from the “transmitting” coil separately. I don’t know if that’s possible to have the single transformer coil effecting the multiple but think so. No bms needed

But how would you avoid overcharging?

The voltage coming from the coil would be fixed. Actually think about it I don’t know😥 . Maybe if the voltage from the main coil is 4 volts when the cell hits four volts no more current would flow. That’s a big assumption. Anyone know if it would work like that? It makes sense to me. Can’t have a current when there’s no voltage difference

We’ve been playing with inductive charging through our battery housing, but the biggest issues we’ve found is the amount of current we can push without making the coil melt will making charging intolerably slow.

I got your point / idea now…

Instead of one big receiving coil, there would many, smaller coils, each coil could charge its own cell group, This way Voltage would not need to be as high and each cell group / pack, would be almost individually charged…

Not so sure about terminating voltage, but in theory it should work - similar like bulk chargers work, I guess… depends probably on how that energy transfer works and what dynamics is involved… perhpaps there could be a little receiver/transmitter, which would let the transmitting coil to shut off completely once cells are charged…

The termination of charge probably should not be the hardest part as I think it is not that hard to measure voltage and then make a switch for dismantling the circuit…

Could u give a little insight onto what amperage you achieved? Some clues would be nice :slight_smile:

Ok so from what you are saying… heat is a problem with higher currents

One more Q - with what distance between the coils you experimented?

This seems to affect the power output/efficiency greatly :slight_smile:

So far we’ve been able to push fairly stable just under 1A without causing too much heat through the coil. In our tests with higher amperage we’ve managed to melt a few coils. Mind you these are fairly compact coils so that we can fit them into our existing electronics housing.

The distance we tested was roughly 9mm between.

@captainjez Did you make custom ones or just experimenting with the current ones made for phone charging?

To me it seems, if using such small coils, that a method of removing heat would be totally necessary… you should try at least with a fan… what amps can you get…!

Turnigy chargers (at least mine) also kick in fan, if amps is over 2.0 for 6s voltage… temp is around 30-40degrees C I think when this happens…

You would only lower the amps/current needed if - like you say - you had a coil for each cell, but how would you align them up for charging? You’d need three at least for a 3s battery pack, and 3 transmitting coils in the charger, all three would have to line up like you have to perfectly align your mobile phone on it’s charging pad…

Custom made coils right now. These were left over coils I had from another project we were working on. Can’t put a fan as we have no room left in our case :slight_smile:

Im not at expert on this one yet… but it looks like there can be ‘‘a bigger transmit pad’’ and many, smaller receiving coils…

I agree about alignment… If the coils/circuit is not that effective, the coils will need to be aligned quite precise…

Anyways, take a look at this - his ‘‘field’’ is wide enough, that he can charge phone and run the tv at the same time:

You might need to switch a few seconds back or forth… dont have sound at the moment :slight_smile:


@captainjez hah I see… anyways would be cool to see how high can you go with a cooled coils… just to know what the amp limits might be with heat removal… heat removal is practised in a lot of fields in electronics anyways, why not use it here, if it would be beneficial :slight_smile: