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d10ng
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Has anyone done any serious work on wireless charging on board yet? I've found a few set of tx and Rx chips and coils that would be suitable and will charge upto 600mah. However most of the coils diameters are to wide to fit between the wheels (HO and UK proto scale 4mm). 

Modules https://www.robotshop.com/uk/12v-600ma-wireless-charging-module.html

But TDK sell wireless charging coils designed for wearable devices. These coils are either round or oblong and will fit between the wheels. 

Seperate coils https://product.tdk.com/info/en/products/wireless-charge/wireless-charge/rx-coil-module/catalog.html

However I'm not great with electronic theory and unsure whether it would be possible to swap the coils over and whether it would even work. I use mainly 1s lipo cells and I have a few small locos with low mah/size cells,  for which wireless charging would be a huge time saver. 
Most of the TDK coils state output at between 1&3W but can't find much info on the coils in the tx/Rx module sets. 
Any one have experience or the knowledge to put me straight? 
Thanks
Dave

Last edited on Sat May 5th, 2018 10:54 am by d10ng

Helmut
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When using 1S LiPos, this one is better suited.
No need for external coils etc, all is ready to use, provided you have the space for the receiver (41x31mm²). The 5mm distance between TX and Rx may also become an issue.
However oblong or round the coils are, the distance must not be greater than 2...5mm at most.

d10ng
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Thanks, That does look useful if not a little big, but as you say the 5mm distance isn't great.
The exterior coiled module suggests in can do upto 20mm but at 2mm thick it may perform better than the thinner smaller coils I was looking at.

dan3192
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Dave, your post regarding on board wireless charging caught my attention. I've been working on this project for over 2 yrs. I'm at the point of adding the required parts to a 1S Li-ion powered GP35 road switcher. The system appears to work very nicely.

Magnetic induction charging applied to HO models is complex. I've had to consider power levels (3W,5W), coil sizes and types, Tx/Rx board sizing, coil spacing and efficiencies, EMF shielding, parts interoperability, integrating charging and BPRC circuitry and fitting OBWC components into an already crowded environment. Testing and evaluating the data to determine an approach has taken considerable time. Outsourcing of parts to accomplish this was also time consuming. Companies such as Texas Instruments, IDT, Wurth Electronics, Digi-Key and the Wireless Power Consortium have been a great source of needed information, one loaning me test equipment for evaluation. Below is a photo of some of the components that will be used for a charging track and the fuel tank mounted electronics.

Many thanks for starting a dialogue on this important topic. The only "fly in the ointment" for me is major surgery scheduled for later this month, so model trains will shortly be on the back burner, hopefully temporarily.

Dan 
        

d10ng
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Dan, That's great work , glad your efforts are starting to pay off. How are you integrating the wireless rx board into the bprc circuit? Are you having to manually switch to the charger as you would with a hardwired charging port?
I'm hoping that I can use the rx/tx board and use a oblong coil which will fit between the wheels, providing a close enough proximity to charge well.
All the best for the operation. 
Dave

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Dave, thanks, and yes, that's my plan. My Tx board will power a round 15mm Tx coil attached to the underside of a piece of grooved plastic to simulate a wooden track crossing. The top surface will be positioned at the same height of the track. I'd like it higher, but I use Kadee couplers which have uncoupling pins that come down to about 1/16 inch above the rails. The plastic piece, with coil underneath, will be attached to the Bachmann E-Z Track you see in the photo. The coil wires will connect to the Tx board hidden under the ties. The light from the board will be seen at ballast level via fiber optic tubing from the Tx LED. The Rx coil may be larger and will be mounted under the engine fuel tank and connected to the Rx board either under the frame or above the Li-ion cell inside the engine shell. Likewise, fiber optic tubing brought to the outside will tell me charge coupling is established when Tx and Rx board lights are on together.


Now to your question. Initially, I'll connect the Rx coil and board wiring, via a double throw switch, to a 1S battery management board, with the battery also connected to the board. When the switch is thrown the opposite way, power will flow from the battery and board to a step-up voltage regulator and then to a Del Tang Rx61x Rx/ESC. I say initially because I've been thinking of a way to completely turn off my engine using a toggle or PB and an on board servo, in which case the wiring would be a little different. This would eliminate quiescent battery drain since it is hard wired to the battery management board. 


Re oblong coils, I found some copper beading wire at a local crafts store that might be perfect for forming my own Tx and Rx coils. Thin transformer wire may also work well. This is a tricky subject all by itself, i.e., what gauge wire, how many turns, single layer or double layer, insulating material, bonding material, solid or stranded wire, etc, etc. Suggest you visit the Digi-Key website (digikey.com) to see if their coils are of interest to you. You should be able to get most of them in the U.K. I don't know if the Tx/Rx imprinted coils referred to earlier can reach stated capacity without almost touching. I think it's a neat idea though. The best I think I'll be able to do is in the area of a 4 or 5mm gap.  I'm trying to stay with the Qi Standard for wireless charging so future parts are compatible. Visit the Wireless Power Consortium website for background information. You will also find useful videos on YouTube. Hope this helps.

Dan                        

Last edited on Tue Jul 31st, 2018 03:50 am by dan3192

dan3192
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Finally spending more time putting together a test track for on board charging. The transmitter (Tx) boards are hard to come by, so have decided to use them off the track assembly and connect the output leads to individual coils mounted in the track bed as needed.

A 15mm round coil is too big; will try a 12mm x 22mm coil instead. Also, the charger receiver (Rx) board gets pretty close to the drive shaft between the trucks, so will need to consider mounting it inside the shell. Photos soon.  

Dan

Last edited on Sat Jul 14th, 2018 07:01 am by dan3192

Bob D
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Great stuff Dan!!!

I want to do it with my O-scale engines, but I'm using 9.6, 11.1, and 12.0 batteries, I don't think there's anything out yet that can provide what I need to charge them.

Bob D
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Great stuff Dan!!!

I want to do it with my O-scale engines, but I'm using 9.6, 11.1, and 12.0 batteries, I don't think there's anything out yet that can provide what I need to charge them.

dan3192
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Bob,

You'll be pleased to know the basic electronics and related are already out there for what you want to do. The challenge is putting all the pieces together.

Sounds like you need some 18650 or 26650 batteries, a 3S battery management board with balance, a DPDTCO switch and a 12V, or higher, power source along with a Qi Standard wireless charging arrangement.

Would also recommend a voltage regulator to maintain consistent voltage and performance as batteries deplete and their voltage drops off. You may lose 10% or so in efficiency, but my experience is, given the powerful batteries we have today, it is well worth it and I would not assemble any future engines without a step-up or step-down voltage regulator.

Another nice thing about induction charging is that you can weatherproof the system for outdoor use.

Keep the faith...

Dan

Last edited on Sun Jul 15th, 2018 04:36 pm by dan3192

Bob D
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Dan,

I guess my hangup was locating a Qi standard charging system that would charge those 9.6, 11.1, and 12v batteries, all I ever saw that were ready made was for a max of 5v.

dan3192
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Working on the problem. Have a solution, but not yet verifiable. 1S battery arrangement is first, then 2S, 3S, etc. Still many "peripheral" problems to resolve.


Dan 

Last edited on Wed Jul 18th, 2018 06:44 pm by dan3192

dan3192
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Sometimes you just can't plan far enough ahead.

It looks like the biggest coil I can get between the rails is around 12mm, good for a 1 Watt system. That's not enough to charge my batteries at a rate I'll be satisfied with, so other shapes will need to be investigated as well as how they get mounted.

I've also found receiver coils are quite "fussy" about what transmitter coils they couple with, so another area to investigate including what coil specifications mean as far as proper selection with other coils while keeping Qi protocols.

Yet another irony; trying to make things simple, but forced to look at another technology that's not so simple.

Dan

d10ng
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Dan,
What is your layout like?
I'm considering putting the charging circuit in the roof of a loco, and a simple overhead bridge type structure in the off stage area. Removes the requirement to fit something between the rails.

Dave

dan3192
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Dave,

There's no layout involved here. I'm building a test track with multiple coil and pcb arrangements as a "proof of concept" type of project. Once I get past this stage, I can focus on how to fit induction charging components in with other locomotive components. 

It looks like I'll need bigger coils which will put them under the rails instead of in-between. This, in part, means revisiting the approach needed for charging, i.e., guided positioning or free positioning. There's a third approach called multiple cooperative flux generation I don't even want to think about.    

For now, I'll have to figure how to get Tx and Rx coils as close together as possible so it works like my static testing did. I've already noticed a peculiarity during the coupling process which might be very problematic. I'll be getting some vendor help next week and will get back...with what I can't say.

Re your overhead charging arrangement, could work, but Rx coil height will vary depending on the type of locomotive. This eliminates a fixed reference point for the Tx coil giving you two height variables instead of one...unless the Tx coil is retractable!

Dan      

Last edited on Mon Jul 30th, 2018 02:51 am by dan3192

dan3192
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(Note: To avoid confusion, this is an edited posting done after Post #20. Thank you Si for your help.)  

I received and reviewed information from TDK on coil selection, enough to start assembling a charging track. The problem was how to make a large hole in the E-Z Track for the Tx coil. I found a Forstner bit shown below at a Home Depot store which worked great.
 



Dan

Last edited on Fri Aug 24th, 2018 06:35 pm by dan3192

davecttr
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Oops! Your image there certainly had interesting effects on my page


The previous replies being empty was even more mysterious

dan3192
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Sincere apologies for the messed up post. Don't know what happened. The option to edit it out is not there. If Admin. can delete it, I'd like to start over again.

Dan

Last edited on Fri Aug 24th, 2018 07:27 am by dan3192

d10ng
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Yep, Google asked me if I wanted the page translated or left in Somalian?

Anyway looking forward to seeing a working example Dan, keep up the good work.

Si.
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Hi Dan  :wave:



I have EDITED out all the 'gobbledegook' from your problem Post ...

... & also Posted your photo back up.



The EDIT button you couldn't find, IS ACTUALLY THERE ...

... it's just that with such a LONG LINE LENGTH of the 'gobbledegook' ...

... you have to 'scroll right' quite a long way, using your Browsers scroll-bar ...

... because the buttons, including EDIT appear at THE CENTER of the Posts width !



You can EDIT the problem Post as you wish now of course as well.

Hope that helps.



All the best.



:)



Si.


dan3192
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This is how the 3/4" hole appears in the E-Z Track.




 
Had to feed the bit into the track base and ties very slowly to avoid damaging the rails.
 
Coil mounting is next.


Dan


P.S. Something going on with my computer, so will stop posting until resolved...


dan3192
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Finally back to trains. Charging track completed.

A 2W Tx coil was mounted in the hole in the E-Z Track plus 24 ga. stranded silicone wiring for connection to the Tx charger board.





Dan

Last edited on Tue Sep 11th, 2018 02:28 am by dan3192

dan3192
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Here's a top view of the coil. Top of coil to top of rail is over 3mm, a bit much. I may have to order the 12mm x 22mm coil I considered earlier, but this might change the intended Rx coil.





Dan

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I mounted a piece of grooved styrene with 4 spacers to the ties and used a fine point brown marker pen and a regular tan marker pen to simulate wood planking.


Next step is mounting Rx coils and boards on to 2 or 3 engines. This also requires adding battery protection circuitry, a run-off-charge switch and maybe a 2nd voltage regulator.


Dan



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Great work Dan!!!

Does the coil magnetize the rail?

I'm thinking out loud here, you will run the engine over the coil and turn the engine off, then turn the coil on to start the charging? If I recall, the Rx has to be off so as not to damage it while charging.

Still want to do this on my O scale engines, but with using 2000 and 2200Mah batteries, I don't think there's anything that'll work yet. Right now I have charging sockets mounted on the engines and plug in the charging jack to charge, a coil inside the rails would be ideal!!!

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Nickel silver (grey roadbed) cannot be magnetized. But part of the induced energy may be carried away by it.

Last edited on Tue Sep 11th, 2018 12:36 pm by Helmut

dan3192
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Hello Bob,

I use Bachmann's steel rail/black roadbed E-Z Track at our monthly train club meeting, but I felt steel rail would likely disrupt the electromagnetic field between the coils, so I purchased a few pieces of their nickel silver rail/gray roadbed track to minimize this effect.

Yes, I'll basically park the engine on the charging track and switch from run mode to off-charge mode. But I'm working on an idea to turn all power off remotely using my Rx, a servo and a double throw switch. This would eliminate all quiescent current flow and I could forget about battery drain for months. I'll post on this if it works.

As for your O scale engines, I think it can be done now. I think you need at least a 5 Watt system. The charging track shown in the photos has a 2 watt coil which sits under the rails. I need to finish up a 1 watt coil assembly that sits between the rails so I can compare this coil's performance at about rail level with the 2 watt coil sitting 3+mm below the top of the rails.

Hopefully I'll then be able to put together a 3 watt system. It will be for a 2S battery arrangement with balance charge capability. I have the parts, also for 3S, but I have to figure out the wiring. I'll be using Panasonic's 2,000 and 3,400 mAh Li-ion cylindrical batteries, which are my "standard" batteries.

I also have some yet to be used Keeppower 26650, 5,200 mAh batteries for wide body diesels or steam engine tenders. BTW, Samsung's 20700 Li-ion battery is available now with a 4,250 mAh capacity! 

Dan      

 

Last edited on Fri Sep 28th, 2018 05:08 am by dan3192

dan3192
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Helmut, you are correct, but sometimes one has to pick "the lesser of two evils". As with much of my experimentation, my models are more "proof of concept" oriented rather than commercially oriented. I tend to use what is available, which started me on this path in the first place.

Should BPRC become a factor in the model railroad industry, I can see silver plastic rail for the charging tracks, and all track, which should eliminate the induced energy problem. 

Hope you agree.

Dan

Last edited on Tue Sep 11th, 2018 09:54 pm by dan3192

dan3192
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I completed assembly of a 1 Watt coil for light duty use, like for batteries in a caboose or similar car for lighting LED's. 




-Dan

dan3192
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The coil sits between the rails and 1mm below the top of the rails. This should help in coupling with the Rx coil, which I estimate will be about 3mm above the rails.





-Dan

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This is the top of the charging track. I will use IDT's color coding to identify the various wattages of Tx and Rx coils.

Next step is rearranging some locomotives for the additional pcb's and wiring, then testing and taking data.

I have 3 Watt coils for a 3rd track for 2S charging I hope to build soon. 







-Dan

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Switching off the power remotely is good and it is hard to beat a physical switch.  The devices used in Pololu's e-switches come close though, with Off-state leakage current that is less than the self-discharge of any rechargeable battery I know of.
Perhaps one of these devices would work for your remote switch.  I use them in my models and have seen no problems.https://www.pololu.com/product/2810  

dan3192
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I'm sure the 2810 switch would work. I have their 750 power switches which I think does the same thing:  https://www.pololu.com/product/750  But with the rebuild I'll have a 1S battery management board (BMB) and Pololu's 2116 voltage regulator:  https://www.pololu.com/product/2116  plus the original DelTang Rx61x receiver.

So I'm thinking I need a SPDT switch instead of the SPST switch I was using to direct power from the Rx coil to the BMB when I'm in charge mode, or to the voltage regulator and DelTang Rx from the BMB when I'm in run mode. I have some SPDT mini switches from Miniatronics I plan to use for this. I hope this makes sense.

There's an option to control the SPDT switch with a servo that I'm thinking about, but I am running out of space. LED lighting is a higher priority.

Appreciate you making me aware of the 2810 switch.

Dan  

Last edited on Mon Sep 17th, 2018 04:47 am by dan3192

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I am interested in your work on this as I would like to use the idea for some of my models. Thanks for posting all the information!

For a solid state DPDT we can perhaps use a dual H-bridge chip. Pololu packages them as motor drivers, I use their #2135 but there are other versions for more voltage/more current. We may need two to get the required switching but that is still much smaller than a servo.

boB

dan3192
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Being an ME, and not an EE, I'm electronically challenged. I'd like to try the 2135, but adding a motor driver adds another level of complexity I'm not sure I can handle.

One of the engines I'm adding wireless charging to is a relatively small road switcher, so not much room. I'm OK with walking over to the engine and switching from run mode to charge mode. At least I don't have to fuss with charging wires, or dirty track or removing the shell and batteries for recharging.

I think a remote on-off feature is better suited for my other, larger engine, where I'll have more room for adding such parts.

Dan   

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I've ordered these 2P3T switches to experiment with for a large diesel engine or large steam engine tender when induction charging is added. I hope to get run, charge and off-test mode capability. This should cover all engine conditions. 






Dan

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Decided to build the 3 watt charging track since I was waiting for delivery of a 1S battery protection board for my engine. I used a 1-1/4" Forstner bit to make the hole...very tricky.

Even though I went very slowly, when the bit got into the ties, pieces went flying. Fortunately the rails were not damaged and the hole looked great.

Dan
 

Last edited on Sun Oct 14th, 2018 01:24 am by dan3192

dan3192
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The coil was difficult to work with. I tried to solder wires to the coil leads several times without success. I wound up using crimping pins and a pair of connectors to make a lead wire for the coil.

A rubber plug and some Kapton tape holds the coil against the bottom of the rails.

Dan




Last edited on Sun Oct 14th, 2018 01:46 am by dan3192

dan3192
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The coil is about 3mm below the top of the rail. I estimate the best I'll be able to do is about 2mm from the top of the rails to a receiver coil under an engine or car. This gives approx. a 5mm gap between coils, so a lot of testing ahead to see how good a magnetic coupling can be made.

Disassembly and rebuilding of a couple of engines has started plus one or two new BPRC engines will be created fitted with charging coils and related electronics. The transmitter side electronics also has to be assembled and wired.

BTW, the white dot signifies a 3W transmitter and its location.


Dan

Last edited on Sun Oct 14th, 2018 02:04 am by dan3192

dan3192
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I disassembled the drives and cleaned, lubed and reassembled them and reinstalled the battery bracket and battery. The electronics will be rearranged to include the receiver coil, receiver pcb, battery protection board and additional wiring for external battery monitoring.

If nothing else, the photo shows how one can fit a good sized battery into a narrow bodied HO road diesel (GP35) for BPRC operation.       

Dan

Last edited on Sun Oct 21st, 2018 04:08 am by dan3192

Bob D
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Nice "Inline" drive system you got there Dan!!! I've heard of a "Straight Eight" but never a "Straight One".

It's been so long since I had a HO engine apart, I might have to crack open one of my old Athearn GPs and take a look!

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@ Bob

Thanks, I trust you noticed that's a Hobbytown drive.

BTW, I looked back at Posts 10, 11 and 12 and I should have mentioned what you need for charging more than 1 battery. If you include a step-up voltage regulator between the receiver coil and battery management board, you should be all set.

But I'm hung up on that Battery Management Board, so please don't try this right away. I have 2S and 3S BMB's I'm not 100% on how to wire up. I got them on eBay from China. It shows the connections around the board, but I need more info. The power coming to the board for charging the batteries and the power from the board via the batteries use the same 2 connecting points, one positive and one negative.

This makes me wonder if I can operate my engine while I'm charging, or do I need a switch to select one or the other. I've noticed I can use my cell phone while it was charging, also my shaver when it was low and needed charging. If anyone knows the answer, please post!

Another unknown is if I need the exact voltage for charging, or can it be higher. One Li-ion or Lipo needs 4.2V, two of them need 8.4V, three need 12.6V, etc. As an example, if I have two batteries in series, the question is can I use a 9V voltage regulator or do I need to get an adjustable voltage regulator and set it to exactly 8.4V?  Could use some expert opinion here too.

And on that DPDT switch I mentioned earlier, I think one can get away with using a SPDT switch. Actually, I have some SPST center off switches that should work just fine.

So, comments please!...so we can get this project "back on track"

Dan         

Last edited on Mon Oct 22nd, 2018 01:31 am by dan3192

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I've done a little homework on my own questions, so will finish up on the wiring and check it out.

For the 1S arrangement, the receiver coil will be connected to the battery pcb via the run/off-charge switch. The pcb should receive around 5V which should be OK from what I've read. For the 2S setup, a VR will be used to boost the voltage to 9V, which also appears to be OK.

The engine is half wired and a little tricky to do since I'm modifying existing wiring instead of starting from scratch.


Dan     

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If you haven't been following what's new in batteries, here's one I hope to try soon. It's Samsung's INR21700-48G Li-ion battery intended, I believe, for the vaping crowd. Maybe also to compete with the Tesla batteries produced at their factory in Nevada.

It has an incredible 4,800mAh capacity compared to the 18650's I'm using now with a 3,400mAh capacity, which at the time I also thought was incredible. The battery is rated at 9.6A max. continuous, 4.8A max. for optimum cycle life.

If these more powerful types become more common, it suggests higher wattage charging systems will be more desirable to more closely match the higher C ratings of these batteries. Time will tell.    

Dan



Last edited on Thu Nov 22nd, 2018 10:26 pm by dan3192

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A little more rework on the GP35 road switcher. The old 5V voltage regulator was removed and replaced with a Pololu 2116 9V regulator just to the left of the switch. Pretty small device. The wire over it is the negative for the system. The assembly will go back on top of the battery.

Below that is a 1S battery management board and a receiver coil with its electronics for charging the Li-ion battery, which will go under the fuel tank. This is a rewire of the original arrangement to confirm the feasibility of on-board induction charging.

Doing this so I don't have to remove the battery for charging. 

Dan


Last edited on Sun Dec 23rd, 2018 03:51 am by dan3192

davecttr
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Dan, I am confused, that receiver coil is huge, will it fit in that chassis?

What charging rate are you expecting from the system?

dan3192
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Dave, the coil is 29mm wide and goes under the fuel tank, which is 35mm wide. The coil matches up nicely with the transmitter coil which is that 3W, 29mm diameter coil shown earlier.

Charging rate will depend on how close I'm able to bring the coils together. I'd be happy, for now, to charge at a rate of 400-600mA. The whole idea is to prove to myself that on-board induction charging is practical and doesn't need track, wiring or hand removal of the shell to charge batteries...they could stay untouched forever in the engine.

Dan       

  

dan3192
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This is the coil I'll be using, given all the variables I had to consider. At least the price is right.    

https://www.ebay.com/itm/Wireless-charger-receiver-module-PCBA-board-coil-Universal-qi-Andrews-diy-/173021522528?hash=item2848e2ea60

Dan

Last edited on Sun Dec 30th, 2018 10:12 pm by dan3192

dan3192
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This is the battery I use for narrow bodied HO engines, and the one for this test with my GP35. About US$6.00 on eBay.

Two are used in my BLI 4-6-4 with a 12V voltage regulator to satisfy the sound decoder. 

I'll be using two 18500 types which I found fit nicely in an Athearn AMD-103 diesel with Hobbytown chassis . They are rated at 2000mAh.

If you follow the 0.200A curve, which I think is typical, you can see the long run times possible with these batteries. I run lower mA on the passenger diesel, thanks to the Escap coreless motor.    


Dan

Last edited on Mon Dec 31st, 2018 05:10 pm by dan3192

Tony Walsham
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Hi Dan.
For those of us who are red/green/brown colour blind, would you kindly find another way of indicating which of the curves is green please

dan3192
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Hi Tony,

It's been a while. How are you? Hope Santa was good to you.

It's the top curve, the one that goes to 15 hours and 3.3 volts. The 2nd curve is for 500mA and the 3rd from the top is for 1000mA. The green mentioned on the chart is the color of the battery (light green).

I wouldn't take more than half an amp or so on this battery. I think the B at the end means the chemistry is high density, slow discharge. If you need the amps, use two in parallel.

I have another Panasonic this size, an NCR18650PF rated at 2900mAh and it has a higher discharge rating.

Take care.

Dan   

Last edited on Mon Dec 31st, 2018 01:17 am by dan3192


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