Internal Di2 Battery Charging - Electronics Help!

[Cavemud]

Hi All

After recently damaging the frame of my Surly LHT, I started a project to replace it with the newer disc version. The project has now escalated in complexity and cost, and I am planning to incorporate the alfine 11 hub with Di2 and belt drive.

The frame is currently being modified by my friendly LBS to accomodate the belt drive and appropriate chain ring clearance, and I am starting to accumulate parts and plan the build.

The di2 wiring and battery will be internally mounted, and the front wheel will incorporate a son dynamo. I'll also be using an Igaro D1 power converter for phone charging etc. (I previously soldered my own little circuit for voltage regulation which I've used for years, but could never get it small enough to fit inside a frame which the igaro does comfortably).

Given that one of the limitations of Di2 will be battery chargimg, and that I have 'on board power' it seems silly not to try to charge the di2 battery from the dynamo.

I have a circuit planned which will incorporate a changeover switch between usb charging, lights and di2 charging, but I'm unsure about charge regulation to the di2 battery.

Charge regulation to a phone is simple, as all the phone requires is a 5v power source and all the charge regulation and voltage protection circuitry is built into the phone. I'm assuming that this isnt the case with the di2 system (presumably the regulation and overvoltage protection are in the external shimano charger?) thus I would need to incorporate this in my system?

Can anybody shed any light on the internal di2 charging system or has anybody attempted anything similar?

The safe solution would be to butcher a shimano charger, but these retail at around £80 and I'm not certain I could fit it inside the frame.

I've found the following product on ebay which seems to do what I need for just a few £'s. (The di2 battery is 7.4v so 2 cell I think).

http://www.ebay.co.uk/itm/282601696427

Any thoughts/help would be greatly appreciated.

Thanks

Ian

[Brucey]

IIRC the system runs on a (regulated?) 7V output nominal from the battery pack. I am not certain that it is possible to charge the standard battery whilst 'using it' i.e. having the possibility of using the gears at the same time as charging. If so you will have to devise some other means of powering the system; if you are always going to have some power from the hub dynamo available (even a small amount) then maybe you could get away with a different (much smaller) battery.

For example if the usual battery is capable of many thousands of shifts, a small battery (or a capacitor) with a regulated output, capable of a few tens or a hundred shifts ought to do. The average current required from the generator to keep the battery topped up ought to be a few tens of mA; not a large load even if the hub's power is mostly being used for other purposes.

BTW a gripe against A11 hubs with Bowden cable shifting is that the index marks do not always represent the optimum alignment of the hub internals. My own A11 is like this. IIRC there is a provision in the A11 Di2 software to adjust the alignment of the motor unit away from the nominal position in case a similar situation exists. Needless to say I don't think you can adjust it without having a computer wired into the system....

cheers

[Cavemud]

Thanks Brucey

Starting with your last point first, the handlebar display for the alfine has a charging connector, so I'll still have the option to connect a shimano lead. I was undecided wether to fork out for the shimano charging lead, but I've come to the realisation that I'll need it to get the system running initially, testing and any potential adjustments.

I guess to address your point about charging and shifting simultaneously, I'll just have to buy the shimano charger and give it a try. All the other di2 parts have arrived now, so I am hoping to do some bench testing of the shifting this week.

I had considered just using a lead acid battery which would be much simpler to charge, but the shimano battery is very light and fits easily inside the seatpost.

With regards to your comment on 'many thousands of shifts' the blogger here https://seasonalcommute.com/di2-battery-life/ suggests he only achieved 17 hours of ride time from an alfine di2, and it was this blog that made me seriously consider the option of charging from a dynamo.

[Brucey]

17 hours of riding? that is frankly pathetic; dunno if it is typical; if so, its a needy baby... I wonder if there was something wrong with his batteries? Was that with the internal battery or the external one? IIRC the nominal capacity is different?

BTW the Di2 alfine hubs lack the return spring internally that the cable-operated hubs have. But provided the CJ is backlash-free where it mounts to the gear selector, an improvised external return spring would allow manual shifting to be implemented on a Di2 hub. If it just doesn't work out using Di2 maybe that would be a good fallback for you.

cheers.

[RickH]

If you look at the temperature line in the 1st graph (note that the scales change between graphs), the period when most daily hours of cycling happened mostly had a maximum temperature of 40F (4C) or less & the minimum was often below freezing. The cold will not have helped battery life. Neither will the fact that the display was set to quite a long stay on setting (5 minutes rather than the 5seconds later on). The 1st graph is labelled "First Battery Cycle", if that means the first ever charge of the battery that could well impact on charge duration (will the battery need to be "conditioned" by its 1st charge or 2?) & things seem to get much better in subsequent graphs.

[Tompsk]

Lithium Ion batteries are not easy to charge safely so I would ditch the Lithium Ion battery and use a PP3 rechargeable (about 8.4V from memory) and charge this from the dynohub via a diode and suitable resistor. The 7V or so can be created from the PP3 using an LM317 regulator to power the Di system. You can then simultaneously charge and draw current from the battery. Hope that makes sense to someone who can solder and tinker with electronics.
Please only try the above if you know what you are doing!

[igarocom]

The dynamo can put out 60V downhill and the fastest riders can get anything up to 100V. A diode/resistor to a 8.4v rated PP3 is not recommended!

Since the D1 has two ports you can simple use an adjustable step-up converter. Something like:- http://www.ebay.co.uk/itm/DC-DC-Boost-C ... 2624485909

[Cavemud]

Thanks Igarocom/Tompsk

I had thought aboit using a more conventional battery, but I like the idea that the di2 will last a while if I need it to and is remarkably small and light (I dont think a pp2 would fit down the frame).

I have the Igaro product which will provide me with a 5v usb output, and could use the shimano charger between the igaro and the di2. This would obviously work and is a fall back plan, but the shimano charger is bulky and expensive. I'm reluctant to butcher one for that money, and the long term plan is to build a similar bike for the wife, so if the cheaper charging option works I save quite a bit.

Inside the shimano charger is a circuit board (I presume) which takes the 5v input, steps voltage up but then also regulates the charge to prevent over charghing. The product linked in my original post also does this for a few pounds.......or at least I think it does, hence the original question.

I have ordered both the cheap charge regulating circuit board and the shimano charger, but neither have arrived yet.

[gloomyandy]

Have you considered just charging a cheap USB battery bank and then using that to charge everything else overnight/when required? Makes the on bike wiring very simple, I'd be surprised if the Di2 battery needs charging very often. You may be able to share the Di2 charger that way? Have you checked to see if the Di2 system is happy with being charged and used at the same time (especially with the charging coming and going)? Some devices can get very upset with a stop/start charging that you can get on a bike. Using a battery bank avoids those issues.

[Cavemud]

USB battery banks are fine for planned charging, but I like the idea if getting instant charge into the di2 in the event that i suddenly realise it needs it.

The wiring is a bit tricky. It looks simple on a wiring plan but will no doubt be a mess of wires once shoved up the tubing. Once I have the frame back I was going to see what sized tubing would fit inside the headtube, then preassemble the wiring inside its own smaller tube. This would make future bike maintenance a bit simpler.

The question about simultaneous charge and use came up earlier in the thread but I wont we able to check this until the charger arrives.

[Brucey]

you could perhaps have two small USB batteries on board, and a changeover switch between them, so that one is being charged at any time and the other is being used to power the system. That way you would always be able to keep running and you would be able to charge both batteries in succession.

The ID of a 1-1/8" steel steerer is 1" and if it is Aluminium it is closer to 7/8". This is big enough to house the most common sort of Lithium cell, but few USB power packs are that small; often they are put into rectangular boxes and the diagonal dimension is slightly too large.

Some frames have a cutout in the head tube where the down tube joins on, and this may allow you to stow the electronics in the down tube. Don't be tempted to drill holes in the DT near the headstock for wiring etc; the frame is highly stressed at this point and is quite likely to crack.

cheers

[Cavemud]

After a few months wait, I finally received my heavily modified Surly Disc Trucker, with a whole new rear triangle to accommodate the tricky chainline of alfine di2 belt drive, and also with sliding dropouts for belt tension.

Ive been building the bike up over the last week or so and I'm really pleased with the outcome. I'd particularly like to thank Peter Butterfield of Butterfield cycles for his patience and determination to get the geometry to work for the di2/alfine/belt chainline.

Tonight I went for my first test ride and was able to switch between phone charging, di2 charging and lights at the flick of a switch.

I just thought I'd update this post with a few of my own questions answered for anyone else thinking of trying this:

1) Shimano di2 will charge and shift at the same time. In fact, the di2 display will only light up to indicate charging if you press the shifter,
2) The shimano charger seems to have more complex circuitry to communicate with the rest of the system. I'm not certain of this, but I tried other charging circuits and the display would not indicate that it was charging. It may have in fact been charging in the background, but I preferred to have confirmation on the display so I stuck with the shimano charger,
3) the shimano charger can be carefully cut open to retrieve the circuit board, which will then easily fit down a 27.2mm seat tube (in fact it fitted up my seat post above the internal di2 battery) but don't forget to wrap it in tape to stop it shorting on the frame.


The system I have is as follows:

1) alfine 11 di2 with belt drive,
2) Internal di2 battery which fits in the seat tube with the circuit board from the shimano charger sitting in the seat tube above it,
3) Igaro usb converter with stability bank,
4) changeover switch

The only sense in which the original plan failed was my failure to get all of the charging electronics inside the frame . Every one of the components used will fit inside a seat tube or head tube, but once all the connectors, wires and heatshrink are introduced it becomes an impossible problem.

In the end I got some 32mm plastic drain tube and put most of the stuff inside that, and zip tied the tube under the pannier rack.

I used screw shut waterproof connectors (similar to the igaro ones) for the connections that might require removal for maintenance, but they add to the bulk considerably.

I suppose it's only a matter of time before somebody like Igaro builds all of this into a neat little unit.