Stealth folding bike - UPDATE

[otas]

Nice job, Otto, I'm glad you got it running OK.

I charge my pack in two halves. I have made up small adapters to connect each pair of 5S packs together, and have shortened the pack leads and configured then so I can just pull out the two paralleled packs as if they were just two 5S packs, isolated from each other.

I could rearrange these for charging to look like a single 5S pack, with all the cells in parallel, but thought it was more hassle to play around with separating out the balance taps each time.

I have a couple of cheap HK ECO-06 chargers, that are powered from a single 12V power supply. To charge the bike pack up I just plug one isolated pack half to each charger. This works OK, but does mean pulling the pack wiring apart slightly to charge.


Jeremy

Jeremy, is it necessary to disconnect the batteries? If we have two packs in parallel and two of these in series, what is stopping us from connecting the positive from one charger to negative of the other charger (they are isolated) and connect this to respective battery terminals with the centre tap connected to the common +/- ? And of course connecting the balancing wires. This can be built on a stripboard using IDC connectors and the balancing JST connectors, they are rated at 1A, so for the power positive and negative they can be doubled up and for the centre tap they can be 4 pins - ribbon cable strands. This would be easier than disconnecting batteries and it can be brought outside for easy connection. We need 2x 6 pins for balancing and 2+4+2 for power, total 20 pins. There will be 20 way ribbon cable in 20 pin IDC,pin/wire rated at 1A, so 2 pins = 2Amp rated, it would take the available 2.5A charging without smoke.
There is so much in the HK shop, that I have missed this little charger and I got the ECO 6-10, if I knew about this little charger, I would go for it. Well, next time. It is so light, that it can be carried on the bike at 170g each, with a small 12V 100W mains PSU. That will do me nicely, sir!
otto

 

[otas]

Hi Chekola, I rode the bike yesterday, but it was so bitterly cold, 3deg C above, so I gave up after 3 miles. I will wrap up proper and try again.
cheers otto

 

[Jeremy Harris]

Sounds like my ride this morning. I got about two miles from home and decided enough was enough, turned around and rode back at full throttle all the way.................

Jeremy

 

[hotrod]

weather to cold roll on summer

 

[otas]

Today I rode despite the drizzle and 5 deg., just 4 miles, fantastic. Throttle LED gauge still on max. I need windscreen wipers for my goggles. Any suggestions? Max. speed 29mph, avg 17.8mph. My front chainwheel is 52, and I can pedal up to 23-24mph, but I have to pedal like mad. I have lost the chain once, what a mucky job to put it back, so I rode just on the throttle. Would it take a smaller rear gear as the front is about the largest it will take? I have to take care in the bend, I was pedalling and my pedal scraped the road, so I am learning to stop pedalling and raise the inner pedal near the bend. Car drivers look bemused, when they negotiate the speed humps and I zoom along... Brakes are bedding in, so they are more efficient now. My next item for the bike are lights, running on DC-DC converter, I have made some LEDs for 12V so I will step down from 40V to 12V. I have mapped out a little circuit, 2.6m long and when it will be warmer and dry, I will do the range test going round until I exhaust the battery.

otto

 

[Jeremy Harris]

Today I rode despite the drizzle and 5 deg., just 4 miles, fantastic. Throttle LED gauge still on max. I need windscreen wipers for my goggles. Any suggestions? Max. speed 29mph, avg 17.8mph. My front chainwheel is 52, and I can pedal up to 23-24mph, but I have to pedal like mad. I have lost the chain once, what a mucky job to put it back, so I rode just on the throttle. Would it take a smaller rear gear as the front is about the largest it will take? I have to take care in the bend, I was pedalling and my pedal scraped the road, so I am learning to stop pedalling and raise the inner pedal near the bend. Car drivers look bemused, when they negotiate the speed humps and I zoom along... Brakes are bedding in, so they are more efficient now. My next item for the bike are lights, running on DC-DC converter, I have made some LEDs for 12V so I will step down from 40V to 12V. I have mapped out a little circuit, 2.6m long and when it will be warmer and dry, I will do the range test going round until I exhaust the battery.

otto

I've been looking at changing the freewheel for one with a taller top gear. Ebikes.ca sell one that might fit: http://www.ebikes.ca/store/photos/FW7Spd1132.jpg with an 11t small sprocket (vs the 14t one that's fitted as standard) but it's slightly wider and would need a change of shifter to fit (the dérailleur should be OK, it's throw can be adjusted to match I think). I can't find a UK or EU supplier of this freewheel, so may end up having to buy it from Canada.

Jeremy

 

[newb]

here u go jeremy

11-32 7spd freewheel

http://www.ebike-solutions.de/epages/62204758.sf/de_DE/?ObjectPath=/Shops/62204758/Categories/Schraubkr%C3%A4nze

also here

http://www.v-fiets.com/shop/Overbrengingen-c-279.html

 

[Jeremy Harris]

here u go jeremy

11-32 7spd freewheel

http://www.ebike-solutions.de/epages/62204758.sf/de_DE/?ObjectPath=/Shops/62204758/Categories/Schraubkr%C3%A4nze

also here

http://www.v-fiets.com/shop/Overbrengingen-c-279.html

Thanks a lot, that's a great help, just what I was after!

Jeremy

 

[jbond]

Is any of the "reduced responsiveness" due to motor current running through the Ping's BMS components? Or is that current path direct to the cells?

It may be. The Ping BMS has two or three paralleled FETs as lo side switches plus a current sense shunt. The discharge current always goes through that circuit, so it's going to increase battery overall Ri by a few mohms. Add in that the pouch type LiFePO4 cells that Ping uses have a fairly high Ri and I am pretty sure that the current peak voltage sag may have been much greater than that with the low Ri, directly connected, LiPo pack.

Do you think there is any improvement worth looking for by modding the Ping BMS in the same way as the controllers with low RDSon FETs?

The old school Li-On batteries from people like Phylion have an inbuilt BMS and are pretty foolproof[1] with relatively cheap simple chargers. Same for the Ping style LiFePo batteries. The problem is the Low C values which then means substantial AHr needed to cope with moderately high currents. That, and the voltage sag under load. I'd really like to see two approaches to dealing with this. First, trying to do something to bump up the C rating of the Ping style batteries by modding the BMS. And second, putting together a BMS solution to make LiPo batteries foolproof. And I guess there's a third, which is to build packs out of A123 cells to get the safety of LiFePo with the high C of LiPo.

[1]Foolproof means safe from fools. And we're all foolish some times! The system should protect me from discharge below LVC, overcharge of individual cells and keep them balanced. I shouldn't have to think about any of that stuff. And I want to just plug a charger in and leave it till the LED goes green. And I really don't want to have to mess around with changing the configuration to charge. The problem is the dangers of getting it wrong with High C cells that won't tolerate a bit of misuse are just too great to be left in the hands of fools.

 

[jbond]

I've left space in the box to add a module for torque control and also to experiment with pedelec control algorithms.

Very interested in this. I imagine a 3-way switch for PAS Off-Economy-Full, with throttle over-ride. And a soft start for the pedelec so you don't get that kick at low speed. Economy would be a deliberately low battery current limiter aimed at encouraging pedal effort and eeking out range.

 

[otas]

here u go jeremy

11-32 7spd freewheel

http://www.ebike-solutions.de/epages/62204758.sf/de_DE/?ObjectPath=/Shops/62204758/Categories/Schraubkr%C3%A4nze

also here

http://www.v-fiets.com/shop/Overbrengingen-c-279.html

Thanks a lot, that's a great help, just what I was after!

Jeremy

Jeremy, have you tried this by any chance? I wonder if it fits the wheel and operates via the existing grip shift?
thanks
otto

 

[Jeremy Harris]

I haven't tried it, Otto, as I couldn't get that web site to let me buy one. As it turns out this was a wise move, as when I went in to my local bike shop to try and order one the chap not only warned me off them but showed me some examples of the poor quality of their construction. To be honest I was pretty amazed at just how poor they were, the metal seemed to be soft as butter and really not at all up to the task. The other point that the local bike shop chap added was that DNP were right at the very bottom of the cost ladder, they apparently produce the very cheapest of the cheap Chinese bike parts.

What I have found is an old stock close ratio Regina freewheel. It's a 12-18, so not as low as the DNP one, but does look as if it will do all that I want. It hasn't arrived yet, so I can't say for sure how well it works. I suspect it might not index, as although it's a six speed it was made before indexed gears became popular. The seller on ebay goes by the name welcometothebikeman and still has a few of these old freewheels left. I'm hoping that with a 50t chainring and the 12t rear sprocket the bike should be able to be pedalled at reasonable speeds, and I don't think I will need the really low gear that the old 28t gave.

Jeremy

 

[otas]

Thanks for results of your homework Jeremy, yes, the DNP looks like stamped from a cheese, not steel. This one looks like an honest job. I got worked up on the 11gear, which would be 27% improvement, this is only 16%. I have friendly machine CNC shop in CR, they are crazy into racing Moped Stadion, 1958 Czech product. I will ask if they coud do a smaller wheel mod. Just for a laugh there is a link! Pour yourself a glass and enjoy! Sorry it is far off the forum subject, but as a minimalist vehicle with 50cc engine, highly tuned for the race may be of an interest.

http://www.youtube.com/watch?v=qXTdktKxgiI&feature=player_embedded

otto