Everything starts with an E

[HibikiB]

Hi everybody! I'm a newbie to electrical things, though reasonably well versed in bicycle building (apart from suspension work) and I can solder a bit.
I have just purchased a complete (used) 26" Cyclatrocity [sic] front wheel kit in an auction, and a (new) 700c kit without a battery.
I'm hoping to use the same battery on both bikes until I get the knowledge and save up the money to do a more personalised build on the 700c.
The 26" is just my local runabout so I don't really mind if the battery isn't performing as well as new. I didn't get a key with the used battery so it's locked to the controller at the moment, making it too long to put it in a homemade frame bag (I sew too!) or a pannier bag. I need to ask Cyclotricity for a spare key..

But back on topic I have some unusual requirements for the more exciting 700c project. I only have room to mount the battery on the fork due to the layout of my fishing tackle and such being already set. I have a good strong steel fork from a Dawes Galaxy Cross and a Tubus Tara rack and I don't mind modifying it.

At the moment I am reading up on the various battery options. I want a 48v (or 44.4v) split pack, equal weight on either side of the fork.
I don't believe in arbitrary budgets, I'll save up for as long as it takes to do a proper job of it. I need a range of at least 40 miles with pedalling. I don't have any real hills on my coastal routes, but I'm HEAVY when carrying my equipment and need to battle some serious headwinds (the fishing is only good when its windy) so I would like to avoid any serious voltage sag.
I'm guessing 600w/hrs is minimum for me.
I'm looking into the RC Hobby King packs but really finding more "ooh that isn't really for newbs" advice where I've been reading (mostly ES) than step by step instructions on how build to achieve my goals. I am a newbie but I can do what I'm told. I don't understand all the abbreviations often used.
I know plug n play Li-ion may be "safer" but want to avoid placing two ready built 18650 frame packs onto the fork, since the lower Ah packs seem to be the same weight/cell count but lower quality /capacity cells used, which would be a weight and bulk penalty. Also voltage sag is a concern, which I THINK points me towards the RC Li-Poly.
I have an idea that the KT 36/48v sine-wave controller may be suitable for overvolting to 44.4v nominal. I found a post here that pointed me to a Bafang 9-pin to KT adapter cable on ebay but they're out of stock.

So I'll end here before this becomes a book. Thanks everyone who has posted great info on the forum and anyone who made it this far through my first post!

 

[Fat Rat]

Hi welcome to the site
And good luck with the projects

 

[HibikiB]

Hi welcome to the site
And good luck with the projects

Thanks. For the welcome.

I have been having a rethink. I'm still learning about the Ebikes thing, reading a lot, but I sometimes forget what I've read.
So
It was well worth checking out the Hobby King packs made for remote control devices, "drones" and r/c cars and helicopters etc. I get that the compactness and ease of configuration around the bicycle frame is a great advantage.
I understand (I think) that the 44.4v nominal that you get when running four of their 11.1v in series is not less real world voltage than a 48v Li-ion battery on most Ebikes, because of the high "C rating" these packs don't suffer from voltage sag when heavily loaded.
On my little "250w" overvolted to 333w continuous the peak watt usage would be only barely into the figures where the high C rating makes a big difference, if I read correctly. On the popular 1kw+ motors that are popular in the USA the lithium polymer packs have significant advantages.
The rate of voltage drop as you use up the usable voltage of the battery is different too. The Li-poly has a higher voltage when it is "empty" so actually it's average voltage is about the same as the Li-ion which begins with a higher voltage and ends with lower.
Did I get that right?

But then there are some other considerations. .
If you are a beginner and you read the posts about living with these batteries it does come across that everyone is getting through multiple chargers and power supplies before they find one that lasts a while, but not forever.
There seems to be no charging system that is guaranteed to work for everyone all the time. Even if you make a list of the choices that other experienced builders finally settled on, there's still always someone else saying that way/product didn't work for them. There's no consistency, no consensus to follow so you can just_buy once and have reliability_.
The Li-poly packs recharge quickly but..
The batteries and chargers and power supplies should be placed in a fireplace during the charge process and must be monitored!
You have to carry a pair of server or large PC power supplies and a very large charger and the battery medic etc if you are going on a road trip. Not like the compact little chargers used for the common Li-ion "ebike" batteries.
So for me, for touring and fishing expeditions, I don't think that Li-poly is a practicable option. I need to be able to carry a small charger or two in my panniers, with a campsite electric hook up and charge my battery inside the porch of my highly flammable tent whole I sleep or on my bicycle.

But I'm glad I had a look at these. They do look nice and compact and good for high power "sport" ebiking near to home.

 

[Steve Bowles]

Great thread title. Everything else was way above my pay grade.

 

[HibikiB]

Great thread title. Everything else was way above my pay grade.

Thanks. Yeah my brain is fried reading up on all this stuff that I don't even understand!

But now I am reading that I may have to re-reconsider the Li-poly. I read that with the addition of a (which? Idk!) BMS it's possible to use one (which? Idk!) of the small chargers and charge slowly just like Li-ion plug n play ebike packs.
So maybe I'll be able to have something compact, affordable, and easily configurable to front panniers after all! I just have to find out what parts to order and how to join them up.

 

[Steve Bowles]

There is nothing about a pedelec that is affordable. Just bite the bullet and get the best bike you can. I think trying to reinvent the wheel is a fool's errand. Unless you have that Master's degree in electrical engineering.

 

[HibikiB]

I'd love to bite the bullet but the question is which bullet to bite! I just need a recommended portable charger and (therefore?) bms for HK Turnigy packs that I can carry in a pannier.

I don't want to have to carry two Hailong or similar boxy 18650 hardcase batteries on the front of each fork leg.
I would like to have something compact, slim, and in four/six/eight separate small bricks so it can be carried on both the front and back of both fork legs, and keeps the weight of 44.4v x 24Ah+ centred and close to the front wheel/steering axis, the controller, and the front hub motor.

 

[wheeliepete]

To get the capacity you are looking for with Lipo you are looking at at least 8kg of batteries. With the battery config. you require you may be better to look at building your own packs with high capacity 21700 cells like the Samsung 50e's. 2 x 24v 20Ah packs will come in at around 4 kg. You would need a battery spot welder.

 

[Nealh]

Lipo C rating tends to be optimistic and the guys on ES reckon that they are far over rated by manufacturers. 2.5c is believed to be a better rating.
Issue with multiple small packs whether Lipo or Lion is all that extra wiring needed to the controller and the extra watts lost because of the voltage travel .
Battery sag is normal (about 1v) with 18650 cells unless you have many cells in parallel and not just 4 or 5. Lipo has less sag typically I was seeing 0.3v but still had a few in parallel.
Lipo balancing can go way if you discharge to low < 3.6v per cell, though you can wire in a switched BMS to manage the discharge better sticking to 10 or 13s format. 12s BMS's I found were not suitable or hard to find one with individual single cell balance with a switch, most tend to be for Lifepo4.

 

[HibikiB]

Okay so to have the weight anywhere near evenly distributed fore and aft of the fork legs (without buying four large packs of seriously low quality /capacity cells), I need to make them myself from scratch.
ie buy a spot welder and nickle strip, learn the technique, and manufacture my own 18650 13s pack from individual cells such as Samsung 50e

This does sound harder than buying packs with wires already sticking out of them that I can join together in parallel with a soldering iron and connectors.
It just makes me wonder why there are really no narrow, 5ish to 8.8Ah, 13s Li-ion packs available, or at least none that I can find.

6s apparently are available in low Ah fairly flat packs but decent cells, 10s fairly small too like 8.8Ah. But if you need 13s there's only high Ah, or the same size box with terribly low Ah cells inside, nothing compact.

 

[Nealh]

For compact you have to go more bespoke, either try your self or get a pro like Jimmy @BGA reworking/Insat to make them.

 

[Nealh]

Majority of pedelecs sold are 36v, 13s is not overly common except in diy market.

13s2p 6ah is smallest you can buy using 30Q cells for about £165/170 or 13s 3p with GA cells £210. Batterie this way work out more expensive.
With Lion multiple packs means more charging time and chargers to do the same job as one larger pack.

 

[HibikiB]

Majority of pedelecs sold are 36v, 13s is not overly common except in diy market.

13s2p 6ah is smallest you can buy using 30Q cells for about £165/170 or 13s 3p with GA cells £210. Batterie this way work out more expensive.
With Lion multiple packs means more charging time and chargers to do the same job as one larger pack.

Thank you very much for the help, I will definitely contact Jimmy and ask about arranging a battery in a sort of 4 "legs" arrangement to fit over/around the front wheel and fork.

I actually thought if it was two paralleled batteries (with a bit of a trough to seat onto the fork nice and close to the wheel) I would be able to uncouple them and halve the charge time with two chargers.. But I guess things are not always that easy.

 

[wheeliepete]

I was thinking along the lines of 2 x 4P7S paralleled packs which could then be charged with fairly lightweight generic 24v chargers.

 

[wheeliepete]

This sort of layout might work, two of these stacked on each fork leg. I hope you can see this, my computer skills are not great.

Edit... help!! how do i make this pdf viewable?

 

[HibikiB]

This sort of layout might work, two of these stacked on each fork leg. I hope you can see this, my computer skills are not great.

Edit... help!! how do i make this pdf viewable?

No worries. I appreciate that you are trying to help.

I haven't seen any 7s packs. Would it be okay to go up to 14s on a KT 36/48v sine-wave controller? If so it's probably easier to configure something symmetrical with 14s anyway.

I was thinking about how it would be arranged for good balance and everything as close as possible to the steering axis.
I will have to do some arithmetic, figure out what dimensions could be and cut up some cereal boxes for a quick mock-up. In my minds eye I'm seeing something that looks like four weetabix inner packets arranged in an X, with a pile of cream crackers (bms and connections box) in the centre to go over the mudguard, oh and spaghetti of course. Then the whole breakfast can be draped over the fork. How my mind works...
If it's in four "legs" the weight can be about 40mm closer to the the wheel as it would not need to be hung off the outsides of the fork. Far more aero as well as stable if the fork is "hidden" in between the batteries. I can make a housing to fit.

 

[wheeliepete]

Would it be okay to go up to 14s on a KT 36/48v sine-wave controller? If so it's probably easier to configure something symmetrical with 14s anyway.

Did you get my idea? sorry for the appauling presentation. It was meant to be cell config. from handle bars looking down. C shaped to allow wrap around fork leg. Yes, the KT should be fine on that voltage and as you say, easier to configure and for charging. Pack size will be around 140mm tall x 130mm wide x 65mm deep. I'm not sure I completely follow your breastfast menu.

 

[Nealh]

I would firstly decide on the pannier arrangement/size then once this is on the bike decide on battery layout, no use sorting battery lay out if doesn't fit.

 

[HibikiB]

Did you get my idea? sorry for the appauling presentation. It was meant to be cell config. from handle bars looking down. C shaped to allow wrap around fork leg. Yes, the KT should be fine on that voltage and as you say, easier to configure and for charging. Pack size will be around 140mm tall x 130mm wide x 65mm deep. I'm not sure I completely follow your breastfast menu.

No I couldn't see a thing lol. I think we're on the same wavelength though. It's all just trying to get it close to the steering axis. U around the fork is fine, My erm.. dead octopus.. quadrapus? would fit down into containers that would be that sort of shape anyway.
Thanks for those dimensions. I'll have a play with the cereal boxes later on.

 

[wheeliepete]

No I couldn't see a thing lol

Brilliant, glad I got my idea across to you, but I think you have the gist of it.