Questions on a new conversion

[saitrix30]

My girlfriend is wanting an ebike conversion to help her along and to allow the two of us to ride together. She currently has a 2023 Specialized Rockhopper Sport in XS. She isn't after lots of speed, just something to help her up hills and to keep an ok pace, so no questions it would be a max of 250w. The combined bike and rider is around ~65kg (10st) so it isn't the most weight. I am wanting to keep the bike to a nice light setup to make handling the bike easier and not hard work for her.

She would only want to go ~25 miles range at most (honestly can see that being more like ~15 miles for most rides), mainly on pretty flat routes, eg converted railway tracks. I have ruled out the use of a mid drive setup due to her being short I didn't think the wider q factor would be very comfortable plus I can see the costs of that going up quickly due to needing shorter cranks (she currently runs 150mm cranks) and offset chainring (due to the rockhopper having a 73mm BB shell).

So this has got me on to looking at a geared 250w rear hub setup. I have tried to research the recommendations but it would be useful to know if I have made the right choice prior to ordering. The battery needs to go on a rear rack from my measurements due to how small the frame triangle is, see attached pic. I have purposely picked a battery setup which keeps the weight down (~2kg battery) with a low weight motor (~2.1kg) as I am concerned what will happen with the handling by adding all the weight at the rear, but unfortunately can't really see another option for where to locate the weight.

Motor - Aikema AKM-100CST 250w 36v (From TopBikeKit)
Battery - 10s2p 21700 Samsung 50E (36v 10Ah) in a Hailong 1 battery case (made by Greenlance). Mounted to the top of a rear rack.
Controller - 15a KT controller integrated in the Hailong 1 case {From TopBikeKit)
Display - LCD9 with left throttle
PAS Sensor - KT BZ-10C (due to the bike not using a square taper bb)
Spokes - Sapim Strong butted

If you see anything glaringly wrong then please say. Also is it a must to have something for programming KT controllers or is this done via the display? Also is there big disparity in display capabilities?

 

[saneagle]

Personally, I'd use a separate controller with block connectors and fit it in a bag somewhere, like one of those triangle bags, then you could use any rack battery you want or even one of those 10S2P bottle batteries that would probably fit in the triangle.

What's this Greenlance battery you mentioned? I don't see it on their website. Link please.

Don't forget that you need the 201 rpm version of the motor for 29" wheels and 15 mph.

 

[Nealh]

There is no programming to carry out with the KT controllers so no additional PC hook up is required, there are a few parameter changes that can be done via the screen.
The changes are purely cosmetic in how the system detects certain signals.

 

[saneagle]

Sorry, I missed the display question. Any LCD except LCD1 should be OK. LCD3 is a good workhorse, LCD4 if you want light and discrete, but it is a bit fiddly to work the up and down buttons. That might be OK for small hands. LCD8 if you want ease of use and colour, but then worry about it getting broken. LCD5 is pretty robust and cheap.

 

[saitrix30]

saneagle,

I have unfortunately measured up even the small 18650 bottle batteries and they don't fit. What I didn't mention is the wheels are actually 27.5", though I can see how it would look like 29"! If it gives you an idea how small the frame is, you struggle to fit a 750ml bottle in the bottle cage.

Good point about the 201rpm, that was another detail I had forgotten to write.

You won't find the battery on the website, I emailed him specifically and got a quote for a custom battery, lead time is 8-12 weeks.

Thanks for the info on the displays there, useful!

Is there a particular reason for a separate controller or is it just to maximise the available battery designs?

Nealh,

That's good to know about the programming, one less thing to have to sort before using it.

 

[saitrix30]

Forgot to ask, reason I was looking at the hailong downtube battery is that's all greenlance has, is there anywhere else trustworthy that I can get smaller capacity, been struggling to find anything other than massive rack batteries with 50x18650 cells in it.

Also does the range of 25 miles sound possible with just a 360Wh battery?

 

[matthewslack]

On flattish terrain with the rider contributing a bit and not trying to maintain 25km/h all the time, 25 miles will be fine on 360Wh.

Range instantly increases when you slow down and/or pedal harder. In other words, the rider to a large extent determines range.

 

[Woosh]

You need about 10wh per mile so 25 miles is very doable with a 360wh battery. However, you need good cells to avoid voltage sag when climbing hills.

 

[Nealh]

Flatish terrain I manage 30 - 35miles form my bespoke HG2 12s/2p , 6ah/264wh battery. Albeit I only use PAS1 and approx. 58 - 65w of power.

Wind , tyre psi and general riding ability and fintness above speed cut off will determine range.

 

[Az.]

Did you consider saddle bag or frog battery?

 

[harrys]

I've built several bikes with the AKM100 motor. Great performance and reliability. However it costs me more than a TSDZ2 mid drive to assemble an AKM kit ala carte. Places like BMSbattery and top bike kit charge a lot to ship a motor/wheel. I just buy the bare motor and lace my own wheels, but Sapim spokes are expensive and I don't save much money, Then add the electronics. You might find savings on a complete package though.

I've come to like my TSDZ2 conversion a lot. My wife prefers her TSDZ2 to her hubmotor bikes. Oddly enough, with OSF firmware, I set hers up for cadence sensing, and it's easier to ride than a hubmotor. They only draw 11A peak, and I burn around 8WH/mile. Makes small batteries feasible. I run mine on a 13x2 Sanyo GA battery, about 250 real WH. Thirty miles is easy, and if I run out, the bike is light enough to pedal home.

My wife's bike has little room for a battery. I also put in a rack and a battery on the rack.


I've entertained the idea of tiny batteries. Built two 13x1 48V4AH packs with Molicell P45A's. I planned to keep them as backups, but should do a field test to see how long they will last. They easily power my Q100H bikes and my TSDZ2, but the effective WH is needed.

 

[Benjahmin]

Kit looks fine to me, with one reservation.
The saddle is so low that the battery will have to sit behind it, meaning it will be quite far back. That, combined with the fact that the hailong1 is quite a tall case, will make it look awkward.
The raising of centre of gravity from the battery should be (mostly) offset by the motor. However the battery hanging out way beyond the rear axle will be the thing that affects handling the most.
I see that the triangle is very small, but I would look at trying to get a bag for the controller in there so the battery case could be shorter.
Have you thought about a handlebar mount for drinks bottle? Maybe something like this:

Pardon our interruption...

If you can get the battery forward and unless your girlfriend is throwing the bike around on gnarly mtb trails, I don't think the handling difference will be overly noticed.

 

[saneagle]

saneagle,

I have unfortunately measured up even the small 18650 bottle batteries and they don't fit. What I didn't mention is the wheels are actually 27.5", though I can see how it would look like 29"! If it gives you an idea how small the frame is, you struggle to fit a 750ml bottle in the bottle cage.

Good point about the 201rpm, that was another detail I had forgotten to write.

You won't find the battery on the website, I emailed him specifically and got a quote for a custom battery, lead time is 8-12 weeks.

Thanks for the info on the displays there, useful!

Is there a particular reason for a separate controller or is it just to maximise the available battery designs?

Nealh,

That's good to know about the programming, one less thing to have to sort before using it.

You can get the block connectors on the separate controllers, which allows for testing if something doesn't work. It's virtually impossible to test anything with the waterproof connectors, plus the wires are separate so you don't get cable problems, and you can swap to a different power controller if it takes your fancy. They come in 14A, 15A, 17A , 20A and 22A flavours.

The Hailong battery behind the seat is going to look daft. If you only want 10S2P, you can use a scooter battery. One of those would fit in the triangle if you make a little box for it.

 

[Nealh]

Water proof cables can be tested but the user has to make up Y leads that can be inserted between the wp connectors to carry out testing.
The easiest cable is the three pin one as it will suffice to test external spd sensor, PAS & throttle.
A nine pin one would need an extra M/F lead to be chopped in half or a pair of tails to make up a Y lead, the Y simply ending up as a household strip connector for simple probe testing .

Not many would go this far but if one owns ebikes and wants to fault find and take the guess work out of the fault finding WP connectors then it is a simple process to prepare.

However if one wants the versitaility of a seperate controller sited in a bag then it is a no brainer to opt for the simplified SM/block connector versions.
W/P controllers are all used with integrated controller /battery mounts ok if one is happy with 15a but if you want more torque/power form your 250w hub then a 22a controller is likely the best option available, so one is looking at a seperate remote located controller.

 

[saneagle]

Water proof cables can be tested but the user has to make up Y leads that can be inserted between the wp connectors to carry out testing.
The easiest cable is the three pin one as it will suffice to test external spd sensor, PAS & throttle.
A nine pin one would need an extra M/F lead to be chopped in half or a pair of tails to make up a Y lead, the Y simply ending up as a household strip connector for simple probe testing .

Not many would go this far but if one owns ebikes and wants to fault find and take the guess work out of the fault finding WP connectors then it is a simple process to prepare.

However if one wants the versitaility of a seperate controller sited in a bag then it is a no brainer to opt for the simplified SM/block connector versions.
W/P controllers are all used with integrated controller /battery mounts ok if one is happy with 15a but if you want more torque/power form your 250w hub then a 22a controller is likely the best option available, so one is looking at a seperate remote located controller.

Whenever I had a defective controller, 4-in-one cable, LCd or anything else on an ebike that I repaired, I cut off the connectors to use as test leads. Your suggestion to make Y-leads is OK, but I normally open the controller and test in there, though that doesn't work for the OEM Hailong type controllers that are potted. Interestingly, the after market ones are not potted.

 

[saitrix30]

Wow thanks for so many replies! Thanks for confirming the battery size is suitable, good to know what sort of Wh to go for. I would be building my own wheels so I have had a thought, I could change to 26" rims at the same time to reduce the BB height, that will allow the saddle to be raised ~25mm.

Is it ok having a battery inside of a bag? I thought I had read about it not being recommended, or have I misunderstood? I am happy to have it in the triangle but felt pretty hard to do. Is it best practice to build a solid frame inside of the bag to put shrinkwrapped cells?

Good point about the battery on a rear rack needs to be infront of the rear axle. Where do people recommend going for a custom battery?

I will have a think about the waterproof connector issue on the testing side of things. I am not going to have brake sensors so just need PAS, throttle & LCD.

 

[Bikes4two]

...... Is it ok having a battery inside of a bag? I thought I had read about it not being recommended, or have I misunderstood?

Some on here have said bags are not good - that however, has not been my experience and I note that @Woosh bikes are happy enough to now sell bag batteries.

Where ever the battery goes and what in, think how protected from impact and vibration during riding it will be?

Battery cells in a metal case such as an OEM bottle battery will have a very hard shell for protection - battery cells flopping around in a loose fitting soft bag that is exposed to impact is obviously far less well protected.

All that is stating the obvious of course but stated to make the point that cells that are tightly and firmly constructed in the battery pack and well fitted into a soft case that in turn is placed in the least vulnerable place will be fine IMHO.

I have three such battery packs - individually I have constructed them with triple layers of the usual cell pack materials and they fit snuggly into tight fitting handlebar bags. I've been riding this configuration for 12 months now and periodically check the pack covering and wiring for chaffing etc and so far there is not the slightest sign of a problem.

 

[saneagle]

Is it ok having a battery inside of a bag? I thought I had read about it not being recommended, or have I misunderstood? I am happy to have it in the triangle but felt pretty hard to do. Is it best practice to build a solid frame inside of the bag to put shrinkwrapped cells?

I'm going to say no. That's a general answer. I'll explain the risks, then you decide.

When the bike is parked, the battery seems quite secure in the bag, but when you go for a ride, the contents of the bag will start shaking quite violently. I've had batteries in panniers literally wear their way straight through the strong fabric. That's not the main problem, though. The wires must not be allowed to move or vibrate because any joints can separate due to fatigue and wires can rub through insulation with disastrous consequences. It's difficult to prevent that in a bag, but dead easy to glue everything in place when you have a hard case.

When we see pictures of ebike fires, the majority of them seem to involve batteries in bags, but we have no details of the mechanisms of failures. Sure, if you're careful to get everything packed tight and tied down properly, risks are minimised. I say it's best to avoid batteries in bags if you can, and if you can't, make sure it's done properly.

 

[saitrix30]

That is a fair point regarding the motion. What I haven't mentioned is I have a 3d printer so I can actually make a hard case to fit inside a bag and to glue the wires down with. I have been looking and seem to be able to get either a 10s3p 18650 or 10s2p 21700 for pretty reasonable cost for the cells, though I will need to do much more research into building packs before I will commit. The plus side is I can get a better weight distribution by doing this, plus if I get the correct size bag the controller can also fit in it (with good separation between the controller and battery).

 

[Woosh]

It is important that the internal connections are immobilised. That is usually achieved by using anti spark XT connectors throughout. If you build your own pack (I don't recommend building your own packs for reasons below), you need to solder the XT tails very carefully.
I don't recommend building your own packs though, because there are generally too many variables to deal with for your own peace of mind . Firstly, you can't be certain that all the cells in the pack are matched for having the same characteristics, capacity, discharge profile because the testing equipment that factories use to batch tests are not generally available. Secondly, you have no way of knowing the QA status of the bms and chargers if you just buy them on the net. Thirdly, new bms-es are tiny, it is very difficult to make perfect soldering of the thick silicone wires.