Mount battery to top-tube of full-sus?

[rilot]

Hey all.
First time post but been lurking for a while, gaining tons of useful information.

I'm looking to convert my MTB to electric and have pretty much decided on a Q128C 201RPM 36V rear hub-drive motor. I've been considering crank-drive kits but I think the hub-drive may be better for me as I want to be able to retain as many of my gears as I can (I have a 9-speed cassette, can I retain this?). I'm also lead to believe that a hub-drive kit is easier to ride unpowered. Happy to have my choice changed though if you guys think I'm heading down the wrong road. I mainly ride trails and roads. No big offroad hill-climbing.

My bike is a 2008 Saracen Ariel 3 full sus:

As you can see, there is no space to mount a bottle battery inside the triangle. Being a full-sus, I can't really go with a rack-mount either (there is another issue in that I tow my son around on his bike with a Trail-Gator and a rack would get in the way of that). So, I was thinking of mounting the battery to the top-tube on the frame with some clamps. Has anyone else done this? I can see there being an issue with the weight being fairly high up but it's not going to be any higher than a rack I think due to the steep angle of the tube on my bike. I was thinking I could butt it up against the seat-post to centralise the mass as much as I can.

Any advice greatly appreciated.

 

[Deleted member 4366]

It's a long way from ideal as a donor bike. High up batteries spoil the handling. If I wanted to convert that bike, I'd be looking at making a custom battery case out of GRP. Another option is to use a triangle bag and buy a triangle battery.

A Q128C would be perfect for what you want, but the 201 rpm one has a max speed of 19 mph when the battery's charged - 15mph when it's nearly empty. It works much better at 48v and will give proportionally more speed as long as you don't use the 48v version of the motor. it'll work with your existing gears.

The crank motors are OK to use with the throttle. The main downside is the more frequent gear-changing and the extra strain on the drive train. you'll also lose multiple chain-rings on the front, which is probably no problem as long as you don't want or need to ride without power.

given the cost of all the conversion stuff, I'd be thinking about finding the perfect donor bike rather than trying to make do with an available one. Swap all your parts onto this, then sell off your frame:

http://www.ebay.co.uk/itm/Rocky-mountain-mtb-mountain-bike-frame-xc-/263049380693?hash=item3d3ef70355:g:NIQAAOSwYIxX~6I3

 

[rilot]

Yeah, I've been considering just buying a new frame as you say. I can probably lay my hands on a hardtail from a mate of mine (it was my old frame).
I was planning to use the 36V version at 48V as that seems to be recommended on here.
I'm still umming and aahing about hub or crank TBH. I can see positives with both. If I went crank then it seems that the BBS02B is the one to go for yes?

 

[Woosh]

hello rilot,

this is an example of fitting the battery to a full-sus.

The kit is a GSM:

http://wooshbikes.co.uk/?cdkit#gsmkit

 

[rilot]

Now that's interesting. I never considered fitting the battery to the down-tube.

 

[Deleted member 4366]

I'm still umming and aahing about hub or crank TBH. I can see positives with both. If I went crank then it seems that the BBS02B is the one to go for yes?

I'd go for the 36v 25A BBS01 from Em3ev.com because it's legal. It's actually a BBS02. You need a good battery for 25A. Ideally, you want one one with a rating of 30A continuous or more.

 

[rilot]

Right, I've decided to actually go with a mid-drive kit rather than the Q128C hub-drive. From talking to a few folk it seems that it will suit the kind of riding I do better (I need to ride very slowly at times when I'm towing my son).

I'm going to go with the BBS02B in either 500W or 750W flavour but I'm a little unsure on the right battery to pair with it (probably going to change my frame as discussed). Or do you think the 36V 500W version would be better? FYI, I weigh 94Kg plus I will be towing a 20Kg child + childs bike.

Would this be OK? (48V 12.5Ah Case-08): https://bmsbattery.com/ebike-battery/817-48v116ah-case-08-bottle-panasonic-battery-pack-battery.html