New Surly Big Dummy build - battery choices

[green79]

First time poster, thanks for all the great information here I've learnt a lot on this forum!

I'm about to put an e-assist and thought I would seek some advice on battery choices. The build is a 24" wheel Surly Big Dummy. I'm looking at an eZee rear hub, 20A Grinfineon controller, 12 pole PAS with a CA V3. I'm not looking at going fast on this as it is a two kid hauler and primarily for dealing with big Seattle hills. I am considering two battery choices:

1. em3ev 50V 12.3Ah Triangle pack in a custom frame bag in the small rear triangle behind the seat tube. Like in this link: http://thelazyrando.wordpress.com/2010/12/01/surly-big-dummy-frame-bag-2/

2. em3ev 36V Samsung Frame pack, 16.5Ah.

The range is about the same (600 watt hours).

The pros of the triangle pack: uses space that I otherwise would not use. It would also have the weight nice and low and centered. I think the controller would also fit in the frame bag. With the frame bag and rear bags hiding the hub motor it would just look like a normal cargo bike. The cons are I can't lock it and it is a bit more expensive than option 2.

The advantage of option 2 are the locking, removable battery case but I lose the front triangle space for water bottles etc. Sadly I can't fit the battery in the rear triangle (I have a 16" frame and the case also rubs against the chain). Weight is slightly higher up but also more to the front to balance the hub motor so weight distribution might be a wash

My questions to are:
Any other considerations I am missing?
Any advice either way?
Any suggestions on ways to lock the triangle battery/frame bag?

 

[dogman dan]

50v will give you more wattage to get up those hills, vs 36v.

 

[mlt34]

Yea I'm still trying to find a good way to lock a triangle frame battery bag. I love those triangle bags for so many reasons, but theft resistance isn't one of them.

For double zipper bags you can use a small luggage lock to lock the zipper pulls together. You can also use a small steel cable to lock a single zipper pull to somewhere else on the frame to prevent it from opening. Or glue it if you don't plan on accessing it often. Hot glue would be semi removable if needed.

A couple options for locking the bag itself to the bike: Rivet the straps onto the bike. If that's too perminent for you, sew the velcro closed. Neither of these stop someone with a bike thief with a knife, but they'll help fight opportunistic theft, where someone sees a bag on an ebike and wants to check out what's in it, or steal the bag entirely.

None of these are great options. That's the problem with triangle bags. I just take my battery with me if I park in a public place. Throw it in my backpack and then explain to the security guard that its not a bomb. Standard operating procedure.

 

[green79]

Thanks for your thoughts!

I'll definitely put a padlock through the two zippers but also want a way to secure the battery itself to avoid having to bring it with me each time. My latest idea is to create a harness for the triangle battery of some kind using metal straps (http://www.oatey.com/img/product/33929.jpg) perpendicular to each other so they couldn't be slipped off and then bolting the harness using a security allen or torx bolt to the water bottle bosses. I could even do this inside the bag by punching holes in the frame bag where the bosses are located.

Any other ideas are welcome!

 

[erik_m]

(post deleted)

 

[green79]

Thanks - i ended up going with the frame pack and using the savings to go with a Thun BB instead.

As a PSA if anyone is looking for reasonably priced custom bags this guy has a pretty good deal on at the moment: https://www.etsy.com/shop/RoguePandaDesigns

 

[dogman dan]

They just take the whole bike, you know.

But to secure the battery to the bike better than sewing shut a bag, something hard that requires undoing some screws is best. A home made box. Screw heads can be epoxy filled. Then a locking door to access the battery for your convenience.