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MB-1-E Part Seven: Securing the batteries connecting them up.
Submitted by MB-1-E on Fri, 05/18/2007 - 08:16
The past few days I've been pretty busy, so didn't have a lot of time to get a much work done on the Mountain Bike.
After working with the acrylic enclosure for a full afternoon, I abandoned the idea. I got all the pieces cut and started gluing it up and then simply changed my mind.
I had a DeWalt jigsaw case that I never use and found that 6 of the 8 batteries fit inside nicely.
I cut the dividers out with a dremel tool so the box was now one open space to work with. Next, I bent some aluminum flatbar to fit inside and used small machine screws to secure it. This would keep the batteries in place within the case.
Once I got this done, I loaded it up with batteries and was able to pick it up and carry it as a unit.
I used a hole saw to cut two holes in the case so it would fit over the top horizontal bar on the bike.
Next, I bent some steel flatbar and made a strong support to hold the weight of the case and two more batteries below. I secured the steel flatbar using the existing water bottle and airpump screw bosses and socket head cap screws.
The case comes up a bit above the top bar, but doesn't interfere with pedaling or sitting comfortably on the bike.
I looked for connectors and wire at the local hardware stores and online but just didn't find exactly what I was looking for. I did order some 6ga welding cable from McMaster Carr that will go from the battery box to the controller and from the controller to the motor.
I also got some jumper cables which were fairly flexible and decided to use this wire for my interconnections at the batteries. As for the connectors, I got some small diameter copper tubing and started making my own. I drilled a small hole through each battery terminal and found some small machine screws and nuts that would secure the connectors to the terminals. I cut the copper tubing about 3/4" long, smashed one end closed to make a nice flat mounting flange. I tinned the cable ends and the copper connectors then heated them until they flowed together. I drilled a hole through the flange then removed any burrs and polished them up on the wire wheel.
I used some heatshrink at the ends to seal the insulation to the connectors and screwed the wire ends to the terminals.
It's a bit of a pain to do each one this way, but I think it will be a lot better connection than using push-on female spade connectors. Once all together, I'll coat the terminals and connectors with some nail polish to seal them.
Once set in the case, I shouldn't have to remove them, I'll just be charging them as a set.
I'll have a DPDT switch set up so I can change the two main leads from 24V series/ parallel to 12V parallel for charging with my Iota 12V charger.
I'll find a good connector that will allow for the controller leads or the charger to connect. I'll just open the case, remove it from the bike, close the case and carry it inside for charging, using the cases carrying handle.
Should I decide to later, I could divide the batteries up into two sets and make some saddlebag type cases for them, but I think this should work well, hopefully I won't need to change it.
Note: This building an electric bike from scratch is definately not for the faint hearted, there is a ton of trial and error and custom work involved and there's quite a lot to it. Those who get a kit should appreciate that most of the details have been worked out for you and only a few minor custom changes needed to make it suit one's individual bike. I'm not complaining, mind you, just trying to give some insight into what is involved in starting from scratch.
I get the satisfaction of success (or failure and having tried). I think I'll end up with close to what I want in an electric mountain bike, but it's no cake walk as I'm sure many here can testify.
Stay tuned for more, I should be getting my controller and jackshaft assembly soon.