Eric's Project #002

[fechter]

I don't know anyone who's used conductive epoxy for building a battery pack. I'd be worried about the epoxy cracking due to vibration and too high of a resistance. I suppose if each sub-pack is connected by flexible wires, there shouldn't be too much stress on the epoxy.

I'd recommend brass or copper for the connecting strips so you can solder to them. Aluminum to copper bolted connections tend to go bad over time.

Make sure your epoxy does not block any vent holes on the batteries (not sure if Emoli cells even have vents).

Personally, I would not try the glue, but if you want to be a crash test dummy for the rest of us, that's great. If it works, it might be pretty slick.

Here's some links for DIY aluminum anodizing:

http://coloured.net/designresources/anodize.html
http://www.warpig.com/paintball/technical/anodize.shtml
http://astro.neutral.org/anodise5.shtml

Got a bathtub full of sulphuric acid?
I couldn't find the reference for the guys that just used Dr.Pepper (phosphoric acid), but I understand that does work too. Rit fabric dye comes in all sorts of colors, so you could be creative.

 

[dirty_d]

the high resistance of lead compared to copper doesn't even really matter at all, when you solder something together the copper parts are already touching or at lease very close to each other. lets say that there are two 10 gauge wires 12" long butted together with .125" of solder separating them. 12" of 10 gauge copper has about .001 ohms of resistance, lead has about 9 times less conductivity than copper. the lead section is (24" / .125)192 times shorter than the copper so it has ((.002 * 9) / 192).00009 ohms of resistance, thats not even measurable. id just use solder for all the connections.

 

[Beagle123]

In my case, I'm not so concerned with the resistance as the ability to attach the batteries to each other. I plan to "kill two birds with one stone." I'm hoping I can make a good connection AND glue them in a row of 6 batteries to metal ends like in my previous pictures. I'm sure the electrical connection will be superior to any connector because when I put a drop of epoxy on the end of the battery, it will expand to about the size of a dime when I press the metal bar to it. Even with lesser conductivity, the large surface area should provide a perfect connection.

I was thinking about this, and I think we do have to pay attention to resistance more than you'd think. We encounter electrical parts like connectors that have stats like "handles 50 amps at 110v" etc, and we assume that this part will work well for us because if it can handle 110v it can sure handle our voltage. But I think that is backwards. My scooter for example will be working with 3.8v or so. You may be thinking, "but its a 48v scooter, so its 48v," but that's wrong. When I connect one battery pack to another (as I will do 14 times) the voltage difference is 3.8v. This lower voltage needs less resistance than high voltage. Using the plumbing analogy, lower pressure would travel much worse through a skinny pipe. That's why power companies use high-voltage lines to transmit power over long distances.

Keep in mind that any little power loss that I experience at 3.8v will be multiplies by 14 times.

Here's an example:

Suppose you're using 6 feet of 12ga aluminum wire. Suppose that you planned on running 30 amps through it at 3v.

Your voltage drop would be 1.145v or 38% (ouch).

Try messing with this calculator:

http://www.powerstream.com/Wire_Size.htm
(bottom of page)

Fetcher, please check my work.

After writing this I realized that I'm using "standard wire." It's shiny silvery metal. Does that mean its aluminum? Maybe I should switch to copper.

 

[Beagle123]

Last Panels on Frame Welded. Motor Mount Welded, Footpegs welded. Trying to Fit chargers into Neck.

I was planning on plugging 14 chargers into power-strips and stuffing them into the neck portion of my frame. But I seriously mis-underestimated the size of neck. There was no way they'd fit. What was I thinking? So I did what any of us would do, I started taking the powerstrips apart. Luckily inside the powerstrips were convienient little pieces of metal that I could use to link the chargers together with, so I get rid of the power-strip's bulky plastic body (including switch).

It was still tough to make it fit. I finally found a configuration that squeezes enough space to make it fit. By making a small triangle of 3 chargers that fit in the absolute tip of the neck, I gained enough room to fit the rest. Close one!

I'm assuming that because the two prongs of the plugs are identical on these chaargers that you can plug them in either way to an outlet. I hope this is true because I'm wiring them in forwards and backwards. It basicly the same as plugging them in upside down.

I'm wondering if I should solder the plugs into place. I don't know what kinds of metal can be soldered. It look like shiny silver metal. I guess it will work.

I was thinking that thiis was turning into one of my dangerous ideas because there's a bunch of exposed sharp metal edges that will be at 110v AC. But I don't think it will be dangerous anymore because I realized that the jack I'm going to plug my power cord into has a ground on it. All I have to do is ground the body of the bike, and if anything shorts, it will just blow a fuse in the house.

 

[dirty_d]

its not that low voltage needs less resistance its that higher current needs less resistance, if you have a connector that handles 110V at 50A then it will handle 3V at 50A just the same, you also shouldn't use 6 feet of 12 gauge aluminum wire between each battery, try about 6 inches of 10 gauge copper :lol:

 

[xyster]

I'm assuming that because the two prongs of the plugs are identical on these chaargers that you can plug them in either way to an outlet. I hope this is true because I'm wiring them in forwards and backwards. It basicly the same as plugging them in upside down.

Yes, it's AC on that side so each charger can be plugged in either direction. Coming along nicely. Looks better than my mess of chargers.

 

[Beagle123]

Looks better than my mess of chargers.

Chargers Assembled

Well xter, thanks to you, here's my "charging slug" (it looks like a slug to me).

I didn't realize how tricky it was going to be to get these chargers to fit into the neck of my bike, but I finally did it. It was slow tedious work that took all day. Its not pretty, but I feel like I've created a masterpiece.

The chrger will fit into the neck as pictured. The single charger fits at the absolute tip of the neck, then the triangle of three, then the big block of chargers, then a few at the bottom.

I discovered that those cheap little connectors that are made to fit a tab into them can be widened a little and made to fit over the prongs on the AC plugs. They fit perfectly. Then I bent the prongs of the plugs to save room, and covered them with heat shrink. See pics.

I'm going to use silicone calk to hold the block together. I think silicone is perfect because its not so strong that I won't be able to take it apart again. In fact, I think I could rub the silicone off the chargers leaving them clean. I'm sure it will hold firmly.

I'm going to put a PC plug on the outside of the bike so I can plug a normal PC cord into the bike to power the chargers. The jack will have three wires coming off with three andersen connectors attached to the ends. There will be a positive and negative lead for the chargers, and a ground lead. The chargers are all wired together so they will just have 1 set of andersen's connectors coming off them. In the pics below you can see the ground lead attached to the bike's frame.

The bottom of the neck will be removable, so if I waant to remove the charging slug, I can unbolt the botom of the neck, unplug the andersen's connectors, and remove it.

 

[xyster]

Interesting prong-bending technique there. I'd be very wary of grounding the bike frame -- with all those little lightly-insulated wires enjoying a bumpy, sometimes wet ride, grounding greatly increases the chance of a short. One positive lead against any part of the frame, and thar she blows....
I don't know of anyone else here that's grounded to the frame -- I assume this is the reason why. Below is an explanation of the reasons for grounding I found quite enlightening:
http://www.ibiblio.org/obp/electricCircuits/DC/DC_3.html#xtocid43852

 

[safe]

"Notice that in this condition, 20 volts is enough to produce a current of 20 milliamps through a person: enough to induce tetanus. Remember, it has been suggested a current of only 17 milliamps may induce ventricular (heart) fibrillation. With a hand-to-hand resistance of 1000 Ω, it would only take 17 volts to create this dangerous condition"

Which makes 48 volts already very scary and 72 volts even worse...

 

[xyster]

Which makes 48 volts already very scary and 72 volts even worse...

Any concentration of power must be handled with a proportionate level of skill, wisdom, and care.

 

[dirty_d]

the 1000 ohms hand to hand would be under extraordinary circumstances though. your hands would have to be soaked with salt water with their entire surface area in contact with the to objects at 20V, like two large pipes.

 

[TylerDurden]

Any concentration of power must be handled with a proportionate level of skill, wisdom, and care.

Awww... I bet you say that to all the girls.

8)

 

[xyster]

Any concentration of power must be handled with a proportionate level of skill, wisdom, and care.

Awww... I bet you say that to all the girls.

8)

TD: Any concentration of power must be handled with a proportionate level of skill, wisdom, and care. :lol:

 

[TylerDurden]

Any concentration of power must be handled with a proportionate level of skill, wisdom, and care.

Awww... I bet you say that to all the girls.

8)

TD: Any concentration of power must be handled with a proportionate level of skill, wisdom, and care. :lol:

Hey, if yer usual lines work for both the bouys and gulls, more power to ya... but I'm not fallin for any simple techie mumbo-jumbo.

On the other hand, if Danica Patrick said that to me, I'd slather her and myself with Permatex pure silicone dielectric grease faster than you can say "fuel-injection".

8)

 

[xyster]

On the other hand, if Danica Patrick said that to me, I'd slather her and myself with Permatex pure silicone dielectric grease faster than you can say "fuel-injection".
8)

Shockingly specific, you must have tried it. Good luck -- sounds like it's high time you found a partner.

 

[Beagle123]

I'd be worried about the epoxy cracking due to vibration and too high of a resistance. I suppose if each sub-pack is connected by flexible wires, there shouldn't be too much stress on the epoxy.

Epoxy is a very strong substance. It is used to bond the heads of golf clubs to their shafts. I'm not worried about the epoxy breaking. I'm worried that I'll never be able to get them apart again, and I'll have to replace whole packs instead of individual cells.

There is a way to break epoxy: You can heat it with a torch, and it will break down. It takes a fair amount of heat to do it. I'd have to really look in to some serious protection before trying to torch my packs. I'd need a really hot torch to get the metal off quickly.

I'd be very wary of grounding the bike frame -- with all those little lightly-insulated wires enjoying a bumpy, sometimes wet ride, grounding greatly increases the chance of a short. One positive lead against any part of the frame, and thar she blows....

The bike's frame will only be grounded when its plugged in. The batteries' positive and negative wires will be isolated as on any bike. The ground wire runs from the third prong on the ac plug to the frame. The purpose is to keep the "hot" 110v ac circuits that run the chargers from electrifying the bike's frame. If they ever came in contact with the frame, it would be 110v.

I was about to say that you might be right because if the batteries came in contact with the frame, it they would get grounded as soon as you plugged in the ac plug. However, grounding a battery terminal won't complete the circuit. It won't short unless there is a path to the opposite battery terminal. The only way for it to short would be if both battery terminals contacted the frame--but that's the case anyway regardless of grounding the frame.

I'd like the frame to be like a big household electrical box. Nothing can seriously go wrong when the housing is grounded (aat least with the ac circuit).

I'm going to have to seroiusly protect all the battery wires. I'll have 14 charging leads that have to be protected too.

 

[Beagle123]

Cover for Neck Made, Battery Jig Made, Jack Installed, Chargers Glued Together

I cut the final piece of tread-plate for the neck cover. This is the removable cover for the bottom of the neck.

I installed the PC jack in the side of the neck and connected the ground wire to the frame (don't worry xter, its removable if necessary). The andersen connectors from this jack will power the chargers.

I glued the chargers together with silicone calk that was left over from my window-install project. Its nice and flexible and it can be broken apart if I ever want to dismantle my chargers.

I made a jig so I can epoxy the batteries together. It's basicly just providing holes that are 1 battery wide, and 6 batteries long. Using this jig, I can align 6 batteries vertically. I will place a piece of metal on a tabletop with 6 drops of epoxy on it, then I'll use this jig to hold 6 batteries upside down on top of the epoxy until it dries. Its important to hold the batteries upside down because the sides of my batteries are connected to the negative (bottom) side of the battery, so any conductive epoxy dripping down the sides would short the battery.

I can only make 3 packs at a time with this jig. Maybe I'll make another.

 

[fechter]

If you ever had to take the epoxy apart, you could heat the connector bar by soaking it in boiling water. This gets the epoxy just hot enough to get soft, but can't get hotter than 100C. I'd guess the plastic insulators inside the cells can handle 100c for a few minutes.

 

[Beagle123]

6 Batteries Arrived--Dismantled, Went Shopping, Made Load Tester

6 of my batteries arrived today. When I took them apart, they were a different color than the first set. They're colored like a brown paper bag. See pics. I'm not complaining because their voltage was better (3.95v). I'm still waiting for 5 more.

I made a load tester like xter's. Its made from four 10 ohm resistors in parallel. The idea is that you test each battery by connecting it to the resistors and see how much the voltage drops. The less drop, the better. My cells started at 3.85v. When connected to the tester, they all dropped to between 3.67v and 3.70v. Since they're all the same, I'm assuming that they're working properly.

I weighed the whole frame. THe total is 19.0 lbs.

I bought a big fuse today at auto-zone. Its a 175 amp "mega fuse." I just want protection against a short (which I've done twice when working on my last bike).

I bought automotive tubing to cover the footpegs so I can put my feet on rubber instead of metal. Automotive tubing is very convenient because they sell it based on the inside diameter. I used 3/8 inch aluminum rod to make my footpegss, so it was easy to find 3/8 ID rubber tubing.

 

[safe]

I weighed the whole frame. The total is 19.0 lbs.

My #002 frame will be in that weight range too. My #001 was about the same. I'd like to get down to the 15 lb to 10 lb range but by that point you are going to have trouble carrying the extra battery weight.

Rigidity is more important than weight at this stage of the developmental game... (when you hit a bump at speed you will thank yourself for building it stronger than needed)

 

[dirty_d]

i see that welding book there in the picture i bought that a long time ago too, so you want to learn how to weld?

 

[Beagle123]

Safe, I didn't really consider rigidity, but its definately strong. You should hear the "Thunk" sound if you knock on it.

Dirty, I have a cheap mig welder. It was pretty easy to point it and pull the trigger. I made some decent welds, but nothing as nice as yours. I wouldn't be totally confident in them. Also its impossible to weld aluminum with it, so I was destined to find an alternative.

 

[Storm]

Hey its looks better then I thought it would when you first started posting....well done, strong too.

congratulations.

 

[dirty_d]

if you buy a spool gun for your mig welder and an argon tank you should be able to weld aluminum, but you would be better off with a tig welder. are you using shielding gas with the mig or using gasless flux-cored wire?

 

[Beagle123]

Thanks Storm.

Dirty:

Ive used flux core wire on steel. I've never welded steel with gas. I actually have a tank of 100% argon that I bought anticipating that I would be welding aluminum. However, welding aluminum with a cheap mig welder is impossible. First of all, you need lots of amps. Mine is only a 70 amp welder. Second, I agree with you that the way to do it is with a reel of aluminum attached to the gun because aluminum wire is too soft to feed down the tube. I'd really like to learn welding, but my options are limited right now.