3rd ebike battery. This time, doing it right

[Philaphlous]

Allllrrriiighht I'm basically just talking to myself here till I actually start putting it together...

1. I believe I've ordered the rest of the parts I need to complete the battery. Hdpe has been ordered. I decided to go with 1/4" thick because I want to keep the weight down. I'll use plastic/drywall screws to join the pieces together.

2. What's the voltage/amperage ratings of barrel connectors? I'm planning on utilizing waterproof 5.5x2.1mm plus for my charge port...since I'm not charging at a high current I figured that would be acceptable. I'd likely be 2A max even with a new charger....

3. I'm going to wire a switch with a voltage meter into the battery near the bms so I can switch on the small volt meter to check the pack voltage. Right now I have to use a multimeter and once I start riding farther I'd like to be able to measure the voltage on the pack itself...

4. I should be able to easily wire up the xt90 connector through the hdpe and secure it with hot glue or epoxy. I'm leaning more toward the epoxy for 2 reasons... 1 it'll bond to the hdpe better and 2 it'll be more waterproof...I want to be able to seal the battery at the joints with a sealant to ensure it is completely water tight. I don't plan on using the battery in the open but instead inside a bag on my bike but I still want it to withstand any amount of water.

 

[Vmw1982]

Did anyone talk you out of soldering these cells together as the heat will defiantly damage them and take a couple hundred mah away?? It’s a great idea to spot weld. You can make one very cheap with a capacitor. Look it up on YouTube. Please.

 

[Philaphlous]

Did anyone talk you out of soldering these cells together as the heat will defiantly damage them and take a couple hundred mah away?? It’s a great idea to spot weld. You can make one very cheap with a capacitor. Look it up on YouTube. Please.

Time and time again this is completely false... The only way your looking at damaging cells is by sticking a soldering iron on the negative side for about a minute....then you might as well expect an explosion... A lot of people on the forum have disproven this idea and I can also confirm with my own cells that if you solder them correctly, there is absolutely no damage...same resistance same capacity...

The wick wire for connecting the cells IMHO is a great idea since it's pure copper...ive see a few other people use it and I love the stuff. Super easy to solder and really handles the current well.

 

[MJSfoto1956]

... defiantly damage them ...

The wick wire for connecting the cells IMHO is a great idea since it's pure copper...ive see a few other people use it and I love the stuff. Super easy to solder and really handles the current well.

Remember though, he's being defiant!

 

[Vmw1982]

Ha ha. My spell check could be better. Are you that annoying kid that pointed everyone’s mistakes out to make your self feel or look better for some underlying childhood reason??? I will have to try this and test the cells and see what happens. I have tried and didn’t work for me. But I wasn’t using Cooper wick which does sound like a really good idea. But I bought a spot welder so I’m gonna use it. What type of solder do you use? Some stiff is hard to get it to stick or melt without a huge iron?

 

[Philaphlous]

I think it's like a 63/37 rosin core. You are having difficulties getting the solder to stick because the surface is smooth. You need to either sand it down or even better, take a dremmel to it with a stone bit and rough up the surface. Once it's roughed up it'll suck up the solder like a kid at Disney with some cotton candy...

Since I've testing every cell I'm basically considering this the safest battery I've ever made...with it encased in hdpe and cushioned in rubber padding the battery should be extremely resilient...Hopefully.

 

[Vmw1982]

I build a lot of batteries. It the Dremel sand stone will work. If I ever need a quick patch job I’ll use that. Or sometimes for bus bars. I do a lot. Of batteries. Anyway. Make sure the battery vents. I’ve had problems with padding it too tight and taping it air tight. That’s not good for the battery. Any questions please feel free to ask. Like I said. I make a lot of batteries. I making 5 right now.

 

[Philaphlous]

Little bit of progress:

I got all the new cells ground on both the positive and negative terminals. I have the design ready. So basically I need to bend the hdpe sides next as I've started to cut the shape of the top and bottom hdpe plate for the shape of the battery.

I'm still waiting on my sensing wires for my bms and in the meantime I can finish the box and create my voltage meter and solder up my xt90. My idea is I need to quickly be able to build the entire battery while removing the old cells from my current battery in a weekend... So I need to do all I can with the cells I've got and basically be ready to just solder up the bms and add the cells and solder them all once I've got the pack ready. Im hoping for no downtime with my commute since I use my bike daily...

 

[ElectricGod]

Looks like a nice pack.

 

[Vmw1982]

Are you testing the cells to make sure they r alll the same mah. Or atleast group the ones the are similar? If not I urge you do this or your pack will lose charge quickly. And make sure every cell is at least with in .1v of each other.

 

[Philaphlous]

Are you testing the cells to make sure they r alll the same mah. Or atleast group the ones the are similar? If not I urge you do this or your pack will lose charge quickly. And make sure every cell is at least with in .1v of each other.

Don't worry. I'll have a bms...but yes. All cells were from Toshiba battery packs sitting in storage brand new with 0 cycles. All cells have been tested from full charge down to 3.1V at 4A to ensure similar IR and capacity, which they all are.

I'll be bending the hdpe this weekend along with hopefully tapping the screw holes and finishing the sides if it doesn't take too long to bend the hdpe. That should give me the shell of my battery back. Once that's done I can really begin to put the thing together. I have this mini volt meter that I'll be wiring up to measure the pack voltage. I'm also including a switch on it so that I can turn it on and off since it'll pull power from only part of the pack...that won't be an issue. I'm currently cutting the wick wire lengths for the pack so I'll start soldering the first few connections.

Hopefully should start picking up speed on the build here soon with lots more pictures.

 

[999zip999]

Take your time those little things are loaded - stored energy. And a hundred connections.

 

[Philaphlous]

I give myself a C+ on fabrication execution...

I got most of the box built over the weekend. I need to use a sealant..likely epoxy to seal up the edges. I was going to bed the entire sides of hdpe into the shape of the box and I quickly realized I'm awful at bending hdpe and I don't really have anything other than my hands to bend it into the shape I needed. So I had to resort to cutting and screwing together...which I guess is OK. Once I get the other side on and the battery finished I want to wrap it in a vinyl wrap so it looks a heck of alot cleaner. It's already really sturdy so it is accomplishing it's purpose as a safe and reliable battery housing for my bike.

One unfortunate thing I discovered is I don't think my bms will fit on the back side of the battery where it juts out.. I may have to put it on the side where the cell contacts are so I will have to insulate the crap outta it...

Ill be soldering up the cells I've got right now here pretty soon along with cutting the holes or the charge port, xt90 and mini volt meter.

 

[Chalo]

I need to use a sealant..likely epoxy to seal up the edges.

I'd go for silicone if you think you might ever want to open it up again for any reason. And because silicone is a better sealant.

 

[fechter]

If the white plastic housing material is polyethylene or polypropylene, most glues won't stick to it. They make a special glue that will stick, but it is not commonly available at the local hardware store. Many types of tape will stick well, however, so you may want to use tape along the edges to keep water out.

 

[Philaphlous]

If the white plastic housing material is polyethylene or polypropylene, most glues won't stick to it. They make a special glue that will stick, but it is not commonly available at the local hardware store. Many types of tape will stick well, however, so you may want to use tape along the edges to keep water out.

It's hdpe all around. Silicone sealant will bond to it if you sand the surface. I'm thinking my slow set marine epoxy will do better. I'm planning on opening 1 side so I'll fill up the other side with the epoxy so it's a pernament bond. Im not too too concerned about water getting in since it'll be in a waterproof bag for now when riding so it's basically like a 2nd layer of protection...........

At this point I'm most concerned about the opening for the volt meter and xt90. I think I'll seal those up with hot glue? But we'll see...

 

[john61ct]

FFR ABS is easier to glue, and tape.

Poly is pretty easily welded.

 

[fechter]

I guess the screws hold it together mechanically, so you only need rain protection. The vinyl wrap stuff will work for that.

 

[Vmw1982]

If the white plastic housing material is polyethylene or polypropylene, most glues won't stick to it. They make a special glue that will stick, but it is not commonly available at the local hardware store. Many types of tape will stick well, however, so you may want to use tape along the edges to keep water out.

It's hdpe all around. Silicone sealant will bond to it if you sand the surface. I'm thinking my slow set marine epoxy will do better. I'm planning on opening 1 side so I'll fill up the other side with the epoxy so it's a pernament bond. Im not too too concerned about water getting in since it'll be in a waterproof bag for now when riding so it's basically like a 2nd layer of protection...........

At this point I'm most concerned about the opening for the volt meter and xt90. I think I'll seal those up with hot glue? But we'll see...

Make sure u don’t seal it all the way. You will create and oven. Make sure your battery can vent!! Very important.

 

[Philaphlous]

Little bit of progress this am.

I'm starting to get the first few series of connections done. Soldering is super quick and it only takes maybe 1-2 seconds tops to solder each cell. I believe I have plenty of wick wire but I think I'm going to run out of solder....

So I think I figured a few things out. 1. I'm going to weld the edges of the hdpe since at around 200c it is a good welding temp and my soldering iron goes to that temp. I also have like 10 different tips I can basically make a welding tip if I need to. That should solve all my issues with bonding the pieces together. I'll still use the screws as mechanical bonding obviously.

I think I've also decided to add a usb charge port. I've find a cheap chinesium usb power adapter from 56v to 5v usb. That should hopefully work well as a backup usb charger if I ever needed one. Ill pick up some silicone covers for it so it'll stay waterproof.

I think I also figured out how I'll be able to squeeze the bms to the back of the pack... I can easily sand or cut the side of the hdpe and make it thinner if need be for the bms to fit.. That shouldn't compromise the structural integrity and it'll keep things nice and compact.

So for now I need to do the seam welding, finish soldering the series of cells I've got together, and cut all the holes for the switch and meter and install those and begin to wire them to the pack. Once I get some extended time I'll take apart, super carefully, my old battery pack to integrate the older panasonic cells to the new pack. These older cells should have very little signs of wear at all.

 

[Philaphlous]

I know its not battery related but I found out my hub motor has 16 awg phase wires... I repeat, a generic 9C clone off ebay has 16awg phase wires! utter cap! I may need to replace them with at least 12awg someday...but that someday isn't now. The length of the 16awg wires is only about 6" tops now and I've replaced my phase wires with 10awg.

Used some liquid electrical tape instead of shrink wrap and I also tapped the inside of my controller aluminum box so there's no chance of a short coming from any wires! The connectors to the phase wires on the motor are staggered XT150 connectors so they should easily handle the current!

 

[Philaphlous]

That moment when you realize your doing it the wrong way...

Taking apart a battery is freaking dangerous with a metal screw driver...lol thankfully I can clip every connection with scissors so I'm not moving them across the cells...

I've got 1 side completely dismantled so now I need to snip the connections on the other side then it should be relatively safe. I use rubbing alcohol to loosen each hot glue connection for the cells which makes it super easy to pull the cells apart. I'm almost out of solder which I ordered some more and more wick wire. This new battery is going to be 50x safer than this old one.

So if you look at the picture, the far right cell has a hole in it from me accidentally arcing the main 48v wire with the cell when I was wiring it...it actually corroded the outside of the cell but the blue layer within the cell is actually holding up. I'm going to junk that cell obviously. And the one that just arced with the screw driver... Ive already pulled off a few cells from the old pack and their capacity is within 0.2wH of the new cells so I'd consider that a win!

I basically have a ton of work to do to get the new battery even close to working. I'm not biking to work anytime soon with the current weather so that's good and even if I do I think I'll be OK with everything taken off the bike except the hub motor...which will look weird but hey..it's what I got. The actual weight of the bike isn't bad with everything taken off... I removed the stupid kickstand which will probably save me like 0.5-1lb.

So after arcing 2 cells I consider myself unfit to work for nasa or spacex. Lol. Jk that'd be awesome to work for them...but anyway my #1 goal of this new battery is safety and simplicity. Well I guess that's 2 goals... But yea. I think I need to coat each connection when I complete it with some liquid electrical glue to prevent any arcing from happening knowing my youthful hands and the slip of a screw driver...I even had my hands on the metal of the screwdriver which blasted my hands in black char...but I'm OK...

So stay tuned for updates soon on my new battery once I get this old one taken apart! I've got some grad school work and travel so that might slow down this conversion but I'd rather do it right then rush it. I do have a lot of parts coming and a new charger which I hope is a lot better than this 56.6V lead acid charger I'm currently using....

I will also have at least 2 usb chargers from the battery! I'm freaking stoked for this feature! I've found some 58v to 5v usb power converters so well see how well they work and are able to charge my phone or whatever. I plan to use it as a backup power source in the event of a power outage.

 

[Philaphlous]

So I've got the old battery about 2/3 taken apart with all the cells separated. I charged up some lastnight and oh my gosh... Im amazed I didn't have the entire battery die or cells explode... I used my 60w load tester to load individual cells at 4amps down to 3.2V. I did similar tests with all my new panasonic cells and all are within the range of 5.900-6.050wH. With the chinese cell I tested, I got 1.5wH after the same test. With the old Samsung cell I got more like 5.0. The same panasonic cell from my used pack got 5.89wH so those are holding up well. But man. I can't believe how little capacity is actually in the crap Chinese cells I thought I could use without a problem.

When it comes down to it now. This new pack is going to be freaking amazing compared to these mixed cells. Over the weekend I'll finish removing all the cells and begin charging and testing all the cells. I think this will be the definitive test to why we shouldn't use Chinese cells from a laptop battery in an ebike! I'm still shocked I got 1.5wH...just nuts!

 

[999zip999]

Before taking the battery apart take the energy out of it. A fully charged battery has a lot of potential stored energy.

 

[999zip999]

If I was deconstructing that battery I start at the negative end and get the first group of parallel cells cutout first then move my way up the chain in groups of parallel cells. How about someone else's input on this would you start at the positive end