3rd ebike battery. This time, doing it right

[Philaphlous]

Congrats on getting the pack into action! Maybe I missed it but what kind of bike and motor/controller are you running?

I probably haven't mentioned that. I've got a 9c clone from eBay. The controller is a shunt modded 12Fet with high regen added also. Ive seen 48A draw with my old battery. Not sure what it is now. I've got a torque arm cut I just need to install it.. Ive got a steel frame trek 800 sport from 2002. Kenda k838 slicks. Phase and battery wires are all 10awg.

 

[999zip999]

Get some kool stop dual color brake pads.

 

[Philaphlous]

Get some kool stop dual color brake pads.

I've got supra 2 ebike pads. They're great for rim vbrakes... 100x better than stock and regen saves them a ton! I'd say at least half my braking is regen

 

[Philaphlous]

Well this is a fun little deviation from utilizing the battery for my ebike.

Im converting the 48v dc to 12v dc then powering a 150w power inverter for my pc. I've done stress testing and playing games without any issues. I used to have issues where once I plugged in the charging cord to the inverter, it would trip the over current and turn off the inverter. Well I think this 12V converter has fixed that now. The true test will be using my wemo wifi plug that has always tripped the inverter every time I turned it on. I believe the inrush current is too high. If that works I'll have a pretty accurate watt meter.
I technically could get a 300w power inverter and maybe use a bigger converter for the 48V adapter but I figured I wouldn't necessarily need that. I ended up getting a cheap 200w converter which I would imagine it's more like 150w continuous and then the inverter would likely max out around 125w instead of 150. So I'm just over speccing the setup but it works great for my laptop!

My laptop is heavily undervolted on the cpu and gpu if anyone is familiar with that. So my max wattage is probably down near 100w max. Notebookcheck has 122w but that's not with any undervolt.

I've got another xt90 coming but for now I'm just pushing in the bare wires into the xt90 from the battery. It'll be nice to utilize this small setup to power anything if need be if the power goes out. Small little battery backup. Only downside is my charging takes way longer than it takes to discharge the battery. Lol.

 

[fechter]

I have a 48v input inverter that runs straight off the pack. I've used it to power my TV and DVD player during a power failure.

I missed it a while back, but on your BMS, the unused balance wires should be all tied to the highest cell. If not, you may get false triggers and shutdown as soon as you try to run a big bike motor.

 

[Philaphlous]

I have a 48v input inverter that runs straight off the pack. I've used it to power my TV and DVD player during a power failure.

I missed it a while back, but on your BMS, the unused balance wires should be all tied to the highest cell. If not, you may get false triggers and shutdown as soon as you try to run a big bike motor.

I used to get bms cutting off because of over current but I believe that's now fixed with a charger that actually has the correct voltage. It used to cutoff around 53.5V charge. Now that everything is balanced it'll charge right upto 54.6V and balance also.

The output wires are soldered directly to the lowest and highest cells..bypassing the bms entirely. I just have to be careful of overdischarge.

 

[Philaphlous]

Battery is working great so far.

I added some foam insulation to protect the cell connections. I still need to weld shut the box edges where they're screwed together.. I finished sanding the edges and making everything fit together really well. All the screws are in and the box is pretty tight. There's 2 openings in the box which kinda has me slightly worried about with water but for the most part that's covered by the jank battery bag that doesn't quite fit...

Charger is painfully slow but works perfect, same with the connector, I just need to solidify the connections with some hot glue inside the housing of the connector. I've also started to get some parts for my bike since summer is nearing!

I definitely need bearing grease...right now I don't have any. So my suspension fork can really benefit from that along with pretty much anything else that takes grease.

I picked up some new Chester clone pedals...my half broken and squishy pedals probably wouldn't cut it if I had to actually pedal home. I'm also actually thinking of finally painting my bike... Ill pickup a wire wheel for the drill and I'll be able to take off the paint down to the bare metal on my old trek 800. Im looking at this spray paint - Seymour 620-1433 Industrial MRO High Solids Spray Paint, Flat Black https://www.amazon.com/dp/B000AYJ0H0/ref=cm_sw_r_cp_api_i_05MPCbDSXTC0S
Apparently that's one of the best types of paint next to getting a bake-able alu gun paint... Im thinking with enough prep this paint should prove to be pretty nice. I'll just need a long weekend to be alble to paint the frame. I might have to split it into 2 sections since I doubt I'll have enough time to do it all at once.

 

[Chalo]

It really is best practice to have your bike running as well as it can possibly run before you add a superhuman amount of propulsion to it.

 

[SamRich]

Sorry to say, but your pack will not last long the way it is built.
You have too many bottlenecks that will stress individual cells, create heat, premature wear and an unbalanced pack with lower capacity and increased voltage sag.

I would consider re-designing the wiring to maximize the number of series connection where the current is the greatest.

 

[Chalo]

Sorry to say, but your pack will not last long the way it is built.
You have too many bottlenecks that will stress individual cells, create heat, premature wear

Those aren't nickel or steel strips. They're copper braid with much lower series resistance than the usual crap used in 18650 packs. I don't know what the effective gauge of the stuff he used is, but I doubt it will be a problem. It might be worthwhile to double it at the points where there's only one strand.

 

[Philaphlous]

The series connections are at least 2 pieces of copper braid (wick wire). The wire is about 0.5mm x 3.5mm. With the connections that look like just 1, I've double layered them to be 2 thick rather than 1.

That shouldn't be an issue with the pack. I'm pulling around 2000w max draw for a few seconds then more around 1000w continuous and the pack doesn't even get warm...

I knew someone would say it. Lol. I've used the solder wick wire since I've started making battery packs, this is my 3rd, and I've never had an issue with this and current draw. In probably the next few weeks I need to insulate the other side of the pack, I'll check the balance of the cells. I've done like 3 balance charges where I just let the battery sit on the charger for a super long time and since the charger stops at 54.6V now, it'll essentially trickle the charge down as it gets closer to the full voltage. Once that happens the bms kicks in and starts to balance. So I know my pack is working as it should.

I'm hoping to start my full 13.6mi 1-way commute this summer. My current 2.5mi commute almost doesn't justify an ebike...

 

[Philaphlous]

Oh and by the way. I've decided to ditch my battery bag idea. I'm going for straight battery box connected to the bike. The shape of the battery matches the frame of my bike so I have the idea of using metal and durable velcro straps to tie the battery down to the bike. I'll cut slots in the long side of the battery and also the side where it'll strap to the bottom tube and downtube and seattube. This should be very quick and easy for me to attach and detach the battery when I'm riding. I'm also going to be welding the inside joints of the battery and using glue to ensure the battery is water tight.

I'll be ordering the straps off amazon here shortly. I think this is really going to streamline my setup. And all the more need for me to vinyl wrap my battery box..

 

[SamRich]

The series connections are at least 2 pieces of copper braid (wick wire). The wire is about 0.5mm x 3.5mm. With the connections that look like just 1, I've double layered them to be 2 thick rather than 1.

It may be better than it seems - so glad to hear that. But it still looks like the distribution of current is not equally balanced across some of the cells. I know form experience that it is a challenge when building a triangle packs, so not trivial to find a better design.

Do you know how much current one braid is rated for?

 

[SamRich]

Oh and by the way. I've decided to ditch my battery bag idea. I'm going for straight battery box connected to the bike. The shape of the battery matches the frame of my bike so I have the idea of using metal and durable velcro straps to tie the battery down to the bike. I'll cut slots in the long side of the battery and also the side where it'll strap to the bottom tube and downtube and seattube. This should be very quick and easy for me to attach and detach the battery when I'm riding. I'm also going to be welding the inside joints of the battery and using glue to ensure the battery is water tight.

I'll be ordering the straps off amazon here shortly. I think this is really going to streamline my setup. And all the more need for me to vinyl wrap my battery box..

Here's what I did on my last triangle pack:
Used 1/8" Polycarbonate (would recommend 3/32" instead)

Used heat gun to shape into shell:

And 1.5" velcro to hold the battery to frame:

BTW this was the Layout for that pack... you can see how each P group has a maximum of series connection. You can see as wanting to maximize the "contact area" between the Green and Red lines:

 

[fechter]

You can make nice, clean bends in polycarbonate by using a bending brake (improvised) and only slightly heating it. Polycarbonate wants to start bubbling up right around the same temperature it gets soft, so hard to heat bend like acrylic or PVC. I've done it cold with good results but it may split near the ends if it's too cold.

 

[Philaphlous]

Yea I get what your saying about the connections, I'm pretty sure this copper wick wire is very low resistance so I'm not too concerned about exceeding it's limits. I'm pretty sure it's somewhere around the 14awg with 1 braid, likely around 10-12awg with 2.

The box is already built and I intended to go with a strong yet Semi flexible material, hdpe was a good fit for this! The straps should complete the batter box along with some foam glued to the sides so it fits the downtube well and then some vinyl wrap.

 

[Chalo]

I'm hoping to start my full 13.6mi 1-way commute this summer. My current 2.5mi commute almost doesn't justify an ebike...

*Hoping* to start a long commute? That's messed up!

 

[Philaphlous]

The wifey has a different opinion on my "fun" 13 mile commute... More like flat tire city...or the potential for there to be one...then I'm screwed... But I do carry a repair kit and new inner tube.

 

[Philaphlous]

Few updates:

I finally switched over from the frame bag to the battery box secured to the frame with velcro straps. Unfortunately the 12" length buckle straps are too long and I need to wedge something between the frame and strap to give the strap a secure connection to the bike...it was actually quite easy to cut slots in the battery and wedge the straps in through the bike.

I think I'll be able to sand and paint the battery box tonight! So that'll at least make it look halfway decent.

I also ordered just now a $25 175mm 54t crankset. Its a single track and it didn't say what chain size so I'm really hoping it's 3/32... Anyway, if it does work it's going to be great because my current 38t chainring doesn't do anything when I'm at speed which is 25mph+. Now I'll be able to pedal and get some exercise while helping the bike out!!!

 

[Philaphlous]

Few more updates:

Had my first experience having some dude yell at me while biking to work... Well another biker coming from the other direction yelled at me. Not sure why...he looked pissed and I slowed down too...it's not like I don't obey the trail rules...Maybe he was just upset he didn't have the power I've got??

Battery and charger are holding up well! Rode in this am on a fully charged battery. Has plenty of juice, I just like going fast so I fully charge or right before I leave in the am.... I top out with speed so I'm constantly at full throttle...im essentially limited by voltage now which isn't surprising on this long ride... I wish I had 72V since my bike is pretty smooth and I could easily handle the higher speed but oh well...those mods would be quite a haul to do and I'm just not willing at this point...

My ride is pretty nice. I ride full speed for a good 4-5ish miles without slowing down or having to stop.

Because I'm maxing out on voltage rather than amps on my ride the battery barely even gets warm through the case so im pretty sure I'm pulling around 650-900w when riding full tilt which isn't much for this battery. That's about 2amps per cell which isn't bad. When I finish the 13mi ride the battery is typically at 49.5V resting so I've got plenty of charge left.

 

[pwd]

Battery and charger are holding up well! Rode in this am on a fully charged battery. Has plenty of juice, I just like going fast so I fully charge or right before I leave in the am.... I top out with speed so I'm constantly at full throttle...im essentially limited by voltage now which isn't surprising on this long ride... I wish I had 72V since my bike is pretty smooth and I could easily handle the higher speed but oh well...those mods would be quite a haul to do and I'm just not willing at this point...

Because I'm maxing out on voltage rather than amps on my ride the battery barely even gets warm through the case so im pretty sure I'm pulling around 650-900w when riding full tilt which isn't much for this battery. That's about 2amps per cell which isn't bad. When I finish the 13mi ride the battery is typically at 49.5V resting so I've got plenty of charge left.

Sounds like the build is paying off. Charging right before you leave is good practice anyway as long as you aren't charging your cells to %100 (4.2V). I like charging to around 4.1V per cell. The less time the cells sit fully charged; the more potential cycles you will get out of the pack.

To address you need for speed; you have a couple of options that don't involve a new battery. The first option I would recommend would be to upgrade to a controller that has a "120% speed" setting/flux weakening/field weakening feature. There are several threads that explain how it works but basically it can get you roughly 3-10 percent more top speed at the expense of more amps and less efficiency when flux weakening kicks in.

The other option would be to swap to a motor with a higher Kv (rpm per volt). This will also require more amps from your battery.

 

[999zip999]

Having fun. You may be able to fit a 54 tooth but a good chance you would have to get a wider bottom bracket and maybe if you have a steel frame a gentle kiss with a 3lb hammer might make some clearance.

 

[john61ct]

Just don't hold charging CV at all if it's at a low C-rate, charge **to** just below the max rated V and stop.

Or if C-rate of charge is high, hold CV for a little while if you want to get SoC up there, but too long / too low endAmps, is indeed stressful.

so I fully charge or right before I leave in the am.... I top out with speed so I'm constantly at full throttle...im essentially limited by voltage now which isn't surprising on this long ride.
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Because I'm maxing out on voltage rather than amps on my ride the battery barely even gets warm through the case so im pretty sure I'm pulling around 650-900w when riding full tilt which isn't much for this battery. That's about 2amps per cell which isn't bad. When I finish the 13mi ride the battery is typically at 49.5V resting so I've got plenty of charge left.

Those latter data points are giving you so much extended longevity the "fully charging just before setting out" is a relative non-issue.

Doing the same every night-before, yes, then back off the top point a bit, really best to do as you're doing.

 

[Philaphlous]

Yea. I'm charging at a painfully slow rate... 1.75A charge rate which means it takes like 6hrs to charge it back up from my ride. Cutoff voltage for the charger is 54.6V as it should be and my bms is working properly so everything should be in spec.

I was finally able to fit the 54t front chainring on and it works great! I even have a chain guard so my pants don't snag on the chainring and my chain stays on over bumps!

For long trips like mine sometimes I totally see the need for 72V. I think I have the lowest/fastest? Wind on the motor so 72V would be a nice upgrade. And the bike is rock solid so bringing things up to 72V would be a welcome speed upgrade...but like I said, Im not going to invest the time and $$$ plus my battery supplier for my panasonic cells closed their doors so I don't have a cheap source anymore.

Plus going 25mph while pedaling seems to piss other bikers off a ton! Im sure it's just an east coast thing but as I'm riding home I get these freaking nasty looks, I imagine the same looks big oil execs look at Tesla owners driving by them... Anyway it's awful. I'd say maybe 10-25% of the bikers look pissed at me while I'm passing them AND I'm pedaling so who really cares? Plus my bike is pretty darn quiet so it's not like I'm causing a ton of noise pollution messing up their vibes...it's confusing. I'm sure if I had 72V I'd start getting people blocking my path and throwing bananas in my path...

 

[fechter]

Plus going 25mph while pedaling seems to piss other bikers off a ton! Im sure it's just an east coast thing but as I'm riding home I get these freaking nasty looks, I imagine the same looks big oil execs look at Tesla owners driving by them... Anyway it's awful. I'd say maybe 10-25% of the bikers look pissed at me while I'm passing them AND I'm pedaling so who really cares? Plus my bike is pretty darn quiet so it's not like I'm causing a ton of noise pollution messing up their vibes...it's confusing. I'm sure if I had 72V I'd start getting people blocking my path and throwing bananas in my path...

They're just jealous. As long as you are obeying the posted rules, they can frown all they want. It's not a competition. It's the Lycra mindset. Around here the number of ebikes is increasing to the point where it's becoming the new norm.