I guess I need to make 72v 35ah battery pack

Theodore Voltaire said:
Thanks Cd, that's good to know. I may not use it on this pack though because it's going to be so tight for space.
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I would recommend not skipping padding like this. Barely paper and heatshrink alone is not going to be enough. I've seen multiple packs like that rubbed through to bare cell casings.
The padding mentioned above comes in multiple thicknesses. I would recommend getting various thicknesses and use thicker where you can manage. Remember it can compress slightly, and the side covers of the Bomber will help compress the sides of the pack more easily.

Cheers
 
Cowardlyduck said:
I would recommend not skipping padding like this. Barely paper and heatshrink alone is not going to be enough. I've seen multiple packs like that rubbed through to bare cell casings.
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In my observation, the padding the matters most is outside the block of cells. I use closed cell foam to shock isolate both batteries and electronics from direct contact with rigid frame elements. If you can keep the cells from hammering each other, then fish paper, heat shrink sleeves, thin plastic dividers or whatever are likely to be more than adequate.

If you use a million little penlight cells, you get a million chances to roll the dice. Just sayin'.
 
Yes, agree with you on the padding location Chalo. Was not talking about it being anywhere but between the cells and bike frame, or between the two halves of the pack possibly.
I've recently seen rub through of heat-shrink + barely paper + cell shrinkwrap at the lower top corners of a battery inside an early model Alpha. Specifically it was pressure from the inside of the rivnut/nutsert flanges and minute movement of the battery over about 4 years and the frame was directly contacting the cells. Was amazing that it didn't result in a fire!

Cheers
 
Cowardlyduck said:
Yes, agree with you on the padding location Chalo. Was not talking about it being anywhere but between the cells and bike frame, or between the two halves of the pack possibly.
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Textile panniers are very effective shock attenuation when they're applicable. Same for handlebar baskets. We love to hard mount stuff, but there are drawbacks to that.
 
This is half of my battery. Worked all day to get this far. It's real slow going because I've never done this before. The blue tape is just temporarily guarding the busses where the bms will hook up. In between the top and bottom there's 2 layers of fish paper, 3 layers of fiberboard, and about 5 layers of double sided heat tape..
20240816_205129.jpg20240816_205114.jpg20240816_172707.jpg
 
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This is how much room I have heightwise. The plastic holders don't quite take up all the room side to side so there's probably enough room for some thin foam padding along with some power wires.
20240816_160248.jpg
 
I worked up to the point where its better for Mr EE to do his thing. This is how we decided to bridge the 2 haves together. Positive on the top left. We have a plan for the main busses. They'll be on the bottom, side, straight down from here., Negative on the left. The bms is going tp be on the right side, end. Sifu bridge.jpgthey're next on the list.
 
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Theodore Voltaire said:
I worked up to the point where its better for Mr EE to do his thing. This is how we decided to bridge the 2 haves together. Positive on the top left. We have a plan for the main busses. They'll be on the bottom, side, straight down from here., Negative on the left. The bms is going tp be on the right side, end. View attachment 358688they're next on the list.
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Mr EE is quite the show off.
 
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Got a lot done in the last 2 weeks. The bms is installed. Next I'm going to run the output cables. Finish with a little more insulating, and then shrink wrap the whole thing. Should be finished with the build by Saturday. 20240905_174134.jpg20240910_175427.jpg20240910_175418.jpg
 
I finally got this bastard to come alive. I didn't know I was going to have to program the bms before it would work. I think I'll need some help going over some of the settings I don't understand. It took me about 3 hours to figure out how to connect to the ANT bms app. I also figured out you have to tell the bms to allow charging, and discharging. I stopped charging at 80v because I'm not sure if I have to tell it what voltage to stop charging at, and I didn't want to over charge it.

One question I have is, the bms came with a switch that I haven't installed yet, that turns off the bluetooth. Do I need this switch, and do I ever want to turn off the bluetooth?

Besides that it's looking pretty good. The difference in voltage between the highest and lowest group is 0.004v.
battery first life.jpg
 
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You should not rely on the BMS to stop the charge. The charger should be of the correct voltage for your cells. 20s should have a max voltage of 84V. The only things I found that needed to be set are number of cells in series and the correct chemistry. Then adjust as you see fit. Setting to the correct chemistry is important and will fill in the voltages in the app for you.
Later floyd
 
floydr said:
You should not rely on the BMS to stop the charge. The charger should be of the correct voltage for your cells. 20s should have a max voltage of 84V. The only things I found that needed to be set are number of cells in series and the correct chemistry. Then adjust as you see fit. Setting to the correct chemistry is important and will fill in the voltages in the app for you.
Later floyd
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Thanks Floydr.
 
floydr said:
You should not rely on the BMS to stop the charge. The charger should be of the correct voltage for your cells. 20s should have a max voltage of 84V. The only things I found that needed to be set are number of cells in series and the correct chemistry. Then adjust as you see fit. Setting to the correct chemistry is important and will fill in the voltages in the app for you.
Later floyd
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Are you sure about that?, My chargers are 84v. This bms is set to stop charging at 4.17v, so it considers 83.4v a full charge. What's wrong with that?
 
At long last my battery is almost finished. I think today's the day. All it lacks is the output plug, and the shrink wrap. I already charged it to 83.4v. That's what it's set for. It took me a while to figure out how to open the ANT app, but it works now. I think this is looking like a good battery so far. The difference in voltage between the highest, and lowest cell group is 0.003v20240912_220839.jpgbattery first life.jpg
 
Success

after the last post I did a little more insulating, and srunk the shrink wrap, and called it good.
So far I've ridden a 7 mile test ride, and it feels really good. I did a few 80% throttle bursts, and I only saw 4v sag. That's a lot better than before. When I got back I removed the side cover and felt the plug, and it wasn't warm. Nothing felt warm.. The 4 battery temp sensors were 31c which is about ambient. What impresses me the most is when I got back home and checked the battery stats it said the difference between the highest and lowest cell group was 0.001v

I'm really glad to get this over with after all summer working on it. I appreciate all the help everyone gave me and especially CD for insisting on foam padding. It worked great, and I probably wouldn't of known to use it.
After a little more testing I'll make a final report.20240914_203101.jpg
 
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Temperature sensor is pretty common. Does the resistance change if you stick it in a freezer for a while?
 
Theodore Voltaire said:
Mr EEs background is military and defense. He added this to my battery.
Anybody know what this is?
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I'm sensing something in jest here.

My guesses:
1. Low melt-point solder butt splice connector with an odd wire sticking out.
2. Some kind of RF/RFID tracking module with an antenna.
 
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Ah, yeah, if the person was using hot air gun solder seals like that to join wires when working on the balance wires that go to each p-group, maybe an unused one fell inside the pack.
 
A-DamW said:
I'm sensing something in jest here.

My guesses:
1. Low melt-point solder butt splice connector with an odd wire sticking out.
2. Some kind of RF/RFID tracking module with an antenna.
Click to expand...
Your first guess is right. I thought it was a fuse. It's a fancy butt connector. The little wire is a power takeoff for something like maybe a sensor. These connectors are how the line power wires are connected to the bms, and output cables.
 
After 50 miles of testing this is the report.

It runs like stink. Off the line feels about the same, but 25 to 30 it's looking for an excuse to pull the wheel up. I cruised over 50 mph and it wasn't even full throttle, and still only 4v sag. I think I can conservatively say it now has 10% better range, but I think I'll find out later it's even a little better than that.

I'm sold on copper composite strips. They were perfect for a battery like this without many parallels, thank you Portugaline.

​




Electronaut 11 2024.jpg
 
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