I have a different style cell charger (yours makes this look much easier and straight forward) but thank you for the visual
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Hi, I’m planing on making a 10s3p pack with Molicel P26A for which the suggested cont. discharge is 25A. Is 0.15mm x 25mm nickel wide enough for the parallel connections? Planing on doing the series connections with 14 or 12 AWG silicone wire. Anybody has a source for 3P 18650 tabs perhaps?
It is not a rule that cells push their rated current.
The current going through the nickel is determined by how much you program the ESC to ask for.
Before building a battery pack I advise learning some of the basics of circuits
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More than enough. U barely need anything for parallel connections.
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From left to right 20 23 14 17 ms (didn’t apply enough pressure on that third weld on the third cell but what do y’all think? Not sure what time to go with. Thanks!
You really wanna be doing it one at a time on spare cells and do a pull tests as u go. None look great . Could be the angle of your rods and too much pressure maybe
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I agree with hatman, try cleaning everything with iso and changing the amount of pressure you apply. If there is grease/oil dirt on the surfaces the welds will be more inconsistent. All of those seem on the weak side but maybe it just because the spots seem narrow or maybe it’s just the picture. Did the nickel tear and deform when pulled off. Are your tips sharp or blunt - i like blunt round tips.
There is also a 3mm no go in the bullseye of the negative terminal. There is some stuff going on inside there - though nothing looks like it is in that zone make your pattern spread out around there. You don’t want to slip and put one there accidentally and damage the cell.
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after looking at many threads and these responses my problem was most certainly the sharpness of my tips. I’m using a lipo that outputs upwards of 800A, and noticed 8-12ms made the pull tests truly tear the nickel. Thank y’all for the critiques!
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Thank you, I know that, but I wan the battery/nickel to be capable of handling its max/save discharge current for longevity and all that. I have had this battery for a while now (NESE) in my board and tried a lot of wheel options, form 85mm urethane to onsra 115m rubber wheels, 165mm pneumatics, and the amp draw is very different for all those wheels.
cell specs related to max current are based on a single cell in open air, no?
how do cells perform when jammed in an airtight box with cells stacked staggered and layers 9x9 for example.
What you think of pouring expanding foam into a square battery box with these connectors and 270 tightly stacked cells. The foam will block all thermal heat transfer but then being in an airtight plastic and kevlar box there isnt any heat transfer anyway. It will be a harder foam intending to secure the cells in case of a drop or crash. Otherwise it’s just cells, the connectors, fish paper, and crazy glue.
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Correct, at room temp.
They run hotter. How much hotter than a single cell in free air depends on the (averaged) charge/discharge current level, the cell’s location in the pack, the ambient temp, air flow (if any), what the cells are wrapped in (fishpaper, Kapton, heat shrink, etc), and whether there is anything else warm/hot nearby.
Depending on what you’re trying to accomplish with the foam it can work great. Carefully consider what the foam will do in lower energy impact situations though. The foam can be compressed with no rebound, allowing the pack to bounce around inside the newly enlarged space. This might happen even with the typical vibrations/shocks seen during a normal ride. Thousands and thousands of small bounces can add up.
Servicing a pack embedded in spray foam will be a nightmare. Foam sheets/blocks might be a better solution. The foam should be non-flammable too.
Any foam will conduct heat away from the pack better than air. The denser the foam, the better the heat transfer. Not sure if closed cell foam is better than open cell foam (if using sheets/blocks).
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Also be aware that if the top venting disks are blocked by the foam you will be increasing the pressure at which the venting disks open.
This delays the response of the venting disks, possibly causing thermal runaway to occur where it wouldn’t have if not blocked, and the higher pressure could cause cells to violently burst their tops open instead.
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2nd Battery from Onsra just died. It’s about 2 years old. I measured the p-groups at the connector where the leads (white wires connect to the BMS). I triple checked the voltages on each group.
Onsra 12S3P LG 18650 SN: TFL44.410.521I07098
Died/cut-off mid-ride, 8 miles in on full charge
Voltage at XT-90: 16.8v
P-Groups:
- 3.65v
- 7.32v
- 10.98v
- 6.74v ?!?!?!?!?!
- 10.39v
- 14.04v
- 17.70v
- 21.3v
- 24.9v
- 28.6v
- 32.3v
- 35.9v
I don’t see any obvious damage or loose wires… Is it worth attempting to save?
Double check the readings at the connector if you can? Note the polarity? Carefully cell by cell. Put a little tape on the probes so only the very tiny tip is exposed so it’s harder to short. Obviously there is a bad group or connection - when fully opened up can you see anything disconnected or broken wires/welds?
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I can’t get a multimeter probe on the sides of the cells that are facing inwards toward the “spine” or center without completely disassembling. If that’s the next step to troubleshoot. I’ll need to do some research on how to safely disassemble the pack. Any links/posts would be appreciated.
I don’t see any obvious damage or disconnections. Though I will say that the welds look like shit from the quality packs I’ve seen built on here.
What project did this 18s8p pack go into?
I am staring at sea of white and blue 21700 Cell with several empty enclosures begging to get stuffed.
Too bad gpt9 can’t swing by and wrap this project up in a day.
@DuckBatterySystems @Skyart or anyone, I’ll buy the things you recommend tonight at ur store without question if it specifically made ur experience cramming 144 cells in a lone star.
If I need a gasket to get it to fit, are those anywhere? What’s the largest reasonable (no riser fuckery ) 18s that fits?
I can work this all out eventually, but I just want to click buy and go out and skate with George in mountains.
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18s8p fits just fine into the double stack lacroix enclosure.
I highly recomend some 151kv motors to go along with thet 18s! And solos!
Later battery nerds! George and I are going streaking near palmsprings!
…I am aware that multiple dual solos are migrating to the high desert this summer. When you say, 150kv, i remember the big 74xx at 179 is a performer?
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