Yeah, split p-groups are the fucking worst
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Big reason why I made 2 CBXR type packs and then quit. It’s the pits.
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I think it’s interesting, the cliché about batteries is somewhat wrong, they are recyclable and we need to support that.
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So where can one get p42as in 'merica right now?
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Updates to my build thread soon. But finally finishing the battery in the bustin sportster. It’s been a royal bitch but I’m happy with how it came out
Since this is BBC, here’s the details that went into it.
P42A 12S4P. This battery has a ton of power… I’ll never touch its 120+ amp cont potential as this is a street board. But I’m confident 120amps is within its safe operating region.
Cells are all glued, fiberglass taped, fishpapered, nickel is 0.2 full P group width 25mm wide up to the PCBs. DR PCBs are spot welder and soldered to the nickel. Series connections intersect the P groups at the nickel/PCB connection, not out on the PCB alone. Series connections are 14awg x3.
Batt main leads are 14awg x2 per side into an XT90S. 12awg would’ve worked, but two 14awgs will fit in an XT90 barrel and are collectively larger. Most importantly, that lets me have two connection points in the main terminals to spread the load a bit.
Space was seriously a challenge
BMS connectors were repinned with new leads instead of soldering extensions. Balance leads run between the PCBs and float on fishpaper. Wavy and free in specific areas so they can flex with the deck. Charge port is fused, runs between the balance leads and crosses under them via fishpaper layers - 18awg.
All groups are encapsulated in 50A urethane pockets that hold them in place and theoretically reduce vibrations and shock. The pockets lock the P groups into place, only by lifting both at the center will each row come out. Fiberglass tape across the PCBs prevents that movement. Even before wiring i could shake the enclosure upside down and P groups would stay in place. The bottom of the deck is lined with 1/8” foam above the cells and the series connections just touch it. An additional layer runs down the center of the deck to apply gentle pressure to the balance leads track.
Temp probe from the BMS is nestled between the negative and positive leads behind the unity. I’ll be keeping an eye on those temps to see how the roughly 4-6” 14awgx2 (about 11awg) is holding up
Maelectrics spot welder. TS100
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Thanks @Battery_Mooch .
I forgot to check imr. They nlet me add them to the cart.
I’m not quite ready to pull the trigger.
Everyone else looked to be out of stock.
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I checked all my 200 model 3 cells. 199 are all between 3.60-3.64V with a large majority being 3.62V. should I group the 3.60v all the same p group and 3.63v in a different group or mix them or it doesn’t matter?
1 cell measured 31.4mV wtf? I measured all cells now with the same voltmeter one after the other and it looks just like all the other cells. What’s up with this cell?
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Try another voltmeter, they do go bad.
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But I used it for all the other cells? So wouldn’t it have gone bad for the ones measured after this?
I have this lion nimh charger. I can put it in this and it will also read the voltage but is it okay to put in the charger or could it break/explode by charging it?
If the battery is running low perchance it can give some weird readings
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We don’t know, there’s no way to tell. It’s certainly not recommended to charge a cell that has been at much too low a voltage for a long time.
The cell is dead, recycle it.
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Looking at building my first real battery soon. 12s6p to fit into a demonseed enclosure I picked up second hand. Been chatting with glyphics about the schematics and come up with this plan. It’s a bit complicated but avoids any nickel series connections.
What does everyone think of this? Anyone want to confuse me with further options etc?
Dimensionally this is not quite accurate. The single row would extend nearly a battery length further at the top.
I have already made up the 3p packs and will be moving on to wiring soon. Balance wires will be a bitch to run without crossing over the parallel and series connections.
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What the fuck am I looking at
You are looking at the nightmare of split p-groups.
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God that looks awful to wire up and run balance wires
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It’s happening lol. Will be complicated wiring but that’s how it fits best. They’re already spot welded and wrapped. I can solder alright and will have decent linkage between pgroups and series. What are your main concerns with it being done this way?
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- Its a massive pain in the ass
- It creates a lot more crossing cables (more potential failure points)
- It is a lot more solder joints and total length of cables (more chances to overheat one of the p-groups while soldering, and more weight/bulk)
- Inductance? (I dont know about this one, I’m no scientologist)
All of this is not to say that it cant be dont right, it’s just a massive pain in the ass to do it right. It sounds like that ass-pain is something you have resigned yourself to, so more power to you!
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Super helpful. So much easier for me to use Ali suppliers.
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