The battery builders club

Good point.
I have amended my post to say that the thickness increase response is not linear.

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Does anyone know what these setting are for? LLT BMS 12S wired for charge only.

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Switch function enables the function of the power switch port. Discharge enables, you guessed it, the discharge. If you run headlights off your main pack this function makes for a great soft switch for turning them on, no physical switch needed.

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Connect the output of the BMS to a NO relay, then nobody can activate your board but you :yum:

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Thx, So I would enable the switch, discharge on the BMS… Wire the light to the BMS discharge. Do I need to use a buck converter or does the BMS take care of that?

Morning all,

@approachinglogic is selling a 12S4P pack here [UK] WTS - Moon drives, MBS Matrix II, Flipsky 6374s, 12s4p 40T, Rockstars with tyres & mini remotes which I would like to buy because it seems like a great price.

However, my experience and confidence in the magical world of electronics, especially batteries, is severely lacking. What would I need to look out for? Is this a good idea, or can someone slap me back to reality so I’m not risking my life for a few pennies?

You absolutely would still need a buck converter unless your lights are capable of the same voltage as your battery


I‘d ask if he has some pictures when he build the battery. Just to know how the battery looks under the shrink. It’s a bit difficult with a Daly bms to check at this stage, but knowing the individual p group voltage does usually also give a good indication in which condition the pack is. If the pack was sitting on storage voltage all the time, it should be in good conditions, but you never know, a bms could also drain a p group to 0V over time if something is wrong.


That better be a solid state relay or it’s gonna get welded shut pretty fast

You could wire the relay to an anti-spark switch instead tho

As long it’s solid state.

Traditional coil relays won’t survive long on a thane board…


Good point, I completely forgot to add battery pics, I have photos of the build process (which was done by @tinp123.

@That_Jamie_S_Guy I’m travelling with work for the next 24hrs so might be slow to reply but I’ll see if I have the photos on my phone!

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Thx, I’ll wire some light on my next battery build. For the BMS switch, is that a rocker switch or a momentary switch…does it matter?

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I thought I it would save space, but after looking at it again. I can arrange the mid group the same as the top group and and still keep the relatively triangle shape.

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Not directly a battery question, or at least it isn’t yet, but does anyone have any tips on how to use a solder gun? My soldering iron is a bit under powered at only 60 40 watts and it can’t fully melt solder on 10 awg wire unless the wire is cut short, but my landlord has a 75 watt gun I can use. It’ll only be for those larger connections but I have no idea what the best practices are when using a gun.

I’m already using the largest made tip size that is available for my iron which is a 4.2mm wide flat tip. So the issue shouldn’t be the tip size but instead the output heat available. I do see that there are some cheap 80w and 100w units on Amazon but they all come with small tips which seem like they’d cause issues too.

Edit: Correction made to soldering iron wattage since apparently mine is only 40 watts oops.

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I do 10awg with a 45w soldering iron just fine. Are you using a conical tip?


If it’s a temperature controlled iron, it might work if the heat is turned way up to like 420C+

If it’s not maybe let it sit 10 min to get really hot?

I can do 10awg with a 60w, but I can’t remember if I’ve tried on a 40w.

There is a great thread on soldering that might have some tips too


I’m using a 4.2 mm flat / screwdriver tip. Largest conical tip I have is 0.2mm and I don’t remember seeing any larger conical tips available for my iron.

It looks to be getting up to around 360 c but that is being measured with a temp gun and might be off since the metal tip is slightly reflective.

I know how to solder with an iron but I just usually solder very small parts for the most part. 1 mm wide small for some stuff. My issue is that I was going to run 10 awg wire through my deck for the battery connection which will act like a giant heat sink.

I don’t know the best way to use the solder gun though since they’re horrible for precision so I never bothered with them before

Hoping someone can help me diagnose an issue.

The other day my VESC (ubox v1) turned off while I was throttling up a hill. I’m pretty banged up but mostly ok. First inclination was a bad connection on the battery, but everything looks good here, right?

What else can cause a VESC to just turn off? Any ideas/tips are appreciated, I’m not the most familar with the ins and outs of batteries

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Does the VESC work now? Was it a fault or a full power off and you were able to power it back on?

The series connections look good, but maybe check the welds and the voltage at the end of the pack while moving the battery around to see if it fluctuates

Do you run the discharge through the BMS?

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