Some electrical questions specific to my build

A few questions, I used the BMS discharge and bypass with loop key set up originally before adding any lights:

  1. I’ve got the MaxKGo LED lights with two LED motorcycle lights for the front and back. Per my wiring diagram, should I connect the motorcycle LED lights negative to the P- on the BMS? The motorcycle lights are rated for up to 80 Volts so I shouldn’t need to reduce the voltage to them.

  2. Is there a way to test the cells in parallel after completing the connections per this set up? I used the WinFly system and slightly modified it - I milled some Delrin holders and am using flat head set screws to push the braided wire onto the battery ends instead of 3D printing. I did take the battery apart as the BMS seemed to show some weird balancing and a few of the batteries were not balanced, so I’m guessing my connections weren’t adequate. I do own a laser thermometer and read I can use that under load to see if each battery is similar in temperature. Am wondering if there is a better way to test each cell after setup as I don’t have a 48V inverter.


I would connect the positive wires for the accessories on the switched side of the loopkey, so where the ESC positive is connected is where the switch would feed from.

I also wouldn’t solder anything to the battery (except the BMS…), make sure everything can be disconnected with an XT90 that way you don’t have to work on stuff while it’s energized.


Tip: Use cable ties to keep XT90 and XT60 from vibrating apart inside the enclosure.

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This sounds really sketchy. But I haven’t used cell holders. Ever. So IDK.

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Terminal like that are used all the time for PLCs without any issues. And that is in factory environments where there is a ton of vibrations, interference, dust etc… So long as the holders are well designed and made it shouldn’t be an issue. personally I wouldn’t use them but I hate them since they hurt my hands to use

I do have one warning for those light strips though. They’re not exactly very robust and may end up getting destroyed pretty quickly. I think mine lasted maybe a month max on my board despite never coming into contact with anything. ( my deck is tall)

What are you trying to test? If you just want to double check the voltage of the parallel group then you should be able to without issue so long as the terminals or a wire connecting to the terminals are still exposed.

Now testing the current of a p group does require you to disconnect the group from the rest of the pack no matter what. unless you specifically designed the battery with switches between each group so that you can easily disconnect the others from it electrically while everything is still physically in the same place

Oh and the interrupt switches you’re using for the lights may slowly kill themselves if there is no anti-spark between the battery and the switch. Usually takes a while to fully kill the switch though and in my experience they fail into a latched off position, so not a huge deal. Just don’t epoxy the button into place, and have some spares available, and you’ll be fine.

Unless the loop key will prevent sparking in which case ignore the above warning. @b264 you’re a fan of loop keys, do they prevent sparking?

@b264 - more like this?

Was looking at the Wiki for Connectors on this site and looking to order some JST or Anderson Powerpoles to let me unplug everything while working on the enclosure. Space isn’t too much of an issue inside my enclosure. I’m using 22 AWG wire for all of the lighting circuits. The Anderson Powerpoles seem easy to use.

You mentioned not soldering anything to the battery - I don’t think I do except the BMS and the power port. Should I put some type of disconnect between the power port and the battery?

I think the flat head set screws work well, I’ll post some pictures. At least on my first battery everything went well, but this one something wasn’t connected (I’m guessing 3 out of 4 were connected in one of the parallel packs) so that’s why I’m trying to figure out a way to check each battery after it’s all connected.

Thanks for your help.

I do have a small section I already need to repair on the LED strip. I don’t recall running it into anything but the strip stops working mid way and I can see some slight damage. I do have enough left over strip to make the repairs, just not sure how I’m going to fix the clear enclosure over the lights. Maybe I can slide them out, haven’t tried that yet - may not be able to slide them back in :slight_smile:

I’ll post some pictures, but the Delrin caps are held into place by 3 mm screws with nylon spacers inbetween. It makes a pretty tight fit, but I threaded some flat headed set screws just above the terminals on both sides of the battery to apply a little pressure to the braided wire - hopefully making a nice connection to each battery pole. But apparently one of the 4 batteries in one of the packs wasn’t connected or part of the circuit and it was messing with my BMS and decreasing my range. So I’m trying to figure out a way to check the connection of each battery once I have it all put together. As far as I know, I can only check each pack and the voltage will show 4.1 or so volts whether 3 or 4 of the batteries are connected properly. Hope that makes sense. So I can’t tell if one connection is bad or not functioning as I want it to…

The silicone can be carefully cut off the strips but then the strip is super weak and you’d want to reinforce it with epoxy if using it on a board. I bought the clamp connectors for mine to avoid that issue, but then they went and broke in other places. :person_shrugging: The only way I think they can work well on a board is if you route out a channel for them on the deck, put the strips in, and then cover them with some clear epoxy. My main build’s deck isn’t thick enough for that so I haven’t tried it myself though

The strips I used to use for indoor lighting, I just filled in the gap with hot glue, but they were static 99% of the time and secured to shelving so the exposed weak and flexible PCB didn’t cause problems after they were mounted. I did have to keep them on when mounting them to make sure they didn’t bend wrong and disconnect. I had long wires between each strip so that they could be completely hidden so if they weren’t tied in place right it could disconnect the wires

Do you have a multi meter with a sound/ continuous circuit mode? (I made up the name so it might be called something else) It beeps if there is a connection between the probes and could help you figure out if there is a bad connection or not.

I can’t really tell if that is a good connector or not just from the description tbh. I just know that they can be done right and safely given how prevalent they are with PLCs.

Here is a photo of the types I know to be good (so long as you make sure you shove the wire in far enough and tighten it enough )

Also all of these worked well too:

Ignore the screw caps I didn’t put those one there. A professor did so that it was easier to connect to the motor

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A fuse. No disconnect.

Ok, I have a fuse between the power port and the BMS.

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Step down converter question. Just realized the input wires look to be 20 Awg, if it’s being stepped down from my 48V battery to 5V for the LED lights, shouldn’t the input wires be 12 Awg or something beefier? I guess I don’t understand the use of a converter if the wires themselves can only handle so much voltage? Or maybe I’m confusing wire voltage limitation with current limitation?

All of those wires should be rated against arcing up to hundreds of volts. The low voltage side of the converter will see more amps, and may benefit from heavier gauges. What’s the power output of it?

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I’m not sure of the power output. It’s just some LED lights for the perimeter of the board… Review below… I think I’m just confusing myself with all of the wiring!