🌠 Northern Light | Switchblade with Reverse-mounted Urethane Gear Drives

[Simeon]

Have you had a look at my recent IG posts?
I don’t update that forum post too often ^^

I don’t weld at the bottom center anymore since it was first discussed here (:

[City-Blade-101]

lol

[rusins]

I noticed one of my gear drives was loose

Well, I guess the grub screws that hold the gear drive to the hanger should have green threadlocker on them. Also I’ve lost a lot of the small bolts on the outside of the gear drive, because I only used blue threadlocker on them. I was scared to use red because I don’t want to melt the POM wheel gear when heating them up to unbolt. But maybe it’s safe? Dunno. Guess I have no choice.

Also the drives scraping the ground had ruined one of the bolt heads, so I had to completely drill through the bolt to disintegrate it

Also note that the plastic guards for 3d servisas gear drives love to jump over the bolts, so use some washers to make sure that doesn’t happen.

[tipsy]

@rusins

because I only used blue threadlocker on them.

Permatex Orange is your solution

[jack.luis]

Use red but only a small amount. Works for me.

[Savage1]

Great thread Raisins!

[rusins]

Thanks! @Simeon has just finished the final 12s4p battery for it too

Here is a photo album of it being built:

[39 new items · Album by Simeon P] 12s4p Rusins

Also shoutout to @Zach for selling me his FlexiBMS, it works!

I also have a green davega on the front now
Will take some sexy photos of the complete build once the battery arrives.

[Savage1]

ooh, thats nice! I got a switchblade coming next week, so this was a good read.

[janpom]

Wow, I thought I managed to build a decent battery but this makes me feel I still have a lot to learn.

[rusins]

@rusins

My charger also goes from solid green to alternating between green & red, but I don’t know what that means. Is it switching from constant current to constant voltage? (The stormcore button blinks if the charger is blinking, and at the same rate. From yellow to green. If I unplug the charger, it stays yellow. Hmm, in vesc tool it says the voltage is constantly switching between 47.7V and 49.3V. Is this some clever charging / monitoring strategy?

Yesterday my Bestech BMS started exhibiting the same issue. And I finally figured out what was wrong:

One of the p-groups instantly goes to full when charging. Took the cells out, 2 of them are definitely sus:

I wonder what made them go bad. Guess I’ll have to replace all 3.

I also noticed that there are nasty black marks on the tabs of my NESE modules. Should I be concerned @Agniusm ? They’re pesent on the other p-groups as well.

[Battery_Mooch]

@rusins

Should I be concerned @Agniusm ? They’re pesent on the other p-groups as well.

PMJI…IMO those marks indicate that the cells were bouncing in the holder, disconnecting/reconnecting and arcing each time.

[Rudi]

@rusins

I also noticed that there are nasty black marks on the tabs of my NESE modules. Should I be concerned @Agniusm ? They’re pesent on the other p-groups as well.

Are these modules used in a board? If individual cells momentarily lose contact due to vibrations, minor arcing can occur. After arcing you get high resistance due to extra oxide in the way and these tabs might see high temps.

[rusins]

I have the modules bolted shut when in operation. That being said, this is a urethane build so the vibrations could have been pretty extreme at times

[Battery_Mooch]

Clean the strips with a bit of alcohol and then check them out with a good magnifier or loupe. You should be able to see the surface pitting from the arcing.

[Rudi]

Arcing also can draw significant current from the cell. Not sure how much they like it.

[Battery_Mooch]

Could you explain how that works?

[Rudi]

In short, this:

To sustain the arc, a considerable amount of energy is required. Intuitively for me it seems that the cell sees both the normal load + the arc load, hence the extra current.

[Battery_Mooch]

Thanks. I don’t think it works that way though.

The arc is sustained by the rising voltage at the gap due to the system’s inductance. I don’t think we can trust those waveforms to be accurate for anything other than the particular scenario they were considering. Having said that, notice that the current and voltage for both scenarios in that illustration multiply out to about the same power level.

When you say “arc load” what do you mean? The load is whatever is connected to the leads at that connection point. The load cannot change just because there is arcing. If it’s a resistive load the resistance stays the same. Discharged caps will still have the same capacitance. The inductance and resistance of a motor’s leads will not change.

The voltage at that connection will rise up to a certain point, “spike”, for the reason mentioned above and I don’t know what the current level is due to that.

Arcing into leads connected to a MOSFET in the off state will only result in the tiniest amount of greater current flowing into the MOSFET’s gate. Arcing into a resistive or capacitive load could result in more current flow but only for microseconds, at the most.

Since the arc lasts only a tiny, tiny fraction of a second I don’t think it can result in any kind of appreciable average current draw from the cell.

[Agniusm]

Sorry, missed thet. I doubt arcing will occure at 4.2V. Could be oxide?! Have you tried cleaning it? Also you could try 2000 grit paper rub

[rusins]

Yeah hit comes off mostly if I lightly sand it. I’ll try doing that this weekend to see if it makes a difference to my range. My remote says I use up 24Wh/km which should give me ~22km range with my battery, but IRL I’m getting only 10km