Battery connector won't come apart

Has anyone had issues with the getting the battery connector apart? I flew a couple weeks ago and it was difficult to get the connector apart afterward. I cleaned up the connector with some isopropyl alcohol and it seemed much better.

I had 4 flights at the Dave Purdin fly-in last weekend and after the last one I couldn’t get it apart at all. It’s still stuck together. Even prying with a screw driver won’t budge it. I had to disconnect it at the ESC.

I just spotted the thread about the 3d printed connector helpers and I’m going to give that a try. But I think I’m going to have to replace all the connectors. That should be fun with a live battery.

My theory is that the first time I charged it, the connector wasn’t fully seated and the connector got warm and caused ‘corrosion’ in it. That corrosion seems to spread from connector to connector since I’m seeing it on the ESC connector and the charger connector. I think I’m going to have to replace all 3.


  • Marc

Did you try putting some kind of lubricant on the connectors? Vaseline or even WD-40 spray should help.
If the contacts are already bad (surface plating scraped off etc) or welded together then you are right to change them, but oil should stop it from happening again.

What is the name or part number of the connector?

At this point it would need to be some kind of penetrating oil. What would be non-conductive? Probably can’t get di-electric grease in there now.

Here’s the connector -

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When soldering or desoldering connectors, wrap the terminal your not working on at the moment with a couple wraps oof electrical tape. I accidentally got melted solder or made contact with both connectors with solder gun. It’s very exciting to have an arc on a 100 volt battery two feet from your face. It blew the old connector completely off both wires, and blew the tip off my soldering gun. Battery and soldergun both still good, new connectors soldered on. James Bartlett suggested trying to set BMS to Max Current Zero to try and isolate, but I couldn’t get my Bluetooth to come on due to damaged ESC and both batteries fully charged. You can apparently only get Bluetooth to come on while actively charging or activating with throttle .

You can also click the BT button on the BT module if you take off the lid of the battery case. That will activate the BT also.

If I had bluetooth. This is batch 2.

Good news everyone… With the help of the connector helpers, I was able to get the connector apart.

So, on to the next question… I want to grease this up so it doesn’t happen again. Should I use non-conductive di-electric grease to make sure there are no shorts, or is it safe to use conductive grease to help the electrons flow?

Hard to say from the photo, but look carefully for signs that the pins and sockets have been too hot, or arcing etc. it would be best to change it in that case.
Otherwise, little bit of grease on each pin and around the plastic parts and see if it goes more smoothly. I don’t think it needs to be anything special, just petroleum jelly.

Thanks Pdwhite. Hopefully that will save the next persons soldering job if it works to set Maxcurrent to Zero

Hey, they should not be getting stuck together like that.

Check your solder connections on the battery and ESC end. It sounds like your connector is heating up to the point of slightly liquifying the plastic and causing them to weld shut. That is one step away from a disaster.

Clean up the female part inside, polish and widen the male bullets. Judging by the picture, the lower male bullet is a bit sqeezed to the centre. So take a round screwdriver, insert it and spread it. Else solder on new connectors. Could also be that you once run with not fully inserted connectors and you melted the resistor inside. After this, every time you connect it is arcing inside(you can hear the popping noise) and thus creates a high resistance. In this case change the connectors.

@jsneeb The plastic of the connectors has not been melted. Any deformation you see in the plastic is from me trying to pry to connector apart with a screwdriver. It still seems to engage fine.

@Allex Comparing it to a new connector the bullet looks the same, but I can try expanding it. In the original post I mentioned that the first time I charged it, it was not fully connected and the connector got warm. I figured that out during that charge and I don’t think I ever ran the motor with it not fully engaged.

I just tested connecting it and I’m not hearing any popping when I connect it. But… I also measured the resistance and I’m getting 315 Ohms between the lower part of the + connector and the upper part. I’ve got a new connector that I did the same test on and I got 5 Ohms.

Is the connector trash once the resistor is blown?

  • Marc

I zoomed in for a closer look. I think your connector was stuck together because it was welded. The evidence for this is the arcing damage where the pin makes contact (where the red dots are) and the resulting soot (black arrow) at the back of the socket.

The cause of it welding could be because of a loose fit on the bottom pin as Allex said.

Because of the damaged surface (you can see the red copper through the gold plating), this connector is probably beyond saving - it could turn into a high resistance and a lot of heat under power, you don’t want that.

Here’s a close-up

Yah, I would swap it out asap. Dont want to fly with this.

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Just a follow-up on this. I did get all my connectors changed out. The battery wasn’t as difficult as I thought. I just did one wire at a time and kept what I wasn’t working on wrapped up in electrical tape.

I changed out the connectors on the controller and charger as well. One thing I did find is that putting too much heat on the male connectors will cause the pins to move around and get misaligned. I ruined one connector just trying to tin it.

The solution I found for this is to just plug one of the spare female connectors into the male connector I was working on. That held the pin in place and kept it perfectly aligned while i soldered on the wires.

I charged the battery for 10 mins and the connector didn’t get warm and all. Haven’t flow with it yet. I’ll probably do a run-up for a minute first to make sure the connector stays cool.

Also, the 3d printed connector handles are awesome! Although I could not find a square nut small enough to fit the openings. I would have edited the file and just make it a hex hole, but it was easier just to order a set from OpenPPG that included the hardware.

  • Marc
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