JST connectors on batteries

[hbb3367]

Funny coincidence: Last week I was watching Josh on the Sparrow build, and while he was doing the electronics he mentioned they were moving from JST to XT30 or XT60 connectors on batteries and ESC's. He mentioned that a JST could be connected backwards. I was a bit disappointed, as I have built several of the FT Minis, and all were powered by JST. And I had never had and issue; Well now I know never to say never.
I programmed the mixes needed for the Vtail, and was showing a buddy how I did it (motor pod/ESC/servos still on the workbench) and I must have plugged the dad-gum thing in backwards...smoke the JST's, burned out the ESC, and burnt 2 fingers.

Good Ridden to JST...going to be much more careful while I too begin to sunset those buggers.

 

[Balu]

Hey hbb,

welcome to the forum. I love that story

 

[dvx216]

Some thing that you are going to be connecting and disconnecting the JST don't have very much surface area and they are flimsy.After talking to another member on the forum I went to XT60.I'm a nooby and I have enough going against me I would hate to crash because of a $1.00 connector or burn every thing down because I was able to plug it in wrong.

 

[pressalltheknobs]

Funny coincidence: Last week I was watching Josh on the Sparrow build, and while he was doing the electronics he mentioned they were moving from JST to XT30 or XT60 connectors on batteries and ESC's. He mentioned that a JST could be connected backwards. I was a bit disappointed, as I have built several of the FT Minis, and all were powered by JST. And I had never had and issue; Well now I know never to say never.
I programmed the mixes needed for the Vtail, and was showing a buddy how I did it (motor pod/ESC/servos still on the workbench) and I must have plugged the dad-gum thing in backwards...smoke the JST's, burned out the ESC, and burnt 2 fingers.

Good Ridden to JST...going to be much more careful while I too begin to sunset those buggers.

If you are not paying attention and push a little too hard you can connect XT30s backwards too - according to the reviews on HK. They are better for polarity but the main reason to use them is...

1. You can solder them onto the size wire you want to use. You don't need a specialize crimp tool.
2. They can carry much more current.
3. They are gold plated and less prone to corrosion

However an XT30 pair including solder weighs around 2g and a JST "RCY" pair is much less than 1g which can be significant for micro builds.

JST RCYs should never have been used on 2S 20C Lipos imo. They are only rated at 3A which may be conservative but its quite a bit under the .8 X 20 = 18A a 20C 800mAH battery is theoretically capable of delivering. Their original use in RC, as far as I can tell, was for the battery connector from the main battery to the BEC or for the radio battery in a gas/glow setup, which are low current uses. This is why the JST RCY is sometimes called as a "BEC" connector. They were never really meant to be used for a main battery of any size.

It was a bit annoying when I received a battery with an XT30 on it unexpectedly though!

 

[B.C. FoamWerx]

I know what you mean, hbb. I was working on my mini guinea wing in the basement when I plugged it in backwards. It smoked and then flamed. It puffed my battery, blew two 12amp speed controllers, and scorched my wing. As the connector melted, I was able to pull the battery wires which stopped the fire. I burned my fingers doing it though. It was a close call and somewhat of a costly one too. we still have yet to get a fire contingency plan in place though. Haven't had a fire since.

 

[Capt_Beavis]

I had a broken JST that allowed me to plug in the battery incorrectly. It fused one of the pins into the batter connector. I am not sure if the ESC is ok or not.