Magic smoke from battery-powered RAK5005 + 4631

I tried to connect a 3.7V LiPo to my WisBlock 5005+4631 today … and got a puff of magic smoke. I believe the puff came from the area indicated by the arrow but can’t be totally sure.

If I plug it back into USB, the battery LED is solid red but the board heats up quickly underneath and doesn’t respond to serial. Should I toss both the 5005 and the 4631 or is there a chance that the 4631 lives?

The bigger question though: what did I do wrong? I’m pretty sure that the specs of the battery match the online docs. And the JST polarity is correct. I’ve had no problems at all powering via USB. This incident has me scared of plugging a battery into my remaining board.

Cheers,
Darran.

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Hi Darran,

It is highly likely that the polarity was reversed. If that is the case, the RAK4631 could still be alive and only busted components are the power components like the regulator and charger ICs.

I strongly suggest you try to power the battery connector first with current limited powersupply if you will test again the WisBlock Core. This will avoid any magic smoke.

I’m on the road at the moment and don’t have a multimeter handy. Before this thread closes though, I’d like to confirm that battery pins are as annotated below (ground closest to the edge, positive on the inside).

I ask because you can see the way the battery plugs in would put that red dot (which I assumed was battery positive) on the inside pin of the 5005-O.

Yes, your understanding of the WisBlock connector is correct.

image

However, I would like you to confirm if the voltage output of your battery match the connector. You have to do this manually. There is no standard polarity on JST connectors. It can be whatever way the battery, cable or connector itself is configured by the vendor.

I’ll have to check with a multimeter once I’m home. I just assumed that the red dot on the battery was positive.

Back at home with access to a multimeter and …

Damn whoever put a red dot on the battery :wink:

A JST-PH is just a connector, how the connections are assigned is up to the device using it, and it happens that the majority of model airplane applications have hit upon an opposite choice from the majority of embedded systems ones, though there are exceptions in both categories.

The red dot on e-flight model airplane batteries is a QC mark not a polarity indicator, usually it’s larger and more central. If I determine the polarity of something and want a self-reminder, I use a bit of permanent marker on the side of the connector shell or housing.

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