Battery Shield 2.0 gets very hot while charging

I did not see the caveat in the documentation concerning leaving the battery plugged into the shield, and it seems that my battery has completely discharged. Despite the fact that I received version 2.0 of the battery shield, the shield becomes very hot to the touch while recharging. I think the heat was mostly localized to the USB side of the shield, but since I do not want to blow up my LiPo battery, I did not leave it hooked up long enough to investigate.

Does anyone have any comments on this? Is it safe to recharge the battery when the shield behaves in this manner?

@mohit is the right person to answer this one.

1 Like

I bit the bullet and charged the battery. The shield became so hot that it was painful to touch—I might have developed blisters if I held my finger on it—but the battery seems to have charged successfully.

If I remember correctly, I don’t believe the shield should be getting too hot to touch, that might be the result of a defective component. But @mohit would know best.

Mostly you want to be sure that the battery itself isn’t overheating. I’m definitely paranoid about any new gadget I get and start charging, and I’ll usually keep an eye on it the first few times I charge it just in case.

1 Like

Just so we know, what modifications have you done to the Battery Shield (if any) and what battery do you have?

One thing to check is that the rate of charging the Battery Shield is set to, is appropriate for the battery that you have.

Hello @NickOveracker
The document does mention about not leaving the battery plugged in when not in use!
http://docs.spark.io/#/shields/battery-shield

When the battery is completely discharged, the charger (MCP73871) needs to precondition the battery. The shield may get warm in this period, but its uncommon for it to get ‘too-hot-to-touch’. Was the Core connected to the shield along with the battery? What is the status of the LEDs?

Both the ICs have thermal shutdown built-in, so they should shut-off when the temperature reaches high levels.

If the shield continues to remain hot, it could be a defective unit.

1 Like

@BDub: No modifications at all, and I’m just using the LPO62530 that was packaged with the shield.

@mohit: I didn’t mean to imply that the caveat wasn’t in the documentation, I just meant that I hadn’t noticed it until after I had fully discharged the battery.

Yes, the shield was plugged into the Core at the time. Right now I am charging the battery again for comparison (it is not fully discharged this time), and the USB side is not abnormally warm.

The lit LEDs when the shield was hot were “CHRG” and “PWR”. For this charge, the state has just transitioned from “CHRG” to “DONE”.

This is one thing I usually never see (if ever) in any lipo battery charger / backpack is the ability to disconnect the battery from the load automatically if it should ever discharge below 3V.

You should never completely discharge your lipo… anything below 2V will damage your battery… possibly making it unrecoverable.

I’m really surprised the MCP73871 even has a preconditioning mode… because this is a very undesirable state to charge a lipo in. The details are, if the Battery Voltage is <3V the MCP will charge the battery at 10% of the programmed fast charge rate, until the voltage is above 3V… then it switches to the fast rate. During the precharge rate, the MCP theoretically should be be 90% less hot than when it’s charging at fast charge.

Definitely do not allow your lipo to discharge below 3V, and certainly not below 2V.

We’ve all done it though! Be safe :smile:

1 Like

Thanks for the information. In spite of the fact that I am pursuing a degree in computer engineering, I am actually fairly new to working directly with electronic hardware. The ins and outs of many specific things, such as the proper use of LiPo batteries, still elude me. With time, experience, and a few hard knocks I hope to fill in the major holes in my knowledge and intuition.

2 Likes

That is unusual. Please update us if the shield fails; we’ll be happy to send you a replacement.

Mohit