Heat issue

[Ramjet1]

I'm getting what appears to be too much heat off the chip while charging a moto droid with 2500mah Nicads in the Minty. Chip is getting really hot. Checked everything, any ideas?

[adafruit_support_bill]

From the FAQ:

When I use the kit, the chip/batteries seems warm or hot...Is this OK?

Its normal for the chip and batteries to be warm or hot, especially when charging a device that is nearly drained. The chip should not get hot or very warm when nothing is plugged in.

The maximum temperature for the mintyboost chip is over 100 degrees C, that is hotter than boiling water. If you are worried, lick your finger (a little) and touch the tip of your finger to the top of the LT1302 chip. If you dont hear a sizzle (of the water boiling away), its just fine.

However, if the batteries are so hot that its painful to touch, start to smoke, burn or melt or leak fluid....something is wrong! Unplug it immediately and remove the batteries if it is safe to do so.

But its really hot and I'm worried!

Yes, this is normal. When the chip is working to charge your gadget, its going to get hot. Normally you never get to see or touch the chips in your chargers so you don't realize how hot electronics get.

Really, its normal for the Mintyboost to get hot!

If you're concerned, you can always do the finger test above. If its too hot, it will sizzle, otherwise, its OK

[Ramjet1]

Yeah, thanks. It got scary hot for the first time ever - maybe it's the droid phone, who knows. Plugged it back in, used the nifty temp probe that came with the vow you sold me and its nowhere close to max temp for the chip. Kinda freaked me out for a minute. Thanks again.

[mitch2380]

I just got my kit and put it together. With no load connected, the board and batteries run around 74-80 degrees F (based on room temperature). The moment I connect a load, the temperature starts to rise. I left it alone for about 5 minutes and came back to a 204 degree chip. I immediately unplugged the load and let it cool back down. I am using energizer lithium batteries and I am charging a Blackberry Bold 9650. I have been over the board twice with a magnifying glass and have found no shorts or cold solder joints. Voltage outputs with NiMh batteries were 4.97VDC from pin 1-4 on USB and 1.97VDC from the data pins to pin 4. Please advise...

[adafruit_support_bill]

Your output voltages sound OK. But there should be no significant current drain or heating with no load connected. Can you measure the current draw from the batteries with no load?

[mitch2380]

Just checked the voltages again as well as no-load current:
4.96V USB pin 1-4
1.98V USB pin 2-4, 3-4

2.17mA w/ no load connected

Board runs at or slightly above room temperature in this state.

[adafruit_support_bill]

204 F is still within spec for the chip (100C/212F). Most smart-phones are pretty current-hungry these days. But, as it says in the FAQ, if you lick your finger and it doesn't sizzle when you touch it, the chip is OK.

The 2.17mA current with no load is a little high though. It should be more like 0.1 mA. What meter are you using? Has it been calibrated?

[mitch2380]

Fluke 177, not calibrated

[adafruit_support_bill]

It's hard to argue with a Fluke. But you might check it against a reliable source to be sure. Aging batteries can be a problem too. When was the last time you changed them?

[mitch2380]

Alright, you'll forgive me if I make a mistake or give unnecessary information. Although I use DMM's quite often (specifically, Flukes) I do not use the series current measurement function very often. I changed the 9V on my meter and tried all four possible combinations of current measurement. I am reading battery output current on the positive leg.

400mA lead connection, DC mA scale reading: 2.20mA
10A lead connection, DC mA scale reading: 0.01mA
400mA lead connection, DC A scale reading: 0.003A
10A lead connection, DC A scale reading: 0.001A

[adafruit_support_bill]

Hmmm. I don't have any experience with that particular Fluke model. The first reading sounds like the most appropriate configuration for an expected value in the sub-0.1mA range. The other three readings are more in line with the expected value. What do we believe?

[mitch2380]

Assuming that I read the correct value of 2.2mA, does this mean I need a new IC? Could it have anything to do with the batteries I am using? How about some other component that failed during assembly or was otherwise faulty upon receipt?

[adafruit_support_bill]

Post some pics of the front & back and we'll take a look for any assembly issues.

[mitch2380]

Here are the pics. The bottom still has some foam tape residue.

[Agent24]

Well, your soldering looks pretty nice to me!