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September 21, 2011
News - September Caption Contest
about 6 years ago
Just play that commercial again... Cadbury Bunny Stew time!
about 7 years ago
Most of the 18650 batteries on eBay are junk. I've probably purchased around 40 batteries of various brands over the last few years. In particular, the Trustfire brand is faked alot. It's kind of sad because real Trustfire batteries are actually pretty good. It's the fakes that are trash. The outrageous claims of 4000 and 5000 mah on those cells are a fabrication. They get away with it because not many people have the capability to test them. To combat this, I have purchased liitokala lii-260 LCD 3.7V 18650/26650 Battery Charger and it should be here any day now. The cost was $21 with free shipping. It charges up the batteries and then discharges them at 0.5A to make the capacity measurement. Afterwards it charges them up so you have a fully charged battery with a numerical result waiting for you. The capacity is 2 cells at a time (It charges and tests both at the same time.). From the reviews that are available, its measurements aren't perfect but they should be good enough. Finally, I will be able to test some 18650's! If you like, I can post results with different cells after I test them. I'd be happy to test some of these cells as well ;)
about 7 years ago
I don't know if this is anything, but I have been going through the schematics to find where VBATT and USB_VCC get connected when the power switch is turned on. There is a net named RAW on the wire just after the power switch connecting to U6. I cannot find any other instance of RAW on the schematic. Is it possible that the RAW net is connected to USB_VCC? When running of of USB, do you need to turn on the power switch to make the board run? (RAW is after the power switch and would connect to VBATT when the switch is closed). If that's true, then there is a trace conecting from the USB_VCC after S2 going to U6 that needs to be cut. At any rate, somehow USB_VCC connects to VBATT when S2 is closed. The switch connection to U6 needs to be traced back to USB conector pin 1. I'm a litle suspicious of the label CHARGE_STAT. It connects pin 1 of U6 back to PC7 on the Atmega. It's possible that charging status LED D4 is always on if pin PC7 is sinking current. The datasheet talks about the LED resistor connection, or connection to a micro pin using a pullup. They don't talk about connecting both at the same time. Also, there is a labeled wire all by itself on the schematic labeled "CHARGE_STAT" just above the voltage divider. It doesn't seem to be connected to anything. It seems strange. Just wondering if that might be causing problems in the netlist. Sorry for the long post. I have been looking at alot of schematics, checking net lists and reading too many datasheets lately...
Why not just up the resistance on R14 and R15? I've routinely used voltage dividers using 100kohm resistors with other micros. The trick is to bypass R15 with a 0.1 uF capacitor (or maybe 0.01uF) after they are replaced. It's hard to tell from the pictures but they look to be 0805 or possibly 0603 package. Removal is fairly simple. One of my favorite tools, (actually it should be upgraded to my favorite tool) is "Chipquick". It is a very low temp solder that is excellent for removing SMD components. You just melt it onto the SMD solder joints where it mixes with the existing solder to lower its melt temp. Once that is done, all of the solder joints remain liquified long enough to remove the offending component. Then, touch up with flux and desolder braid. After that, pop on the new resistors. That should drop the current consumption to 20 uA. Still not perfect, but a nice improvement.
No public wish lists :(