Ian.culverhouse wrote:I have removed the battery from the circuit that I made and am now using a Sparkfun LiPo charging board and it appears to be charging. It reads 3.8v when I put the DMM across the terminals. How long do these take to charge? It is a LipO battery from Sparkfun, I believe it is the one with the charge protection built in, is there still a risk of flames?
The time it takes to charge is dependent on the output current of the charger. With most lipo cells you do not want to charge over 1C rate, meaning a 250mah battery should be charged at no more than 250mah, resulting in a 1 hour charge approximately, depending on the state of charge when you started.
Also, lipo's as stated earlier should not be allowed to discharge to less than 2 - 2.7 volts depending on the quality of the cell.
If allowed to drop below this they are potentially dead and if you do try to bring the back, DO NOT charge them at the 1C rate, more like .1 C rate.
If you notice the cell PUFFING, with your limited experience using these, DO NOT try to charge/use them. You will certainly cause a fire.
The chemistry needs to maintain a charge in order to keep the internal resistace to a minimum. If there is no chare they are essentially a big, low wattage resistor wrapped in flammable material/chemicals, inside a vessel that will build up pressure, meaning explosion, or a large (relatively) jet like plume of flame out of a hole that opened up due to the pressure.
Anything using a lipo certainly needs voltage detection ability to cut power when voltage drops this low. Most devices using them do have this.
I would just throw that cell away and get a new one and be more careful next time.
