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  • DennisG58 commented on gravityisweak's instructable Coat Hanger Drill Bit4 months ago
    Coat Hanger Drill Bit

    I have used this on my planes, too. Also sharpened brass tubing.

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  • Recycle Your Dead Old Laptop Battery

    Not sure of your nomenclature, so will try this. The multiple cells that are in the diagram are the individually monitored cells. The wires shown as + and - that just disappear upward are the wires that get the charge voltage. Is that what you were saying?

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  • Recycle Your Dead Old Laptop Battery

    If you are looking at the charger board linked on ebay, the + and - leads are the output of the battery. For clarity, they are not shown going to the ultimate + and - of the schematically shown battery. What happens is that the whole battery is charged via the + and - leads. Meanwhile, each cell is tapped and the charger board monitors voltage of each one. The board keeps the cell voltages balanced by discharging the highest voltage cells during the charge.

    It might be good to mention two key concepts. For safety and well as efficiency Lithium cells of all types must be prevented from their voltage 1) dropping too low or 2) going too high. Most types can burst into flames if not kept within their operating margins! This is the reason for individual cell monitoring. Remember the need to keep cell voltage from being run too low and put cutoff circuits into play when operating you devices! I have read that running voltages too low is usually more dangerous than overcharging.

    A safety tip for parents is to only use dry cells for children's electrical experiments. Any other type of battery can provide so much current that an electrical short might cause burns or a fire. Arcing also poses an eye danger.

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  • DennisG58 commented on deba168's instructable Make 4 Useful Things From 9V Dead Battery11 months ago
    Make 4 Useful Things From 9V Dead Battery

    Another problem with using the Lithium cells is the danger of fire from running voltage down too low and/or charging to a voltage too high. A low voltage cutoff device is needed for the discharge side to automatically cut off power. Additionally, the cells MUST be kept at matched voltages. Use of a balancing charger is a must. Do not leave unattended while charging. Do not charge on a flammable surface. In short, stick with normal dry cells, especially with youthful users . When a lithium battery fails, it may explode, creating a 2500-degree fireball that will start nearby things on fire, also.

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