Recent content by kpatz

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  1. K

    New battery, top is totally uneven. Should I return it?

    Looks like it's just the shrink wrap that is uneven? That should be fine. Assuming the cell fits, and works fine, use it.
  2. K

    N batteries

    I remember as a kid seeing N cells sold in stores back in the 70s. They were tiny. I'm guessing they were used in slot cars and some mini penlights, maybe keychain lights or something. I don't see them in stores anymore but they can be found online like on Amazon. Now with mini lithium...
  3. K

    noob question on "wasted" voltage

    This is why current regulation is recommended for LEDs rather than voltage regulation. Forward voltage can vary from LED to LED, and even with things like age, temperature, and current. Let the LED drop whatever voltage it wants, and feed it the current it needs (without giving it too much)...
  4. K

    noob question on "wasted" voltage

    When you have 2 resistances in series in a circuit, the voltage will be divided between the two resistances. If they're equal, the voltage will be equally divided. The current will be determined by the voltage divided by the sum of the resistances. Let's take a 6V battery and two 500 ohm...
  5. K

    noob question on "wasted" voltage

    Voltage can be thought of as "pressure" if you think of water. The voltage overcomes resistance to allow a current to flow. At a given resistance (pipe thickness), the higher the voltage (pressure), the more current (amount of water) will flow. If you drive a 3 volt LED directly from a 6 volt...
  6. K

    Charging old cell, reports 1.91V???

    Did you measure it while it was on the charger? The charger is going to put a higher voltage in to charge the cell, and since you say the IR is high, the charging voltage will be on the high side as well. Take it out of the charger and you'll get a correct voltage reading. The charger stops...
  7. K

    30v 18650 cell! About to explode??

    The meter is showing millivolts on the bad cell. You can see the units display change on the top right corner of the LCD from "m V" to "V" when you test the good (blue) battery. You can also tell because it's reading millivolts when the probes have no battery connected. The bad cell is dead...
  8. K

    30v 18650 cell! About to explode??

    Are you sure the meter was giving you volts? If the battery is completely dead it may have been giving you millivolts. The units should show on the display. There's no way you'd get 30V from a lithium cell no matter what. It would have gone kaboom long before reaching that voltage. I'd toss...
  9. K

    changed batteries and flashlight won't turn on

    Some flashlights have overly tight battery holders so the springs can't push the battery into contact all the time (my Thrunite TN4A is like this). If your light is like this, try pushing the battery so the positive end (or whichever end doesn't have a spring) is making contact. Also, if these...
  10. K

    Recovered a Li-Ion discharged to zero

    The battery probably has protection circuits built in, causing it to cut off once it reaches a certain discharge voltage. Now you say the phone said it was at 0%. Was this with the battery powering it, or when you connected it to a charger? If the battery was powering the phone and it said...
  11. K

    Looking for a good SLA battery tester

    If there was a direct conversion of CCA to amp hours, I could do that, but I don't think they correlate that well. CCA is a measurement of how much current the battery can deliver in a short time to start an engine. Ah is a total capacity before the battery is run down. Different measurements...
  12. K

    Looking for a good SLA battery tester

    It doesn't have to be 100% accurate... I know that would require draining the battery. But some devices, such as the Auto Meter RC300, can give an estimated Ah rating of a battery in just a few seconds. I think you enter the battery Ah rating from the label into the device, it does a load and...
  13. K

    Looking for a good SLA battery tester

    I have multiple APC UPSes in my home and sometimes the batteries fail in them, but also I've had the UPSes themselves fail, which means I may be recycling perfectly good batteries. I am looking for a decent SLA battery load tester that can test the battery, tell me if it's good or bad and...
  14. K

    What is "parasitic drain" and is it important ?

    Re: What is "parasitic drain" and is it important ? If the parasitic drain is only a few microamps, I wouldn't sweat it... the cell probably self discharges more than that. If it's hundreds of microamps or into the milliamp range, then it's more of a problem and you'll have to remove...
  15. K

    Best rechargeable AA/AAA batteries?

    Eneloop AAs are ~1900mAh and have very low self discharge. Eneloop Pro AAs are 2550 mAh, but they have more self discharge than regular Eneloops. The Pros are intended for use in high current draw applications like high-lumen flashlights. Regular Eneloops are better for lower current drain...
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