Friday, August 27, 2021

Building the Less Chinese Power Bank

 started with the salvaged 9Ah, 12VDC lead-acid battery put in a small plastic toolbox from Ace Hardware.  It took a while but they are called "female connectors" to go on the flat battery terminals. To get them on the wires to the female cigarette lighter socket involved crushing the clamps on the female connectors.  They I verified functionality by taking this combo to my mount.  It powered up.  To make it more convenient, I drilled a whole in the top of the toolbox to push the socket through. 

The socket is 1.05" OD.  I have a 1" Forstner bit, but the socket does not quite fit and filing was not doing it, so I did an episiotomy, slicing at the edges to let the head through a tight space. 

The last time I watched a real episiotomy, I was almost sick thinking of her pain but compared to pushing our son out, this was probably unnoticed.   I put an aluminum block under to prevent insertion into the socket pushing it down. Tomorrow I graft the cigarette lighter end on the 15VDC wall work and verify that it charges.  A digital volt meter or LED is purely
a luxury.  Both the female disconnect and wire nuts are Taiwanese. 

I believe the charger is doing its job.
With the charger plugged in, I get 13.2V at the battery terminals.  Unplugged 13.17V.  I assume that overcharging a lead-acid battery is deleterious in some way.  Until I put a DC voltmeter in the circuit, I will leave the wall wart unplugged.

Charging voltage.  It drops voltage fast enough that I suspect the battery is too old.  (I bought about four years ago, I think.  But unlike when I swapped the battery out of the old power bank, I can do this quickly and easily.)  From 13.1 to 12.7 V in 7 minutes with no load but the display.  Time for a new battery?  But I recharged it, and has been holding 13.3V for several hours. 

The display is currently held on by Scotch tape.  I need the next size machine screw and nut below 4-40.  Do you have two?  D&B Supply in Eagle had them 2-56 screws ($0.45 each) and nuts ($0.55 each).

I still need a couple spacers at the end of the box.  I had no pieces of acetal large enough.  Aluminum would take a long time to mill.  Milling oak chars and makes smoke.  My chopsaw just is not precise enough for a tight fit.

My wife pulled out two jewelry boxes; one required decapitation to fit adequately. 
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4 comments:

  1. JeffAugust 27, 2021 at 10:48 AM

    "It took a while but they are called 'female connectors' to go on the flat battery terminals. To get them on the wires to the female cigarette lighter socket involved crushing the clamps on the female connectors."

    Those are commonly called spade terminals and are common as dirt. You should get a wiring crimper tool (special pliers) to strip the wires and make the crimp connections to the wires.

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  2. JLW IIIAugust 28, 2021 at 10:46 AM

    Read the following article. Charging batteries is more complicated than you are making out.

    https://en.wikipedia.org/wiki/IUoU_battery_charging

    ReplyDelete
  3. JLW IIIAugust 28, 2021 at 10:47 AM

    Read the following article. Charging batteries is more complicated than you are making out.

    https://en.wikipedia.org/wiki/IUoU_battery_charging

    ReplyDelete
  4. B August 28, 2021 at 3:56 PM

    Might try discharging that battery at a 10 amp rate (you can use a headlight (incandescent, not led) or other 12 v lamp that is big enough, or a 1.2 ohm load of any kind)) until the battery voltage goes below 10.5v, then charging it at a higher rate than your wal-wart will give it (try using your car and a set of jumper cables) until it is fully charged.

    It is possible that the battery is slightly sulphated. Doing this twice or three times will help remove the sulphation. let the battery cool between charge and discharge cycle.

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