1. this guy is the best.  So generous of him, and he is a good teacher.   Now, whether I can build a powerwall, that's another thing :  )

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2. O.yes Mr.jehugarcia….That a BIGGGIST secret ,,batt tester,,
   Good Luck in 2017.y.

   Hello from Latvia

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3. You can make a device to do a quick differential voltage measurement (across two different loads), and then calculate the differential resistance.
   You can also use a standard ESR meter, and use a capacitor in series (just to block dc) while taking measurement.
   Both of these test (first one being superior) will yield a somewhat reliable judgement on the health of a rechargeable battery.

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4. Hi Jehu, I have been watching a load of your videos! I want to easily check the mAh capacity of mine too! I am trying to decide between buying the following devices: LiitoKala Engineer Lii-500, the Foxnovo F-4S, or the Opus / Floureon BT-C3100. Which one is best for measuring an accurate capacity? I already have a Nitecore D4 for simple (smart) charging but I want to measure the real mAh of some 18650 batteries that I have salvaged from laptops. If I have one of these discharging / testing devices do I still need to leave them for weeks and see if they lose charge?

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5. Which type baterry is the Best? LG. Samsung .Sanyo. Panasonic. for 18650 cells

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6. The most useful of your videos (for my purposes) I've seen yet. Thanks for the insight.

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7. i like your idea of how to add a few cells to a weak capacity battery in series.  
   I learned something once again. Thanks!

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8. doing all this work building these battery cells would it not be advantageous to design and build a box that you can just drop batteries into and bolt together to complete the wiring of the cell and also easy reusable cell case on battery replacement

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9. I love the videos.  Are you finding good cells among the ones that come to you below 3.0v?  I bought a batch recently that are mostly in the 1v and 2v range.  Are these beyond hope?

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10. Keep up the focus, don't loose sight.  Common sense is uncommon in todays ADDS environment.           Number theory and probability statics are where you are but you can not see what is smacking you in the face.  Too many whatevers.  You are worrying about why are not all the wave heights  the same in a storm in the ocean.  Think of you, the car, and the battery as if  it's you, a plow, and a horse.  You do not kill the horse to plow the last row.  You may need the horse tomorrow. 
    Battery 101.  Forget about 50% of it's maximum capacity and just "cherry pick" the best part. If the weakest cell that you want to use is 1500 mAh, then the whole pack is only going to be worth 750 mAh per cell times the total number of cells.  Your plow horse will love you.   It will be there for you every day. 
    Heat (entropy) and temperature build up will do ugly things to batteries (and the horse).   I you can settle for 1/2 amp per cell (continuous), temperature will not be a problem when discharging or charging.  Otherwise, the cooling system will eat you alive.    
    If you can swallow all this, think of recharging the beast.   At 1/2 amp, a 1000 mAh cell (remember it is being "Cherry picked from 2000 mAh cell) will take 2 hours to recharge.   
    Bottom line, "I think that your going to need a bigger boat – JAWS ".   So, It's going to take more cells,   If there is anything left of your ego, you will grow old and happy in your battery powered car.   This isn't hyper BS.   SSDD.  Quit feeling bad about not finding the last lost penny in the sand at the beach. 
    The old story.  You are standing atop a mountain.  You see the next mountain across a valley with a dense forest, wall to wall.  Your task is to get to the top of the next mountain peak.  When you get into the forest, you get  lost amongst the trees.  You need more data to navigate.  Indians marked the trees to stay on course.  Moral of the story, do not get lost in the forest among the trees.
    Was the goal to carve a fat hog, i.e. cheep batteries, or bask in the glory of a free ride, i.e. electric car or get a PHD at the school of hard nocks or spend  mega bucks trying to save pennies.  
    Do not kill the messenger.   I got my stripes with electric  RC airplanes.   After a few trips around the block (steep learning curve),  it fell into place.   A battery pack is like a tank of gas.  When it gets low, (battery) , replace it with a full one.   When you go home, recharge all he battery packs,  It got so good, I got into video cameras for inflight video,
    DAAAAA, camera batteries, round and round we go, when it stops, nobody knows.
    Bare with me, I want you to win ! !   After all, I had a '61 rag top bus that I nursed for another lap on the OD when I as in college and working,  It was fun.          .                                       .  .

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11. maybe testing the internal resistance will reveal the bad cells

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12. you could buy a multi charger which can charge more than 12 cells at the same time

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13. You may have been an average guy, but those days are long gone.  The average guy doesn't apply themselves like you do.  I hope that I can do what you do here in the Midwest.

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