Episode: 3816
Title: HPR3816: Post Apocalyptic 4s5 Battery Pack  
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr3816/hpr3816.mp3
Transcribed: 2025-10-25 05:53:16

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This is Hacker Public Radio Episode 3816 from Monday the 20th of March 2023.
Today's show is entitled Post Apocalyptic Forest 5 Battery Pack.
It is part of the series Hobby Electronics.
It is the 10th show of Mechatraniac, and is about 8 minutes long.
It carries an explicit flag.
The summary is, tough battery design worthy of the Post Apocalyptic Robotics Database.
Hey what's up is Mechatraniac, Mechatronics, maniac here again on the spyware audacity.
Today I'm going to put something into the public domain that's not at all abominable.
It is pretty cool.
Well the MP3 player last time was pretty cool too, but it's also abominable.
So hopefully you can access the images.
They're going to help, maybe not mandatory, but it will help to look at the images.
So pick 0 is the 4s5 battery schematic.
You might have seen last time I did a video about the mobile computer battle stations.
And you may have recall that that point that I had a 4s4 system means 4 series for parallel.
So this time I'm going for s5, which is one extra parallel.
But I had this all sealed up, but I noticed that my voltage was dropping off.
I was charging the computer.
So I used to go from this BMS module to the boost converter that turns the 16.8
and below from the battery to 19 volts to charge my laptop.
And the boost converter, it's just a board with some stuff on it and has a little pot
that you can adjust for the output voltage and that's it.
So yeah, you definitely need a volt meter if you're going to do boost converter stuff.
But anyway, the zen of post-apocalyptic robotics has smiled upon me.
But anyway, I was, like I said, I was noticing that the voltage was dropping.
And then on the board, you can measure between 0 and between 0 and 4.2 volts,
between 4.2 volts and 8.4 volts and all those test points.
So I checked and from 4.2 volts to 8.4 volts, it was much lower than the other ones.
So I took those apart and so I get to show you the inside,
because I didn't have that camera when I was building this thing originally.
So this is the really zen of post-apocalyptic robotics here,
because I had the 4s4 that I built the last time and I had problems with it disconnecting at
points. I had to like open it up and resolder it all the time.
So I needed a solution for that. It's just wrapped in cardboard.
So I needed something like stable, like metal or something as base plates,
so that it would be rigid and not have flex to it and not wreck the solder points.
And what I found is that a DVD drive case like for a computer or whatever works perfectly.
It's like the perfect size when you set up.
If you look at pick one, you can see the dimensions of it.
And it just so happens that a DVD drive case fits perfectly over this,
like the two halves of it. There's one half of the DVD case that has more
about like a lip on it and that's actually nice.
On picture six, you can somewhat see the lip coming down.
So pick one I cut through the tape and cardboard and you can see on pick two,
you can see the ribbon strip of metal that's holding the batteries together.
Pick three is another detail of the solder points between the two cells.
And pick four is actually, so I took that ribbon off.
This is bank two between the 4.2 and 8.4 bolt points.
And one or more of these cells was bad.
Actually on pick four, it shows the new cells in there.
Pick two, you can see they're different colors.
So when I took that strip off the one side, I could measure each voltage without
having to remove the strip on the negative terminals.
So I found two that were low and we're actually depleting while I was measuring them.
So okay, so I've got some new ones in there.
Hopefully they'll be better.
Snug them in there, pick five and pick six.
I've got the DVD case on there, pick seven,
taped it right up real nice.
And pick eight shows the BMS board.
So I use a solar power cell to our solar power panel to charge this.
And I built some more panels as well, but it works really well from the solar panel.
And pick nine is an outdoors picture of it in action.
And so all this stuff is post-apocalyptic, sourced from dead electronics, except for the BMS.
But at some point should be able to do that as well.
I recommend watt hour YouTube channel.
He does a analysis on one of the 12 volts units, which is only three cells.
This one has four, which is better for my purposes, because it's perfect for
charging with the 18 or 20 volts that I get from my solar panel.
I've also added a mall X connector.
And that actually plugs into my battle station where I have the boost connector set up,
which is actually the case for my laptop that it originally can.
It's getting a bit beat up now.
It's only cardboard, but I covered it in tape.
I won't go into that today.
We'll just keep it on the BMS stuff.
So last time, if you want to zoom in on pick eight, you might be and should be able to see.
So the last time I did a major brain shark, because if you can see the input and output,
if you look at my schematic, the input and output are the same terminals plus and minus,
which I found to be bizarre, because on the on the 1s chargers that I one of which I used on
the previous podcast about the abominable post-pocalyptic MP3 player, it has separate input and output.
So this was confusing for me.
Well, it wasn't confusing.
I just had a brain shark, the totally the wrong thing, and went from the battery zero volts,
and the battery 16 volts directly from the battery for my output.
And I didn't realize that the input and the output are the same.
So you just plug that in.
And before I had to worry, because I was going directly from the battery,
there was nothing stopping it from over discharge,
I had to worry about it draining the shit out of my battery,
even though the boost converter stops around 8.4 volts.
That's already too low.
You want it to be around 12 volts.
Anything goes below 2.5 volts on your cells.
It's bad for the cells.
So that's really good to know.
Now, once it goes below 2.5 volts on any cell bank,
it will just automatically turn it off.
So that makes it a lot better.
All right, I think that's about it for now.
Hopefully it's not too confusing.
The schematic should make sense.
All right, this is the McTry FHPR out.
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