SqueezeAMP boxes

[chill]

Rather than pollute the original thread any more I thought I'd move the discussion of the boxes for SqueezeAMP to a new thread.

I've had a go at making 3D-printable boxes for a variety of configurations of SqueezeAMP with 2- and 3-cell arrangements of a couple of different cell sizes. There could be quite a few combinations, but the files in this post cover a good range to get us started.

I started with a basic base and lid to hold the PCB securely. Then I added different lids to accommodate fans, if the SqueezeAMP needs cooling. Then I added some options to hold the cells/cell packs. I've made STL files of all these options - they're all in this zip file. The images below show what's in each file. All of the lids fit all of the bases.

Basic base


Basic base with side entry (for PCBs with right angle battery connector)


Lid with vent


Lid with 16mm fan


Lid with 30mm fan


Base for 3x16340


Box for 2x18650


Base with 2x18650 lid


Box for 3x18650


Base with 3x18650 lid


Photos in the next post.

[chill]

And some images of them in use:

2x18650 version






3x18650 version


3x16340 version


For the 3x16340 base, these 13.5mm x 11.5mm battery terminals work well. You can use 2 or 3 cells, provided you wire up the terminals correctly to put them in series.

[sle118]

Nice work! I'm definitely going to print a 18650 version today; my SqueezeAmp board has been exposed for too long!

[chill]

Nice work! I'm definitely going to print a 18650 version today; my SqueezeAmp board has been exposed for too long!

I'm guessing you have the 2-cell PCB. The 2x18650 box is easy to put together. I made the 3x18650 box bigger than it needed to be to just hold the battery pack, because it needed wiggle room to get the connector through the opening. It's a bid of a fiddle to fish it through the opening, but it's doable.

[mherger]

> I'm guessing you have the 2-cell PCB. The 2x18650 box is easy to put
> together. I made the 3x18650 box bigger than it needed to be to just
> hold the battery pack, because it needed wiggle room to get the
> connector through the opening. It's a bid of a fiddle to fish it
> through the opening, but it's doable.

Now I don't know where this question would belong... but do you have any
numbers/guesses/experience about how long different configurations of
batteries would last?

--

Michael

[sle118]

I'm guessing you have the 2-cell PCB. The 2x18650 box is easy to put together. I made the 3x18650 box bigger than it needed to be to just hold the battery pack, because it needed wiggle room to get the connector through the opening. It's a bid of a fiddle to fish it through the opening, but it's doable.

Not sure which version I have (it's one of the first units built. I have to chek how the charging circuit was populated). I'll tpost some pictures later, if my spools are still dry enough for a good print!

[chill]

Now I don't know where this question would belong... but do you have any
numbers/guesses/experience about how long different configurations of
batteries would last?

Yes, I got about 9 hours playing LMS-to-Toslink from a pair of 700mAh 16340 cells (2x2.59Wh = 5.18Wh). You can scale this according to the capacity of your cells. My 2-cell 18650 pack is rated at 2600mAh and 19.24Wh, so should give (19.24/5.18)*9 = >30 hours. My 3-cell 18650 pack is rated at 3400mAh and 37.74Wh, so might give (37.74/5.18)*9 = ~65 hours.

I think! I'm getting a bit confused with the mAh ratings and the different voltages!

[chill]

I think! I'm getting a bit confused with the mAh ratings and the different voltages!

What I don't understand is why the 3-cell 18650 pack's rating of 37.74 Wh is almost twice as high as the 2-cell pack's 19.24 Wh, when it only has 50% more of the same cells. Is it because the 3-cell pack delivers it's energy at a lower current (higher voltage), so it can extract more energy from the cells?

[chill]

If that is the reason, it seems to make the 3-cell version disproportionately better for this application (approx 30% better than a 2-cell version of the same size). The SqueezeAMP draws about 80-85mA on 2 cells, so should draw around 50mA on three cells. If the lower current draw means the cells can deliver more energy, that's a good thing, isn't it? Is all of that extra energy lost as heat somewhere though?

Or have I got this completely wrong?

[philippe_44]

What I don't understand is why the 3-cell 18650 pack's rating of 37.74 Wh is almost twice as high as the 2-cell pack's 19.24 Wh, when it only has 50% more of the same cells. Is it because the 3-cell pack delivers it's energy at a lower current (higher voltage), so it can extract more energy from the cells?

Well, it should not be that different, so it's a lot of marketing hype. Yes, you can do a deeper discharge with lower currents vs higher current bursts (Li-Ion has a very abrupt discharge curve), but I don't think you'll reach that much improvement as the amp is not like a RC. I've set the cutoff voltage at 3V per cell