[vixr]

Hey all,
    I'm on my third set of NiMH batteries in the PPAv2 I built back in '05. I had to make some minor changes to the fast charging configuration to lower the upper max temp threshold to 112 F. These eneloop cells cant tolerate the temps the old green skin cells I had in there. These eneloop cells come fully charged, so it didnt take long to top em off.
 

 
Here is the board a few minutes after starting fast charge. The LM317 regulator is at 116 F... cells are cold

 
here it is after 35 minutes of fast charging, it just latched to trickle...cells are warm at 112 F
 

 
Fast charge in black hot...
 

 

[tangent]

Interesting.
 
Does your camera not have a way to include the temperature scale in the frame, so you can interpret the photos after losing this connection? I mean, a year later, will you remember what gray value 182 means in these particular photos?
 
Is the charging voltage well-optimized?  Meaning, if you dropped it any farther, would the charge current start dropping?
 
If you haven't done that optimization, you're making the regulator turn voltage into heat unnecessarily, which is contributing to the heat of the cells through air convection.

 

[vixr]

Sensei,
    The monitors on the host platforms the imagers are installed on do have the ability to display temps and colors, my bench monitor is just simple NTSC composite vid... I used the PPA battery board configuration calculator at the audiologica page and it suggested 23.7 volts and I use 24... everything else is by the book, straight from the guides you wrote. I have played with the voltage on my personal benchtop PSU and the current (240mA) doesn't start to drop until the voltage goes down to 19.2 volts.The current is almost cut in half at 19.2 volts

 

[tangent]

The current shouldn't instantly drop in half. It will be rock steady when there is enough voltage, then roll off gently — linearly, in fact — the farther you drop below the minimum voltage.

 

[vixr]

  The current shouldn't instantly drop in half. It will be rock steady when there is enough voltage, then roll off gently — linearly, in fact — the farther you drop below the minimum voltage.

its kinda hard to tell with my power supply, it has an analog meter. The needle just doesn't bounce as high.. I'm lazy and rarely hook up the DMM to see the exact numbers

 

[vixr]

I really should say that after all this time, like a thousand hours (all battery powered) this PPA still is the coolest amp. It has never given me a bit of trouble and sounds as fabulous as the day I built it.

 

[wakibaki]

Interesting. I always wanted an IR camera for diagnostics. Photograph everything when it was working right.

Now I see it is quite simple to convert a digital camera to IR. I don't know if you get something that can see long enough IR to be useful. This is something I would check out if time permitted. Perhaps someone else will find it interesting enough to investigate.

 

[vixr]

so, my PPA turned sweet sixteen this year... still working perfectly. Charged it up this morning and let her rip. Coolest thing ever.