Re: javi's battery project

--- In jallist@yahoogroups.com, "japus10"  wrote:
> 
> Hi Phil & all,
> 
>    As you already know I work in a calibration lab., I'm just 
making 
> this tool for the "energy supervisor departament". Also I'm not an 
> expert to say exactly how it will be connected (surely the other 
> departament have st to say here), I'm just making a instrument and 
> they will use it.

  
  No offence Javi but this reminds me about left hand door engineers 
and right hand door engineers :)
The left hand door design engineers doesn't know how to open the 
right hand door
:)

Shoud be a communication between the service electrician operator, 
cheef of energy department (who is a cheef and maybe doesn't knew 
exactly how many batteries, what power per element and so on) and 
Javi's brain department. 

> 
>   A damaged cell can be in short or reversed, so we can spect a 
power 
> supply in the range -2.5V ... +2.5V/cell. 

Is this tested in reality ? A damaged cell has indeed reversed 
voltage? This should never happen with good maintenance algorithm.
When the cell voltage is 0 is enough to know the cell was discharged
and must be replaced or forced to charge.

Is this factible (for a 
> PIC)? At least to me seems to be a dificult task (think in a power 
> supply of 0.8V, or better, think in -0.2V).
> 
>   The Vasile's solution of last post (powering the PIC from some 
> cells in serie) seems to be clever idea. Perhaps I can "split" the 
> problem into 3 or 4 optoisolated solutions (cmos analog 
multiplexers 
> can manage up to 18V). But here I've a new problem: if I've 4 
> independant boards and the Vcc on one of them is the input of 
another 
> (using analog multiplexers), don't will be all inputs electrically 
> connected?  .... will exist a difference of 60V between to 
pins? ... 
> and ... boom!! ? 

No, I was thinking in a different way. We will number the cell 1, 2, 
3, 4 and so on.
The cell 1 will have a PIC supplied between - of the cell 1 and + of 
the cell 4 (normal condition 1.2x4 = 4.8V, the limits for PIC running 
is 2.8V LF series, 20C degree). The OA+PIC will be optoisolated, I 
like more and more Wouter's solution with 38KHz modulator and IR 
transmitter. A simple zenner diode must protect the PIC against more 
than 5.6...6V (tested, any PIC works ok at 6V and no power 
disssipation/package greater than datasheet say)

The analogic stage will measure just positive voltage, it has 
nonsense to measure an already broken cell, we must start the theory 
having good cells, this is the reason why we measure, to avoid zero 
or negative voltage cells.

The cell 2 will have another PIC supplied with gnd on - cell2 and Vcc 
at + cell 6. Another IR transmitter at 36-38KHz on his tail.

And so on. Now let see how smart are the people on this list. How 
could be supplied the N-3, N-2 and N PIC modules  which are supplied 
at the end of the cell's series ? There is no more cell's left !

A hardware daisy chain could be implemented (cell 1 measured, go to 
cell2 etc, using one optocoupler between any two measuring cells 
device), or if IRDA is used, then interrogate the cell you want and 
wait the answer (it needs a bidirectional IR on every cell, so better 
directly an IRDA pair, but is more expensive)

The great advantage of one IR transmitter/cell is the one you already 
went out from that nasty room where cells are. IR works ok up to 15m, 
you have infinite power there so no problem. Even an IR repeater may 
be used so, finnaly the signal may be transmitted through a laser 
beam up to your cubicle (if IBM style...)


OK Javi,
I hope you have understood my opinion,
Vasile








> 
> 
> 
> 
> Regards,
> Javi.
> www.japus.org
> 
> 
> 
> 
> 
> 
> 
> 
> > Ok, now when I used to work in a telephone exchange the golden 
rule 
> was to 
> > never, ever connect any wires or things to individual cells. The 
> current 
> > capacity of these things is massive. You get an accidental short 
> and the 
> > fireworks are spectacular. I remember one of my colleagues 
> accidently 
> > shorting out one of the 50v sub main busbars with a 1/4" drill 
bit. 
> Wow! He 
> > was in shock after that.
> > 
> > I can't imagine that you would consider having some kind of loom 
> wired up, 
> > dropping off on individual cells. Do you? That's really, really 
> dangerous.
> > 
> > My solution, (an adaptation of previous suggestions), would be to 
> have 24 
> > individual, self contained PIC systems transmitting IR signals. 
> These would 
> > be powered by the cell itself, each having its own step up 
> > regulator/inverter. Each would continually monitor and transmit 
the 
> current 
> > voltage reading. Using a simple random time period would ensure 
> that 
> > transmit contentions don't matter, eventually a clean signal 
would 
> get 
> > though. (A Circuit Cellar project described this method using RF 
> > transmitters several years ago). You'd only need an indication 
> every few 
> > minutes. A failing cell would be identified long before the 
voltage 
> across 
> > it reversed. Anyway, a failed cell would be detected by its 
missing 
> signal. 
> > Each cell would transmit its own ID in the report.
> > 
> > A separate PIC would monitor, record and report the signals, 
> generating 
> > appropriate alarms when necessary. If coupled to a PC you could 
> have a 
> > fancy graphic display.
> > 
> > You would need to pay attention to hermetically sealing each 
> monitor as the 
> > sulphuric acid environment is pretty corrosive. Also, you'll 
> probably get 
> > electrolysis on each terminal connection.
> > 
> > This would be a very interesting project, it's a shame I don't 
have 
> your 
> > job, I'd love to take a crack at it.