Corbin, Since I don't want a BMS, the price is excessive, in my opinion. If I
wanted a BMS, then I would consider the price to be appropriate.
Damon, see above. My price point is based on product versus perceived value.
I'll pay through the nose to get exactly what I want, but I really don't want to
pay for something that won't be used, as in a BMS.
Damon and Matt, I've been in touch with Ken from PakTrakr and he's told me that
the LiFePO4 version will handle up to 40 cells, although I need only to read 20,
but the worst of it is that it pulls from three cells out of eight. That's a
recipe for unbalance, in my opinion. My experience with the PakTrakr is that the
resolution or the accuracy is lacking, although Ken did say he's added an extra
digit to the right of the decimal point. That's no good if there's no accuracy
(reported often in other forums) and no good if the pack goes unbalanced on a
regular basis. Other LiFePO4 pack users have reported very little trouble in
keeping a balanced pack, and don't have mid-pack loading.
Doug, I'm probably going to destroy what little grey matter I have remaining,
but your solution appears to be just what I want. I don't have the skills to
modify computer mice to squeak voltage readings at me, although I find the
concept intriguing and the execution impressive. It's that sort of thing that I
very much enjoy to read about. Success with items at hand is far better than
collecting esoteric materials and devices, although it appears that the Gangster
stuff falls about in the middle. It's really what I was hoping to find and I've
also discovered the forums for that platform.
I noted the video and audio module for the Gangster. I don't think that fits
into my limited programming skills, but it makes me consider that Norm's display
might be fed from a Gangster. I realize that the product is called the Gadget
Gangster. I like the name!
What's an EVILbus? Is there a link available?
I'm hopeful that there are people in that forum as good as the people in this
one!
------------------------------
From: corbin dunn <
[email protected]>
Hi Fred,
The Elithion Lithiumate BMS will do this. I'm using it for my new EV, and I like
it a lot. Affordable is relative...it is probably $1000-$1200. Depending on the
cost of the batteries that is quite affordable.
------------------------------
From: "
[email protected]" <
[email protected]>
Well, I've been working on something for the past few months, but I haven't
said anything about it here on the EVDL because it might seem a silly way
to go. I've actually got a prototype system running on my workbench right
now that uses USB computer mice to send cell voltage info to a laptop.
Each mouse monitors the voltage of 4 cells, using the three mouse buttons
and the scroll wheel.
Basically, I removed the microswitches on each mouse button/wheel and
replaced them with optos. A PIC chip at each cell measures the voltage
every few seconds, then closes/opens the opto to simulate mouse clicks. A
Java program running on the PC displays reads to mouse clicks on the USB
ports to display real-time info and record the history.
My goal was that components would cost less than $1.00US per cell. Each
mouse cost 99 cents and measures four cells, so it was like buying a
pre-made circuit for 25 cents per cell. I'm trying to find a way to
increase it to 6 cells per mouse, using some of the chip's other
functionality, which would make it even cheaper per cell. Peripheral stuff
(capacitors, optos, resistors) adds up to about 60 cents per cell.
Hey, I told you it was silly.
------------------------------
From: damon henry <
[email protected]>
Ok, wasn't sure what your price point was. Seems like you could use your
paktraker that you are already familiar with. It would not give you individual
cell data, but you could wire one sensor across multiple cells and still get
some pretty useful data.
------------------------------
From: "matt lacey" <
[email protected]>
If you are going to use the paktrakr with lithium cells,
make sure the first "12v" lead isn't connected to the actual pack.
The power for the module comes from the first battery, pulling it outta
balance relative to the rest of the pack.
------------------------------
From: Doug Weathers <
[email protected]>
Last year I built a datalogger out of a Parallax Propeller chip and some sensors
and a microSD card slot. It flew into space on a sounding rocket (peak
sustained G-load of around 18 gravities), recording data on the microSD card all
the way. I got it back in perfect condition.
Note that I didn't (and still don't) know what I was doing. I'm just an aging
computer hobbyist, not an EE or even a CS grad.
The Propeller is quite easy to program (lots of code already available for
download from the Propeller Object Exchange), and it's dead simple to wire up.
We went from concept to sack of parts to delivery in six weeks.
However, if I had it to do over again I'd probably just start with one of these:
<http://gadgetgangster.com/find-a-project/56?projectnum=257>
Already has the microSD slot on it.
Then you could some of these to it:
<http://gadgetgangster.com/find-a-project?subcat=33>
Note the prototyping module with the RCA coax jacks on it. Looks like it would
work nicely for an implementation of Lee Hart's EVILbus. Hmmm.
The Propeller chip has 32 I/O pins, all of which can be used as either analog or
digital input or output, or as a serial port, or I2C or SPI buses, or audio or
video, or whatever else you can come up with. There's no reason you couldn't
have several of these all talking to a dashboard unit with a user interface.
The problem of sensing the battery voltages - safely - is left as an exercise
for the readers. What's the minimum amount of easy-to-make hardware required at
each cell? A current-limiting resistor?
end of compiled messages
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