Low Cost DAQ - 48 analog inputs - switch?

[gdirwin]

First post - I am building an electric vehicle (converting a 2001 RAV4), and have 45 lithium batteries connected in series (about 4 V each).

I want to add a low-cost DAQ card to a PC in the car (USB or Ethernet based) that will allow me to monitor the individual battery voltages (as well as the total pack voltage, pack current etc...).  I will write a program that will need to read the analog voltages and then display them on a graph etc... as part of the overall car computer.

I have searched and found very expensive (>$1000) cards with 48 SE inputs, but am hoping for a lower-cost solution.  I also found "Paktrakr" and it looks exactly like what I want to do, but would prefer something integrated with my car pc.

Note there would be 46 wires from the battery pack, and I probably will need to use differential inputs to the A/D to obtain better accuracy.

I do not need to monitor all channels at once, so could a switch or multiplexer be used (note the high pack voltage) to reduce the # of channels needed on the card (to keep the cost down)?

Any suggestions? 

In advance, thanks!

[gdirwin]

Anyone?

[K C]

Hi,

Do you want to build it yourself or do you want something of the shelf ?

[Doug_L._Bear]

With regard to NI products this would be your cheapest solution:

http://sine.ni.com/nips/cds/view/p/lang/en/nid/203823

Any sort of switching solution, at least with NI products is going to be more expensive than just getting the card with the mutiplexer built in as our switch cards are only available in PXI form factor.  You could get a card with DIO lines and build your own switch, then just use a cheap analog input like a USB 6009 to read it all in on one channel.  You would need a lot of DIO lines to be able to recreate a multiplexer though, and a lot of external relays.

[Rumi]

Hi I was wondering if you have found the solution? I have the similar problem as my analog inputs are excess than my DAQ device's (USB 6212 ) physical channels, I was thinking to use the multiplexers or switches (MAX4545)s probably more than 8 pieces but I am not sure about how to use DAQ device to generate digital clock signal for the switches? If you have got the solution, could you please let me know?

Many thanks.

[gdirwin]

No solutions yet (at least economical answers) - still hoping for more ideas from others though...

For my application, there is a produce called Paktrakr that does measure 48 voltages and can send the sampled info to a computer via a serial port (low tech, but will work).

I am also consider a PLC instead of a computer/capture card - also looking for a bood one at a low-cost.

Garth