Voltage logging

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Grumpy-b
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Voltage logging

Postby Grumpy-b » Tue Jul 12, 2011 11:43 am

Does anyone know of a simple cost effective way of gathering voltages of a battery pack or cells, whilst a vehicle is on the go, then downloading them for analysis afterwards. This is in relation to my Berlingo which I want to be able to record the various voltages during use to help me better understand when the cells are are failing.

Any ideas, must be readily achievable. Not to complex and cost effective.

Regards
Grumpy-b

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ChrisB
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Re: Voltage logging

Postby ChrisB » Tue Jul 12, 2011 8:09 pm

I've been wondering about something to do this :?

Looked at something like this http://www.picotech.com/data-logger.html

Just not sure its what would be right ?

ChrisB
I reject reality and substitute my own !!!!!!

Wilfried
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Re: Voltage logging

Postby Wilfried » Tue Jul 12, 2011 11:10 pm

There are modules (but you need a laptop to connect them) or you have stand-alone loggers. (After the data collection, you can connect them to a pc for reading and analyzing your data.)

A module: http://www.velleman.eu/distributor/prod ... ?id=350526

A standalone: http://www.lascarelectronics.com/temper ... logger=153
Wilfried EV Network 1940702

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ChrisB
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Re: Voltage logging

Postby ChrisB » Wed Jul 13, 2011 6:23 pm

Touble is we need one with 27 inputs :shock:

Going to be quite expensive using the individual usb sticks I feel :lol:


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Grumpy-b
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Re: Voltage logging

Postby Grumpy-b » Wed Jul 13, 2011 8:09 pm

This looks interesting. Ebay 120741848172

Grumpy-b

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PHEV
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Re: Voltage logging

Postby PHEV » Thu Jul 14, 2011 10:16 am

That will do what you need, but take care not to leave it plugged in whilst not in use, it will run cells flat (draws of the first 2-4 cells iirc) with time..
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Beemer
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Re: Voltage logging

Postby Beemer » Sat Jul 16, 2011 1:43 am

PHEV wrote:That will do what you need, but take care not to leave it plugged in whilst not in use, it will run cells flat (draws of the first 2-4 cells iirc) with time..

If you are drawing off a couple of cells then they are being forced out of balance which is bonkers. They who know, know nothing.

Have a look at this page:
http://www.evdl.org/pages/battbridge.html

Image
In place of one of the resistors you can fit a variable to match the other resistor. If both are variable then you can alter the sensitivity.

Fit as many as you like. This functions to show a voltage discrepancy. It's super cheap and passive. You can fit as many as you like but in my book, it's a dummy to suck on. If your cells started balanced then there is nothing to make them become awry.

In an ideal world you could make them all say, 2.7V, then charge up. Stopping when the voltage curve is touched. This way they cannot eat the weakest when bottoming out if the voltages drop down together.. That's why all these cells are called a pack. Like a pack of starving dogs.

Andrew

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retepsnikrep
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Re: Voltage logging

Postby retepsnikrep » Sat Jul 16, 2011 4:52 am

You need a BMS with data logging capability ;) I don't think there is a very cheap or easy way to do it otherwise.

Two of our 16 cells boards would give you upto 32 channels/cells.
Regards Peter

Two MK1 Honda Insight's. One running 20ah A123 Lithium pack. One 8ah BetterBattery Nimh pack.
One HCH1 Civic Hybrid running 60ah A123 Lithium pack.

Grumpy-b
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Re: Voltage logging

Postby Grumpy-b » Sat Jul 16, 2011 2:14 pm

Not really what I was thinking about when I started this.
I just wanted a way of logging the cell voltages on my berlingo (Ageing Nicads)when they are proving to be a pain and starting to fail. I didnt wish to just wire a cell up and see what its doing but to log its performance over the journey and capture the way its performing, and being able to do more than one would mean I could compare its performance to others.

Thanks for all the suggestions

Grumpy-b

Beemer
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Re: Voltage logging

Postby Beemer » Mon Jul 18, 2011 8:54 am

Surely, to log cells voltages you have to wire them up.

However, a Ni-Cd cell that is losing its capacity will heat up a lot more than the others when the pack is being charged. Try the finger test on each terminal, lol.

You could try or buy one of those temperature guns?

In your van you should have a BMS of some sort. (rqd for chemical cells). Something will definitely monitor cell temperatures to knock down the charge rate as they tend to suffer thermal runaway.

You never know, there may be a test point that the official garages used as part of the servicing routine. I know for a fact the EV-1 (NiM-H cells) had such a connector where the mechanic simply connected a little PDA to the pack near the floor between the seats and it showed the voltages of the packs and highlighted if any were out of tolerance.


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