# paktrakr SOC



## edsammy (Jun 15, 2009)

does anyone know how the paktrakr determines a packs SOC?
thanks


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## TheSGC (Nov 15, 2007)

The PakTrakr uses Voltage and voltage drop over time to measure the SOC of the pack. 

I have a PakTrakr installed in my Civic EV and finally cleaned up the noise and just started to take range tests and gathering data with the PakTrakr and a conventional volt meter for comparison.


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## edsammy (Jun 15, 2009)

thanks for the quick response. i would like to know what the results of those comparisons are. are you happy with the paktrakr system?


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## TheSGC (Nov 15, 2007)

I am happy with the PakTrakr as I can monitor every battery in my pack. I have noticed that it seems to be conservative on it's SOC gauge, but I am only have a few runs on me and I have not even come close to running out of power.

The Volt meter and the PakTrakr seem to show voltages about the same, give or take a 0.2 volts. I had some trouble with noise on the line, but I think I solved it with ferrite cores on the serial cables, and installing heavier gauge wire for the traction pack.


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## edsammy (Jun 15, 2009)

thanks for your input


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## dimitri (May 16, 2008)

PakTrakr rocks! Can't go without it...

Well worth the price

And, BTW, LiFePo4 SOC is pretty damn good on it, I have no idea how they do it with voltage jumping up and down every second as you drive, but it works like a charm.


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## edsammy (Jun 15, 2009)

i have been reading all of your good reviews on it and you convinced me to go with it over the link 10.


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## edsammy (Jun 15, 2009)

does any one know if there is some kind of converter chip inside the paktrakr serial cable or is it just a basic cable?


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## bblocher (Jul 30, 2008)

dimitri said:


> PakTrakr rocks! Can't go without it...
> 
> Well worth the price
> 
> And, BTW, LiFePo4 SOC is pretty damn good on it, I have no idea how they do it with voltage jumping up and down every second as you drive, but it works like a charm.


Awesome. I think I'll end up phasing out my high priced POS BMS I got and replace with this, my new VB modules for LiFePO4 and some form of AMP gauge. I just wasn't sure how I'd track SOC well.


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## zeeman1953 (Apr 5, 2009)

TheSGC said:


> I am happy with the PakTrakr as I can monitor every battery in my pack. I have noticed that it seems to be conservative on it's SOC gauge, but I am only have a few runs on me and I have not even come close to running out of power.
> 
> The Volt meter and the PakTrakr seem to show voltages about the same, give or take a 0.2 volts. I had some trouble with noise on the line, but I think I solved it with ferrite cores on the serial cables, and installing heavier gauge wire for the traction pack.


Hi, I have a Paktrakr and want to be sure I read it right when I am using it. As I drive my car, the SOC (and the "fuel gauge" E....F) begins to drop from 100% to 99%, 98% ........to 65%, etc. Does this % (and E.....F) reading mean I can go until it reads 0% and I am the the end of my useful driving distance range...OR, does it mean that at 0% is the maximum I should discharge the batteries?


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## kittydog42 (Sep 18, 2007)

I used one of these for awhile and had a problem with the parasitic discharge it created on the first three batteries of the main string. I ended up replacing it with a Cycle Analyst. On a related note, I have a used PakTrakr system for sale with two remotes (good for up to 24 LiFePo cells) and a current shunt, PM me for details. I believe more remotes could be purchased.


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## jaspersk (Jun 26, 2008)

zeeman1953 said:


> Hi, I have a Paktrakr and want to be sure I read it right when I am using it. As I drive my car, the SOC (and the "fuel gauge" E....F) begins to drop from 100% to 99%, 98% ........to 65%, etc. Does this % (and E.....F) reading mean I can go until it reads 0% and I am the the end of my useful driving distance range...OR, does it mean that at 0% is the maximum I should discharge the batteries?


I don't have a Paktrakr but I have used specific gravity to check my SOC while doing a test run on range. If you have lead acid, everyone says to never go below 20% SOC or your cause damage to the batteries. Using SG readings I found that by the time I got down to 30%, my car was undrivable at street speeds. You don't want to take lead acid batteries below 1.75V/cell or you damage them. With my controller limiting battery volts to 1.75V/cell, I couldn't drive much faster than 15-25 mph so 30% is my absolute bottom limit but again that is for lead acid and SOC reading based on specific gravity readings.


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## TheSGC (Nov 15, 2007)

zeeman1953 said:


> Hi, I have a Paktrakr and want to be sure I read it right when I am using it. As I drive my car, the SOC (and the "fuel gauge" E....F) begins to drop from 100% to 99%, 98% ........to 65%, etc. Does this % (and E.....F) reading mean I can go until it reads 0% and I am the the end of my useful driving distance range...OR, does it mean that at 0% is the maximum I should discharge the batteries?


You really should only take it down to 20% to preserve battery life and because lower than that, you will have little to no power left. However, you should do a few tests: take the EV out for a spin down to 50% and then park it, shut off power and check the battery voltages to make sure they are read close to 50%. I recently took my EV out for a 15 mile run that it should have done with ease, but after 12 mile I lost just about all my power when the controller went into low voltage shutdown, and the PakTrakr read a measly 20% left, instead of the expected 50%. The Paktrakr reads the lowest batteries, and two of my where not getting charged properly. I had 2% battery left according to the PakTrakr and I was crawling home slower than a baby can crawl.


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## dimitri (May 16, 2008)

When I bought PakTrakr for LiFePo4 pack I asked Ken Hall if SOC display shows "real" SOC or "safe" SOC. He said that SOC display for LiFePo4 is quite safe, i.e. if display shows 0% SOC that means you should be somewhere at 80% DoD.

So far this corresponds to my observations. I have driven my car to 5% SOC on display, yet my lowest cell was still resting just above 3.0V, although sagging under 3C load to 2.6V-2.7V.

Hope this helps.

P.S. Don't forget to set your display mode to Lithium, by default its set to FLA and it resets to FLA every time you disconnect remotes.


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## TheSGC (Nov 15, 2007)

dimitri said:


> When I bought PakTrakr for LiFePo4 pack I asked Ken Hall if SOC display shows "real" SOC or "safe" SOC. He said that SOC display for LiFePo4 is quite safe, i.e. if display shows 0% SOC that means you should be somewhere at 80% DoD.
> 
> So far this corresponds to my observations. I have driven my car to 5% SOC on display, yet my lowest cell was still resting just above 3.0V, although sagging under 3C load to 2.6V-2.7V.
> 
> ...


Now that is good info! I have always thought that was the case, I just had a few stubborn batteries telling me otherwise, which I have almost finished sorting out.

So I guess the Paktrakr does let you go to 0 % with a safety margin, Which is probably why when I was at 0% the other day, there was still plenty of safety juice left.


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## TheSGC (Nov 15, 2007)

Just another thought- today I took me EV out 16.5 miles (farthest driven yet) and the PakTrakr identified 2 bad batteries, and gave me lots of warning before I could feel the effects (warning started at 15 miles). Under load, most of my batteries were at 11.2 volts, except for two- one was at 10.4 volts and another at 7.5 volts! These are 12 volt batteries, and will be getting exchanged very soon (18 month free replacement is coming in handy)


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