# Soliton1 with GBS 100AH cells



## Kurtdiver (Aug 7, 2011)

Soliton1 allows for setting 'minimum pack voltage with no current' and 'minimum pack voltage at full current'

How much sag should I account for each GBS 100AH cell at full current? I have the discharge curves for 3C, but what I've seen others use are numbers like 2.5V per cell which is lower than the 3C chart.

Here is link to the charge and discharge curves: 
http://www.easlithium.com/sites/default/files/Charging Discharging Curves_0.pdf


Thanks for your help.
-Kurt


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## Ziggythewiz (May 16, 2010)

What's the most you pull? How far you take them is entirely up to you. I don't think there's a lot of experience with GBS around here, so you make have to just add your own curve and extrapolate where the best cutoff point would be.


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## GizmoEV (Nov 28, 2009)

Remember that the controller will see the voltage at its terminals not at the pack terminals. Setting the fully loaded cutoff at 2.5V won't hurt your cells. As Ziggy said, it is up to you how far you want to discharge them. You might want to start with 3.0V as the no load cutoff and 2.5V as the under load cutoff. That will likely mean close to 100%DOD.

Make sure you use some sort of Ah counter and only use 70-80Ah of your pack. The controller cutoffs then will just protect your pack if you go beyond that very far.

For my TS 200Ah pack when discharged to 90%DOD with a 7.5A load the lowest cell voltage was 3.178V so 3.0V no load may be a little bit low to start out with.
http://www.diyelectriccar.com/forums/member.php?u=11313


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## Tesseract (Sep 27, 2008)

Kurtdiver said:


> Soliton1 allows for setting 'minimum pack voltage with no current' and 'minimum pack voltage at full current'
> 
> How much sag should I account for each GBS 100AH cell at full current?...


That graph is, shall we say, overly optimistic. I just load tested a 4-pack of GBS-100Ah cells at 300A and they each quickly dropped to 2.80V. So for a top-balanced pack you could set the "minimum pack voltage at full current" parameter to as low as 2.7V per cell, but that would be pushing it. For a bottom balanced pack you could set the same parameter to 1/2 the nominal voltage (ie - to 1.7V per cell, which is the maximum power point) though there are definitely diminishing returns below 2/3rds nominal. 

You also need to account for any resistive voltage drops from your battery cables, etc., as GizmoEV pointed out. A good way to empirically determine how much sag to allow is to actually measure it with the Soliton logger program. Set maximum battery current to 3C and both minimum pack voltage parameters artificially low then go hammer on the throttle. Record the battery voltage at a few entries throughout the log file where a "high pack current" warning is set (and preferably without duty cycle at 100%). Note that as the pack is depleted the battery voltage will sag more at a given current draw, though not nearly as badly as lead-acid.


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## Kurtdiver (Aug 7, 2011)

I relaxed the voltage minimums on the Soliton1 and took it for a spin. That made a world of difference with regards to acceleration! Under hard acceleration, it would hit 600Amps. Previously on a full charge it would max at 200Amps. That extra power was amazing off the line. I was also able to get the car up to 100MPH in 4th gear, with power to spare, but I had to stop because if you get caught in my state going that fast, you lose your license for a year. I'll have to save the top speed test for a racetrack.

http://kurtsprojects.blogspot.com/


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## dougingraham (Jul 26, 2011)

At the moment I am running with just 33 cells of the GBS 100AH. I am still building the front battery box which will hold another 19 cells.

I am running the voltage down to 2.0v (2.7 no current) and have the motor and battery current set to 1000 amps. It is frightening in 2nd gear with all the torque. My pack is bottom balanced so I am not overly worried about running it down that low. I am looking forward to getting the rest of the cells in the car.

After looking at your blog I wanted to add that I am running 2000 amps per second slew rate. This is perhaps a bit excessive but 300 was too slow.

Best wishes!


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