[rwaudio]

Originally Posted by kakheath

rwaudio, I assembled a 4s3p set of my batteries as a power supply and still seem limited to 10A charge and discharge. Can you tell me why I can't change the setting to 40A? Can you send me your pl6 file so I can check it out? I've been talking to a guy from Quantum Hobby, where I bought my PL6, and he seems convinced that I can do 6 at a time and get the individual capacities if I use his "special" connecter set. We'll see. So far I've tested about a half a dozen down to 2.5V and they ranged from 18.2 to 18.9Ah. I'm not sure how much extra will squeeze out if I go down to 2.25V or even 2.0V.

My usual preset is attached, it's set to 38A charge/discharge but you can change it to 40A. Make sure that under the supply tab you have it set to battery power and not a power supply or it won't do regenerative discharge.

While your guy is technically correct, you can do 6 at a time. I didn't have consistent results doing so. There is a good 0.4ah left between 2.5 and 2.0v however 2.0 didn't let me charge again right away because it took awhile for the cell to recover above the 2.55 minimum voltage for this chemistry. That's why I chose 2.25v as my lower limit.

Be careful about what "special" connector set he tries to sell you and what he charges. This is all you need, and you simply wire it up with alligator clips or whatever method works for connecting to your cells. I use one of these with two clips when testing a single cell.
http://www.usastore.revolectrix.com/...-10-9-Position

Also make sure you upgrade your stock cables if charging at 40A I switched to 8awg and still have some heat. I simply soldered 8awg car stereo power wire to some banana plugs I had laying around. On the cell end I have my aluminium bars set up with the 8awg clamped between two bars and another bar that I slide the tab between and tighten it up. I then attach the alligator clip to the remaining bare cell tab so that resistance in the connections doesn't mess with the voltage reading for the charger.

Hope that helps.

[kakheath]

Originally Posted by rwaudio

My usual preset is attached, it's set to 38A charge/discharge but you can change it to 40A. Make sure that under the supply tab you have it set to battery power and not a power supply or it won't do regenerative discharge.

While your guy is technically correct, you can do 6 at a time. I didn't have consistent results doing so. There is a good 0.4ah left between 2.5 and 2.0v however 2.0 didn't let me charge again right away because it took awhile for the cell to recover above the 2.55 minimum voltage for this chemistry. That's why I chose 2.25v as my lower limit.

Be careful about what "special" connector set he tries to sell you and what he charges. This is all you need, and you simply wire it up with alligator clips or whatever method works for connecting to your cells. I use one of these with two clips when testing a single cell.
http://www.usastore.revolectrix.com/...-10-9-Position

Also make sure you upgrade your stock cables if charging at 40A I switched to 8awg and still have some heat. I simply soldered 8awg car stereo power wire to some banana plugs I had laying around. On the cell end I have my aluminium bars set up with the 8awg clamped between two bars and another bar that I slide the tab between and tighten it up. I then attach the alligator clip to the remaining bare cell tab so that resistance in the connections doesn't mess with the voltage reading for the charger.

Hope that helps.

I get "Safety Code 20: Bad Cell Count" when I use this setup. Any advice to correct this issue?

What do you use as the supply setting? I had it set on the last one (13.2V(4S)...A123...).

[rwaudio]

Originally Posted by kakheath

I get "Safety Code 20: Bad Cell Count" when I use this setup. Any advice to correct this issue?

What do you use as the supply setting? I had it set on the last one (13.2V(4S)...A123...).

Do you have the balance plug wires hooked up? You need to use these wires or the charger can't measure voltage properly. I bought the balance board for my first PL6, but only the pigtail for the 2nd.

Under "options" then "start setting" you have to pick one of the choices under "node wiring".
FMA would use the black and red wires for a single cell.
XH/EH would use the black wire and first white wire for a single cell.

For the supply I'm using 13.2v...A123..9200mah and it seems to work well.
Make sure you increase the battery amps in/out to 40.

[kakheath]

Originally Posted by rwaudio

Do you have the balance plug wires hooked up? You need to use these wires or the charger can't measure voltage properly. I bought the balance board for my first PL6, but only the pigtail for the 2nd.

Under "options" then "start setting" you have to pick one of the choices under "node wiring".
FMA would use the black and red wires for a single cell.
XH/EH would use the black wire and first white wire for a single cell.

For the supply I'm using 13.2v...A123..9200mah and it seems to work well.
Make sure you increase the battery amps in/out to 40.

I got it working - finally. Thanks to your help. You're right about the stock output wires not liking the 38A current. They got very hot. I only did this once. I have since went to Home Depot and got some 6awg wire and some nice aluminum connectors for attaching to the cell. I also bought some nice banana clips that would accept the 6awg wire for connecting to the PL6. I just need to solder the 40A fuses to them I'll be set. I didn't want to work on it last night being Valentine's day and all . I will try to complete it tonight.

I think I'm gonna order the combo pack of two more PL6s. They come with the y harness and male2male connector.

I saw on your site that you are doing some interesting work on cell monitoring/balancing/charging involving PCBs. What is the latest on this work? I'd be interested in a simple and inexpensive cell level monitoring system.

[rwaudio]

Originally Posted by kakheath

I got it working - finally. Thanks to your help. You're right about the stock output wires not liking the 38A current. They got very hot. I only did this once. I have since went to Home Depot and got some 6awg wire and some nice aluminum connectors for attaching to the cell. I also bought some nice banana clips that would accept the 6awg wire for connecting to the PL6. I just need to solder the 40A fuses to them I'll be set. I didn't want to work on it last night being Valentine's day and all . I will try to complete it tonight.

I think I'm gonna order the combo pack of two more PL6s. They come with the y harness and male2male connector.

I saw on your site that you are doing some interesting work on cell monitoring/balancing/charging involving PCBs. What is the latest on this work? I'd be interested in a simple and inexpensive cell level monitoring system.

According to FedEx both my PCB's and my parts from Digikey should arrive today, so if I have some time tonight (and everything arrives) I'll solder up the first boards and get ready for testing. I'll be posting the results.

[kakheath]

Originally Posted by rwaudio

I did try that as well, and didn't get consistent results. During discharge it will stop the lowest cell and only discharge at 1A to the cut off point which is not the same as the 38A setting I was using. Perhaps I didn't have it configured properly to do it this way but that was just my experience.

I would get a true capacity on the first cell to discharge but once the first cell hit the low cut off it messed up the results for the remaining cells. During charging it does work, but if the cells are very far off the whole balancing thing doesn't work very well with cells of this capacity. Shunting a maximum of 1A doesn't do much on a 38A charge if the cells aren't at the same SOC.

I gave up on that and went to a single cell, if you have any tips on how to do that better I would be happy to hear them. For me getting a capacity number under the same conditions every single time is more important than shaving off a bit of time.

rwaudio, did you test the same cell multiple times with different C ratings? I heard the spec capacity is based on 1C discharge. I'm wondering what the impact is of the 38/18 = 2.1C discharge is having on the capacity. Have you compared this to a 1C or 0.5C?

I had been previously stuck in 10A or 0.5C mode, and am wondering what this impact will be when trying to be consistent with the cells. Now that I'm charging/discharging faster using 38A, will I need to go back and retest the 13 cells I already have data on? I suppose I could test a few of them and if the offset is consistent, just apply it to the rest.

Also, my cutoff voltage has been 2.5V instead of your 2.25V. Do you think this is significant?

[rwaudio]

Originally Posted by kakheath

rwaudio, did you test the same cell multiple times with different C ratings? I heard the spec capacity is based on 1C discharge. I'm wondering what the impact is of the 38/18 = 2.1C discharge is having on the capacity. Have you compared this to a 1C or 0.5C?

I had been previously stuck in 10A or 0.5C mode, and am wondering what this impact will be when trying to be consistent with the cells. Now that I'm charging/discharging faster using 38A, will I need to go back and retest the 13 cells I already have data on? I suppose I could test a few of them and if the offset is consistent, just apply it to the rest.

Also, my cutoff voltage has been 2.5V instead of your 2.25V. Do you think this is significant?

I have actually tested that. (thoroughly on one cell and more random testing on a few others)
The capacity at 0.5C and 2C were virtually identical, 1C was actually slightly lower. In my testing the cells were cold at 0.5C and 1C and a tiny bit warm at 2C, I think this heating contributed to the better performance of 2C vs 1C in these cells. (just like drag racers that are faster the 2nd run because they heat up the cells the first run (with back to back runs)). I would say that if you are grouping the cells in a similar way to what I'm doing it really doesn't matter what voltage and C rate that you use as long as you do the same thing for every cell. Based on my experience you will probably have similar results with your 10A testing and 38/40A testing. I found ambient temperature played a bigger role in capacity variation than C rate. (I'm sure there is a limit though were very high or very low C rates would make this statement invalid).

I would say the difference between 2.5 and 2.25 is marginal and pretty consistent between cells, as long as you measure the same way every time it doesn't matter very much what voltage you choose. I picked 2.25 somewhat at random but I have to continue with that number since I've done it that way to start. I think in the real world there is no point trying to get anything below 2.5v on "average" to allow for a low group that might hit 2.0v. However with the tight capacity grouping that is possible when measuring them all the cells should be very close at the top and bottom.

[kakheath]

Originally Posted by rwaudio

I have actually tested that. (thoroughly on one cell and more random testing on a few others)
The capacity at 0.5C and 2C were virtually identical, 1C was actually slightly lower. In my testing the cells were cold at 0.5C and 1C and a tiny bit warm at 2C, I think this heating contributed to the better performance of 2C vs 1C in these cells. (just like drag racers that are faster the 2nd run because they heat up the cells the first run (with back to back runs)). I would say that if you are grouping the cells in a similar way to what I'm doing it really doesn't matter what voltage and C rate that you use as long as you do the same thing for every cell. Based on my experience you will probably have similar results with your 10A testing and 38/40A testing. I found ambient temperature played a bigger role in capacity variation than C rate. (I'm sure there is a limit though were very high or very low C rates would make this statement invalid).

I would say the difference between 2.5 and 2.25 is marginal and pretty consistent between cells, as long as you measure the same way every time it doesn't matter very much what voltage you choose. I picked 2.25 somewhat at random but I have to continue with that number since I've done it that way to start. I think in the real world there is no point trying to get anything below 2.5v on "average" to allow for a low group that might hit 2.0v. However with the tight capacity grouping that is possible when measuring them all the cells should be very close at the top and bottom.

What's your opinion on the top balance or bottom balance debate? It sounds like you are top balancing your cells. Is this correct?

[rwaudio]

Originally Posted by kakheath

What's your opinion on the top balance or bottom balance debate? It sounds like you are top balancing your cells. Is this correct?

I'm in the boat that likes top balancing. Arguably the only time you can have complete failure causing fire or something like that is when charging, so I would prefer to have the cells top balanced for that reason only.

However for cell safety I love the idea of bottom balancing, so that's where the careful measurements and obsessive grouping comes from in the 3P groups that I'm creating. In theory as long as I stay within a current range where small IR differences in the cells don't cause a difference in SOC over time then my cells should act like they are both top and bottom balanced.

Only time will tell though and I'll have to see if that actually happens.

I love the work that EMW is doing both on their display and charger. I will be going with the both of those products in the future. (hopefully the display sooner than later when the full featured version is available) Right now my charging system will be top balanced by default, however when I switch to the EMW charger I would have the option to top/bottom balance but I have a feeling (and hopes) that they will be virtually one in the same.

[Nuts&Volts]

Originally Posted by kakheath

I got it working - finally. Thanks to your help. You're right about the stock output wires not liking the 38A current. They got very hot. I only did this once. I have since went to Home Depot and got some 6awg wire and some nice aluminum connectors for attaching to the cell. I also bought some nice banana clips that would accept the 6awg wire for connecting to the PL6. I just need to solder the 40A fuses to them I'll be set. I didn't want to work on it last night being Valentine's day and all . I will try to complete it tonight...

Got any pictures of your PL8 setup? I need to upgrade my output wires on my PL8, but haven't had the time to research a good solution. Links would be awesome too!

-Kyle