Module Capacity not improving after cycles

I've had similar experiences with packs...

But I think your main problem is fact these chargers don't measure mah very well because they're cheap and aren't designed for these type of modules and in general when you charge NiMH ~30% of the mah you send is lost as heat, and also it's really hard to drain a battery of 100% of its charge so 6800mah is only going to be achieved with losing a lot of that charge as heat.

On the other hand my buddy with $30K in lab grade testing gear can precisely measure and recondition everything and never has to go below 6v to do it.

But with these hobby chargers, I charge modules in stages to cool off 3/4 way through and then once they get up to 8.7v or so shut it off then and ignore the mah measurement because they've never seemed accurate.

After that putting the pack back in and using a Prolong charger to balance the whole pack will balance all the modules and then I let sit a few days and measure voltage again to see if any have self discharge problems. Also load testing, using a thermal camera to look for cells running hot and a bunch of other things. And if you want to build your own Prolong Charger for less than $100 we have a thread about that we're currently working on: Build Hybrid Battery Maintenance Gear For Under $100 | Page 2 | PriusChat

 

With the amount of times you've charged them to a full charge I'm surprised you haven't seen signs of deterioration. NiMH don't put up with max charge very many times before they start to fall off a cliff.

 

One issue I see right away is that you are doing the charge cycle first. Depending on the cooling air flow being provided, with an 8000mah cutoff, you're likely getting the modules pretty warm at the top of the first charge. Then you're waiting 5 minutes and starting the discharge cycle. The modules aren't going to like that, especially after repeated cycles. I always do a discharge first, to measure how much energy was still stored in the module in it's "as removed from the car" condition. It's an easy way to see which modules are likely problems. This way, you also start your first charge from a know condition (depleted), instead of starting a charge when all 28 modules are at a varying state of charge.

There are many things that can affect your results. I use these same chargers (7 of them so I can do all 28 modules simultaneously) and have thousands of cycles on each of them. The cooling fans sometimes get noisy, but they just need a bit of lube now and then. They have been extremely reliable. They are also extremely repeatable and I haven't experienced any significant problems. The absolute accuracy of the unit is unimportant. What is important, is repeatability. There's no magic here. It measures current and time to determine mah. It doesn't have to be expensive to be repeatable. Many people are happy with the accuracy/repeatability of a $5 multi-meter. Why worry about the accuracy/repeatability of a $200 hobby charger?

I have capacity numbers obtained from 56 brand new modules and many low mileage modules. Using those numbers as my standard, I can easily compare numbers from other used modules to see how they stack up to 'new' modules.

Things to look at:

What gauge wires are you using for your charger connections? Is it adequate for the current you're trying to use? I use 16 gauge clear speaker wire. It's conveniently marked with one of the wires having a black line down it's length. I use that for my negative. My discharge is set to 1.5 amps and my charge is set to 2 amps. I discharge to 5.8 volts. With my wire gauge, wire length and discharge rate, 5.8 volts at the charger is about 5.95 volts at the module terminals. Depending on your gauge and length, 6 v at the charger is likely 6.2 or higher at the module.

What type of connector are you using to fasten it to the module terminal? I use U shaped terminal lugs crimped to my wires and nuts to securely fasten each wire to the module stud. This ensures a very tight connection.

Are all your charge cycles going to the 8000mah cutoff or are they stopping early? I use an 8200 cutoff with d-peak set to 20mv. I have the time limit disabled because the time limit will also stop the discharge. How much gets charged into the module is also important. You can't have a good discharge number if you don't have a good charge number.

Do you have adequate cooling provided to the modules during cycling? I have a Gen 2 case bottom mounted on my work bench with Gen 2 fan (powered by a Prolong Charger and fan harness) and slightly modified Gen 2 ductwork providing air flow to the base. When I put a clamped set of 28 modules on the base, I end up with 100% (fan speed 6) flowing upward between my modules while cycling to keep things cool. Even then, the modules will get warm. I use a 20 minute delay from the end of discharge to start of charge, with cooling flow maintained at all times. Inadequate cooling will make results very variable.

 

Which is EXACTLY why I have said on here occasionally but repeatedly that "battery reconditioning" is a farce......in most cases.
Give up. You have wasted too much time already.

 

I'm having trouble with seeing the results of my scan. I have the same charger. It is the red one & the buttons are labeled differently. The video on youtube that I watched to teach me how to do this had a white model. After the scan was complete, he pressed the "Batt. Type" button and immediately saw the mAh. When my scans were complete, I pressed the "mode/esc" (which is in the same position as "batt type" in the white model in the video) button to see the result the results of the scan. It didn't show me the mAh. It sent it back to the settings. I tried pressing and holding it longer, but that didn't do anything. The other buttons don't take me to the info that I need. I've read the manual that came with it and found a more detailed manual online, but neither provided me with the information I need. I've reached out to the guy in the video and the manufacturer, but neither have responded.
Those of you that have the red model, what should I do to see the charge & discharge information after the scan is complete?