Correct me if I'm wrong... (new Gen1 owner)

LOL... good one. You're so right. At least with the Civics, I developed a very reliable method for identifying bad modules.

My expectations are very low. I'll gnaw my way through this pack and see what I get.

 

Still working to get the pack cleaned up. Bus bars are stubborn. A little soak in some sulfuric acid followed by a de-funking and buff with wire brush gets them pretty clean.

There is a sticky brown substance that looks deliberate along the top of the bus bar plastic retainer strips that is on many of the nuts and bus bars. Is this an adhesive?

Preliminary results are very discouraging. Trickle charges (50-350mA) of individual modules to > 7V typically results in either an inability to retain voltage or a run into the 8V range. 8V under such a low current with only a couple hundred mAh input is indicative of very high internal resistance.

I did a 1C forming charge and 1A discharge of #38 (6.74V). I let a full 24 hours lapse between charge and discharge, and it was only about 1800mAh. I'll cycle it a few times and see if I get any improvement.

Otherwise, the plan is the same... I'll do a grid charge to peak voltage and see what I get on module discharge. Already looking for replacement packs.

Steve

 

Hey Eric. You've probably seen enough of my blatherings back and forth with EQ1 on IC. I'll go through the motions on this pack. The bus bar inserts were cleaned up last night. I'll button everything back up and modify my grid charger to output 1.41V/cell (322V) to keep the charge peak voltage on the "gentle" side. I'm already working to line up Gen3 packs to source new modules.

Thanks,

Steve

 

Bob, thank you for the link. That is very interesting. My goal is to identify any viable modules and set aside others for "tinkering".

usnavy, I touched on the method of cleaning the bus bars in #22, sulfuric acid followed by the scraping off of what I believe is some sort of adhesive (the acid makes this about 50% easier) and gentle brushing with a brass-bristled brush. Here is a before/after shot:

20150912_231552.jpg - Google Drive

I finish with a soak in a baking soda paste.

Steve

 

Bob,

The above is the only thing on which I have any input as the rest of what you discuss is well outside my experience.

I don't know that the above is true with NiMH in general. Perhaps it applies to consumer NiMH cells or maybe even the prismatic type, but from my experience with the Honda IMA "D" cells, nothing like that happens. The Insight community is currently experience significant benefits from deep discharging both sticks and packs. It's an extremely effective tool in eliminating voltage depression and restoring balance. For whole-pack discharges, the polarity of the bulk of the cells in the pack is reversed. The worst of them can be run reversed for many hours, though under low current (less than 700mA for me). When discharge capacity is measured to 1V/cell following a deep discharge, capacity is typically 20-25% higher for a given load. This has also held true for individual sticks taken to 0.03V/cell avg, although the reality is that 5 are reversed and one is around .3V.

I've been playing with the one module I mentioned above (#38). It's responding to aggressive cycling. My charger has a voltage regulated auto charge function that runs the max current up to a max voltage, then tapers current. It will eventually hold current and cut-off with deltaV. The module was accepting a 9A charge and subsequently discharged 2500mAh @20A to 6V. It discharged an additional 400mAh extracted during a constant 6V load taper between 20A and 1A. I read a summary paper this afternoon that suggests the panasonic prismatic cells can be discharged to 0.8V/cell. I took it to 4.8V @1A with taper to 50mA and pulled another 250mAh out of it.

The next discharge to 6V yielded 2900mAh @ 20A and terminated at 3350mAh @1A.

Eric,

Thanks for the encouragement. I don't know that I regard any of this fun, but it's interesting and easy to obsess over

Steve

 

would have sworn you had a 989 from the pics... I have one too. It's great for hands-free cycling, but the Turnigy Reaktor 300W unit has greater capability and it logs data for export to logview (I currently have that disabled because the log is full from another project). It's basically a clone of an iCharger 206B. They're only $65 from Hobbyking, but they need a 12V PSU.

I really like the decreasing discharge feature. It allows one to set a finish discharge based on initial in terms of percentage. I like to leave it at 5% so a 20A terminates at 1A and a 1A terminates at 50mA. My Avatar is actually a couple of them connected to HCH2 stick pairs discharging into a previously discharged stick pair. I can completely discharge all of the modules in an HCH2 pack @20A in under two hours. Very handy.

I've brainwashed a couple of the Honda IMA folks into these units. They lack the ~80W discharge capability of the 989 with only 20W of internal dissipation capability, which makes hand-free cycling a little slower, but they make up for it in their 300W regenerative discharge capability... plus... it's like reusing the juice! One could start with depleted module and a full 12V auto battery of sufficient capacity and do hands-free cycling. I typically just discharge into a pair of series connected HCH2 sticks, 14.4V and 6500mAh capacity.

 

Let it rest for about half an hour. Here's a sample chart for a tapering discharge (20A discharge to 6V, hold 6V and taper current to 1A):



I really don't like the voltage profile... prefer a flatter slope.

 

Pretty sure this whole pack qualifies. The two highest voltage modules will only put out 2-3.5Ah. I'm running cycles on the next two highest (#35 & #37).

Cycle parameters as follows:

• 20A "Auto" charge to delta V. Typically limits peak charge to 9A and tapers significantly before deltaV cutoff.
• 5A discharge to 4.8V w/taper to 10% further limited to 20W, so initial discharge is about 2.8A and it ramps up to 4.2A at 4.8V, then it holds 4.8V and tapers to 500mA. Total reported capacity includes the taper portion as well.

One charger is logging the cycles. I still need to download the other.

The downside to these chargers is the 20W limitation on internally dissipated discharges. I'll strap together about 13Ah of HCH1 sticks in series at 14.4V, which should accommodate a few cycles at 20A regenerative discharges to see if these things wake up.

One thing that struck me is how prone these are to swelling. While I have them secure in the pack, it's a little disturbing to see the one module swell and create gaps that are slightly more noticeable than those of its neighbors. The pack "creaking" periodically was also disturbing.

Module Testing

 

Thanks for the warning. Mike D experienced this and documented on his site back in the day. Cautions about this phenomena abound. When I read that keeping them in the pack works well, that appealed to my lazy.

 

That explains why it looks like all the terminals leaked.

20150912_183221.jpg - Google Drive

I'll see if I have any test strips. I assume a leak is more likely at the positive terminal, though it looks like the leak is on the negatives?

Thanks,

Steve