Eeeewww, Battery Death

OK so here's my problem. The car came with some batteries that were not maybe real well known for reliability from a company called HAZE in China and were nearly a year old when I got the car plus who knows how they were treated while EcoMotion (the original dealer) had them.
There was also this one single DEKA Intimidator battery from the East Penn Co. in the US. Added to bring the pack voltage up to 84V. Supposed to be top quality. Same 100 Amp-Hour rating as the HAZE and fairly expensive, like $220 or $240 each. Guess which one dies? Yup, the DEKA lasted about thirty cycles - despite - the high bucks BattEQ battery management system.
So, we get ahold of the dealer, who turns us over (quite appropriately) to the battery maufacturer's rep, who eventually says "Yeah, we'll get you a new one." and after a week or two they pick up the failed battery and a week or two later (after some nudging) they drop off a new one. Total elapsed time is like TWO MONTHS.
I wonder how the battery guy would feel if his new car developed a gas tank leak and the gas tank supplier took two months to get him parts (which he would then have to install himself...) I don't really know him, but I bet he'd be really pissed-off to be without his new car for two months.
Fortunately I had a spare battery.

In the mean time the BattEQ system gets recalled and I get involved in the design of the VoltBlocher boards as noted earlier. I didn't have enough boards for the whole pack. Battery #5 was behaving really well on it's own so I didn't put a board on it for like two weeks after all the others had their's. Guess maybe it wasn't doing so well after all because it started to fail about two weeks later. Right about the time the new DEKA arrived. What a stroke of luck!
Just to make sure it's OK (and to break it in a little) I ran a couple cycles of charge test. Discharge at 5 Amps until the voltage drops to 10.8 and then charge up (Bulk charge phase to 14.5V - etc.) Funny thing happens: at 5 Amps (actually 4.93) disharge rate, a 100 Amp-Hour battery should last 20 hours. The most this one will do is 16 hours. 20% low. Hmmm.
Maybe it takes a few more charge cycles to come up to full capacity? We'll see. Swap it into the car in battery slot #5. A fully charged pack should be capable of going over 20 miles. This pack would only do about 18 as the original #5 was a little weak by the time I tried this. Still with a worst case commute of 12.8 miles we should be fine, eh?
Not for long. The new DEKA seems almost fine for a while. It was 0.3V lower than the others pretty much all the time. Seems a little odd, but I have one other that runs a little low and it's holding up fine. I set the VoltBlocher to limit it to 14.4-14.5V during the high current bulk charge phase and a little higher during the later (generally lower current) phases.
All goes well for about 20 charge cycles. I limited the initial miles/charge as the battery got broken in but it was running the longer commute (12.8) within a week. About two weeks later I have a 'short' commute of 7 miles (with charging a the other end) which I had been doing for a couple days at that point. I ended up going an extra 2 miles that day and the new battery dropped way off in mile 8. The next day I fired up ye olde data-collection system and captured the voltage spikes down as the new battery crapped out at just about the same place. By around the 26th or 28th cycle on the new battery it was effectively dead.
Me and the battery dude are going to have another dance. You watch, they'll try to blame it on the charging system. I OTOH have actual data. We'll see. Meanwhile I'm cycling one of the other 2+ year old batteries to see if I can swap it in while we wait. Again.
Moved the VoltBlochers further forward between the seats so I can keep a better eye on things. That part seems to be working good.