Understood,
ok, well at 155v under 30watt load, with most at 15.5ish, I got 2 taps at 15.
the really bad one was actually among the best voltage this time. I think the best was 15.68.

still, I'm hoping the main issue at this time was the one group of cells which was only reading 8 volts while rest for reading 14 and a half -which hopefully has been rehabilitated. It's a little curious why I got a pack failure instead of a voltage imbalance error. 8 vs 14.5 is pretty glaring.

I upped to the 45watt drain a little ago, trying to get to 144 to do the math and see how I'm able to arrange the rest of my day.
IF it turns out that there's no way that I can keep discharging and be back in time for it to not be at risk of damage can I pause discharging and then resume later without concern? I know the voltage will recover a little bit but the actual SoC won't be changed, and the voltage should land back at where it was under load before too much time or current passes right?
If a super low load is still better than none I could plug two 14watt CFLs and pray they don't pop.
I might be able to pull it for charging next sat too.

 

Also...for the record... you were right... I should not have bought this car.... lol

But hopefully, still able to make the most of it.

 

That kind of tap spread is very bad. At 155V, they should be tight. Given that you has at least a few months of reliable use, I think this is likely due to the fact that you never fully charged the pack.

Do not use CFL unless you're happy with the current they yield. I recommend you Pause and resume later.

A follow up to your previous questions - 100% SoC is the ONLY place you can "balance" the cells with any degree of certainty based on charge current and time. With every discharge, you have no idea of the SoC of the individual cells. Some will be depleted, the strongest will likely be at 20% or more.

 

Given the previous months of operation, I think you have something salvageable. Build your own grid charger with a PS that can drive the fan, and you'll probably be able to get trouble free operation for a few months at a time.

We can't know for sure until you fully charge the pack.

 

I hear ya...
bad news: one taps is VERY off
14.65
14.65
14.52
14.66
14.65
13.26
14.6
14.43
14.6
14.64

7 are very close, so that's something....
just under 142v now....

I can deal with a few months at a time.
I'm checking my math but I think I got 4.58AH to 144v
does that sound reasonable? It seems high to me

5.25hrs at 380mA
.58hrs at 575
2.33hrs at 570
1.67hrs at 560

wow that's still a huge improvement from the 3.67 I got yesterday! Chopping 4.58 to 2.25, at 550mA
just under 4 hours IF I had fully charged the pack.
how long/low so you suggest?
problem child is down to 11.5 at 137v pack

 

I'm thinking stop draining soon TBH, 12 cells at 11.5 means average under 1v per cell....

EDIT: dropped down to 60watts for half hour.
just before doing that the bad tap was at 11, under the 90watt bulbs (560mA)
after the half on the 60watt it had recovered to 11.5
shut down at 136v... scared that one tap has a cell or more at risk.

I gave it 2 hours to rest from discharge and then hit the charger back on.
I'll run it tonight, 2100 to probably about noon tomorrow... should land it just above normal op range but doubt it will make a meaningful recovery impact... and then see what I can do next weekend.

One question I have is how much is recovered capacity vs just overcharge in which just came back out (and didn't change anything) a whole extra amphour is pretty huge, even if the ECU can still see I have a tap in crap condition.

no way to tell which of the two sticks is the one with the problem (assuming it isn't both) without a teardown right?

 

You did the right thing on the termination. There is never a need to wait for charging following a discharge.

These are rated for 6500mAh, and it's pretty common that you'll get significantly over 5000mAh even when they're so old. They start suffering in other ways (SD and IR) more so than capacity. When discharging at such a low current, you're getting most of the goody at 144V without going all the way to 1V/cell or 120V.

The 9 taps look good. How does the low tap compared to the last measurement?

It's still inconclusive, but it's the one to watch.

 

it did that thing which crummy batteries do where they have good voltage until you load them. It was actually the highest voltage while charging and even early in the discharge but then came down much faster later. It was 11.5 during the 60watt discharge (which terminated at 136v...) just subtracting that from 136 and dividing the rest by 9 has it a whole 2.3v under what the average of the rest of the taps.
but unless I didn't get a good measurement it was at 8.7v when the pack was at 137v last time so even if it was at 11 flat (during there larger bulb drain) that's still an improvement.

 

Highest while charging and lowest while discharging is almost always a red flag indicating failure or pending failure. Definitely keep an eye on that one.

 

what SoC should I aim for when I reinstall in 2.5 hours? It sat on the charger from 2100 until now (still running) and currently is at 168v.
if this charge follows yesterday's pattern: in 2.5hrs it will be at about 170.0. (Yesterday 170.35)

interestingly, at 168.5. Most taps are lower than they were at 164v. Think I recall NiMH do that when full (volts dip a little).

at this moment they are all charged to within .04 of one another