1) yep
2) yep
3) yep, I got that one right
4) Correct, except after deep discharge, at least 4 hours of grid charging must be done prior to attempting to start. The battery must be brought back up to a functional state of charge. 100°F is temp limit.

 

Okay, so now I have some questions regarding how to evaluate a battery's condition. I removed the battery from the 04 HCH1 MT after driving it and getting it to full charge (showed 18-20 out of 20 bars.) Total voltage was 166.2V read with my digital multimeter (dmm). I hooked it up to my MV grid charger. Initial voltage showed 167V (charger display has no tenths). After 11 hours of charging, I had to stop for the night and the voltage was 178V on the charger. I should note that the reading from my dmm just after disconnecting was 173.9V. I do not know which device is more accurate. ***I have attached an excel file with all the data I refer to in this post.***

Question 1) Did I charge too long or not long enough?

The direction was to "charge 3-5 hours after voltage stops rising" but in another post I thought I remember it as "when the voltage hasn't changed for >1hr". The problem is, since this older MV charger does not display tenths or hundredths, it is hard to determine when voltage has actually stopped rising. From the graph I made later, I'd say it was still rising but I'd like a more experienced opinion. I don't want to overcharge and damage the battery. In the future, I'll take readings with the dmm so I have more precision.

Question 2) Is this battery beyond hope?

When I went back after 12 hours, the voltage was already down from 173.9 to 167.2 (dmm readings), almost back where I started. Another 8.5 hours later I was at 165.9, already below pre-grid charging voltage. Uncertain and out of time, I left it until this weekend. After 4 days & 20 hours of resting, the voltage was now down to 160.1 & after another 8 hours it was 159.9. This self discharge rate seems really bad to me. (By comparison, the battery from the other HCH1 went from 155.3 to 155.2 in the same 5 day period.) Unfortunately, I only took tap voltages twice - once pre-charge and once post-self -discharge. They showed a variance of 5.9% and 7.9% respectively.

Question 3) Do I need to start a deep-discharge from a full grid charge?

I am going to see what gains I can get from discharge/charge cycling so I need to know where to start. From the standpoint of benefit to the battery, is it better to start discharging from a full charge? If the answer is no, should I do it anyway for the sake of gathering the data during discharge for evaluation?

Question 4) What are the tests/benchmarks for evaluating battery health?

In the car, I know you can look at fuel economy and frequency of recalibrations, but these cars (and hybrids in general) are new to me so I have no data. I'm looking for static tests if possible. I have read in other threads about using 12V battery load testers on sticks but having read your comments on stick-level work, I'm trying to avoid that if possible. Is there a way to load-test the entire battery at once?* I will collect the discharge data you suggested earlier but I won't know how to translate that into a meaningful assessment without help.

* I probably have 8-12 bulb holders and heavy gauge wire. If it was meaningful, I could combine series and parallel wiring to create a significant short-term test load that wouldn't blow the bulbs. (The most expensive/hardest part would be finding enough large watt incandescent bulbs, but I also have some work lights with 500w halogens,)

 

SoC gauge in car is meaningless on an imbalanced battery. It's an average.

1) Not long enough. The tap voltage deviations should be very small following a proper grid charge. I don't know the MV current, but IIRC, it's around 260mA. 260mA * 11h = 2860mAh, which is less than 1/2 the pack. Per prior recommendations, 10,400mAh input.

2) Unable to assess based on data following an incomplete charge. NiMH voltage settles analogous to lead acid. You charge to 14.4, yet it settled to 12.7 within 24 hours. NiMH voltage has little correlation to state of charge. Overall disparity in tap voltages is a bad sign, but that's true of a battery that may recover to reasonable functionality.

3) Yes.

4) Consistency.

 

1) So the 10,400mAh charge recommendation is regardless of starting state? I thought that if I was at 80% that maybe meant that I already had 8320mAh in it (10400*0.8). Then 11 hours of charging at 285mA (my MV charging current) would have put me at 11,455mAh total. Wishful thinking I guess. Unfortunately I didn't take the tap voltages immediately after the charge so I don't know how close they were at that point. I only know that after nearly 5 days of self-discharge they were worse than before the grid charge. Please don't take this as sarcastic but how can I input a charge of 10400mAh with a grid charger that has in input current of 260-285mA? By my math, (10400/285) that would take 36.5 hours. That seems to contradict the recommendation not to exceed 24 hours of charging. What am I missing?

2) I will redo the grid charge and record tap voltages immediately after. If I am to charge for 3-5 hours after voltage stops rising, how do I know when to start that count? Since my charger doesn't show 10ths and my total voltage was already 177, I thought it had stopped rising. When it bumped up again 3-1/2 hours later I no longer knew where I stood. I will track that the voltage with a better volt meter this time but what should my metric be? When it hasn't risen .1 volts for an hour? .01 volts?

4) By 'consistency' do you mean the degree of uniformity between tap voltages at various stages of (dis)charge or something else?

 

The goal of grid charging is to force all cells to 100% since that's the only place they can be balanced.

1) What is your starting state? Since you don't know it, that's the only way you can be certain you are fully charging all 120 cells. Again, "80%" is at best an average of all the subpacks, and it may also reflect the result of only the highest subpack. It's essentially meaningless especially considering the extreme disparities in your tap voltages.

2)

Post #4 in this thread:
charge with 10,400mAh input to insure all 120 cells are pushed to 100% SoC. Active cooling. Should pack air exit temp exceed 100°F, terminate charge. Should voltage peak and fall back >1V, terminate charge.

4) Everything, especially how you record data. Comparing different values gathered with different instruments decreases their diagnostic value.