Thanks for the extensive reply. I will get down to business next week (need to gather needed tools and also I need a car for the next few days - not really comfortable driving around with 12V being charged only in limited range).

Now to the responses:
You are right, I'm from Europe. The voltage is 230VAC here (just tested at the outlet).

Just to make sure that I understand correctly, I make this discharge of sticks after I test them with 100A tester (so they will already be severely discharged I suppose)?

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I set a D>C cycle on T6200, but I guess there is a bug in software, so I couldn't see the discharge capacity, that's why it's missing. With all later sticks, I manually set the charger to discharge and then charge, so I could get all information properly.

Because I was only able to charge them for much less than 6000mAh. I was following ideas from this guy at that time (https://www.greenhybrid.com/forums/f...ry-pack-28610/) where he made decisions upon charge capacity.

You are right, I used aligator clips, will get ring terminals for the next "session" (or use the trick with bolting down aligator clips).. Again I followed ideas from the topic linked in the previous reply and that guy went as high as 9mV. So you suggest to always use 4mV cutoff?

Yes, I have a temperature probe connected to my charger and it never went higher than ~37°C (was charging with rate of 1C). I also always had a colling fan flowing air over the charging stick (and until they cooled down completely).

 

Generally speaking 6 year old advice is likely not current.

14) Yes. The load test will only consume about 250mAh.

1) Understood. #10's paltry discharge of about 2500 suggests it's in bad shape.

2) Again, charge capacity is irrelevant and misleading. You can shove 6000mAh into a stick that can only deliver 2500 in some circumstances.

3) Yes. 4mV only. The screw/sandwich method should be comparable to ring terminals. Also important to "pinch" the bullet connectors together with the zip tie.

4) Are you sure you did it on the hottest cell? Rate of temperature change due to thermal conductivity between cells is VERY poor compared to the rate of internal cell temperature change. Very important to monitor sticks near the end of the charge cycle to ensure you're checking the hottest cell.

 

A little explanation:

The grid charge/discharge cycles are intended to gently recondition the pack as effectively and likely more quickly than the single-stick method - certainly with less TOUCH time than would be associated with 3+ cycles with the SkyRC unit. You'll be able to walk away and let it go overnight in some cases.

You're looking at about 36 hours per cycle with 3 cycles taking 108 hours. Going single - assuming 1C in/out and you're looking at as much as 120 hours with LOTS of touch time and likely unable to run nearly continuously unattended.

Note that if you want to accelerate the discharge, you can pile on more bulbs and/or use higher wattage. Above 132V, you can hammer them with whatever you wattage you want, though you'll want to monitor it much more frequently. Below 132V, limit it to the 2X 60W bulbs.

The cycling reconditions the cells by eliminating all voltage depression.
The full charge with the grid charger gives high confidence that all CELLS are at true 100% SoC and eliminates issues with -dV NiMH charge termination.
The 7 day sit helps amplify any issues the sticks may have particularly as it relates to self-discharge - outliers stand out more.
Many charger's IR functions have no known relation to reality, but are useful in COMPARING the sticks. A good number to have, but a load test is still needed.
The LOAD test is a very useful simulation of an actual in-car discharge. Outliers stand out like a sore thumb.
The final discharge to 6V is to confirm they have usable capacity. A low capacity stick may show good voltage and respond okay to a 15 second load test, but will fail to perform in the car.

 

I regularly checked each cell with my hand and moved the probe to the hottest one.


I started the process per your instructions two days ago and I am updating the existing Excel sheet with collected data. Currently I'm doing a second grid charge.

I have some additional questions.

a)
You wrote that I should do second and third discharge both to 60V. Why is that so? I read here (https://hybridautomotive.com/pages/sd) that second should be for example to 72V.

b)
Can I record battery resistance after the next step with battery tester? My charger shows battery resistance during operation, and I will do discharge to 1V/cell at the end (when I can note down shown resistance).

c)
Is there a reason why I should go with 1A discharge rate and not higher (my charger supports max 5A)?

Thanks

 

a) Because I make my own recommendations based on my personal experience.

b) Sure

c) Doh. I meant 5A. Old habit as many use the junker 1A IMAX B6 chargers.

Based on the numbers in your sheet, and my estimate of the current from the 2X 60W/250V bulbs in parallel, you are pulling about 5Ah out of the pack.

 

Okay, the sticks are now resting and I will continue with the process next Friday.

On a side note, is it possible to do anything that would make this car to charge 12V battery regardless of the RPM (install alternator, hack existing DCDC converter or maybe install some 3rd party DCDC converter)? I searched around, but haven't found any definite instructions.

 

(1) yes, but it's challenging. You have to fabricate a bracket and find the right belt.
(2) No.
(3) Yes. This solution or a modification thereof would work, 1000W peak, 75A peak, 10-13.2V adjustable, https://www.insightcentral.net/threa.../#post-1401181

EDIT: With a healthy 12V and conservative accessory use, nightly charging would likely get you a reliable 50 miles range. Alternator deletion is a popular ecomod for increase mpg.

 

Thanks for the link.
Unfortunately, I live in an apartment, so I can't easily charge the 12V battery without actually taking it out of the car and inside with me. And I want the car to be "self sufficient", so it got to charge 12V properly by itself.

I will look into option 3, if we can't fix the battery pack.

 

Okay, all data is now in the sheet. What do you think?

I used ring connectors when discharging sticks then.


I will now put the pack back together and grid charge it, so the sticks don't lay empty.

 

Honestly, it looks pretty great:

.04V total deviation after 7 days. Good.
.08V deviation in loaded voltage. Good.
.04V deviation prior to 5A dch. Good.
22mΩ deviation - probably a junk reading as the loaded voltage are much more consistent than the IR deviations. The measured IR would demand a 2.34-3.66V drop, and the actual loaded voltages were very consistent.
Less than 300mAh deviation in capacities right around 4000mAh. Good.

That many goods = great.

That pack should work. I suspect your initial efforts did not adequately recondition the pack.

When you reassemble, torque all stick bolts to 60 in-lb.