Wow! It is taking a long time. After tonight I will have worked thru the whole pack. I have been charging to DeltaV then they sit to see which ones lose charge the most in a given time. A guy at Revolt said a faster way would be to use a battery tester connect to a stick and turn it on for 5 seconds and it would show which ones are weaker. I will start that in morning.

 

Does this sound reasonable. I don't have 2 weeks to wait for the sticks to drift down.

 

Matt knows his stuff. He's built a business around it.

I subject mine to a 90A load with a carbon pile battery tester from Harbor Freight. It is the most critical aspect to determining stick health.

I've duplicated this setup, except I use the master switch from an HCH1 pack to instantly apply the load rather than dial it in:


Healthy HCH2 sticks should run 60 seconds before they hit 6V on the stick-attached multimeter. It's also wise to monitor the per cell voltages as he does to make sure you're not reversing a cell at that high of a load or seeing one cell substantially lower than the others (like half).

The voltage recovery he mentions in his video is nothing more than the cell heating and becoming more efficient. They have a happy spot around 100°F.

As I've cautioned, what you're doing is only checking low discharge rate capacity, which will tell you nothing about how the stick will perform in the car. I have a significant number of sticks that test to 80-90% capacity, but when you hit them with a heavy load like what the car uses, they crap the bed.

Lastly, you should do 2 rounds with one week between runs to establish the self discharge rate. These high discharge rate cells can self-discharge very quickly. You want that to be less than 1Ah of capacity lost after a week of sitting.

I determine capacity by:
90A for 60 seconds
15A to 6V/stick
10A to 6V/stick

When I bleed down with a 5W load, I can get another 1000mAh out of it... but that's useless capacity... capacity your method will count towards the total.

 

Well that's a sticky wicket!! I'm trying to find out the bad cells and replace them. I got battery tester from Habor Freight too but it is just s meter with what looks like s was of airplane cable wire for resistance. I have exorcized these cells up and down hoping that will decrease their internal resistance. If I had time to let them set for a week would that be the best way to determine how good or bad that cell is?

 

Absolutely not. Nobody in their right mind would try to replace a cell.

Monitoring cells allows you to identify problems in sticks. A stick that tests good but has one cell that has substantially lower voltage is probably going to deteriorate faster and should probably be replaced if you can't establish that you've eliminated the voltage depression on that cell.

I assume you got something like this:

http://www.harborfreight.com/100-amp...ter-61747.html

I went with the carbon pile tester because I can get some idea what level of current is flowing regardless of the voltage. What you have is certainly better than nothing; however, I can't say what current it's actually pulling on a 7.2V stick. I would assume it's approximately 7.2/13.2 * 100 = 55 Amps.

When I have a 500A tester running at 90A, I'm not worried about running it for 60 seconds vs. the 10 seconds it recommends. I would be concerned about running the smaller unit for more than 20 seconds.

"Exercising" the cells won't do anything for IR. The only thing that has demonstrated improved IR is extended (months to years) self-discharge periods to low levels (less than 0.5V/cell).

"Exercising" cells provides limited correction of voltage depression by driving the weakest cells to lower thresholds. The deep discharge method I described to you a while back has yielded a consistent 20-25% improvement in usable capacity by eliminating voltage depression, it it only needs to be done once (negligible benefit from subsequent cycles). It does nothing for internal resistance.

As to your question, the best way is to repeat the same way you used to establish your final "post-refurb" capacity. When you change your method, you change the results.

 

That's exactly what I got. It looks pretty basic. This is all very complicated. I just want to get this friend of a friends car working. I have learned a lot but I haven't scratched the surface.

 

The 20 to 25% increase in usable capacity is actually a great improvement.

 

Only if capacity is all that matters, and that is definitely not the case with these sticks. I have a dozen+ sticks that will test at 80-90% capacity at a 10-15A discharge rate, but when you load them with 90A (something the car can readily do), they crap the bed.

A stick with 70% of the rated capacity that CAN deliver a 90A load for 60 seconds is WAY better than a stick at 100% of the rated capacity that can't deliver that current.

Yes, this is complicated. I've tried to relay that at every turn. The techniques found all over the place concerning 3-5X cycling at low discharge rates don't get you much - typically 5-10% on capacity assuming you have a cell or two suffering from voltage depression, but they tell you nothing about how the sticks will work in the car. I have found them essentially worthless, hence my drastically different recommendations.

Steve

 

I'm trying to put the 06 civic battery back together. I numbered all the individual sticks but somehow I have them mixed up. Does anyone have a picture of the cells in battery case in correct order?

 

Earlier in this thread:

https://www.greenhybrid.com/forums/f...tml#post237789

Great starting point to help you reassemble the whole pack.

Thanks again Ross!