Checking Battery Capacity with C9000

[kimck99]

Hi,

I had a Tenergy 2600 NiMH that I charged on 10/20 and wanted to know the current capacity. So using the Powerex C9000, I discharged at 500 mah. When it was done, it showed the total discharge of 1650. I let it rest for 2-3 hours and decided to use the "Break In Mode" to check the actual capacity and set the capacity at 2400 mah. (I know that this battery would not have a capacity of 2600 so decided to set it at a lesser value.)

Well, after the break in period was over, C9000 showed a value of 1585. Well, that got me scratching my head. How can the break in mode have a lower value than when I discharged knowing that the battery was setting around for 1.5 weeks? I was expecting a higher number. Any thoughts?

Separately, with the C9000, what is the best practice for checking the capacity of a battery? Is it better to use the BREAK IN MODE or use the CYCLE mode? If Cycle mode is better, how many cycles should one set it?

I have read many threads on C9000 but given the numerous topics and pages of information, I probably missed the best way to check capacity. So, I appreciate in advance everyone's help/pointer to existing thread.

 

[Mr Happy]

Actually, the jury is undecided as to whether to enter the true capacity or the label capacity when doing a break-in or conditioning charge. My intuition tells me to enter the true capacity. If the measured capacity comes out higher then nothing is lost, you can enter the new measured capacity for the next break-in cycle.

But that said, I think you just have under performing cells. Plenty of cells out there perform way below what the label says.

In answer to your main question, the break-in mode on the C9000 will give you the best estimate of capacity you can obtain without more expensive equipment.

 

[kimck99]

Hi Mr, Happy,

Thanks for the reply. I don't have a lot of faith in Tenergy batteries in both their rating and quality. I have 2 dozen of their R2U's and they are not much better in terms of actual capacity to the rated value and their ability to hold a charge for long duration. (Separate topic...)

With regards to the to seeing a lower value after Break In really surprised me. I will do another break in to see what it is this time.

Given the wide range of Tenergy cells, I wanted to check the capacy of all the cells I had so that I could group/pair the cells with like capacity. I will use the BREAK IN mode as you suggest.

Thanks.

 

[45/70]

When I check the capacity of my cells, I just charge them like I always do. I don't see any point in using laboratory methods when you want to determine the capacity of your cells. I charge them up, usually at 0.5C+, let them sit about an hour, a day, or whatever, then run a discharge at a rate corresponding to how they are used. That gives me a better idea of their actual capacity. I mean, I don't usually charge my cells at 0.1C, or discharge them at 0.2C in anything I use them in, so.....:thinking: Seems rather pointless to me.

A couple times a year, I'll do a standard "Break In". This really doesn't tell me that much. It's good for the cells, but the voltage drop and capacity at 0.2C discharge rate is meaningless, relative to how the cells are actually used.

Dave

 

[kimck99]

Hi 45/70,

I have a mix of the Tenergy 2600 NiMH batteries from two separate purchases and I 'm pretty sure that the capacity will vary greatly between cells. So, I decided to embark on baselining all the cells. The cells are used in Wii/Xbox controllers (which I believe would be low current draw use) to flashlights. So, using the BREAK IN mode to baseline will help me pair like-capacity cells.

For the Eneloops/Imedions I have, I'm not too concerned about the capacity other than keeping the cell which were charged at the same time together as their capacities are pretty consistent across all the cells.

Thanks

 

[45/70]

I wasn't suggesting that everybody should look at it like I do. I'm just saying that a realistic evaluation of your cells, should test them under similar conditions to how they're used.

For your Tenergy's, for example, you have a wide range of discharge rates that they're used under. I'd charge them however you normally do, and then pick something in between the estimated discharge rates that you use them, like somewhere between 500 and 700mA. This would allow sorting out the weaker cells that could be used in the lower drain devices, and the better cells for your flashlights and other higher drain devices.

Under a 0.2C discharge, cells will appear to be closer together than they really are, because there will be a minimal voltage drop with such a light load. A higher discharge rate, again, something close to how they're used, will make sorting them out a lot easier.

Again, I'm not saying everybody should do it this way. It's just how I do it.

Dave

 

[kimck99]

Hi 45/70,

I understand your suggestion and appreciate the input. I may separate out my high drain use batteries and my low drain use in the future. The first step is to just baseline what I have and take it from there.

Thanks for sharing. I've been away from this site for more than a year and in the past 2 weeks, it's been fun catching up and re-learning what I thought I knew a year ago... not to mention how expensive the last two weeks have been.