Using the Universal grid charger

[Mike Dabrowski 2000]

All really good questions.

At 350ma, the voltage on a good pack is self limiting, (plateau), if the voltage continues to rise even at that low current, there is likely some bad cells happening, and the voltage rising to over 180 would confirm that. he never chage to over 180, is more a warning for in car charging, which can put way more than 63 watts into the pack
The thermal aspect is also going to be self limiting, as even if the full charge current was turned into heat, we are only talking 63 watts, spread over the whole pack.Fan will easily keep that under control, with any reasonable inlet temp.

The PTC is a non linear resistance, that hardly changes until the temps get into the + 100 F range. The 80-85 value we see on the charger is the conversion from the nominal 20 ohms, and if the value gets over 100, there is some cell or cells that are getting over 100F, so a single hot cell will stop the charge due to the PTC limit.

The temp dif is a meaningful measure of the pack temperature rise, with the in temp pretty much telling us the ambient, (open the hatch on a warm Insigt when it is cold out side, and you wil see the in temp drop very quickly) and thew outlet is going to be close to the pack core temp if the fan has been running. I will sometimes set the cutback to 180, and let the pack temp dif stop the charge if I am in a hurry, very similar to how many power tools determine the full charge condition.
The limits and adjustments are there so we can figure out what works for different problem packs.
Just about finished my daily e-mails, so I can start playing with the test.

[Varak]

On my last few soak charges, the charger has been cutting off early due to reaching 180V. Typically, this has been after 4-5 hours of total charging (starting voltage anywhere from 152-160).

Some of this may be to much colder weather (40s), but it is probably just highlighting the further deterioration of my pack. I expect I have a few cells/sticks with extreme IR.

Currently, I am receiving a P1449 code after 200-300 miles, and that number continues to get smaller and smaller.

Edit: I have the GCM1 (Maintenance Charger)

[Mike Dabrowski 2000]

Varak, and any other charger owners, can you add your charger serial number, or charger type to your post, so I can better understand the numbers.
If your soak charging a lot without a good discharge, that can elevate the final voltage, and actually reduce capacity, as it does not allow capacity recovery:
From a battery manual:

Voltage Depression (Memory Effect)
A reversible drop in voltage and loss of capacity may occur when a sealed nickel-metal
hydride battery is partially discharged and recharged repetitively without the benefit of a full discharge. This is illustrated in Fig. 29.13. After an initial full discharge (cycle 1) and charge, the battery is partially discharged (in this example to 1.15 V) and recharged for a number of cycles. During this cycling the discharge voltage and the capacity drop gradually (cycles 2 to 1. On a subsequent full discharge (cycle 19) the discharge voltage is depressed compared to the original full discharge (cycle 1). The discharge profile may show two steps, and the cell does not deliver the full capacity to the original cutoff voltage. This phenomenon is known as voltage depression. At times it is referred to as ‘‘memory effect,’’ as the battery
appears to ‘‘remember’’ the lower capacity. The battery can be restored to full capacity with a few full discharge-charge cycles, as illustrated in Fig. 29.13 (cycles 20 and 21).
The voltage drop occurs because only a portion of the active materials is discharged and
recharged during shallow or partial discharging. The active materials that have not been
cycled change in physical characteristics and increase in resistance. The active materials are restored to their original state by the subsequent full discharge-charge cycling.
The extent of voltage depression and capacity loss depends on the depth of discharge and can be avoided or minimized by discharging the battery to an appropriate end voltage. The effect is most apparent when the discharge is terminated at the higher end voltages, such as 1.2 V per cell. A smaller loss occurs if the discharge is cut off between 1.15 and 1.10 V per cell. Discharging to an end voltage below 1.1 V per cell should not result in a significant voltage depression or capacity loss on the subsequent discharges. Discharging to too low an end voltage, however, should be avoided, as discussed in Sec. 29.4.6. The effect is also dependent on the discharge rate. To a given end voltage, the depth of discharge will be less on discharges at the higher rates. This will increase the capacity loss as less of the active material is cycled.
While the memory effect may result in reduced battery performance, the actual voltage
depression and capacity loss are only a small fraction of the battery’s capacity. Most users may never experience low performance due to this behavior of the sealed nickel-metal hydride cell. Often memory effect is used incorrectly to explain a low battery capacity that should be attributed to other problems, such as inadequate charging, overcharge, or exposure to high temperatures

[jime]

Originally Posted by Mike Dabrowski 2000

Varak, and any other charger owners, can you add your charger serial number, or charger type to your post, so I can better understand the numbers.
If your soak charging a lot without a good discharge, that can elevate the final voltage, and actually reduce capacity, as it does not allow capacity recovery:
From a battery manual:

Voltage Depression (Memory Effect)
A reversible drop in voltage and loss of capacity may occur when a sealed nickel-metal
hydride battery is partially discharged and recharged repetitively without the benefit of a full discharge. This is illustrated in Fig. 29.13. After an initial full discharge (cycle 1) and charge, the battery is partially discharged (in this example to 1.15 V) and recharged for a number of cycles. During this cycling the discharge voltage and the capacity drop gradually (cycles 2 to 1. On a subsequent full discharge (cycle 19) the discharge voltage is depressed compared to the original full discharge (cycle 1). The discharge profile may show two steps, and the cell does not deliver the full capacity to the original cutoff voltage. This phenomenon is known as voltage depression. At times it is referred to as ‘‘memory effect,’’ as the battery
appears to ‘‘remember’’ the lower capacity. The battery can be restored to full capacity with a few full discharge-charge cycles, as illustrated in Fig. 29.13 (cycles 20 and 21).
The voltage drop occurs because only a portion of the active materials is discharged and
recharged during shallow or partial discharging. The active materials that have not been
cycled change in physical characteristics and increase in resistance. The active materials are restored to their original state by the subsequent full discharge-charge cycling.
The extent of voltage depression and capacity loss depends on the depth of discharge and can be avoided or minimized by discharging the battery to an appropriate end voltage. The effect is most apparent when the discharge is terminated at the higher end voltages, such as 1.2 V per cell. A smaller loss occurs if the discharge is cut off between 1.15 and 1.10 V per cell. Discharging to an end voltage below 1.1 V per cell should not result in a significant voltage depression or capacity loss on the subsequent discharges. Discharging to too low an end voltage, however, should be avoided, as discussed in Sec. 29.4.6. The effect is also dependent on the discharge rate. To a given end voltage, the depth of discharge will be less on discharges at the higher rates. This will increase the capacity loss as less of the active material is cycled.
While the memory effect may result in reduced battery performance, the actual voltage
depression and capacity loss are only a small fraction of the battery’s capacity. Most users may never experience low performance due to this behavior of the sealed nickel-metal hydride cell. Often memory effect is used incorrectly to explain a low battery capacity that should be attributed to other problems, such as inadequate charging, overcharge, or exposure to high temperatures

I'm a little confused by this post Mike. Since I don't see the indicated figures anywhere, and they don't make sense in the context, it appears that you are referencing some material from a handbook. That would be fine, but just wanted clarification.

[jime]

Mike,

Could you just give us a quick update on where Labview compatiblity stands with regard to operating systems. I tried to review this thread, but it doesn't paint a coherent picture. I see that a few folks are showing graphs, so it iw working for some. I'll just ask my questions and perhaps you have a simple and quick answer.

1. Which operating systems are proving compatible with Labview? XP, Vista, Win7, Win8 ?
2. Does the current version display data as it occurs, or is the current capability limited to data recording with display after the fact.


I do see the video tutorials in your site, so I will look at those if there is any hope of getting it to work on my systems.

Thanks as always

[Mike Dabrowski 2000]

Jime,
When I copied the the excerpts from the Handbook of Batteries third addition by David Linden,and Tom Reddy the graphs and tables did not copy. The text tells the story, about the need for discharge to recover capacity.
The book is available on line as an electronic book, and there is a 4th addition available.
On the datalogger,
XP is the best platform.
The datalogger generates a real time graph of inlet and outlet temperature, battery volts, and rate of change slope data.
It also logs that data and much more to a datalog file with a CSV format for the full database so it can be imported to excel.

You can also print a hard copy of the graphs, all calibration variables, the cycle data, or file comparisons,to the connected system printer, and with a PDF converter program, the print can be to a PDF file.
All of the variables including the Tech variables can be read and modified from the program as well.

[jime]

Got it Mike. No XP machines in hand but perhaps eBay has some old ones.

Thanks

[bluesight]

I have a number of older notebooks around that are too slow to be generally useful, but they do run XP. The one I use for the datalogger is an old Gateway running with XP Pro, Version 2002, SP3. To get a serial port, I happen to have a full docking station, but you can also use a relatively cheap USB to serial port adapter (which I also have). This machine is pretty anemic (Mobile Pentium III, 933Mhz, 640MB RAM and 20GB hard drive) and has to be considered obsolete. But it works OK for watching and recording the charger stuff. Maybe you can find something similar that is being recycled, especially if people have to pay to throw electronics away like they do here.

B

Originally Posted by jime

Got it Mike. No XP machines in hand but perhaps eBay has some old ones.

Thanks

[Rush]

Originally Posted by Mike Dabrowski 2000

While the memory effect may result in reduced battery performance, the actual voltage depression and capacity loss are only a small fraction of the battery’s capacity. Most users may never experience low performance due to this behavior of the sealed nickel-metal hydride cell.

and then

Originally Posted by Mike Dabrowski 2000

. The text tells the story, about the need for discharge to recover capacity.

I'm confused also Mike. The text says 'small fraction', and 'Most users may never experience' and then you say that there is a need to discharge to recover capacity. But you don't say how often, or after what length of time, or any other parameters...

I have one of Eli's new MaxIMA packs, and IIRC, he has said, or someone has said not to use the grid charger on it.

I appreciate your information, but could you supply some guidelines?

[Eli]

I'm OK with people grid charging their packs overall, though I'm a little hesitant to warrant them through say, PHEV use. I really believe in this case conservatism is the name of the game. My recommendation for some time now has been a once every ~6 month maintenance charge on a new pack.

I'll make a post soon that helps explain why, but I wish I could figure it all out first.. which I know isn't possible, lol.