Maha MH-C9000 SUPPORT / FAQ Thread

[willchueh]

I would like to start this thread to answer user questions about the MH-C9000. The 2nd post contains a FAQ which shall be amended from the time to time.

For features and general pre-sales questions/discussion, please use this thread:
http://www.candlepowerforums.com/vb/...d.php?t=140144

William

[willchueh]

MH-C9000 Frequently Asked Questions

Updated Jan. 5, 2007

Using the BREAK-IN mode, I am seeing a charging capacity much higher than the capacity I programmed. Why is the battery overcharged?

When using the BREAK-IN mode, the charger puts in 1.6 times the capacity of the battery (entered at the start of the charge). This does not cause any harm to the battery as the charging rate is very low (only 10% of the battery capacity). The increased total charging capacity compensates for energy lost as heat. This is the charging scheme recommended by International Electrotechnical Commission (IEC).



I am charging some older batteries and see that the charging capacity is much higher than the capacity I programmed. Why doesn't the charger terminate correctly?

The charger terminates by voltage and by temperature simultaneously. For certain older (and low quality) batteries, they do not produce the proper negative delta V signal (a small voltage drop at the conclusion of the charge) needed for the charger to stop. At the same time, the battery temperature failed to reach the termination limit as the charging rate was probably too low.

To address this issue, you should attempt to perform a BREAK-IN mode on the batteries first. You should also use a higher charging rate.



When using higher charging current, the charging capacity seems to reduce. Is this normal?

When charging at higher current, the charge completeness reduces thereby lowering the charging capacity. This is to prevent battery overheating. This typically occurs at a rate greater than 1500mA. Generally speaking, 1000mA achieves nearly full charge completeness for AA batteries.

Even after the charge ends (DONE appears on screen), the charger will apply a topoff charge and continuous maintenance charge. Despite that the capacity on the screen no longer increases, the batteries are being topped off.

If you would like to achieve better charge completeness at higher currents, a small fan can be added to cool the batteries externally.



Why is it not recommended to charge battery below 0.33C?

When charging below 0.33C (except in BREAK-IN) mode, the batteries may not produce a sufficient end-of-charge signal for the charger to terminate correctly. Although the temperature sensors will safeguard battery overheating, lower charging rate might not cause enough heating in the batteries to trip the sensors.

If low charging rate is desired, you should use the BREAK-IN mode. Charging in that mode is terminated by only time (1.6 times battery capacity) and temperature.



After the charge begins, why do I see an abnormally high voltage (~ 1.6V to 2.0V) on the screen?

In the first few seconds, the MH-C9000 performs a proprietary "high impedance" check to filter out batteries unsafe to charge including non-rechargeable batteries. During this time, a high current is applied and voltage measured to determine the impedance of the battery.

The voltage will return to normal by the second time voltage data is displayed on the screen.



Why doesn't the charging and discharging current reach the set values exactly? I thought the charger is supposed to be precise.

The charging and discharging current are pulsed, thereby causing the displayed current to go up and down. The capacity calculation is based on the actual current rather than the set current so capacity calculation remains accurate.



I am using the CHARGE mode. Why is the capacity different than my battery capacity?

The capacity displayed in any charging process is called the "charging capacity." This is the amount of energy put into the batteries. This number does not equal to the battery's capacity as it is dependent on the amount of charge already in the battery as well as the battery's internal resistance.

For example, a half used 2000mAh battery may only show a charging capacity of 1000mAh since the battery is half full.

It is normal for the charging capacity to exceed battery capacity by as much as 30% depending on battery brand and charging rate.

To determine the battery's useful capacity, you must look at the "discharge capacity." Such information is available in the REFRESH & ANALYZE, BREAK-IN, DISCHARGE, and CYCLE modes. Note that the battery is not recharged in the DISCHARGE mode.



How do I tell if the capacity displayed on the screen is charging or discharging capacity?

If charging or discharging is in-progress, a blackbox contain either CHARGE or DISCHG will be displayed on the screen. The capacity shown during charging is always the charging capacity. Similarly, the capacity shown during discharging is the discharging capacity.

In the CHARGE mode, the final capacity displayed (after DONE appears) is the charging capacity.

In the REFRESH & ANALYZE and BREAK-IN mode, the final capacity displayed is the discharging capacity. The battery have also been recharged after the discharge.

In the DISCHARGE mode, the final capacity displayed is also the discharging capacity. However, the battery is not recharged.

In the CYLCE mode, the capacities saved in memory always refer to the discharging capacity.



When I discharge certain batteries, the current seem to taper off near the end of the discharge and seems to take very long to finish. Why and does this affect the capacity of the battery?

This is normal for batteries that exhibt high internal resistsance. MH-C9000 measures the voltage of the batteries while briefly pausing the discharge (every few seconds). For high resistance battery, this voltage might differ from the actual voltage of the battery. For the MH-C9000, it is not designed to maintain set current when battery is below 0.9V.

This does not affect the calculated capacity as the realtime current is used in the capacity integration.



Using the CYCLE mode, why do I see a "0 mAh" capacity on the screen? What happened to the saved battery capacity?

A CYCLE is consisted of:
Charge > 1 Hour Rest > Discharge > 1 Hour Rest (repeats for programmed number of times)
The discharge capacity is saved into the memory at completion of discharge but cannot be reviewed until that cycle is completed (after the 1 hour rest). During the rest, a zero capacity is displayed.

During this period, all previously completed cycle data can be viewed, but not the most recent cycle. It will become available after that particular cycle is completed.

Cycle data can be accessed anytime after completion of the first cycle by using the "UP" and "DOWN" keys.



There is an arrow that moves below the slot number. What does it mean?

The LCD screen displays information a slot at a time. The information (capacity, current, time, voltage) is displayed twice before moving on to the next slot. The arrow points to the slot reporting.



Is it normal for the batteries to get warm during charging?

Yes, batteries do get warm during the charge due to both internal heat and heat produced by the charger. Lower charging rate can yield lower battery temperature, but it is not recommended to go below 0.33C or 0.33 times the battery capacity.

Adding an external fan can also cool the battery.



The manual makes recommendations for charging rates. How about discharging rate

Most NiMH batteries can accept discharge rate up to 3 times its capacity. A higher discharge rate will yield lower capacity.

For accurate capacity measurement, use the BREAK-IN mode which complies with IEC standards (0.2C discharge rate).



Is the MH-C9000 compatible with the new "low self-discharge" batteries (e.g. Sanyo Eneloop)?

Yes. Follow the same charging rate recommendations for general NiMH batteries.



What is the maximum capacity supported by the MH-C9000?

The maximum capacity supported is 20,000mAh making it compatible with future technologies.



The charger cannot detect my battery. What can be done?

Virtually all batteries can be detected by the charger. Therefore, if a battery cannot be detected, it is likely not making good contact with the charger. This can be caused by improper seating of the battery or battery not meeting the IEC dimension standard. Try rotating the battery or placing it in another slot.



There is a faint noise emanating from the charger. Is this normal?

The charger can produce some high frequency hum, which is generated by the high frequency pulse charging and switchers.

[coppertrail]

Thanks Bill!

[dekelsey61]

Thank you very much- William. Lots of imformation to help us out. Great work.
Dan

[thekobk]

I orderd a 4 pack of maha 2700's with my new charger and was wondering do I need to put the new battery's on discharge mode before I put them in break in mode?

[willchueh]

I orderd a 4 pack of maha 2700's with my new charger and was wondering do I need to put the new battery's on discharge mode before I put them in break in mode?

thekobk,

You can use the discharge mode, if desired (I recommend 500mA), but not necessary. For most cases, simply use the BREAK-IN mode which does the following:

Charge at 0.1C (270mA) for 16 hours
Rest 1 hour
Discharge at 0.2C (540mA)
Rest 1 hour
Charge at 0.1C (270mA) for 16 hours

Once should suffice. Be advised it takes quite a while (39 hours).

This is also useful for batteries that've been in storage. From my experience, it can do pretty wonderful things to dead batteries.

William

[thekobk]

Thank you William for your response. So far I like this charger alot. Might give my bc900 away as a christmas gift. The bc 900 was a good charger but this things is the cats meow.

[dekelsey61]

William, Thanks for all your help with this new charger. I am using the break-in mode on 4- 2700mah batteries that has had a faster discharge rate than all the rest of my batteries. With the break-in mode will it help batteries that have a faster discharge rate than other ones? This charger is GREAT!! Thank you.
Dan

[Mike abcd]

I orderd a 4 pack of maha 2700's with my new charger and was wondering do I need to put the new battery's on discharge mode before I put them in break in mode?

IMHO, I'd definitely discharge them first or better yet, condition them with the refresh mode a couple of cycles or until the reported capacity stabilizes.

It takes 12 hours at .1C to fully charge a fully discharged NIMH cell per Duracell. That's also what I found when I did a quick test. Anything beyond that is overcharging and overcharging, even at .1C, is not good for NiMH cells. A 16 hour charge at .1C is roughly a 30% overcharge and can be a LOT more if the cell isn't fully discharged beforehand. I've found quite a few new cells with substantial initial charge out of the wrapper.

I know popular wisdom is that new cells should be "formed" with a 16 hour .1C charge but I can't find any cell manufacturer who advises it.

I also believe new cells require cycling and won't exhibit stable or full capacity on the first cycle. I've even seen poor cells that require 4-5 cycles such as the Lenmar junk. I just don't believe that you have to abuse them with overcharging based on my experience.

Running for my flameproof suite now...

From the FAQ.
"Using the CYCLE mode, why do I see a “0 mAh” capacity on the screen? What happened to the saved battery capacity?

A CYCLE is consisted of:
Charge > 1 Hour Rest > Discharge > 1 Hour Rest (repeats for programmed number of times)
The discharge capacity is saved into the memory at completion of discharge but cannot be reviewed until the cycle is completed (after the 1 hour rest). During the rest, a zero capacity is displayed. However, as soon as the rest is completed, you can use the “UP” and “DOWN” key to access the capacities saved in memory."

Ouch, I hope this gets modified in a future firmware. Sounds like a bug, sloppy programming or a very foolish design decision. I guess I'll be doing a lot of seperate charge and discharge cycles on mine instead of using the "Cycle" mode.

Does anybody know if you can insert multiple cells at once and only have to set the parameters once like the BC-900? If not, I hope that also gets changed in a future firmware revision.

Mike

[Mike abcd]

Question:

Does the C-9000 only perform a 1 hour .1C top off charge after charging terminates based on dT/dt and not on -dV/dt or maximum temperature limit?

Is there a reason that it uses a .1 C 1 hour top off and not the .1C for 1/2 hour advised by Duracell, Sanyo and Energizer?

Mike

[Curious_character]

Hm, Maha recommends charging at no less than 0.33C, and says the new charger supports batteries up to 20,000 mAh. I conclude then that it's capable of a charge current of 6.67 amps. Impressive!

c_c

[willchueh]

Ouch, I hope this gets modified in a future firmware. Sounds like a bug, sloppy programming or a very foolish design decision. I guess I'll be doing a lot of seperate charge and discharge cycles on mine instead of using the "Cycle" mode.

Mike,

It seemed our FAQ response is very unclear and perhaps misleading. Sorry! Fortunately, I don't think the problem you are worried about exists.

Basically, there is a one hour period during a SINGLE cycle which the capacity FOR THAT CYCLE cannot be viewed. All previously completed cycles can be accessed at anytime.

Here is an example:

You are at the 5th cycle, just after the the charger enters the post-discharge rest. Pressing the UP and DOWN key you can review 1st through 4th cycle, but you cannot see the capacity from the 5th cycle until the end of the rest period.

William

[Mike abcd]

Mike,

It seemed our FAQ response is very unclear and perhaps misleading. Sorry! Fortunately, I don't think the problem you are worried about exists.

Basically, there is a one hour period during a SINGLE cycle which the capacity FOR THAT CYCLE cannot be viewed. All previously completed cycles can be accessed at anytime.

Here is an example:

You are at the 5th cycle, just after the the charger enters the post-discharge rest. Pressing the UP and DOWN key you can review 1st through 4th cycle, but you cannot see the capacity from the 5th cycle until the end of the rest period.

William

I still understand that as not being able to view the result of the LAST discharge cycle until 1 hour after the LAST discharge cycle completes.

That's just wrong. You have the capacity measured in the dischage test. Why wait an hour to provide it to the user? The rest period isn't going to change the result.

Mike

[SilverFox]

Hello Mike,

Got your flame proof suit on...

IMHO, I'd definitely discharge them first or better yet, condition them with the refresh mode a couple of cycles or until the reported capacity stabilizes.

If you do a "forming" charge first, the capacity of the cell will stabilize pretty much on the first discharge cycle. With cells that have been "formed" you actually see very little change in capacity during cycling.

It takes 12 hours at .1C to fully charge a fully discharged NIMH cell per Duracell. That's also what I found when I did a quick test. Anything beyond that is overcharging and overcharging, even at .1C, is not good for NiMH cells. A 16 hour charge at .1C is roughly a 30% overcharge and can be a LOT more if the cell isn't fully discharged beforehand. I've found quite a few new cells with substantial initial charge out of the wrapper.

I know popular wisdom is that new cells should be "formed" with a 16 hour .1C charge but I can't find any cell manufacturer who advises it.

I also believe new cells require cycling and won't exhibit stable or full capacity on the first cycle. I've even seen poor cells that require 4-5 cycles such as the Lenmar junk. I just don't believe that you have to abuse them with overcharging based on my experience.

Running for my flameproof suite now...

Mike

Duracell has excellent information. It has long been known that if we only charge to 90% of full capacity, keep the cells cool, and avoid prolonged trickle charging, the cells will last a lot longer. Unfortunately, they don't supply any data to back this up. Their cells are not advertised as being able to run for more cycles using their charging procedure, and if you follow it precisely, you will find that you loose around 10% in capacity.

Let's look at the 12 hour 0.1C charge. With cells that have been formed and cycled and in general are broken in, a 12 hour charge will get you within 95% of full capacity. This is charger dependent. Constant current chargers do better than pulsed chargers. 14 hours gives a little overcharge, but does a better job of redistributing the electrolyte within the cell. 16 hours is considered a "standard" charge according to the battery testing standards. The battery manufacturers use the "standard" charge to rate the capacity of their cells. While they don't come out and directly say so, I suspect Duracell uses the "standard" charge to rate their cells as well.

You have to ask yourself, “If the cell is fully charged at 12 hours, and can be damaged by overcharging beyond that, why does the industry standard call for a 16 hour 0.1C charge?”

Yes, the 16 hour charge does overcharge the cell. However, that little bit of overcharge seems to enable the cell to operate at its fullest potential right away. The next time you charge the cell, it will not develop hot spots, and if you use several cells in a battery pack, you find that they stay in balance better. The 16 hour charge also allows for better balancing of the cells within a battery pack.

The alternative is to do several cycles.

In "normal" use, people won't observe the slight performance improvements that come from cycling, and no one wants to baby sit a "forming" charge. People would be outraged if the manufacturers insisted on them doing a forming charge prior to use. The people may even insist that the manufacturer do the forming charge at the factory before sending the cells out. Sanyo, and others, originally did this along with adding a few cycles to the cell before sending it out. Cost cutting has eliminated this step as being unnecessary for "normal" use.

There are some of us that are "performance" users. We measure run time down to the minute (and sometimes down to the second). We measure light intensity changes with a lux meter and are very interested in getting the best performance from our cells. We are also patient enough to do a 16 hour charge, and have the equipment to dial in the 0.1C charge rate. We also want "fully" charged cells in order to get every minute of run time we can from the charge.

The abuse comes from extended trickle charging. A cell is going to be as full as it can get in 16 hours at 0.1C. If you let it continue to charge for a week, the electrolyte will start to dry up. If you continue the charge for a year, you will see a performance drop.

Duracell offers some interesting graphs. While they are not based on “standard” test parameters, they are very informative.

Let’s take a look at they cycle test data for an example. The standard cycle test calls for a 0.1C charge for 16 hours, followed by a 0.2C discharge to 0.9 – 1.0 volts. This is continued until the capacity of the cell is at less than 80% of its original capacity.

Duracell offers a cycle test graph showing the effects of cycle life with charging and discharging temperature. They charge at 0.25C for 3.2 hours. This gives you roughly a 75% full cell. They discharge at 0.25C for 2.4 hours. The interesting part is that they measure capacity every 50 cycles by charging at 0.33C for 5 hours followed by a 1.0C discharge to 1.0 volts. The 0.33C charge for 5 hours works out to a 165% charge. I find it interesting that this is actually a higher overcharge than charging 16 hours at a 0.1C rate. It is also interesting that charging at a higher charge rate is more efficient, so it is a significant overcharge. To get the same results as charging for 16 hours at 0.1C when charging at 0.33C, you only need to charge for around 4 hours.

Fortunately, batteries handle a reasonable amount of abuse and still work well. Duracell offers some excellent advice, and looking at it from a consumers point of view, I agree with it. However, when I want peak performance from my cells, I will consider giving up some “longevity” for improved performance.

Tom

[dekelsey61]

Hi Tom, Can you answer this question I have about a forming charge helping with faster than normal discharge rate. Will it work and help?Thank you and have a Happy Holiday!
Dan

William, Thanks for all your help with this new charger. I am using the break-in mode on 4- 2700mah batteries that has had a faster discharge rate than all the rest of my batteries. With the break-in mode will it help batteries that have a faster discharge rate than other ones? This charger is GREAT!! Thank you.
Dan

[SilverFox]

Hello Dan,

I don't think so. A high self discharge rate usually indicates separator damage inside the cell. A new cell is about the only thing that will fix that.

Tom

[N162E]

IMHO, I'd definitely discharge them first or better yet, condition them with the refresh mode a couple of cycles or until the reported capacity stabilizes.

I totally agree with this. All information concerning "Forming" or "Breaking in" of new batteries is based on them coming out of the package in a discharged state. I don't know that all new Nimh batteries are DOA and I do know for sure that the newer low self discharge ones are seeming to be coming out 75+ percent fully charged. My money says play it safe and discharge first

It takes 12 hours at .1C to fully charge a fully discharged NIMH cell per Duracell. That's also what I found when I did a quick test. Anything beyond that is overcharging and overcharging, even at .1C, is not good for NiMH cells. A 16 hour charge at .1C is roughly a 30% overcharge and can be a LOT more if the cell isn't fully discharged beforehand. I've found quite a few new cells with substantial initial charge out of the wrapper.

I know popular wisdom is that new cells should be "formed" with a 16 hour .1C charge but I can't find any cell manufacturer who advises it.

From what I "READILY' found in the Duracell site they specified overnight charge. I did not see anything referring to initally forming the cell at any special rate.

I also believe new cells require cycling and won't exhibit stable or full capacity on the first cycle. I've even seen poor cells that require 4-5 cycles such as the Lenmar junk. I just don't believe that you have to abuse them with overcharging based on my experience.

Running for my flameproof suite now...

From the FAQ.
"Using the CYCLE mode, why do I see a “0 mAh” capacity on the screen? What happened to the saved battery capacity?

A CYCLE is consisted of:
Charge > 1 Hour Rest > Discharge > 1 Hour Rest (repeats for programmed number of times)
The discharge capacity is saved into the memory at completion of discharge but cannot be reviewed until the cycle is completed (after the 1 hour rest). During the rest, a zero capacity is displayed. However, as soon as the rest is completed, you can use the “UP” and “DOWN” key to access the capacities saved in memory."

Ouch, I hope this gets modified in a future firmware. Sounds like a bug, sloppy programming or a very foolish design decision. I guess I'll be doing a lot of seperate charge and discharge cycles on mine instead of using the "Cycle" mode.

I concur with this totally, this is a flaw not a feature in the programming.

Does anybody know if you can insert multiple cells at once and only have to set the parameters once like the BC-900? If not, I hope that also gets changed in a future firmware revision.

I mentioned this previously. Being to set custom profiles or just being able to adjust defaults here would go a long ways. Global settings per cycle could also go a long ways.

Mike

Kudos and compliments to MahaPower and Mr. Chieu. We asked and they listened. This is essentially a design asked for and built for enthusiasts. This is a great Rev 1, I can't wait to see what is coming.

[Thujone]

+1 for bug [Not Feature]

This will be quite irritating. "I've got a cookie for you, you can have it in an hour" is not cool at all.

I still understand that as not being able to view the result of the LAST discharge cycle until 1 hour after the LAST discharge cycle completes.

That's just wrong. You have the capacity measured in the dischage test. Why wait an hour to provide it to the user? The rest period isn't going to change the result.

Mike

[summerwind]

mode.

Does anybody know if you can insert multiple cells at once and only have to set the parameters once like the BC-900? If not, I hope that also gets changed in a future firmware revision.

Mike

Mike, when you say multiple cells, do you mean with all having the same capacity rating?
i was thinking this as well, but then realized that one could charge different capacity cells and program each as required.
are you meaning that all slots should be programmed at the same time?

[coppertrail]

Content of post removed.

[N162E]

WIth the BC-900, you insert all your cells, then plug in the AC Power cord. You then set the charge current and mode for all 4 cells.

Is this a new procedure? I've always put my batteries in with the BC-900 plugged and then set the charge current within 8 seconds. My BC-900s are always plugged in.

I checked the BC-900 manual and it specifically says that batteries are to be inserted after the charger is plugged into AC supply.

[kitelights]

Is this a new procedure? I've always put my batteries in with the BC-900 plugged and then set the charge current within 8 seconds. My BC-900s are always plugged in.

I checked the BC-900 manual and it specifically says that batteries are to be inserted after the charger is plugged into AC supply.

ditto

My apologies for posting - this is a Maha MH-C9000 SUPPORT / FAQ Thread.

[coppertrail]

Is this a new procedure? I've always put my batteries in with the BC-900 plugged and then set the charge current within 8 seconds. My BC-900s are always plugged in.

I checked the BC-900 manual and it specifically says that batteries are to be inserted after the charger is plugged into AC supply.

My apologies gentlemen, I stand corrected. The manual does mention plugging in the AC power before inserting the cells. I must have read the "insert cells before ac" on a forum somewhere and confused it with the manual's instructions.

[Mike abcd]

Hello Mike,
Got your flame proof suit on...

Sorry for the delay in replying. I don't know if you remember but we've had some discussions about a year back here and later at rcgroups. Been gone from here but the Cree XR-E got me back for a bit.

Any chance you could get a moderator to move these posts to another thread. I hate cluttering this one although it seems even existing questions aren't getting answered here.

If you do a "forming" charge first, the capacity of the cell will stabilize pretty much on the first discharge cycle. With cells that have been"formed" you actually see very little change in capacity during cycling.

I frequently see capacity stabilize on the first fast charge cycle with decent cells. When it doesn't I suspect it's because of a short charge cycle due to a"false -dV/dt" peak as additional electrolyte gets "exposed"/"connected" causing what would be a short term drop in voltage.

The only time I've seen capacity take more than 2 cycles to stabilize is with really bad cells like some Lenmar NoMem ones that I got with voltages well below 1.0 V. I suspect they were very old stock and would have taken multiple cycles even with your method.

Duracell has excellent information. It has long been known that if we only charge to 90% of full capacity, keep the cells cool, and avoid prolonged trickle charging, the cells will last a lot longer. Unfortunately, they don't supply any data to back this up. Their cells are not advertised as being able to run for more cycles using their charging procedure, and if you follow it precisely, you will find that you loose around 10% in capacity.

I don't know if it's alwyas been there and we both missed it or it got recently added but they do give data now! Take a look at Section 6.2.6 Rate of Temperature Increase (dT/dt).
http://www.duracell.com/oem/Pdf/others/LithBull.pdf

The comparison only used a discharge to 70% and frankly I find the longevity increase disappointing in view of the loss in charged capacity assuming they used the 1/2 hour .1 C top off charge. Their data shows it takes 250 cycles for the useable capacity of the -dV/dt to drop below the dT/dt. I guess I'm going to stop being a fan of dT/dt charge termination. Suddenly made me worry that the C-9000 I have enroute was a bad purchase but then I remembered it uses a 1 hour .1 C top off charge which should result in about the same capacity as a -dV/dt termination would with a cycle life somewhere in between since the additional charge is being put in at a slower rate.

Let's look at the 12 hour 0.1C charge. With cells that have been formed and cycled and in general are broken in, a 12 hour charge will get you within 95% of full capacity. This is charger dependent. Constant current chargers do better than pulsed chargers. 14 hours gives a little overcharge, but does a better job of redistributing the electrolyte within the cell.

I only ran one .1 C 120% test using a BC-900 but I definitely saw a full charge compared to a 1000 mA -dV/dt charge. I started with a 1000 mAH fast charge, 500 mA discharge and logged capacity. Then I made sure the cell was fully discharged using the 100 mA rate. I then charged at 200 mA. The BC-900 actually terminated the charge at 117% of the capacity previously measured. I then discharged it at 500 mA and then did another "fast charge check". The ".1C 120%" actually had the highest measured discharge capacity of the 3 cycles by a small amount. Seemed pretty convincing to me so I didn't repeat it. I will try again with the C-9000 although I'll be surprised it I see only 95% capacity. Even so, a .1C 12:30 charge would fully charge a FULLY DISCHARGED cell if you're right.

16 hours is considered a "standard" charge according to the battery testing standards. The battery manufacturers use the "standard" charge to rate the capacity of their cells. While they don't come out and directly say so, I suspect Duracell uses the "standard" charge to rate their cells as well.

You have to ask yourself, “If the cell is fully charged at 12 hours, and can be damaged by overcharging beyond that, why does the industry standard call for a 16 hour 0.1C charge?”

It may be a standard for rating capacity but I don't know of ANY manufacturer who advises using it for current NiMH cells. Do you? Sanyo even states "Overcharging shortens the life of the Twicell, and for this reason, low-rate charging is fundamentally not suitable". Energizer and Duracell also point out that overcharging at .1 C is bad. Of course, the issue with slow charging is that you can't avoid an overcharge without knowing the current charge state and the capacity. Fast charging allows relaible charge termination without knowing either. Slow charging doesn't.

I suspect the development of the standard dates back to the NiCad era where cells were far more tolerant of abuse. It's intended to max out the capacity for rating purposes. Current NiMH cells don't get damaged enough in a single cycle to make much of a difference in the capacity measurement and provide a strong impetus for manufacturers to change the standard. Standards can be a nightmare to update or replace so it lives on. That doesn't make it a good thing to do with current cells.

Yes, the 16 hour charge does overcharge the cell. However, that little bit of overcharge seems to enable the cell to operate at its fullest potential right away. The next time you charge the cell, it will not develop hot spots, and if you use several cells in a battery pack, you find that they stay in balance better. The 16 hour charge also allows for better balancing of the cells within a battery pack. The alternative is to do several cycles.

I don't consider a 33% overcharge "a little bit" and typically it's far worse because few folks can properly fully discharge their cells first without over discharging them. IMHO, the average user would be far better off performing 2 fast charge cycles with a partial (>50%) discharge in between. It's also faster...
[/QUOTE]
In "normal" use, people won't observe the slight performance improvements that come from cycling, and no one wants to baby sit a "forming" charge. People would be outraged if the manufacturers insisted on them doing a forming charge prior to use. The people may even insist that the manufacturer do the forming charge at the factory before sending the cells out. Sanyo, and others, originally did this along with adding a few cycles to the cell before sending it out. Cost cutting has eliminated this step as being unnecessary for "normal" use.

There are some of us that are "performance" users. We measure run time down to the minute (and sometimes down to the second). We measure light intensity changes with a lux meter and are very interested in getting the best performance from our cells. We are also patient enough to do a 16 hour charge, and have the equipment to dial in the 0.1C charge rate. We also want "fully" charged cells in order to get every minute of run time we can from the charge.
[/QUOTE]
Tom, I don't know if I qualify as a "performance" user but I have an Extech light meter, a DMM with a PC interface, a LiON/LiPo charger that reports mAH delivered, a BC-900 and a LOT of retired chargers I accumulated over the last 20 years. I did my first run time tests about 15 years ago when I started using the first power hungry handheld GPS units available. I'd never log run time on an NiMH/alkaline app to the second as my high school Physics and Chemistry teachers made sure I respected significant digits by taking off credit for answering with too many digits but I do log tenths of a minute on LiPo r/c heli use where it's meaningful.

I want max run time too but recognize that overcharging or discharging can cost dearly in life cycles. Of course that's far more true with LiOn and LiPo where a single cycle can ruin it.

The abuse comes from extended trickle charging. A cell is going to be as full as it can get in 16 hours at 0.1C. If you let it continue to charge for a week, the electrolyte will start to dry up. If you continue the charge for a year, you will see a performance drop.

Outside of flagrant abuse, cells die a death of a thousand cuts. I prefer not to cut mine unless I get a meaningful return. I guess we should agree to disagree on whether a "forming charge" provides a "meaningful return" vs fast charging with proper termination.

Duracell offers some interesting graphs. While they are not based on “standard” test parameters, they are very informative.

Are there any standards other than for capacity measurement? It does seem that most cycle life tests are done with fast charging and -dV/dt termination but I don't know if thats a standard. Seems like that's all Sanyo uses for life cycle testing.

Let’s take a look at they cycle test data for an example. The standard cycle test calls for a 0.1C charge for 16 hours, followed by a 0.2C discharge to 0.9 – 1.0 volts. This is continued until the capacity of the cell is at less than 80% of its original capacity.

Any references to that "standard"?
[QUOTE]
Duracell offers a cycle test graph showing the effects of cycle life with charging and discharging temperature. They charge at 0.25C for 3.2 hours. This gives you roughly a 75% full cell. They discharge at 0.25C for 2.4 hours. The interesting part is that they measure capacity every 50 cycles by charging at 0.33C for 5 hours followed by a 1.0C discharge to 1.0 volts. The 0.33C charge for 5 hours works out to a 165% charge. I find it interesting that this is actually a higher overcharge than charging 16 hours at a 0.1C rate. It is also interesting that charging at a higher charge rate is more efficient, so it is a significant overcharge. To get the same results as charging for 16 hours at 0.1C when charging at 0.33C, you only need to charge for around 4 hours.
[QUOTE]
The charge/discharge is providing 133% charge input so the cell gets fully charged as long as it starts out that way. The graph doesn't show the number of cycles, only the "% cycle life". To me, it just looks like they wanted to accelerate the testing to determine the relative effect of temperature and hence were willing to accept reduced cycle life. Personally I think the assumption that the charge methadology doesn't affect the relative effects differently with temperature questionable.

I actually did 2 cycles on four Energizer 2500s to check your contention that fast charging was significantly more efficient. The results on the BC-900 were inconsistent so I'll call it inconclusive but seemed to lean in the direction of fast charging being less efficient. As charge in vs tested capacity, I got 125%, 127%, 124%, 126%, 120%, 122%, 115%, 118%. I might try it again with the C-9000 out of curiousity.

Fortunately, batteries handle a reasonable amount of abuse and still work well. Duracell offers some excellent advice, and looking at it from a consumers point of view, I agree with it. However, when I want peak performance from my cells, I will consider giving up some “longevity” for improved performance.

I fully agree with that. We just appear to disagree on whether a "16 hour .1C forming" overcharge offers any performance benefits that can't be attained with less effect on longevity. As a single one time event, it's probably moot but I see folks using that as a standard charge technique on cells and packs that are only partially discharged. That kind of abuse costs dearly in cycle life with no benefits at all IMHO.

BTW, I first stumbled in here looking for battery testing info and have found your testing among the best I've ever found for NiMH/LiON. I sincerely appreciate your contributions. Frankly it's what usually brings me back
here as I'm not a true flashaholic although most folks who know me would
think so. I won't but a light unless I have a high expectation that it fills a need I have for a size*runtime*brightness appreciably better than something I already have hence my current high interest in Cree XR-E and
LiON to feed them. I have gotten pretty addicted to r/c helis though ;-)

Mike

PS Can we start a new thread if you want to continue this? I suspect a moderator might respond better to a request from you to move our posts than an unknown member like me.

[EngrPaul]

I got mine today.

Even though I read the manual fully, I didn't realize that you had to program each bay. I thought that I could insert 4 batteries quickly and set one program for all of them.

Secondly, I didn't know what the optimum charge rate would be, assuming one is not in a hurry and simply wants to have best performance. It clearly stated the optimum discharge rate, but not an optimum charge rate. It gives an acceptable range (0.33C-1.0C) but doesn't really tell you which one is best.

So I referred back to a Duracell NiMH paper I had on PDF. It said:

Duracell recommends a three-step procedure that provides
a means of rapidly charging a nickel-metal hydride
battery to full charge without excessive overcharging or
exposure to high temperatures. The steps in sequential
order are:
1) Charge at the 1C rate, terminated by using
dT/dt = 1°C(1.8°F) /minute.
2) Apply a C/10 top-up charge, terminated by
a timer after 1/2 hour of charge.
3) Apply a maintenance charge of indefinite
duration at C/300 rate.

So I decided to use C=1.0 and round down to the next lower 0.1A.

I re-read the manual and saw that Powerex follows Duracell's guidelines for top-off and maintenance charges at the end of the cycle.

So these are my two requests for the manual or FAQ: (1) Point out that each bay needs programmed individually, and (2) define what the optimal charge rate is, not just a range.

[EngrPaul]

Hm, Maha recommends charging at no less than 0.33C, and says the new charger supports batteries up to 20,000 mAh. I conclude then that it's capable of a charge current of 6.67 amps. Impressive!

c_c

The input is rated 12V at 2.0 A. With 24W total input, the maximum current it could supply to batteries is about 15A. This would limit you to two batteries at a time.

[EvilLithiumMan]

Is it too early to start hacking the MH-C9000? You know, any undocumented features accessed only by undocumented key presses? I.E., if you power up the C9000, you'll see it go through a diagnostic check and the display counts down from 9.9.9.9. to 0.0.0.0. and then shuts off. However, if you power up the C9000 while holding down the 'UP' button, you'll see it do something a little different once the display gets to 0.0.0.0.

Am I looking for anything specific? Well, not really. But if there was a way to program all four slots at once, it'd be nice to know about it.

[coppertrail]

Last night I put some Sanyo 2700s through a break-in cycle. About 10 min ago, the power in my home went out for about 1 second and then came back on.

I looked at the charger and it had reset itself, displaying "charge" mode at the default rate.

Based on this experience, it seems that the following is true: If the power goes out, even momentarily, the charger resets itself to the default mode. I understand this could be alleviated by plugging the unit into a UPS system. But, if not, and one is 36 hours into a "Break In" cycle, all that will be lost, and one must start out from the beginning?

[wptski]

I've been reading some of the posts of users that received their C9000's. I got my two yesterday. I think that this is going to be one of the most complex operating chargers so far.

I used some almost new 1000mAh PowerEx AAA cells. I charged two and discharged two on one unit. Using the second unit I then took the discharged pair and inserted them into slots 1/4, charging at 1A and charged two more that came out of my cordless mouse at 1A also in slots 2/3.

I took a extended nap. I didn't note the time that I started the charging. All were done with slots 1/4 charging for just over an hour for just over 1Ah and slots 2/3 charging for 30-35 min. for just over .5Ah. So slots 2/3 finished way ahead of the others. Makes sense as they weren't depleted. Ah! Looking at the thermal image, slots 2/3 are warmer than 1/4 and appear to be still charging, I assume this the topoff charge. But why didn't it topoff slots 1/4? Looks like this charger doesn't always do a topoff charge for some reason! There's probably some real complex answer for this.

Remember that the center two slots showed DONE in half the time compared to the two outside slots.

BTW: Happy Hoildays!!!




[/

[moldyoldy]

Hi Bill,

FWIW, for years I have noted that cells that are charged from a full discharge do not heat up as much at the end of a charge compared to cells that are charged from, say, about a half discharge. IOW, the cells that charged from a full discharge were cooler at the end than cells that were charged from about 1/2 discharge. I am not sure why, but it has happened often enough with multiple chargers and cells that I am rather confident of the situation.

Also, it has sort of been a test of chargers to take a cell that just finished a charge in one charger and insert it into another charger to see if the second charger will probably determine end of charge. and yes, the cells get hot!

Tim