Maha MH-C9000 SUPPORT / FAQ Thread

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willchueh

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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:
https://www.candlepowerforums.com/threads/140144

William
 
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willchueh

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Re: Maha MH-C9000 SUPPORT Thread

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.
 
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thekobk

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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?:huh2:
 

willchueh

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thekobk said:
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?:huh2:


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

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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.:rock:
 

dekelsey61

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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

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thekobk said:
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?:huh2:

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...:whistle:

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

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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

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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

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Mike abcd said:
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
 
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Mike abcd

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willchueh said:
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

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Hello Mike,

Got your flame proof suit on... :)

Mike abcd said:
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...:whistle:

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

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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
dekelsey61 said:
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

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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

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Mike abcd said:
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...:whistle:

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.
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

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+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.

Mike abcd said:
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

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Mike abcd said:
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?
 
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