Maha MH-C9000 SUPPORT / FAQ - continuation

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.
 

Black Rose

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I read a good portion of part 1 of this thread and it seems like all the big issues have been resolved with this charger.

The only thing that has me questioning getting one vs a BC-900 is the rather random clicking and squeeling. For the ones that do this, how loud is it?

My current charger is completely silent unless you put your head right next to it, then you can hear slight clicking.
 

Mr Happy

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It makes a quiet whistling noise that pulses once a second. How much it bothers you might depend on the sample and how acute your hearing is. Other chargers I have make a similar noise -- most likely caused by switched mode regulator circuitry.

To my ears I can only hear it in a quiet room if I am close to the charger. For a teenager with really sharp hearing it might sound much louder. It doesn't bother me at all though; it gives me a comforting feeling that the charger is working.
 

Codeman

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When I first got mine, I could hear it if the TV was off or on low and I was within 2-3 feet. It's become background noise to me, so I don't even notice it anymore. If it was me looking to buy, I wouldn't let this be a reason to not get the C9000.
 

Black Rose

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Thanks for the feedback guys. Just ordered one.

I'll use it in my computer room instead of the hallway outside our bedroom like I do with the other charger. If nothing else, it will amuse the cats for a bit :)
 

Black Rose

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I'm now running a second set of ROV NiMh AA cells through a Refresh Analyze cycle and my cells are in pretty bad shape.

Out of the first batch of ROV NiMh AA cells, two of them are showing 1/4 of their capacity, one cell in the second batch has finished and it also is showing 1/4 of it's capacity.

These cells were originally charged in a timed charger (22 hours) and later charged in a smart charger. I stopped using the timed charger when I got the smart charger.

Looks like I'm going to be running the Break-in cycle on all my batteries.
With the amount of batteries I need to put through the break-in cycle, I think I should have bought a second C9000.
 
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Black Rose

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Yesterday I was running a Refresh Analyze cycle on my second batch of 2000 mAh ROV batteries.

One of the ones that is having issues showed a charge rate of 3950 ma :eek: and was very hot to the touch.

The FAQ says that the rate can be "much" higher but that seemed to be a bit excessive. I took the battery out and let if cool down.

I then put it back in to do a discharge on it before I run a Break-in cycle to see if I can bring the battery back to life.

Given that this particular battery is only has about 500 mAh capacity at the moment, was the 3950 ma normal? Another one of the cells in this bunch also has low capacity but showed the normal charge rate.

BTW, I was using 1000 ma charge and 500 ma discharge settings.
 

Mr Happy

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Yesterday I was running a Refresh Analyze cycle on my second batch of 2000 mAh ROV batteries.

One of the ones that is having issues showed a charge rate of 3950 ma :eek: and was very hot to the touch.

The FAQ says that the rate can be "much" higher but that seemed to be a bit excessive. I took the battery out and let if cool down.

I then put it back in to do a discharge on it before I run a Break-in cycle to see if I can bring the battery back to life.

Given that this particular battery is only has about 500 mAh capacity at the moment, was the 3950 ma normal? Another one of the cells in this bunch also has low capacity but showed the normal charge rate.

BTW, I was using 1000 ma charge and 500 ma discharge settings.
The one that reached 3950 and got hot must have missed the normal charge termination. Considering you were using a 1000 mA charge rate, it must be a fairly sick cell to have done that. It neither generated a -dV signal, nor exceeded 1.47 V.

Although it takes ages, it is probably a good idea to run a break-in cycle on old and badly performing cells as the very first step before trying a normal refresh on them. If the break-in shows a lower than expected capacity, run another break-in and see if it improves by 10% or more. If it does, keep doing break-ins. If it doesn't, you are better to put it in the recycle bin and replace it.
 

TorchBoy

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One of the ones that is having issues showed a charge rate of 3950 ma :eek: and was very hot to the touch.
A charge rate of just under 4 amps? (3950 mA, note capitalisation). I've never seen an MH-C9000 vary by that much on charge - even on discharge 1183 mA is the highest I've seen.

Do you mean it had been charged 3950 mAh?
 

Black Rose

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I have some 750 mAh AAA cells that I want to run through the Break In cycle.

The C9000 doesn't allow 50 mAh steps in break in mode, so do I enter 800 mAh as the capacity and slightly overcharge them, or set 700 mAh as the capacity and under charge them?
 

Mr Happy

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I'd go with 700. The actual capacity may come in under 750 anyway.

The break-in mode is always going to "overcharge" the cells. Even at 700 mAh, it will apply a charge of 1.6 x 700 = 1120 mAh.
 

TorchBoy

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While you probably want more than a largely cynical answer, if 750 mAh is a typical capacity exaggeration then 700 mAh is probably closer to what they really are. But the 16 hour Break In will fill them anyway.
 

Black Rose

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I have a question regarding the accuracy of the Capacity reported by the C9000 after a break in cycle has completed.

I just took the second set of 4 non-LSD Rayovac AA 2100 mAh NiMh cells off the C9000, and they too have lost a significant portion of their capacity.

The kicker with these cells is that I have had them for just over 6 months and they appear to be crap already. They were previously charged using a Rayovac charger and were used in Wii controllers. Compared to my other non-LSD cells, these ones were used properly (with the exception of the questionable Rayovac smart charger)

The 8 cells capacity as reported by the C9000 range from a low of 1240 mAh to a high of 1409 mAh.

The reason I am asking about the accuracy is that I am going to contact Rayovac about these particular cells since they are relatively new and were charged in a Rayovac branded charger designed for NiMh cells.

I've already replaced them with Eneloop and ROV Hybrids, but am ticked that they went bad so fast. They only cost $14 for the 8 cells, but still shouldn't have crapped out this soon.

EDIT 3/31/2008: I contacted Rayovac about these cells and was told that these cells (NM715-40P with green/chrome/black battery labels) are 1400 mAh cells. If true, that would explain what I thought was a serious capacity loss.

However, the information provided from Rayovac does not match the data sheet posted on their technical site around the time these particular batteries showed up in the retail channels.
 
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TorchBoy

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Black Rose, you could try putting them through a few cycles on the C9000, and see if they improve at all.
 

Eugene

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I noticed that my rayovac cells test at a much lower than rated capacity compared to sanyo cells. I have sanyo's that are 7-9 years old that are down up to 80% capacity and 4 year old rayovacs that are down to 75% capacity.
 

Mr Happy

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I have a question regarding the accuracy of the Capacity reported by the C9000 after a break in cycle has completed.
The accuracy in general is quite good. In case you have any doubts about your particular sample of the C9000, you can check it by putting a set of Eneloops through a break-in cycle. You should find with those a reported capacity in the 1900 to 1950 mAh range.

It's not unheard of for some cells to be significantly down on their capacity though. I have a set of XG 2400 mAh that came with a charger, hardly even used, and they won't read higher than about 1600 mAh on a break-in cycle.
 

Black Rose

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Black Rose, you could try putting them through a few cycles on the C9000, and see if they improve at all.
I think I'll put the crappy ROVs on my MH-C800S and run some conditioning cycles on them. The conditioning cycle on the C800S only takes about 16 hours vs the 45+ with the C9000.

I still have 24 Eneloops and 16 ROV Hybrids to break in yet, so I don't want to tie up the C9000 for these questionable cells right now.

The accuracy in general is quite good. In case you have any doubts about your particular sample of the C9000, you can check it by putting a set of Eneloops through a break-in cycle. You should find with those a reported capacity in the 1900 to 1950 mAh range.
I've got a few Eneloops to break in :), so I'll use that as a benchmark since they are the cream of the crop of LSDs and seem to have very reliable capacities.
 
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