Which 9V battery for a radio microphone: 8.4V 300mAh or 9.6V 230mAh?

Older radio microphones needed the full 9V that alkaline batteries provided, so 7.2V and 8.4V NiCD and NiMH batteries did not last long before dropping below the minimum voltage needed by the microphone. In response to this need, MAHA developed 9.6V rechargeable batteries. More recently, newer mics have been designed to work with the standard NiMH battery voltages of 8.4V. As a result of this development, Maha released their 8.4V rechargeable battery. As they have 7 cells inside the battery instead of 8, each cell can be bigger, and the battery has a higher capacity of 300mAh.

If you have mics that are less than 3 years old, we recommend the higher capacity 300mAh 8.4V batteries which will give you around 5-6 hours from a full charge. If you have older mics, go for the higher voltage 9.6V 230mAh batteries to ensure compatibility with your microphones. The 230mAh 9V’s will still give you around 4 hours of runtime.

At our church, a service is typically 90 to 120 minutes, plus a rehearsal of 90 minutes. The batteries are fine to run for the rehearsal time and the service. We use the 8.4V 300mAh batteries some of the radio microphones and in the wireless foldback headsets. Just last month we started using SHURE SLX radio microphones. We are using Powerex 2700mAh AA rechargeable batteries, and these are also lasting through rehearsal and the service. We recharge the batteries after every service, as the NiMH chemistry is fine to be topped up, and does not need to be fully discharged before recharging.

Low self discharge 9V batteries?

Is there such thing as a low self discharge 9V battery?

Well, no, not really. And due to the internal structure of a 9V battery, there is not likely to be one released using the technology used inside the IMEDION and eneloop AA batteries.

But does it matter?

According to some people, the Maha 9.6V batteries are of a high enough quality, that they are in effect a low self discharge battery. Here’s a comment from a Maha 9.6V battery user in relation to using Maha 9V rechargeable batteries in smoke detectors:

“…I consider a smoke detector application to be low power such that
the self discharge characteristic of the battery will be the primary
driver as to length of use before recharging/replacement. With the maha
9.6v batteries in a various detectors, the run time is somewhere
between 6 and 12 months before the “replace battery” beeper kicks in -
all depending on the specific detector. The combo ionization/smoke
detectors or CO2 detectors draw more current than just ionization
detectors. Will those 9.6v batteries still supply sufficient current to
signal a _loud_ warning buzzer or beeping close to the end of their
useful charge? There was a CPF thread a while back that discussed that
aspect at some length. I tested a few of these specific Maha 9.6v
batteries under something I thought was close to end of charge - I had
to plug my ears to let the detectors sound off long enough to be
believable. No problem….

…While a 9V battery with the label of “low discharge” does not appear to
be available, in my experience the Maha 9.6v battery possesses
sufficiently adequate electrical/chemical characteristics to come close
enough to a “low self-discharge” battery for my usage.

BTW, you really need to purchase the Maha MH-C490F charger that charges
four 9.6v or 9V cells intelligently in a few hours, not all night as is
usual with 9V charging stations. and then leave the cells on trickle
charge after charge termination for longer than an hour. I credit that
charger for saving 4 existing older 9v batteries from the recycling
bin. It took a few charging cycles but the old 9V batteries were
sufficiently rejuvenated to become useful again.”
bcwang

MH-C204W rapid charging and trickle charging process

Here is a question we received from a customer today. I thought it was worth sharing…

Hi,

I have MH-C204W battery charger I bought from you about 2 years ago. Its instructions sheet states \”do not mix batteries of different capacities ….\”. Your website states \”.. you can charge two different sets of two rechargeable batteries …\”. Is this true for all MH-C204W models or is this a later update to this product.

This is true of all MH-C204W battery chargers. The MH-C204W charges AA and AAA NiMH rechargeable batteries in pairs, and the pairs should match. However, you could have a different capacity and/or brand in slot 1&2 to what you are charging in slot 3&4. Similarly, you could charge a set of AA batteries in slot 1&2, and a set of AAA batteries in slot 3&4

I have also noticed that at the end of the quick charge cycle the batteries are only about 90% charged but leaving them on for another 2-3 hours adds another 8% or so to the voltage. Is this what should normally be done for a \”fuller\” charge\”?

The 204W will charge the NiMH batteries at a rate of 2000mA until they are almost full, approximately 97% of capacity. The battery charger then detects that the NiMH batteries are almost full by constantly monitoring the voltage, and it will switch to a 50mA trickle charge. If you leave the battieries in the charger for another hour or two, you will get another 2% or 3% charged capacity.

difference between MH-C800S and MH-C801D

The main difference between the MH-C800S and MH-C801D is the charge rate. The 801D charges at 2000mA, so 2700mAh AA rechargeable batteries take 1.35 hours to charge if completely flat, and 2100mAh low discharge AA rechargeable batteries take just over 1 hour. The 800S charges at 1000mA, so the 2700mAh batteries take 2.7 hours to charge if completely empty.

Both battery chargers have a “soft charge” function which will charge at half the normal rate.

The other difference is that the 801D has a commercial grade power supply with a DIN connector, whereas the 800S has a smaller wall-wart style power supply.

Which Maha Powerex battery charger should I buy?

Maha have several AA battery chargers to choose from. So which one is best for you?

This is a question we get asked a lot, so I thought I would pen a quick guide to help you work out which battery charger models models offer which functions and features:

Do you need to charge 8 AA batteries at a time? 800S 801D
Do you need to charge your AA batteries in an hour? 204W 801D 9000
Do you need to charge batteries from a 12V car adaptor? 204FA 401FS 9000
Do you need something super small for travelling? 204W
Do you need something affordable but still ’smart’ and reliable? 204FA
Do you need to charge cells individually, rather than in pairs? 401FS 9000 800S 801D
Do you need something to recondition batteries, identify problem batteries, and match your batteries into similar capacities? 9000
Do you also need to charge C and D cell batteries? 808M

11/2/08 EDIT: We have added a  Battery Charger Comparison Chart so you can compare the Powerex battery charger models you are interested in.

How do AA NiMH rechargeable batteries compare to AA Lithium Batteries in a camera?

We now sell Energizer AA Lithium batteries for $17.95 for 4 batteries. My Pentax K100D DSLR will get about 1400 non-flash shots on four of these lithium AA batteries. No other AA batteries can provide that many shots: I have taken about 660 shots from a new set of eneloop slow discharge AA batteries, and should get more once they have been used a few more times. Imedion slow discharge AA batteries should give me more photos than the eneloops based on reports on the whirlpool forum, but I havent tested that myself yet, as I’ve been too busy to do much photography lately. They’ll get a good workout over Christmas, and then I’ll update this post.

Since I take an average of about 500 shots per month, I would use about four sets of AA lithium batteries per year, and the cost to use lithium batteries would be $72 per year. Compare this to the cost of using rechargeable AA batteries at $21.95 for a set, and 4c to recharge them 4 times, and I am in front by $50 in the first year, which would be enough to pay for our most popular 4 bank AA battery charger. So while lithium batteries are great to keep for a backup, I’ll keep on using rechargeable batteries for now.

How to recharge Eneloop and Imedion batteries for optimal performance and longevity

Eneloop  and IMEDION rechargeable batteries have a very slow discharge rate. This means they are more likely to have some power left in them when you recharge them.

If you are use a timer battery charger (also known as a trickle charger) to recharge Eneloop or Imedion  batteries, you need to completely discharge them first. If the Eneloop/Imedion batteries are only partly discharged, and you use a timer charger to recharge them, the timer charger doesn’t know they aren’t empty. It always assumes the batteries are empty, and the battery charger will charge the batteries for the set amount of time. This will give the batteries more charge than they need. This overcharging will heat the batteries and will reduce the number of recharge cycles you will get from the batteries during their lifetime.

To overcome this problem, use a Maha Powerex battery charger, and you can recharge Eneloops or Imedions without running them flat first. The Powerex battery chargers measure the delta voltage (change in voltage) of the batteries as they recharge, and as batteries reach full, the voltage chage stops, or goes into a slight negative Delta V, and will stop charging the batteries, ensuring maximum performance from each recharge. Also, by only charging the batteries until they are full, the batteries are not overheated, which maximises the life expectancy of your Eneloop or Imedion batteries.

MH-C9000 WizardOne FAQ

Here are a few Frequently Asked Questions regarding the Maha Powerex WizardOne MH-C9000:

What are the recommended charging and discharging current for my battery? 
The recommended charging current is 0.5C, or 0.5 times the battery capacity. The recommended discharging current is 0.25C, or 0.25C times the battery capacity. Here are some settings for common batteries:

2700mAh Charge: 1300mA Discharge: 700mA
2650mAh Charge: 1300mA Discharge: 700mA
2500mAh Charge: 1200mA Discharge: 600mA
2300mAh Charge: 1100mA Discharge: 600mA
2200mAh Charge: 1100mA Discharge: 600mA
2100mAh Charge: 1000mA Discharge: 500mA
2000mAh Charge: 1000mA Discharge: 500mA
1000mAh Charge: 500mA Discharge: 200mA
900mAh Charge: 400mA Discharge: 200mA
850mAh Charge: 400mA Discharge: 200mA
800mAh Charge: 400mA Discharge: 200mA
700mAh Charge: 300mA Discharge: 200mA
650mAh Charge: 300mA Discharge: 200mA
600mAh Charge: 300mA Discharge: 200mA

Is there a way to charge batteries without pressing buttons? 
Yes! The charger defaults to CHARGING mode at 1A if no button is pressed 10 seconds after inserting the batteries. This is the default auto charging mode and does not require you to program the charger.

My brand new Powerex batteries are showing a lower capacity than the label in the MH-C9000? Should I return these batteries? 
When tested using the REFRESH/ANALYZE mode, the capacity will be lower than the capacity on indicated on the battery. To obtain a capacity that is closest to the rated capacity, use the BREAK-IN mode, which is similar to the process used by manufacturers to test and rate the batteries.

Furthermore, most batteries have a typical and minimum capacity. The Powerex 2700mAh batteries, for instance, has a 2700mAh typical capacity and a 2500mAh minimum capacity. Therefore, a Powerex 2700mAh that tests to be higher than 2500mAh using the BREAK-IN mode is considered within specification.

The charger only allows capacity (in the BREAK-IN mode) to be entered in increments of 100 mAh. My battery is 2650 mAh. How do I enter that capacity? 
Simply round up to the next capacity. For 2650 mAh battery, use 2700mAh capacity.

Can I leave batteries in the charger? Does the charger keep the batteries topped off? 
Upon completing the charge, the MH-C9000 goes to a very slow charge current (less than 10 mA) to keep the battery topped off. This “trickle charge” stops only when the batteries are removed. It is okay to keep the batteries in the charger as the batteries will always be ready for use. However, exercise common sense when keeping appliances constantly plugged in the wall.
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 batteriesy 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. Even though the capacity on the screen is not increasing, 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, the batteries may not produce a sufficient end-of-charge signal for the charger to terminate correctly. Although the temperature sensors will safeguard from batteries overheating, a lower charging rate might not produce enough heat in the batteries to trip the sensors. If a 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 the second time voltage data is displayed on the screen.

I thought the charger is supposed to be precise. Why doesn’t the charging and discharging current reach the set values exactly?
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. Thsis is so that the 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 is not the battery’s capacity because there is already some charge in the battery, as well as the battery’s internal resistance. For example, a half used 2700mAh battery may only show a charging capacity of 1350mAh 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.” Discharge capacity is available in other modes, such as REFRESH & ANALYZE, BREAK-IN, DISCHARGE, and CYCLE. 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 the screen will display a black box containing either CHARGE or DISCHG. 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. 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 the memory always refers to the discharging capacity.

Using the CYCLE mode, why do I see a “0 mAh” capacity on the screen? What happened to the saved battery capacity?
A CYCLE consists of:
Charge > 1 Hour Rest > Discharge > 1 Hour Rest. This cycle will repeat for the 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 (including the 1 hour rest). During the rest, a zero capacity is displayed. As soon as the 1 hour rest period is completed, you can use the “UP” and “DOWN” key to access the capacities saved in memory.

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. A 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.

What is the maximum capacity supported by the MH-C9000?
The maximum capacity supported (in BREAK-IN mode) is 20,000mAh making it compatible with future technologies. In CHARGE mode the maximum capacity supported is 4,000mAh. If AA batteries reach a capacities higher than 4000mAh, the charger will stop charging them once 4000mAh is added to the cell. If the cell was removed and placed in the charger again, the MH-C9000 would add another 4000mAh to the AA battery, or stop when the cell was fully charged, whichever occurred first.

The manual makes recommendations for charging rates. How about discharging rate? 
Most NiMH batteries can accept a discharge rate up to 3 times its capacity (3C), however, a high discharge rate will yield lower capacity. For accurate capacity measurement, use the BREAK-IN mode which complies with IEC standards (0.2C discharge rate).

The charger cannot detect my battery. What can be done?
Virtually all batteries can be detected by the charger. If your 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 the battery not meeting the IEC standards for battery dimensions. You can try rotating the battery or placing it in another slot.

Can I use slow discharge batteries in the MH-C9000?
All NiMH batteries can be used in the MH-C9000 charger. Brands such as Sanyo Eneloop batteries and Uniross Hybrio batteries are all able to be charged and discharged in the Maha MH-C9000.

Is it OK to use the BREAK-IN mode on Sanyo Eneloop and Powerex Imedion slow discharge batteries?
Yes, this forming charge will assist in establishing a good internal formation of the batteries. Discharging prior to BREAK-IN mode is optional. Overcharging during the BREAK-IN mode does not harm battery as the charging current is very slow.

Why doesn’t the charger show “DONE” instantly when I insert fully charged batteries? 
The charger takes several minutes to detect whether or not a battery is fully charged. It is normal for the charger to put in a small amount of charge to fully charged batteries.

The MH-C9000 is showing “HIGH” error for my batteries, but the batteries charge fine in other chargers. What can be done? 
The MH-C9000 features a high impedance tester which can screen for a defective/damaged battery. Most consumer chargers on the market do not have this feature, and therefore will allow charging batteries that may no longer be suitable for use. Maha recommends that batteries triggering a “HIGH” error be disposed for safety reasons, as charging damaged batteries may result in overheating or explosions.  However, if you feel the HIGH error is due to a false detection, try charging the battery first in another charger, or drain the battery first using the DISCHARGE mode on the MH-C9000. This is recommended only for advanced users.

How does the MH-C9000 detect end-of-charge signals from the batteries? 
The MH-C9000 uses a combination of Negative Delta V, Zero Delta V, Peak Voltage, time and temperature to determine the end-of-charge. In addition, proprietary algorithms are used.

Can any battery charger recharge Maha PowerEx NiMH Batteries?

This is a question we get asked regularly, so here’s an explanation: Maha batteries will charge in any NiMH battery charger. Thats the short answer.

Now here’s the longer answer: Not all chargers are created equal

My first battery charger was an Energizer. The above image shows part of the back label. This is a timer charger. Timer chargers simply provide charge to the batteries for a certain amount of time, in this case: 15 hours. They provides the same amount charge to all batteries, irrespective of capacity. Thus their suggestion to remove (lower capacity) NiCD batteries after 5-6 hours. This type of charger will overfill lower capacity batteries, and probably not fill a 2700mAh AA battery, resulting in less performance on both counts. This is affectionately called a “dumb” charger.

You will always get better results in a charger which measures the voltage of the batteries as it charges, and stops charging when the battery is full. This ensures a full charge without overcharging, ensuring maximum battery performance, and maximum life for the battery. Smart huh? This is why they are called “smart chargers”.

Another type of charger is fifteen minute “rapid chargers”. They are hard on batteries, and will not competely fill the battery as much as a 60 to 100 minute charger. Charging batteries in 15 minutes also causes the batteries to heat up a lot and reduces the life of the battery.You will get a fuller charge and longer life from your batteries if you choose a charger that takes 60 to 100 minutes to recharge the cells.

Another way that a good charger extends the life of batteries is by offering a “soft charge” option. Some chargers have a 12 hour charge option, but unlike the “timer chargers” we have talked about, they utilise measurement of the change in voltage to prevent under charging or over charging the batteries. If you don’t need the batteries charged straight away, choose to use the soft charge option on your charger.
A slower charge will heat the batteries less, and provide even more life for your batteries.

NiMH batteries lose 1-3% charge each day when not being used. For maximum performance, use a charger with a maintenance charge to keep them topped up. Some chargers have a trickle charge option. A constant trickle will keep them full, but is more charge than they need. A maintenece charge will give them just enough to keep them full.

Maha chargers address all these factors, and thus provide the highest performance for your NiMH and NiCD batteries.

MH-C1090F 9V battery charger Frequently Asked Questions

How many batteries can I charge at the same time?

You can charge up to Ten 9V batteries at the same time in the Maha MH-C1090F 9V fast charger.

Do I have to charge 10 batteries at a time?

No. The MH-C1090F has ten individual charger circuits, so you can charge any combination of 1 to ten batteries.

How will I know when the batteries are charged?

When the batteries are fully charged, the LED beside the battery will change frm red to green. Each battery is charged individually, so it will be cahrged to it’s full potential.

Do I have to take the batteries out once they are charged?

No, when the batteries are charged, the 1090F charger will measure the slight negative change in voltage and know that the battery is at full capacity. It will then switch to a trickle charge to keep the batteries at full capacity until they are needed.

We tried using rechargeable batteries in our microphone but they went flat in the middle of a performance. How do we avoid this from happening?

Todays rechargeables have much higher capacities than even 2 years ago. Our customers are getting 3 to 5 hours from their microphones using the Maha 9V batteries and the Maha 490F or 1090F. This is enough for almost any performance! Rather than leave them in the microphone for several performances, take them out after each performance, and put them back in the charger.

Do I need to run the batteries flat to keep them in good condition?

The older NiCad batteries were succeptibe to the memory effect if not empties. NiHM batteries have a different chemistry, and do not require emptying. Also, the Maha charger uses a unique Flex Pulse charging method which conditions and enhances 9V rechargeable batteries as they are charged.

Can I use the MH-C1090F ten bank charger to charge my older batteries?

Yes. The Maha 1090F is compatible with 7.2V, 8.4V, and 9.6V batteries, so long as they are Rapid Charge Capable 9V rechargeable Batteries. It is also capable of capable of reviving older 9V rechargeable batteries which may no longer be accepting a charge.

We use a LOT of batteries. Is this charger suitable for commercial use?

The 1090F is designed for commercial or home applications. Many professional stage compnies use Maha battery chargers and 9V rechargeable batteries. The charger is very well made, and comes with a 3 year replaceent warranty.