Recommended battery charge rates in MH-C9000

We sometimes get asked: “what is the best charge rate to use in my MH-C9000 for my batteries?”.

We recommend 0.5C as a standard charge rate. That is 0.5 multiplied by the battery capacity. Here is an example:

0.5C charge rate x 1000mAh battery capacity = 500mA charge rate.

If you are in a hurry, you can use a charge rate up to 1C without concern of damage, but at 0.5C charge rate you will get a more complete battery charge. A slower charge will result in a slightly higher capacity, and it is easier for the battery to absorb the energy at a slower rate, which will contribute to a longer battery life. So why not charge even slower and get more charge capacity and more battery cycles from the rechargeable batteries?

Using a slower charge rate has a diminishing marginal benefit. Going any slower than 0.5C does not result in much difference to energy capacity or battery longevity.Futhermore, we recommend a minimum charge rate of 0.3C. Below 0.3C it is more difficult for the MH-C9000 to detect the change in voltage and know when to terminate the charge.

As a guide, here is a chart for our main battery models:

Will using a fast battery charger shorten my battery life?

The battery life of a rechargeable battery is affected by how hard you make it work when recharging. Aggressive battery charging will shorten the number of charge-discharge cycles you get from your batteries before you start to see a decline in capacity and/or performance.

The recommended maximum charge rate from most battery manufacturers is 1C, or 1 x the Capacity of the battery. For a 2700mAh AA battery, the maximum charge rate is 2700mA. A 15 minute rapid charger is very aggressive, charging at 4C. Absorbing the energy so fast will cause the batteries to become quite hot, and will shorten the life of the batteries. Any charger that takes 1 hour or longer to charge batteries will meet the 1C recommendations.

For example, The MH-C801D has a standard charge rate of 2000mA for AA batteries, so it is below the maximum recommended charge rate for our 2100mAh IMEDION AA batteries and our 2700mAh Powerex AA’s. The MH-C801D also has a SOFT CHARGE feature, which halves the charge rate to 1000mA, making the charging process even easier on the batteries. I would recommend using the SOFT charge feature whenever you have the time to charge your batteries at 1000mA, and feel free to use the 2000mA charge rate when you need batteries charged fast.

MH-C808M battery charger for rechargeable C and D batteries

Christmas is once again approaching, and for those people with kids, that means new toys, and new batteries to power them. While an increasing number of toys use AA batteries, many larger toys need the capacity of a C or D battery. The cost of powering those toys with disposable C or D batteries adds up, and contributes a substantial amount to landfill each year.

Rechargeable C and D batteries solve this problem, providing 3 times the power of disposable batteries, so the toys don’t need the batteries changed as often, and since each battery can be recharged hundreds of times, the landfill is substantially reduced by using rechargeable C and D batteries. Rechargeable C and D batteries are available in High Capacity Powerex C and Powerex D rechargeable batteries, and also as Accupower Low Self Discharge C batteries and Accupower Low Self Discharge D batteries. LSD batteries are great for toys and other devices which are not used regularly. The lower self-discharge rate of these batteries means they are ready to use when you need them, and are perfect for use in large Maglite torches.

To recharge C and D batteries, you need a battery charger capable of charging the C and D size batteries. While other C and D battery chargers do exist, the Maha Powerex MH-C808M C and D battery charger can charge 8 C batteries in 2.5 hours, or 8 D batteries in just 5.5 hours, and is also capable of charging AA and AAA batteries. It can charge any mix of different batteries at the same time, terminating the charge of each separate battery once the battery is full. By constantly monitoring the change in voltage (Delta V) of each battery, the battery charger ensures the battery is fully charged, but not over-charged. The status of the cahrge on each battery is also displayed on a backlit LCD screen, making it eacy for anyone in the family to use.

The MH-C808M includes a Conditioning feature to discharge batteries, which helps keep batteries heathey when they are not being used regularly. When conditioning/discharging with the MH-C808M, we recommended that you put the highest capacity cells toward the left of the charger as the heat from the discharge circuit is on the right. Higher capacity cells will generate more heat, so by keeping the higher capacity cells away from the heat, the charger and batteries will run cooler.

It is easy to see why Maha call the MH-C808M the “Ultimate Pro Charger”.

How to use BREAK-IN mode on the MH-C9000

The BREAK-IN mode ion the MH-C9000 is the perfect way to start your new rechargeable batteries lives. It helps to properly form the chemical structure inside the batteries by charging and discharging them gently, at a fixed charge and discharge rate, which is proportional to the capacity. BREAK-IN mode is also useful for rejuvenating old batteries that have not been used for several months.

Doing a BREAK-IN cycle on the MH-C9000 is a 39 hour process, irrespective of battery capacity. To do a BREAK-IN on your AA or AAA batteries, I recommend you discharge the batteries first. This is not necessary, nor is it mentioned by MAHA in the MH-C9000 user manual, it is just a personal preference. To discharge the batteries, place a battery into the first slot, then use the arrow keys to move the mode to DISCHG. Press the ENTER key, and press ENTER again to use the default discharge rate. Discharge on the first slot will start. Repeat for each slot. If your batteries are fully charged, discharge will take 4-5 hours. Once each slot shows DONE on the LCD next to the slot number, remove all batteries, and wait 5 seconds.

Place the first battery into the first slot. Use the Up and Down arrow keys to select BREAK-IN mode. Use the Up and Down arrow keys to set the battery capacity. Press the ENTER button. Repeat this process for slot 2, 3, and 4.

The charger will charge at 10% of the battery capacity. For 2100mAh IMEDION batteries, the charger will calculate the charge rate as 210mA (0.1C) and charge at that rate for 14 hours. After 14 hours of charging, it will rest the batteries for 2 hours, then discharge at 420mA (0.2C) until it detects the batteries are empty, which will take around 7 hours. It will then rest the batteries again for 2 hours, then charge them again at 0.1C for 14 hours.

At the end of the 39 hours, the battery capacity will be displayed. This mode of the MH-C9000 follows the IEC standard for measuring battery capacity

to measure a battery capacity as per the standards set out by the IEC (International Electrotechnical Commission).

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 One Community 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 yet. 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.