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Old 05-11-2014, 11:17 AM
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Default MAHA C9000

I invested in the analyzer. I use Energizer 2300 ma batteries for my scanners. There are a bunch of charge/discharge rates. While I'm waiting for the charger, any recommendations on the settings? Thanks!


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Old 05-11-2014, 9:20 PM
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Lightbulb Use the lowest setting

I use 200ma for 2000mah batteries and 300ma for 2700mah batteries.

When I first purchased my C9000, I had just about every brand of NiMH battery available (Energizer, Panasonic, PowerEx, Duracell) and it was not too long before the charger refused to charge them. The C9000 will display "HIGH" because it detects the internal impedance of the battery to be too high (whereas those cheapo chargers may continue charging the same batteries for a year or more).

To make a long story short; as each brand of battery I had died off one by one, I replaced them all with Sanyo Eneloops. I use the 2000mah versions in analog scanners, and the 2700mah batteries in digital scanners and cameras. I love the low self-discharge rate they have. Now about 5 years after putting the first Eneloops into service, they are still faithfully charged by the C9000. Note that I don't believe in high charge rates as I feel it shortens the life of the battery.
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Old 05-11-2014, 9:22 PM
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Sounds good. Thanks for the insight. I've been using the Energizer batteries with the C801D charger, but I decided to go with the analyzer after trying to resurrect a couple of unused batteries from a few years back. Sounds like I made a good investment.
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Old 05-12-2014, 3:44 AM
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Quote:
Originally Posted by gmclam View Post
I use 200ma for 2000mah batteries and 300ma for 2700mah batteries.
Those low rates would be applicable only when doing a low current "break-in", ie about 0.1C of capacity. The Maha will figure this out for you when you initially tell it the size of the cell when doing a break-in.

For *normal* charging, Maha recommends using at least 0.5C (upped from 0.3C in older docs). In fact, it is factory default to charge 2000mah batteries, with 1A current if you do nothing more than install the batteries and walk away. This higher level of current is needed to accurately get a "delta-V" end of charge signal. Many of us think the default was specifically tuned for Sanyo Eneloops which are typically 2000mah capacity.

If you want to fine-tune it, say you have 2500 mah batteries, then you can manually override the default, and set it for a 0.5C in this case of 1200-1300 ma charge current. This will result in about a 2 hour charge and is actually preferable to extended slow-current charging, when you use modern batteries from this century.

When measuring the capacity of cells, you first charge them fully, and then take a measurement from the DISCHARGE cycle. You can manually discharge at a 0.2C rate like the manufacturers do. In other words, to test your 2000mah cell, you would fully charge it, and then manually set the discharge rate to 400ma. The Maha will give you the capacity after the discharge is done. Do NOT confuse the metered charge current to get to full capacity with the discharge capacity test. The dishcarge test is the one you want.

Instead of tying up the board here, you can review a still-active 8 year old thread on the excellent C9000 here and will help dispel urban legends that linger on from experiences in the 1980's.

Maha MH-C9000 SUPPORT / FAQ Thread

You paid for quality fast charging, along with a number of other features, so do not be afraid to let it do what you paid it to do.
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Old 05-12-2014, 2:41 PM
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I bought the Maha charger so that batteries would be charged in parallel, rather than in series (all of my scanners charge the batteries in series at 150ma); each battery could take the charge it needs and I'd see some relative health of batteries as they age.

I have read articles on the issue of properly detecting end of charge voltage as just posted, but yet to see issues related to it on the batteries I use. My issue is to get the longest life out of the battery, and as long as you don't overcharge, I don't see how a charge rate of 0.5C helps that (compared to a slower rate).

I'd like to see science on this not published by the charger manufacturer. Thanks
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Old 05-12-2014, 3:50 PM
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Talking maha c9000 charging rates

This comes from FAQ MH-C9000 - Maha Energy

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

these are the settings i use and never had a problem and owned a c9000 for about 2 years.
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Old 05-13-2014, 12:50 AM
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Quote:
Originally Posted by gmclam View Post
I have read articles on the issue of properly detecting end of charge voltage as just posted, but yet to see issues related to it on the batteries I use. My issue is to get the longest life out of the battery, and as long as you don't overcharge, I don't see how a charge rate of 0.5C helps that (compared to a slower rate).
Most everyone thinks that way, but they fail to take into account aging / capacity loss and internal resistance. The delta-v provides the most accurate end of termination signal regardless of battery state, whereas simple timing at low currents may work fine initially for brand new batteries, but that timing changes as they age - and if not adjusted by the consumer by measuring things like internal resistance, the battery is overcharged. What consumer has the gear to measure that?

Perhaps this may help - consider that early on the engineers at Maha consulted some of those in the Candlepower forum group for feedback on proper charging. Advice from Silverfox is highly recommended, although there is a litany of other knowledgeable members.

A look at slow charging

Note that the only timed charge cycle on the C9000 is the break-in. When you use the normal charge mode, and manually throttle the current too low (under 0.5C), there will be no delta-v termination signal, and the C9000 will fall back to other methods like temperature, or a termination on a high terminal voltage, like 1.48v per cell - which is a bit of overcharge.

In other words, you are now overcharging your cells by forcing the C9000 to fall back to other termination methods when you place them in anything but the timed break-in mode. Temp and battery terminal voltage are just two of the fallbacks - there are more, but they are proprietary.

Essentially, unless you absolutely know the percentage of discharge of EACH of your batteries, know the internal resistance value, and accurately calculate / offset the timed charge based on those parameters, the higher-current delta-v method (the signal comes from the battery itself) will net you longer life-cycle use.

Another tip: over the years, many charger and even battery manufacturers have mistakenly called 0.1C a trickle charge. It is not and is a slow-charge, which slow-roasts the electrolyte if left on long term. A TRUE trickle is 0.01C of current. Guess what - the Maha C9000 knows the difference, and when charging is done, leaving cells in the 9000 won't hurt them since it applies VERY low current - ie a true trickle.

Tip #2: Maha knows about the Peukert effect. When the delta-v termination signal is received from the battery, you can still put in about 100ma or so more capacity with a gentle top-off. Maha doesn't mention it, but it will supply about 60ma for two hours after the "done" indicator lights before falling to about 10ma trickle. Thus, if you absolutely need to have that last little drop of capacity, wait for two hours if you happen to actually catch the "done" indication light up.

One thing consumers fear is heat - and rightly so. But there is a difference between hot and too-hot-too handle. Nimh when charging is exothermic, and it is normal to feel warmth. If you can't hold them in your hand without immediately dropping them, then you have problems. This fear of any amount of heat also leads to the slow-charge-is-always-best mindset, not knowing that slow-roasting your electrolyte is a bad idea as well.

Basically, charge at a reasonably fast rate, let the delta-v do the signalling, and be done with it for best overall results.

Last edited by hertzian; 05-13-2014 at 1:27 AM..
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