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Old Jan 11, 2005, 1:17 AM   #1
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Just last week, I have experience a small problem with my PowerBase 2100mAh 1.2V NiMH AA batteries (2 pairs). These batteries came with a MAHA charger (can't remember the model), it's supposed to be an intelligent one, and offers a trickle charge. The problem, a pair of these batteries are under charged. I find this very odd because:

1. I do not interchange my batteries, in fact each set were color-coded to avoid such "accident".
2. I only use this seton my A70 and the company's A75, and both cam needs 4 AAs.
3. I always charge eachsets of batterytogether. No intercharging.
4. The charger and batteries are just about half-a-year old.


So the questions are:

1. Any idea what caused this?
2. Do I need to fully discharge a NiMH before recharging or can I just charge them as is? Any pros and cons to discharging?

Thanks.
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Old Jan 11, 2005, 5:09 AM   #2
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Definitely not Ben....no need to fully discharge nimh batteries at all. So my guess is...either 1 more more of the batteries are faulty. Or the charger could be faulty. nimh don't have memory effect ... they do have some kind of life span though...but should be for at least a few years of constant use. This is what I've found in general anyhow.
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Old Jan 11, 2005, 8:38 PM   #3
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Thanks Kenny. Good to know there's no need togo about the process of discharging them. Btw,my charger was MH-C401FS.


Edit: I just chance upon another thread regarding the Maha MH-C401FS, it seems that the charger does have an uncanny ability to charge the batteries at a "not uniform rate", I guess this was why some my batteries gave up faster than the other.

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Old Jan 12, 2005, 12:49 AM   #4
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Sincethe camera takes 4 batteries, how do you know that just two of your batteries were "undercharged"?

With the Maha 401, there's no need to keep track of pairs of batteries. Just charge all four together and wait til all the lights on the charger turn green.

There are a couple of reasons why you might have encountered short battery life.

First, different conditions can greatly impact battery life. For example, hooking up the Canon to the computer to download photos seems to eat battery power for me. Also, extensive use of the zoom motor is going to consume a lot of power. Likewise, shooting in very cold conditions is going to reduce battery capacity.

Second, NiMH batteries discharge just sitting in the camera. So, if the batteries had sat for a couple of weeks to a month, they could easily be down to half capacity.

Third, I have tried to discharge a set of 2200 maH batteries in a Canon A-75 with the LCD turned on, the flash on, the red eye light on. I gave up somewhere past 400 photos. This means that you may be recharging nearly full batteries. This is not harmful to NiMH batteries, but it can over time temporarily reduce the effectiveness of the charge. If you even encounter unusually short life after a recharge, you might want to fully discharge that set of four batteries by using themuntil the camera shuts off.

This is going to sound contradictory, but chargers can also get fooled by batteries that have been discharged too much. The charger falsely detects a full charge and shuts off prematurely. This can usually be corrected by putting the batteries back in the charger for a second go-round. I have found that the end-of-charge detection is sometimes more reliable in the 401's fast charge mode.
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Old Jan 12, 2005, 3:26 AM   #5
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hwc,

it's not really about what action can drain the batteries faster. but rather a set ofidentical batteries that worked together and charged together didn't get the same amout of charge. It's like A, B, C, and D powered my A70 together for 400 shoots output, and they are down to probably 5% of the capacity. I charged them for 2 hours or so, that would mean they should all be about 100%. But no, A and C are both 100% but B and D are just 50%. But of course I didn't know that yet until the A70 gave up at 150 shoots because B and D couldn't give no more. Anyway, the problem seems to be with the charger.

Discharging your batteries with the Canon A series is gonna be a pain. Use equipments with bigger motors, such as toy cars or the older model walkmans.

The contradictory statement you wrote. It does sounds contradicting, a charger whose suppose to know when fully charge was achieved could not really tell. But well, we did experience this enough to confirm your statement is true. Btw, yanking the batts and recharging them again was 1 way of how I found out that 2 of my batts are under charged.

thanks.
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Old Jan 12, 2005, 8:06 AM   #6
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I see..does this mean that the charger is faulty? I just use a maxell p2000/2001 charger for my nimh AA's. I just have two...for charging 2 by 4 sets of batteries at the same time if necessary. They work just great. Turns off by itself after it's finished charging as well.
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Old Jan 12, 2005, 11:44 AM   #7
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...ben wrote:
Quote:
hwc,

It's like A, B, C, and D powered my A70 together for 400 shoots output, and they are down to probably 5% of the capacity. I charged them for 2 hours or so, that would mean they should all be about 100%. But no, A and C are both 100% but B and D are just 50%.
I don't understand what you mean by charging for "about 2 hours". With the Maha 401, you should always charge until the red light for each battery changes to green.

If you are using the SLOW charge setting (300 mA), this could take as long as 8 hours for your 2100 mAH batteries, depending on how depleted the batteries were. If you pulled the batteries out of the charger before the lights turned green, it would be a pure guess at how fully charged they were and there could easily be signficant variations among the four batteries.

In the FAST charge mode (1000 mA), the batteries should be fully charged and the lights turned green in roughly 2 hours or less.

I use401 pretty much exclusively in FAST charge mode. All of the manufacturer recommendations I've read indicate that NiHM batteries prefer high charge rates and the "fully charged" detection is more reliable at higher charging currents because the change in voltage that has to be detected by the charger is more distinct. Trickle charging (or very slow charging like the 401's SLOW mode) really doesn't suit today's high capacity NiMH batteries.

In any case, if you just use your set of batteries until they reach the point where the camera shuts off, then put them in the charger and leave them on charge until the lights turn green, you should be back in business.
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Old Jan 12, 2005, 9:24 PM   #8
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Kenny_Leong wrote:
Quote:
I see..does this mean that the charger is faulty? I just use a maxell p2000/2001 charger for my nimh AA's. I just have two...for charging 2 by 4 sets of batteries at the same time if necessary. They work just great. Turns off by itself after it's finished charging as well.
I'm not sure if I should call it faulty or just unable to fully recognize if a battery is completely charged.


@hwc,

Let's put it this way, you have an A75, you have a 401 charger and your 4 AA2100mAh identical batteries. You fully charged your batteries, placed them in you A75, and went on a shooting spree. After 3-4 dozen shoots, A75 reports to you that your battery have run low. First, you would be confused because normally you should be able to take over 400 or so pictures with your 2100mAh. But nevertheless, you took out your batteries and charged them in your 401. After 2 hours or so, you see all your batteries are fully charged... as in green lights. Youyanked out batteries but with suspicions, count to 10 and placed them back in your 401. But what do you get? 2 green lights and 2 red lights. Wierd? Yeah, weird. You yanked them out again,count to 10 and put them back in the 401but still 2 green lights and 2 red lights. This time you decide to leave them in the 401. The 2 red lights turned green after an hour or so. You yanked them out, count to 10 and put them back in the 401, this time around they are all green lights. And still, you yanked them out, count to 10 and put them back in the 401 just to make sure that they are indeed green lights... and they are.

That's what happened. That's how I knew that 2 out of 4 of my batteries were under charged.
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