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Old Oct 14, 2003, 5:30 PM   #1
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Default My Canon A70 is very picky with NiMh AA batteries. Pls help!

My month old A70 behaves very strangely in respect to NiMh AA batteries. When I 1st got A70 I immediately inserted 4 Kodak 1600 MaH AAs that I removed from my main Olympus C-5050Z camera. Batteries were recently topped and Oly was working fine with them. A70 simply wouldn't switch on displaying "'Replace battery pack" message and shutting off! Then I returned same batteries back to Olympus which happily switched on and continued to make shots just fine. Same story happened with a backup set of GP 1700 batteries - Oly's happy, Canon throws. Only when I fully charged the batteries A70 became happy. By the same token Canon would refuse 1/3 drained alkalines that Oly will happily use. Moreover, after meager 50 or so shots A70 rejected batteries with the same message while Oly accepted same leftovers.

That all seems really strange considering that it's C-5050Z with much bigger LCD, heavier zoom lens, bigger flash and more demanding internal processing should be much more picky about not enough juice in batteries. All professional reviews of A70 (Imaging Resource, DP Review, etc.) that did battery life testing indicate that A70 has a formidable stamina and is much better in this respect than Olympus C series.

All above made me to believe that I have a defective unit and I exchanged it for the new one making sure it came from a different batch. I couldn't believe when same story repeated with a new A70! Same thing - it'll switch on only with the fresh set of NiMh or alkalines. Anything about half drained will be rejected while supposedly much more power hungry Olympus will happily go on on the same batteries.

Did anyone observed same behavior? Any ideas about causes? What NiMh brands you have success with A70?

Admittedly my all 3 sets of NiMh batteries are about few years old and by now should be pretty worn out by few hundreds of recharges by MAHA C204F charger. Could it be that Canon is more picky about characteristics of power delivery of old batteries? Or maybe it doesn't like certain NiMh brands (MahaCell, Kodak, GP) other than Canon's own rechargeable pack?

I'll appreciate and help. Thanks a lot!

PS. Just please don't tell me I have another defective unit, I already past my 14 days return period
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Old Oct 14, 2003, 6:07 PM   #2
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It seems that many problems are not just down to the batteries but the monitoring of their charge state which is usually done using the terminal voltage. Look at some of the probs with proprietary packs and their 'intelligent' on board charge monitoring chips.

The camera has to give reasonable advance warning of low charge and this is pretty difficult just relying on terminal voltage. However if the measurement of capacity remaining is too optimistic you'll get a battery fail during media write and that's a disaster.

I'll bet if you put 4 AA alkalines in the camera with a terminal voltage of 1.5 volt per cell you have no probs - at least as long as those batts can reasonably last.

Elsewhere I posted about cell voltage after charge. Some of my batts were at 1.3 volt, others at 1.48. A new set charged a couple of times can consistently show the higher voltage. The lower voltage cells can usually be 'revived' by fast charging a couple of times.

So, I think the cam maker has a problem. The terminal voltage of NiMh is not as consistent as might be expected with used cells, possibly not even across brands. I don't think my batts are widely different in charge state, but I am going to do some experimental discharge tests. They all come off the charger warm to hot but the terminal voltage variation which is crucial to what the camera measures is a puzzle. Even worse if the camera uses this to retract the lens and shut itself down - as I don't believe my lower voltage batts were significantly discharged.

My advice is to use a digital voltmeter and compare your older batteries coming off the charger with newer ones. If this is a persistent problem with owners, Oly may eventually have a firmware fix they call a warranty repair, which just recalibrates the battery monitor to set a lower level for warnings - so try complaining first. Incidentally are your camera and batteries at unusually high or low temperature where you are? VOX
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Old Oct 14, 2003, 9:30 PM   #3
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Originally Posted by voxmagna
My advice is to use a digital voltmeter and compare your older batteries coming off the charger with newer ones.
This is absolutely correct. Many digital voltmeters (even very cheap ones) have a 'battery test' facility. This measures the voltage across a standard resistor, i.e., the current delivered under load, and is a much better indication of battery condition than the off-load (open circuit) voltage.

For example, my very cheap Caltek DVM uses a 37ohm load on its 1.5V AA battery test range, and says 40mA is a 'working fine' current, (having been designed for 1.5V disposable cells).

My oldest, cheapest, recently charged set of 1300mAh AA Ni-MH cells all give 37.2mA on 'battery test' and 1361 or 1362mV open circuit voltage, and I conclude the set is well balanced and in good shape. Using both o/c voltage *and* discharge current through a standard load would probably reveal the rogue cells that are causing everyone's problems.
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Old Oct 15, 2003, 4:38 PM   #4
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Hi, What I can't figure out though is once a I've identified a 'rogue' cell (or actually a pair), 2 or 3 recharges often fixes it. UNLESS it's because the charger is charging in pairs or 4's and certain cells mixed with others never get the correct charge share. Of course in the camera it's the opposite - all batts are in series so the lowest charge batt. determines the shooting time.

So the answer seems to be use a charger which treats each battery separately, or monitor the terminal voltage as described and re-charge in pairs with those chargers fitted with a 2 cell switch.

If the charger only charges 4 at a time then you might never equalise the rogue cell, so pull out the bench power supply set for constant current, stop watch and diode, or flatten all of them to the same level of discharge - and re-charge. VOX
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Old Oct 19, 2003, 8:51 PM   #5
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Default Problem with A-70 Battery Life

The problem with Ni-MH batts mentioned in here are due to one or more of the following reasons other than having broken charger or cells:

1. Mixing Different Brands of Batteries - batteries from different manufacturers yields different performance. The internal resistance, capacity, nominal voltage, fully charged voltage, fully discharged voltages can vary quite a bit.

2. Mixing Cells With Different Life-Cycle Spent/Used - Batteries performance will degrade as they go though each charge/discharge life cycle. A brand new cell and a cell that has gone through 200 charge/discharge cycle will differ in their performance even in the case of from the same manufacturer. Mixing older cells and newer cells will decrease the set's performance.

3. Using 2-Channel or Single-Channel Charger - Charger plays a very important role in the performance of your Ni-Mh batteries. As you know, 2-channel chargers charge 2 cells at the same time and single-channel chargers charge 4-cells at a time. Either way, the charger treats the set as one cell and charge the set as one cell, not as individuall cells. Why is this important?

Some of you might have already heard that sometimes it takes 2 or 3 charge/discharge cycles to bring the batteries to their top performing state. Those situation usually only happens when you use a 2-channel or single-channel charger. It takes 2~3 cycles (conditioning cycles) to bring the cells to the same performance level (or specification) so when after the conditioning cycles, the cells are at closer specification and the 2 or single channel chargers can now charge the set like they are really one single cell per channel.

Here are some suggestions that can help maximize the life and performance for your Ni-MH batteries.

1. Use high quality cells. This is the most effective way of ensuring high performance. Different manufacturers produce cells with different performances. Depends on the materials used and manufacturing process, Ni-MH batteries may or may not have memory effects. Consistency and performance can also vary by the manufacturer. Obviously, higher quality materials will lead to better cells with less internal resistance and memory effects. The manufacturing process has very much to do with consistency of batteries. Batteries manufactured with fully automatic production process will yield more consistent result. Production processes involve human are prone to human errors/variations, and therefore would yield wider variation in batteries’ actual specifications. (I can’t tell you or black-mail which brand of the batteries sold out the are produced using semi-automatic production process.)

2. Use a high quality 4-channel charger. - A high quality 4 channel smart charger not only yields best performing batteries, it also allow you to get the most out of your batteries’ available life cycles. 4-channel charger has 1 detection and charging circuit for each individual cell. It can charge one cell instead of 2 or 4 cells at a time like the 2 and single channel chargers. 4 channel chargers are able to detect the individual cell’s condition and charge the cell using settings best suited for the particular cell’s condition. This way will make sure that your individual cells are fully charged using the best setting for the cell possible without having to go through the conditioning cycles.

3. Group cells with the closest possible characteristics. - For those performance enthusiasts, do this if you want the most out of your Ni-MH batteries. Using more that one cell together at the same time is consider the same as the battery pack applications in laptop computer. In manufacturing laptop battery packs, cells are tested, sorted, and grouped according to their internal resistance, capacity, and nominal voltage. This will ensure that the battery pack will yield maximum possible performance and life cycles. Below are the steps to test and group batteries for best possible performance.

a. Use batteries with close internal resistance. - Since not too many people have the professional equipment to test the batteries' internal resistances and actual capacities, the easiest way to have the close range in internal resistance and capacity is to use batteries from the same manufacturers produced (and bought) at the same time.

b. Measure, label, and sort each cells according to their nominal voltage. - Fully charge (a 4 channel charger recommended) and then discharge (use it on your camera until your camera ask you to change the battery) the batteries. After discharge the batteries, take them out from the camera and let them set for at least 1 hour. (For brand new cells before initial charging, you can measure the voltage directly without going through the charging and discharging cycle first.) Measure each cell's voltage with the test meter, label the voltage on the cell and sort them according to the voltage measured. Use at least a 3 digit digital voltage meter or multi meter to test and sort the battery. For example, the meter must be able to read and display the voltage such as 1.35 volts, not just 1.3 volts.

c. Group the batteries that have closest nominal voltage. Group the batteries by the closest voltage measured according the your battery usage (2 or 4 cells at a time). - Group the cells that are closer in their voltage measured, the closer they are the better it is. Label the set with a permanent marker for future identification purpose. For example, if your camera uses 4 cells at a time, pick out and label 4 cells that have closest voltage to one another with “A”. Do the same for another set but label them with “B”. Use and charge the cells by the set you have sorted and labeled.

As in your case “albau”, your Canon A-70 may have a higher minimum operating voltage requirement than your Olympus C-5050Z. When Ni-MH are being charged, their voltage will increase to higher than their nominal (rated) voltage. That’s why your A-70 works when your batteries are fully charged. But as you use your camera (discharging the batteries), Ni-MHs’ voltage will drop as well. When the batteries’ voltages drop down to a certain level, your A-70 will refuse to function properly. In this case, it’s the voltage your battery provides that determine if your camera will operates or not, not the capacity of the battery. Rechargeable batteries are consumable products. Like a car battery, Ni-MH batteries’ performance WILL decrease as they go thru each cycle. The amount of time that your batteries provide the voltage needed by you’re A-70 will decrease as well. It’s time to get new batteries after they have gone through that many cycles. I suggest you getting 2,000mAh cells or higher to extend the up time of your A-70.

Any question about rechargeable battery? Don't hesitate to ask Mr. Battery.
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Old Oct 23, 2003, 12:47 AM   #6
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Great thread!

Too bad for those who don't have access to MAHA chargers, like me!

Still, I managed to find a french brand of a set of NiMH batts and a charger, and I even got 4 days out my Oly C-740UZ on a set! That was only after one cycle...
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Old Oct 29, 2003, 7:33 PM   #7
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Go with Powerex 2200 batteries.

You will not be disappointed!

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