Need GOOD slow charger for HIGH batteries

My MH-C204F charges too fast for the really HIGH batteries I want to try to 'fix'. Is there a GOOD charger that terminates well for NiMH cells. Prefer single cell / channel. AA - 200Ma (NOT pulsed) AAA - 80Ma (not pulsed)

Trying to use the 100ma setting on C9000 does not work as it is pulsed charging with 2,000ma 1/20 of the time. HIGH condition batteries just don't charge at all by design. Similar issue with the c204F, it charges too much too fast also.

I think you're getting the point, as to why "HIGH" cells aren't really worth bothering with.

The best thing I can think of, to do what you want to do, is to look for a an old, used 14-16hr NiCd charger. These are around at thrift shops etc. and usually have a charge rate very close to your requirements. I just converted two 4 bay NiCd chargers like this (an Eveready and a Panasonic, that were identical, except for color and labeling), for parallel and series balanced charging of Li-Ion cells, using a hobby charger. I checked the charge current, before I did the conversions and it was ~150mA for "C" and "D" cells, and ~50mA for "AA" cells. You might give that a try.

Dave

InHisName said:

Is there a GOOD charger that terminates well for NiMH cells. Prefer single cell / channel. AA - 200Ma (NOT pulsed) AAA - 80Ma (not pulsed)

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The Duracell CEF20 charger is almost made to measure.Take a look at the PDF . The currents are about 40% higher at 280mA and 110 mA respectively but you get the functionality of single channel operation and smart termination.

PeAK said:

The Duracell CEF20 charger is almost made to measure.Take a look at the PDF . The currents are about 40% higher at 280mA and 110 mA respectively but you get the functionality of single channel operation and smart termination.

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I got that charger. It will charge a few of the HIGH batteries but it ALSO has a HIGH condition to kick out the charging.

More of my NiMH are approaching HIGH conditions and I have a number of LOW current usages that they will still work great at for a long time. IF I can get a decent charger to keep them pumped up. Prefer single charging cells so each can be managed by its own insertion time etc. OK cells can be charged without really awful ones confusing which is the bother.

Here is the desired specs:

• Charge 1,2,3 or 4 cells
• Charge AAA 45-70ma
• Charge AA 85-125ma
• NO timeouts or smart-alec terminations, just low current charging and use my watch and stick notes.
• Optionally nice to have a low current discharger function.

I have a Maha C9000 but it seems to always use 2000ma in pulses. I want LOW currents all the time. I also have MAHA C204F but that one seems to charge to fast and thinks the crap cells are full prematurely also. Most every charger I have investigated is WAY more than the above. I know I have missed many, so point me to what I am looking for.

You can point me to near matches too.

InHisName said:

I know I have missed many, so point me to what I am looking for.

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Um, did you read post #2? Made to order for your application. Cheap too!

Dave

I am also in need of something to deal with HIGH batteries, but in my case they are NiCd cells from my solar lights.

My C9000 and C800S reject them right away.

Even my 6 hour Rayovac charger rejects them, but it is labelled "NiMh Only".

If the CEF20 would accept NiCd cells, I'd try that.

What i would use is one of those AA-AAA 8X230ma chargers with discharger, its a most usable item for many things. but i dont know for sure if it will do HIGH.
why? because its slow enough for AA , but not slow enough for AAA, it has a discharger so you can get a few cycles in, which can reduce the high resistance, its Cheap, it does each battery as a single item , even though it is cheap.
they all still have timers for "safety" no biggee if you aint seen your batts in 9-12 hours , you dont luve them anyways
http://www.thomasdistributing.com/s...html?SP_id=&osCsid=a98rm8a91donrsllit8gi3gna7
sorta like this one. but NOT that one, it doesnt do singles.
http://www.zbattery.com/Vanson-Computer-Controlled-1-10-AA-or-AAA-Battery-Charger
looks like this one but 800ma is the adapter rate, not the charge rate, so this might be the same type of thing.
http://cgi.ebay.com/8-AA-AAA-batter...temQQimsxZ20100316?IMSfp=TL100316142008r14859
and certannly not that one,
http://www.batteryspace.com/ch-v698810channelssmartcharger20pcsaa2600nimhbatteries.aspx
and it really isnt this one, or is it?
http://www.batteryspace.com/search.aspx?find=6988
it might be this one the one with NO SPECS , grr.
oh wait, eureka , that is it
http://www.batteryspace.com/ch-v698810channelssmartcharger20pcsaa2600nimhbatteries.aspx
average of 220 mA charging current


they used to be easy to find, and for $25 USD too, so look around $50 is to much. they have v-drop termination, but dont expect any good AA to terminate using it, because the charge rate is to close to the c/10 thing so its a slow charger for AA. Times out at with about 2000ma charge in a battery, Tops off at a pulsed 25ma (23ma average) takes a full day to discharge and recharge a set, finishing by a very slow topping. and the full DAY+ is why it had to hold many many items and work singularly. we put Riser Feet on the bottom of it , because not enough air flow around it.

the exact one i use is a V6988, but there are many similars. its BLack its low profile, its from CHINA, and it has a red button to set discharge, and green/red leds for each single cell item, and its listed at 250ma. Vanson used to have junk just like it, and you could find one on e-bay everyday.
i can get it to CYCLE batts that would not start-up in other chargers, and that is what i wanted to do was get a few cycles in them. Without cycling (DISCHARGE) i wouldnt even bother to try, because without doing a full chemical changeup, you wont get the other chargers to work with it still.

the key factors for a charger like this for US were Many many cell items (8-10) slow charging but possible to have terminations (or it will fry AAAs) . about 200ma , these are 250ma with a stop and check that averages them out to 230ma. (close to 1/10c)
Must have Discharge function, because usable high resistance batteries are in great need of a few full cycles.
as far as them always charging high batteries, they wont ALWAYS, sometimes a battey might need to be put back on 2 times to get it going, or might need to be manually pushed on a power supply.

i also agree that High are not usually worth dealing with, unless they ARE high because you didnt deal with them. meaning if you have been USING/CYCLING them and they got this way they are complete trash not worth touching, they will probably also have high self discharge. if they are high due to the lack of use and cycles then you might have a battery that can be used in other STUFF , but still not a battery that is as good as some good new one.

Yeah the C9000 seems to test the cells with quite a hefty amperage to start with (if choosing a program which include charging - all except pure discharge). If cell voltage rises too much they're rejected. Unfortunately it doesn't make any difference for AA and AAA.

I'd say you don't need no slow charger. Not worth the bothering. But another low cost charger could be the thing you need.
Over the years I've collected a few of them. One that I find really good is the Tecxus TC 6000. It if able to charge cells which the other chargers refuses. Not a turbo charger but reasonable fast as 500 mA for AAA and 1 A for AA and above. Only thing is that discharging is quite slow at 300 mA if I remember correct. In fact it's the charger I use the most.

Maha C9000 as you say has a tendency to deny high internal resistance AAA's regardless of they're really dead or still useable and it makes a high pitch noise. My Conrad Charger Manager 2010 is also very good and charges just about anything both fast and very gentle - it's even better than the C9000 - while still charging cells fully but that one has fans which are annoying (even changed them to quality ones).
So I mostly use the other chargers to verify the health of my cells. For daily use I mostly use the TC 6000 - it works fine and is noise free (at least to the human ear).

If you can find one, my Energizer CHM-39 has decent constant current rates and cut-offs, and it's surprising well built:

Bones said:

...

Fortunately, its primary charge rates are a bit more suitable for low self-discharge cells:

CHM39 Primary Charge Rates: AA = 170mA x 14 hours = 2380mAH | AAA = 80mA x 14 = 1120mAH | 9V = 23mA x 14 = 322mAh

Even better, it doesn't appear to trickle charge, so there's no concern with occasionally forgetting that it's in use.
.

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Most recently, I've been using it to keep a series of Energizer AAA cells alive for use in very low drain devices such as mice and seldom used remotes. They're now approaching 6 years old and still lasting 4 to 6 months between charges.

I've got a pair of MAHA MH-C124S chargers (55-80ma) which I haven't used in years, if you think one of those would help you out. They hold 1 to 4 AA or AAA cells. The datasheet says they have 4 independent charging circuits.

InHisName said:

More of my NiMH are approaching HIGH conditions...

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This is interesting. I wonder what you might be doing to these cells to make this happen to them?

There are two kinds of high internal resistance: reversible and irreversible.

Reversible is the so-called "memory effect", which is related to large crystal formations inside the cell and happens naturally if cells are stored without being used or if they are charged slowly. It can be reversed by using the break-in cycle on the C9000 one or more times.

Irreversible is when the cells dry out inside and is caused by severe overcharging or by over discharging cells in series so they become reverse polarized.

Another kind of irreversible change is when the cells have been through many cycles and have reached their natural end of life. If this happens you just need to dispose of the cells and buy new ones.

Good points Mr H. :thumbsup:

Mr Happy said:

Reversible is the so-called "memory effect", which is related to large crystal formations inside the cell and happens naturally if cells are stored without being used or if they are charged slowly. It can be reversed by using the break-in cycle on the C9000 one or more times.

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One way to determine if your cells are suffering from the above reversible condition, is to first do a 16hr 0.1C charge. Then discharge the cells at a slow rate, such as 100mA, on a charger that shows the capacity of the cells after the discharge. Unfortunately, the C9000 is not the best choice for this, as it pulses the discharge current (PWM) at 1A, but it can work. The BC-900(x)/700 does a better job, as it pulses at 500/350mA, making it about twice (or more in the case of the BC-700) as effective. Ultimately, a non pulsed, or lower pulsed current discharge is desirable, as the cells will be more effectively discharged.

If the discharge results in anywhere near the normal capacity, there is a good chance that the cells can be recovered with a few 0.1C 16hr charges, each followed by a slow discharge. On the other hand, if your cells do not come anywhere near the normal capacity after the first slow discharge, they are likely suffering from one of the other irreversible conditions that Mr H mentioned.

The point being, if the capacity is there, but you just can't get it out, except at slow discharge rates, the problem is likely large crystal formation in the cell, causing high internal resistance. If the capacity isn't there even at very low discharge rates, the likely cause is permanent damage to the cell, and there is little chance for anything but a temporary, partial recovery. Of course, you can still use the cells in wall clocks and such.

Dave

tsmccull said:

I've got a pair of MAHA MH-C124S chargers (55-80ma) which I haven't used in years, if you think one of those would help you out. They hold 1 to 4 AA or AAA cells. The datasheet says they have 4 independent charging circuits.

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If you would like to sell one, I could get interested.