Maha MH-C9000 SUPPORT / FAQ - continuation

clintb said:

Wow, 45/70, all that in and out of the charger sounds like one heck of a mess. I submit to you something easier for single cell discharging.

Viola!
http://www.integy.com/st_prod.html?p_prodid=1421&p_catid=199

Click to expand...

Agreed! If that unit worked with the cells in parallel, I 'd say it might be useful, however it states that a 4 cell charger is required. This suggests that one would use a hobby charger which would discharge the cells in series. That wouldn't be nearly as effective. The idea is to keep bumping each individual cell down to it's lower limit to break up any crystallization. This just won't work as well if the cells are in series.

I want to point out that I don't use, and am not recommending anybody use the procedure I outlined in my previous post, unless you really really want to try to revive some cells. As Tom loves to frequently point out, crap cells are just that, crap cells, but if you want to try one more time, just to make sure, then go for it!

Dave

Ah, the craptastic Integy webpage strikes. That unit actually discharges the cells without the use of an external charger. It does, however, have a switch so that you can hook up a charger on the back and charge the four cells in series.

For discharging, power with a 12V power supply and insert the cells. It has a diode to keep the cell from going into reversal.

clintb said:

Ah, the craptastic Integy webpage strikes.

Click to expand...

Good description! There certainly is (not) a wealth of information about the unit. I briefly looked at some of their other dischargers and was surprised to find some of them are recommended for NiMH cells/packs and have a 0.0 Volt cutoff. :thinking:

At any rate, that unit may do the job just fine. It's a bit pricey for something that, in my case, would rarely ever be used, if at all. Still, I guess if you were serious about reviving "crap cells" it'd be worth looking into. In the R/C world, of course, I imagine such units are quite popular.

OK, back on topic.

Dave

Mr Happy said:

When a cell is in such a bad way the break-in charge is the way to go; a refresh cycle is unlikely to make much improvement.

If you run your crap cells through a break-in cycle on the C9000 do they improve or do they remain high resistance?

Click to expand...

Finally finished running through my "crap" cells through a break-in. I discharged them all first, with one of the cells discharged through the CBA II at 2amp discharge using a cutoff voltage of like 0.2v. Watching the discharge, it immediately dropped down to like 0.5v, but slowly the voltage crept up to 0.9v and higher as it discharged. So something definitely was holding back the voltage potential that got better as power was pulled out of the cell.

Now this break-in with the c9000 might have done more bad than good, this is what happened.

-16 hours @250ma
-3 of the 4 cells on discharge was instantly done giving a reading of 0mah capacity. Only the one cell I did a high current discharge on gave a reading on the c9000, of around 1800mah (powerex 2500mah cell).
-Then they all did another 16 hours @250ma

Ouch! that means 3 cells just got 32 hours of 250ma charging with no discharging in between which probably hurt them even more than before. I'm going to do the high drain discharge on them to try to revive them the way I did for the one cell.

But this is one flaw I see on the c9000 that I hope gets addressed in future models. Pulse discharge with high amperage won't take enough energy out of the cell to condition them unless the termination voltage is revised. In my case, all 4 of these cells run great on the L1D on High for a long time, so they are very usable. If I just trusted the c9000 0mah capacity, I would have thrown them out. Now I have to re-evaluate a lot of cells I put in the "junk" heap since they actually might be ok still.

bcwang said:

Finally finished running through my "crap" cells through a break-in. I discharged them all first, with one of the cells discharged through the CBA II at 2amp discharge using a cutoff voltage of like 0.2v. Watching the discharge, it immediately dropped down to like 0.5v, but slowly the voltage crept up to 0.9v and higher as it discharged. So something definitely was holding back the voltage potential that got better as power was pulled out of the cell.

Now this break-in with the c9000 might have done more bad than good, this is what happened.

-16 hours @250ma
-3 of the 4 cells on discharge was instantly done giving a reading of 0mah capacity. Only the one cell I did a high current discharge on gave a reading on the c9000, of around 1800mah (powerex 2500mah cell).
-Then they all did another 16 hours @250ma

Ouch! that means 3 cells just got 32 hours of 250ma charging with no discharging in between which probably hurt them even more than before. I'm going to do the high drain discharge on them to try to revive them the way I did for the one cell.

But this is one flaw I see on the c9000 that I hope gets addressed in future models. Pulse discharge with high amperage won't take enough energy out of the cell to condition them unless the termination voltage is revised. In my case, all 4 of these cells run great on the L1D on High for a long time, so they are very usable. If I just trusted the c9000 0mah capacity, I would have thrown them out. Now I have to re-evaluate a lot of cells I put in the "junk" heap since they actually might be ok still.

Click to expand...

You didn't need to run 16 hours@250 mA, you could have taken it more gently as I suggested above:

Mr Happy said:

It shouldn't hurt, but if you're worried try running just the first 6 hours of a break-in charge and then manually interrupting it before trying a discharge again.

You might want to be conservative about the entered capacity too. Start with 2000 mAh instead of 2500 mAh until you know what the real capacity is.

Click to expand...

Even so it is unlikely it did much harm, probably just failed to do much good.

I bet if you put a good cell in your L1D it would run brighter than one of these cells? Given the cost of that light I wouldn't devalue it by running crap cells in it.

bcwang said:

I discharged them all first, with one of the cells discharged through the CBA II at 2amp discharge using a cutoff voltage of like 0.2v. Watching the discharge, it immediately dropped down to like 0.5v, but slowly the voltage crept up to 0.9v and higher as it discharged. So something definitely was holding back the voltage potential that got better as power was pulled out of the cell.

Click to expand...

You're wasting your time discharging under performing cells at high discharge rates. High discharge rates only draw from the smaller particles in the cell. It takes a slow discharge to break up the larger crystalline formations. Until you free up the compounds in the cell, I doubt any amount of forming will have much effect.

Dave

Depends what you mean by OK, I suppose. Were you charging at 200 mA, not 250 mA?

Dave, does the voltage recover because it starts drawing from the large crystals?

bcwang said:

...
But this is one flaw I see on the c9000 that I hope gets addressed in future models. Pulse discharge with high amperage won't take enough energy out of the cell to condition them unless the termination voltage is revised. In my case, all 4 of these cells run great on the L1D on High for a long time, so they are very usable. If I just trusted the c9000 0mah capacity, I would have thrown them out. Now I have to re-evaluate a lot of cells I put in the "junk" heap since they actually might be ok still.

Click to expand...

It it the MH-C9000's pulsed discharge at high amperage versus a continuous discharge at low amperage that's at issue here?

In other words, is it that a pulsed discharge at high-amperage to 0.9 volts draws out less energy than a continuous discharge at low-amperage to 0.9 volts?

Or, is the issue with the charger discontinuing the discharge at 0.9 volts instead of some lower voltage?

Mr Happy said:

You didn't need to run 16 hours@250 mA, you could have taken it more gently as I suggested above.

Click to expand...

Um, break-in mode on the c9000 of a 2500mah cell is 16 hours@250ma am I wrong? That was your gentle suggestion!

Bones,

I'm not sure what difference a pulsed discharge vs continuous discharge makes for helping condition a cell. The issue I mentioned is the fact that it terminates discharge when it hits 0.9v. which under a high pulse load means there is substantial energy in the cell left if that cell drops a lot of voltage under higher loads.

I can take that same cell that was instantly terminating discharge on the C9000 with it's 100mah discharge setting (1am pulsed at 10% duty), and get over 2000mah out of it with a true 100mah constant discharge to 0.9v on the CBA II, this is right after taking it out of the c9000 discharge mode with it reporting 0mah capacity.

TorchBoy said:

Dave, does the voltage recover because it starts drawing from the large crystals?

Click to expand...

The short answer is, yes. A cell with large crystalline formations will recover to a higher voltage than a cell in good shape, after being discharged at a high rate. The reason being that under heavy discharge, only the smaller particles (crystals) are able to sustain the load. The large crystals can't release energy as fast so their basicaly not involved (this is also one of the causes of "voltage depression"). At a slow enough discharge rate, the larger crystals don't have any problem supplying energy, and all seems well.

Here's an analogy. Compare 70 grains of Fg black powder to 70 grains of FFFFg black powder. They both have the same amount of energy, but the FFFFg being smaller granules, burns faster, and thus releases it's energy faster than the Fg. The Fg with it's significantly larger granule size burns slower and therefore releases it's energy slower, over a longer period of time. Pretty much the same thing is going on in the cells. Eh, maybe not such a great analogy, but hope you get the idea.

Back to NiMH cells, if you have "crap cells" there's really only one of two reasons that they're "crap". One is the separator is deteriorated. There's not really anything that can be done here. The other is the large crystal formation problem. The idea here is to break up the formations into smaller parts and then do a forming charge to mix the chemicals back into the mix. It's also important to mention here, that if you have a cell that has large crystal formations within it, and you charge the cell at a high rate, the crystals can cut into the separator and damage it during the process. At this point you have an irreparable "crap cell"

I'm no expert on this phenomenon, but when I first got my CBA II, I did a lot of research and playing around with "crap cells" Ask Tom, I'm pretty sure he thought I was nuts! It was interesting, because at low discharge rates, particularly near the end of discharge, you can actually see the formation breaking up. The voltage will drop slowly down and then suddenly shoot up. "Hey I busted up a crystal". Ahem, anyway I felt like I learned something of value from "crap cells".

OK, back on topic!

Dave

bcwang said:

I'm not sure what difference a pulsed discharge vs continuous discharge makes for helping condition a cell. The issue I mentioned is the fact that it terminates discharge when it hits 0.9v. which under a high pulse load means there is substantial energy in the cell left if that cell drops a lot of voltage under higher loads.

I can take that same cell that was instantly terminating discharge on the C9000 with it's 100mah discharge setting (1am pulsed at 10% duty), and get over 2000mah out of it with a true 100mah constant discharge to 0.9v on the CBA II, this is right after taking it out of the c9000 discharge mode with it reporting 0mah capacity.

Click to expand...

The early version of the C9000 measures the off-load voltage, which avoids this situation. Trouble is, discharges can take a loooong time with a crap cell - I guess you can't have the best of both worlds! (Well, maybe you could if this behaviour was selectable somehow, with a firmware revision....)

Cheers

bcwang said:

...
I'm not sure what difference a pulsed discharge vs continuous discharge makes for helping condition a cell. The issue I mentioned is the fact that it terminates discharge when it hits 0.9v. which under a high pulse load means there is substantial energy in the cell left if that cell drops a lot of voltage under higher loads.

I can take that same cell that was instantly terminating discharge on the C9000 with it's 100mah discharge setting (1am pulsed at 10% duty), and get over 2000mah out of it with a true 100mah constant discharge to 0.9v on the CBA II, this is right after taking it out of the c9000 discharge mode with it reporting 0mah capacity.

digitor said:

The early version of the C9000 measures the off-load voltage, which avoids this situation. Trouble is, discharges can take a loooong time with a crap cell - I guess you can't have the best of both worlds! (Well, maybe you could if this behaviour was selectable somehow, with a firmware revision....)

Cheers

Click to expand...

Click to expand...

Thanks, got it.

Incidentally, I have an original edition MH-C9000, and have observed the extended discharge times on certain cells.

Is it safe to conclude that those cells that take considerably longer than their brethren to discharge to 1.0 volts are not as healthy, and either closer to their recycle point or in need of more conditioning?

This is predicated on the cells being identical in all other respects of course.

Bones said:

Thanks, got it.

Incidentally, I have an original edition MH-C9000, and have observed the extended discharge times on certain cells.

Is it safe to conclude that those cells that take considerably longer than their brethren to discharge to 1.0 volts are not as healthy, and either closer to their recycle point or in need of more conditioning?

This is predicated on the cells being identical in all other respects of course.

Click to expand...

In my experience, yes. I use this behaviour as a good indicator of when to get rid of a cell - they are of no use to me if they won't hold at least a 1 amp discharge. (This hasn't happened with an Eneloop yet, they're all I use now).

Cheers

RE: 'CRAP CELLS' and attempting to use them as long as possible, I'm with you... :thumbsup:

45/70 said:

...I use crap cells in wall clocks, LCD thermometers, and such with great success. They run devices anywhere from 3-6 months between charges and have done so for years after turning into "crap cells". I'll be damned if I'm going to put a brand new eneloop in them! :nana:

Click to expand...

And, the fact that the BC-900 can further DISCHARGE cells that the MH-C9000 can't, YEP! :thumbsup:

45/70 said:

...When cells are this bad (ie. they won't discharge in the C-9000), it is absolutely mandatory to do a slow discharge before attempting the break in. You need to break up any crystallization in the cells, which I'm sure are present in this situation. The CBA is a great way to do this as well as discharge the cell, but as bc pointed out, it's takes forever. The BC-900 is a good alternative (sorry Maha). What I have done, is discharge the cells at 100mA in a BC-900. Pull the cells when the discharge stops...

Click to expand...

But, I don't understand this :thinking:

45/70 said:

...When you're totally sick of this phase, or your patience runs out, whichever comes first , charge them on whatever charger will work, at 1C for about 5 minutes, let them rest a few minutes, then go back and do the discharge routine again. It doesn't hurt to repeat all this 2-3 times...

Click to expand...

What does '5 minutes @ 1C... ...2-3 times' accomplish that a R&A Full Charge wouldn't? I.E., how does this 'cycle' any more chemicals?

45/70 said:

...When cells are this bad (ie. they won't discharge in the C-9000), it is absolutely mandatory to do a slow discharge before attempting the break in. You need to break up any crystallization in the cells, which I'm sure are present in this situation...

Click to expand...

For *REALLY* CRAP cells, YEP once again. :thumbsup: After a DISCHARGE with the MH-C9000 @ 100mA and then the BC-900 @ 100mA, for the *REALLY* CRAP cells, I use a 'Superman 1AA Flashlight *FREE* from Duracell' to further discharge the cell (I point the flashlight at where I'm sitting and end the discharge when the lamp 'suddenly' dims. At this point-in-time, all of the CRAP cells I've experimented with will recover to over 0.9VDC UNLOADED).

45/70 said:

...This is the only way I've found to do a proper break in on "crap cells". The theory is, if there are large crystalline formations in the cell when trying to form it ("break in"), the chemicals won't properly redistribute throughout the cell...

Click to expand...

We pretty much agree here - 'Break up the large crystals first!' :twothumbs

45/70 said:

The short answer is, yes. A cell with large crystalline formations will recover to a higher voltage than a cell in good shape, after being discharged at a high rate. The reason being that under heavy discharge, only the smaller particles (crystals) are able to sustain the load. The large crystals can't release energy as fast so their basicaly not involved (this is also one of the causes of "voltage depression"). At a slow enough discharge rate, the larger crystals don't have any problem supplying energy, and all seems well...

Click to expand...

Agree! I've seen some of my *REALLY* CRAP cells POP higher in voltage during discharge (on my BC-900) and, from what I've read on the CPF Archives, it's due to the LARGE crystals breaking up.

45/70 said:

...Back to NiMH cells, if you have "crap cells" there's really only one of two reasons that they're "crap". One is the separator is deteriorated. There's not really anything that can be done here. The other is the large crystal formation problem. The idea here is to break up the formations into smaller parts and then do a forming charge to mix the chemicals back into the mix. It's also important to mention here, that if you have a cell that has large crystal formations within it, and you charge the cell at a high rate, the crystals can cut into the separator and damage it during the process. At this point you have an irreparable "crap cell"...

Click to expand...

Huh? How??

From my readings of the CPF Archives (SilverFox), HIGH charge currents produce SMALL crystals and LOW charge currents produce LARGE crystals. So, how can a LARGE charge current cause existing LARGE crystals to puncture the separator more than a SMALL charge current?

Bones said:

...Incidentally, I have an original edition MH-C9000, and have observed the extended discharge times on certain cells.

Is it safe to conclude that those cells that take considerably longer than their brethren to discharge to 1.0 volts are not as healthy, and either closer to their recycle point or in need of more conditioning?

This is predicated on the cells being identical in all other respects of course.

Click to expand...

Please explain further - i.e. I don't understand your point.

Logically, how can a cell discharging @ XXXmA to 1.0VDC display THE SAME mAh capacity @ YY or YY+ZZ minutes? mA times hours equals mAh - right?

For "...those cells that take considerably longer than their brethren to discharge to 1.0 volts...", what is their mAh?

IMO bottom line, Capacity equals Capacity. I note what mA a 'calculated' Capacity is for and use my cells accordingly. (i.e. LOW Internal Resistance cells can supply a higher mA PER hour than HIGH Internal Resistance cells.)

TakeTheActive said:

Please explain further - i.e. I don't understand your point.

Click to expand...

When the C9000 (the first version) finds that a cell cannot sustain the requested discharge current without the voltage dropping too much it decreases the discharge current to a lower value and prolongs the discharge to help it complete fully.

I'm a little confused over this current size/crystal size thing too. Does lots of slow charging cause big crystals? I'm sure SilverFox said fast charging keeps cells vibrant. Or is it important to charge at about the same rate they'll be discharged at?

I tested a friend's Eneloops last night. He slow charges, but uses them in a digital camera (fast discharge if using flash?). They don't seem to hold a very good voltage, and before we left the cells to have dinner I noticed at least one had recovered 0.05 V (from 1.09 to 1.14 V). How much recovery indicates a significant large-crystal problem?

TakeTheActive said:

(i.e. LOW Internal Resistance cells can supply a higher mAh than HIGH Internal Resistance cells.)

Click to expand...

So Eneloop with its low internal resistance should have a higher capacity than high capacity cells with slightly higher internal resistance? Are you saying there's a direct correlation?

Mr Happy said:

When the C9000 (the first version) finds that a cell cannot sustain the requested discharge current without the voltage dropping too much it decreases the discharge current to a lower value and prolongs the discharge to help it complete fully.

Click to expand...

Is that deliberate, and a pulsed discharge current, or is it an underfed continuous current that would be a high pulsed current if it was able to? I suspect the latter.

Mr Happy said:

When the C9000 (the first version) finds that a cell cannot sustain the requested discharge current without the voltage dropping too much it decreases the discharge current to a lower value and prolongs the discharge to help it complete fully.

Click to expand...

Wel, not really - it seems that it is an unintended consequence. What is actually happening is that during discharge, the early version measures the voltage off-load, so the voltage of a high impedance cell is able to bounce back to a value of 1V or greater, therefore the 9000 keeps trying to discharge. As soon as the discharge recommences, the voltage sags so the discharge rate cannot be sustained at the programmed rate, therefore it takes longer.

Cheers