New to recharging / MH-C9000 usage, beginner questions

I just got my first charger -- a used MH-C9000 with 26 Powerex 2700s and some cases for $25 locally off craigslist, which I think is a lucky deal.

The Powerex 2700s aren't particularly useful to me, but I'm going to offer to let my girlfriend's sister have a crack at them for her 3 young kids. I'll get myself some Eneloops or other LSD. Before I ship off the Powerexes I'm trying to get them into good shape with Refresh & Analyze / Break-In modes. The charger manaul says:

Group batteries with capacity within about +/- 5% of the rated capacity.

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What does this mean -- ( MAX( actual_capacities ) - MIN( actual_capacities ) ) <= ( 2700 * 0.05 )?

Also, when searching the forum re: this question I came across some posts where people were saying batteries should be discharged before being put through the break-in mode on this charger (maybe before the refresh & analyze mode too?). I didn't think of that, but it seems to make sense once I heard it. However, the manual says nothing of the kind. In fact it more or less explicitly tells you you can run refresh & analyze 3 times in a row, and run break-in mode 1-3 (or 4?) times in a row after that.

So what's the deal -- is it necessary or important to run discharge mode between break-in cycles and / or refresh & analyze cycles? If so, how could they not mention that in the manual? If you don't need to do it, then how does that work, pumping all of that current into already fully charged batteries?

I got a printed manual with the charger, but I immediately went to find a digital version. I couldn't find one on Maha's website, so I searched the web and at this point I've found 2 different versions of the manual, neither of which match my printed one. I'm sure they're mostly the same, but one difference I've noticed is the instructions for inserting batteries. My printed manual explicitly says to insert AAs positive end first and AAAs negative end first. This one communicates the same thing by illustration only and this one says to insert the negative end first, period. What's the significance of how you insert the battery? Is it just trying to tell you the easiest way to do it, or is there some more serious effect? And either way, why does it vary between these different versions of the manual?

So far I've been inserting AAs positive end first and haven't had any trouble. Sometimes it's tougher to get them out though. What's the best way to do that? Somewhere I saw someone say that this charger has a habit of ripping casings, and I could see how that would be, considering the snagging I'm running into when removing batteries. And it may just be a coincidence, but one of the batteries I got with the charger is missing the casing (should I recycle that one?).

Another difference is that my printed manual and the second PDF above say that refresh & analyze mode rests for two hours, while the first PDF above says it rests for one hour.

Thanks for your help

I wouldn't bother using the refresh/analyze/break-in stuff. It may be of some use to old batteries that are dying a slow death, but new batteries (especially LSD cells like Eneloop) should have no problem with just using the regular charge method regardless of how long it has been since they were last used. Breaking them in when new may give you a few extra percent capacity, but you'll get that anyway after using them a few times.

Antares said:

What does this mean -- ( MAX( actual_capacities ) - MIN( actual_capacities ) ) <= ( 2700 * 0.05 )?

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When using rechargeable batteries in sets, the closer they are in capacity, the less likely that one will be driven into reverse charge. After analyzing the capacity of your batteries, you should group them by capacity when using them in sets, e.g., if you need 4 batteries for a device and you have a choice of 2440 mAh, 2445 mAh, 2525 mAh, 2570 mAh and 2680 mAh, use the first 4 together (2570 - 2440 = 130; 130 is less than 5% of 2700); do not use the last 4 together (2680 - 2445 = 235; 235 is greater than 5% of 2700).

So what's the deal -- is it necessary or important to run discharge mode between break-in cycles and / or refresh & analyze cycles? If so, how could they not mention that in the manual? If you don't need to do it, then how does that work, pumping all of that current into already fully charged batteries?

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Since the 2700s are not LSD, they are probably discharged already but I would run Refresh & Analyze first rather than Break-In. Refresh & Analyze will detect a full charge and terminate. It is also a much shorter cycle than Break-In so I would do it first before deciding whether Break-In is required. Also, since the batteries are used, they may be so tired that they can't be reconditioned.

What's the significance of how you insert the battery? Is it just trying to tell you the easiest way to do it, or is there some more serious effect? And either way, why does it vary between these different versions of the manual?

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Do whatever works for you. It largely depends on the battery; the wrapper design on some brands wrap around the negative end more than others and are therefore more susceptible to tearing.

Another difference is that my printed manual and the second PDF above say that refresh & analyze mode rests for two hours, while the first PDF above says it rests for one hour.

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AFAIK, the current model rests 1 hour for the Break-in cycle and does a 2-hour rest/"top-up" phase during Analyse & Refresh but older models may have been different. But I've never timed it.

At least for the break-in, it is highly advised to do a complete discharge first. Just think the case to have a fully charged cell and apply a break-in on it - it will be exactly (and worse) like a dumb slow charger overcharging the battery for 16 hours!!! Given break-in is used to rescue batteries, especially the weaker ones will suffer excessive wear if they are not fully discharged first; I learned the hard way. I had such instances of batteries falling due to break-in (which were good enough just prior the break-in) because they were not being fully discharged in my attempt to improve a bit their capacity. Break-in is not needed on LSD, unless if you want to accurately determine the overall capacity.

Thanks for the replies.

Etsu said:

I wouldn't bother using the refresh/analyze/break-in stuff. It may be of some use to old batteries that are dying a slow death, but new batteries (especially LSD cells like Eneloop) should have no problem with just using the regular charge method regardless of how long it has been since they were last used.

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I don't know what you consider old, but I'm using it on used Powerex 2700s (not LSD). I'll be glad to skip it when I get some Eneloops or other LSD.

Yamabushi said:

When using rechargeable batteries in sets, the closer they are in capacity, the less likely that one will be driven into reverse charge. After analyzing the capacity of your batteries, you should group them by capacity when using them in sets, e.g., if you need 4 batteries for a device and you have a choice of 2440 mAh, 2445 mAh, 2525 mAh, 2570 mAh and 2680 mAh, use the first 4 together (2570 - 2440 = 130; 130 is less than 5% of 2700); do not use the last 4 together (2680 - 2445 = 235; 235 is greater than 5% of 2700).

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Ok, so it looks like I interpreted the instructions correctly.

Yamabushi said:

Since the 2700s are not LSD, they are probably discharged already but I would run Refresh & Analyze first rather than Break-In. Refresh & Analyze will detect a full charge and terminate. It is also a much shorter cycle than Break-In so I would do it first before deciding whether Break-In is required. Also, since the batteries are used, they may be so tired that they can't be reconditioned.

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On the first set I did Refresh & Analyze like 3 times and then ended up doing a Break-In. So for the next set, I figured I'd actually save time overall if I went straight to Break-In.

Yamabushi said:

Do whatever works for you. It largely depends on the battery; the wrapper design on some brands wrap around the negative end more than others and are therefore more susceptible to tearing.

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Ok, so I guess there's no significant reason to insert or extract the batteries in a certain fashion other than ease and to try to avoid tearing the wrapper? Why do different versions of the MH-C9000 manual specify different things about how to insert the batteries?

apagogeas said:

At least for the break-in, it is highly advised to do a complete discharge first. Just think the case to have a fully charged cell and apply a break-in on it - it will be exactly (and worse) like a dumb slow charger overcharging the battery for 16 hours!!! Given break-in is used to rescue batteries, especially the weaker ones will suffer excessive wear if they are not fully discharged first; I learned the hard way. I had such instances of batteries falling due to break-in (which were good enough just prior the break-in) because they were not being fully discharged in my attempt to improve a bit their capacity.

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If that's the case, how could they fail to mention that in the MH-C9000 manual?

Also, since posting here, I noticed that the MH-C9000 FAQ on thomasdistributing.com says that you don't have to discharge prior to running Break-In mode and that it won't harm the battery to do so (run Break-In without Discharge first).

Antares said:

Thanks for the replies.

...
If that's the case, how could they fail to mention that in the MH-C9000 manual?

Also, since posting here, I noticed that the MH-C9000 FAQ on thomasdistributing.com says that you don't have to discharge prior to running Break-In mode and that it won't harm the battery to do so (run Break-In without Discharge first).

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The manual fail to mention several things and mentioning something like that would possibly move away several users from doing that process or considering it an easy-to-use feature. They fail to mention maha discharges at 1A pulses even if you set a discharge of e.g. 200mA only. The break-in has two reasons of existence: 1) determine capacity 2)attempt to saturate a weaker battery so to bring it to normal performance again. For good cells, if the battery is fully charged and you do a break in without discharge, they just take a good abuse and shorten the life of the battery, this is common sense really. The case is 0.1C is just minimal enough not to do major damage right away. Would you put fully charged batteries in a dumb charger for 16 more hours to charge even if the charge rate is slow enough i.e. 200mA (this is 0.1C on a 2000mAh battery)? This gets much worse if we have a weak cell. The big "pitfall" here with maha in our attempt to rescue weaker cells is the 1A pulsed discharge performed. Weaker cells may be able to provide almost all their capacity but they may be unable to deliver 1A current at any given time (they wouldn't be weaker cells otherwise, would they?). I had such a battery, which delivered about 85% capacity and had an IRC of 1.75 (it could provide that 1A current), placed it on break in after discharging it first, the break in filled the battery, the battery right after the fill-up failed to deliver that 1A for whatever reason (it may could deliver e.g. 950mA current) and of course maha reported 0 mAh capacity obviously. Then it started another 16 hours charge at an already fully charged battery. The outcome of this was a battery that registered an IRC of 2.75 just right after that break-in and it was of course useless!!! Do you believe they would write down something like that in the manual? I've learned the hard way and the outcome is, always fully discharge before a break-in and if the discharge can't be done with maha (due to the 1A pulsed discharge) find another means to do it before a break in.