NiMH Cycle Weirdness - What's going on here?

NiMH Cycle Weirdness - What's going on here? (Full Version)

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RickVB -> NiMH Cycle Weirdness - What's going on here? (7/26/2003 9:41:07 PM)
I have three brand new 1800mah NiMH packs that I got from OnlyBatteries.com. I am using my Dymond Super Turbo to charge them exclusively, always in a NiMH mode. I charged each one at a 200ma rate first; they each took from 1825 to 1875mah of charge. Next, I cycled them at 500mah discharge, 900mah discharge. Every time I cycle them (so far), the discharge and charge decreases! The second time I get about 1650mah both on charge and discharge, the third time about 1450mah, the fourth time I get about 1300mah. I haven't cycled any of them more than four times yet, but they've all behaved exactly the same. I haven't dinked with any of the default overall settings like voltage thresholds on the Super Turbo. What the heck is going on here???

Flying Geezer -> NIMH (7/26/2003 10:07:01 PM)
Try letting them cool for an hour, before discharging them.

Red Scholefield -> Re: NiMH Cycle Weirdness - What's going on here? (7/26/2003 11:15:36 PM)
[QUOTE]Originally posted by RickVB I have three brand new 1800mah NiMH packs that I got from OnlyBatteries.com. I am using my Dymond Super Turbo to charge them exclusively, always in a NiMH mode. I charged each one at a 200ma rate first; they each took from 1825 to 1875mah of charge. Next, I cycled them at 500mah discharge, 900mah discharge. Every time I cycle them (so far), the discharge and charge decreases! The second time I get about 1650mah both on charge and discharge, the third time about 1450mah, the fourth time I get about 1300mah. I haven't cycled any of them more than four times yet, but they've all behaved exactly the same. I haven't dinked with any of the default overall settings like voltage thresholds on the Super Turbo. What the heck is going on here??? [/QUOTE] Any idea of where OnlyBatteries.com gets their cells from? From their web site it appears you may have gotten some manufactured in China where some production lots are fine and others they are not. Good process control isn't something you can easily copy. Rapid capacity fade with cycling is one indication that the manufacturing process has slipped out of range somewhere. But you got them at a price almost as good as Radical R/C Sanyo packs.

RickVB -> Re: Re: NiMH Cycle Weirdness - What's going on here? (7/27/2003 7:05:42 AM)
[QUOTE]Originally posted by Red Scholefield But you got them at a price almost as good as Radical R/C Sanyo packs. [/QUOTE] Um, no, I paid $9.33 a piece for them; I don't think Radical R/C is anywhere near that. Small consolation if they're worthless. Do I understand that that is your diagnosis?

Geistware -> NiMH Cycle Weirdness - What's going on here? (7/27/2003 7:17:25 AM)
Red, at higher loads, would the voltage drop lower even though the available capacity is the same. I would think that a 1650maH pack with a 200ma load will have a higher voltage at 10% of rated capacity remaining compared to the same pack, same remaining capacity with a 1000ma load.

Red Scholefield -> Re: Re: Re: NiMH Cycle Weirdness - What's going on here? (7/27/2003 4:48:18 PM)
[QUOTE]Originally posted by RickVB Um, no, I paid $9.33 a piece for them; I don't think Radical R/C is anywhere near that. Small consolation if they're worthless. Do I understand that that is your diagnosis? [/QUOTE] That is the best shot I can give without having the samples in hand. :cool:

RickVB -> Update (7/29/2003 11:45:37 PM)
Red, the last three cycles (I'm up to seven) on one pack has leveled off to about 1650mAH charge, 1500mAH discharge after 24 hours. This seems to fall within the +/- 10% expected capacity and 10% charge loss per 24 hours rules-of-thumb. Are these still throw-aways in your opinion?

Red Scholefield -> Re: Update (7/30/2003 12:18:33 AM)
[QUOTE]Originally posted by RickVB Red, the last three cycles (I'm up to seven) on one pack has leveled off to about 1650mAH charge, 1500mAH discharge after 24 hours. This seems to fall within the +/- 10% expected capacity and 10% charge loss per 24 hours rules-of-thumb. Are these still throw-aways in your opinion? [/QUOTE] I wouldn't use them in my best plane, but if you keep your eye on them, preflight loaded voltage check, etc. You might get some decent use out of them. Particularly if they seem to finally settle out and the capacity stays fairly constant for a while.

IronZ -> NiMH Cycle Weirdness - What's going on here? (7/30/2003 12:09:41 PM)
Did you do some slow charging, without peak detection, to "form" the batteries? Might be worth a shot. IronZ

RickVB -> NiMH Cycle Weirdness - What's going on here? (7/30/2003 7:34:11 PM)
[QUOTE]Originally posted by IronZ Did you do some slow charging, without peak detection, to "form" the batteries? Might be worth a shot. IronZ [/QUOTE] My understanding that ~C/10 is the rule for forming charge rate. As I wrote in the first posting, I charged them first at a 200ma rate. That resulted in a ~1850mAH charge.

IronZ -> NiMH Cycle Weirdness - What's going on here? (7/30/2003 9:16:00 PM)
Was that on the Super Turbo? They may be false peaking on the ST. I had to slow form my NiMH's 3-4 times on a slow multi charger without peak to get them to start peaking correctly on my Supernova. It is my understanding (and experience) that you need to form them without peak detection. You might want to give it a shot. IronZ

RickVB -> NiMH Cycle Weirdness - What's going on here? (8/1/2003 1:31:32 PM)
Yes, all the charging has been done on the ST. Each one has charged over 1850mAH the first time (at 200mA), and the dropped drastically. I tried different rates for the second and subsequent charges for each of them, including 200mA for the last one, and it didn't make any difference, I never saw anywhere near 1800mAH again.

elevator_up -> NiMH Cycle Weirdness - What's going on here? (8/1/2003 7:17:25 PM)
I had a similar problem once with firebird batteries (ie high discharge). I cycled 4 times at c/10, 2 hour min between cycles. It took a long time but it brought them back to normal.

Shortman -> NiMH Cycle Weirdness - What's going on here? (8/1/2003 11:13:07 PM)
break them in with a wall wart charger, not the Dymond Super Turbo...

RickVB -> NiMH Cycle Weirdness - What's going on here? (8/1/2003 11:40:20 PM)
[QUOTE]Originally posted by Shortman break them in with a wall wart charger, not the Dymond Super Turbo... [/QUOTE] How can you say the charger has [COLOR=crimson]ANYTHING [/COLOR] to do with the forming when the first charge ON THE SUPER TURBO has always been full rated capacity plus???

IronZ -> NiMH Cycle Weirdness - What's going on here? (8/2/2003 4:23:25 AM)
A nice slow charge is required to properly form and equalize the pack. You charged at the proper rate but with peak detection. NiMH's have the tendency to need a few slow peak-less charges to properly equalize. The first charge was capacity... but now they are not. If you research it, you will find that what I stated above is true. If you don't have a non-peak detecting charger, you can use a walwart, but it will take a WHILE. You may have some crap batteries or you may just need to do the above. We're just offering our opinions. IronZ

RickVB -> NiMH Cycle Weirdness - What's going on here? (8/2/2003 6:21:00 AM)
[QUOTE]Originally posted by IronZ A nice slow charge is required to properly form and equalize the pack. You charged at the proper rate but with peak detection. NiMH's have the tendency to need a few slow peak-less charges to properly equalize. [/QUOTE] The only difference between a wall wart and using the ST for this is that the ST charges to a detected peak before shifting to a trickle rate (which is set to 50mA) that is similar to the typical wall wart rate (50-60mA) anyhow. Since they generally sit for a few hours on trickle before I get to disconnecting them, I still don't see the difference...

IronZ -> NiMH Cycle Weirdness - What's going on here? (8/2/2003 9:21:04 AM)
The difference is simple. With the ST they can false peak. The cells aren't stable and the charger may pick up a peak voltage when in reality the cell is just not stabilized yet. I've had it happen on my SN. After a few non-peak charges, my batts have worked flawlessly. ANY good battery seller/manufacturer will tell you to do at least one break in charge without peak detection. Usually with NiMH's it is a few times. Good luck. IronZ

RickVB -> NiMH Cycle Weirdness - What's going on here? (8/2/2003 10:00:19 AM)
You're still ignoring the fact that the ST switches to trickle mode after the peak (note again the initial forming charge was only run at 300mA). 50mA is 50mA, is it not?

mauiglide -> NiMH Cycle Weirdness - What's going on here? (8/2/2003 10:03:33 AM)
I was just wondering if you tried charging/discharging on another battery maintainence system? See what the difference would be. I have a feeling that the charger you are using is false peaking and you do not have a full charge on the batteries. Good luck.

IronZ -> NiMH Cycle Weirdness - What's going on here? (8/2/2003 12:07:20 PM)
[QUOTE]Originally posted by RickVB You're still ignoring the fact that the ST switches to trickle mode after the peak (note again the initial forming charge was only run at 300mA). 50mA is 50mA, is it not? [/QUOTE] I'm not ignoring anything. Your ST goes to trickle mode. The trickle is adjustable from 0-250mah. Are you sure it is at 50mah? Also, how long do you leave it on the charger after the peak is detected? I just received two fresh NiMH packs from RadicalRC and after one slow charge on the walwart, I cycled and charged it and it peaked at 284ma. Now it goes to trickle, guess what, it is going to take a LONG time to top off don't you think? I'm a little confused as to why you are arguing against the forming process. If you want to hear that they are junk batteries, then fine, they are junk. I would personally try everything before I pitched them. As stated before good luck. That's all I have. IronZ

Shortman -> RICKVB (8/2/2003 12:40:02 PM)
Rick VB your still ignoring the fact that you need to form the pack with a break in charge by a wall wart charger... Trust me, I have the Dymond Super Turbo charger, and 3 NiMh packs to prove it... the Dymond Super Turbo doesnt form a NiMh pack because it fast charges it before it goes into trickle charge mode.... read this from radical rc and then you will see Radical RC Dave (a battery expert) [QUOTE]Here are the basics for getting the best out of your new battery packs. First and foremost! NEVER NEVER put ANY new battery on a Peak Predictor / Delta Peak or any other type of fast charger without giving it a break-in charge at C/10. Capacity 10 is the overnight un-terminated safe charge rate for NiCad and NiMH cells. You can plug it in and forget it. If you have a 280mah pack of any cell count, the C/10 rate is 28mah. This rate or less is what you need to break in the pack. A 1400 mah pack needs a charge rate not over 140 mah for its first charge. The charge rate can be less than C/10 but should not be over. Your charge time will be (Capacity X 1.6) / charger output in MAH. This will give you the time to full in hours for a first charge. If you take a new pack and put it on a Delta Peak or Peak detect charger or any other kind of NiMH rated fast charger it will not be filled up. I don't care what the instructions say. I'm sure they say to never charge a new un-conditioned battery on them. If they do not tell you not to charge new packs on them then they are wrong. The voltage curve is measured and calculated by these chargers in order to predict the peak. The voltage curve is not normal on a brand new pack. It needs one slow conditioning charge before the curve becomes stable. Try as you may, you can't fill up a new battery on one of these chargers. After it's first C/10 charge, it will work fine. We've had many customers write us saying "I've cycled this pack 3 times now and it has not come up anywhere near where it's rating is." I remind them to put one slow overnight charge on the pack, they always write back and say "You were right! It cycles perfect now." So, we've been there many times. Don't suffer the frustration of trying to fast charge a new pack if you want the best out of it. After it's initial break in charge you can fast charge all you like. In fact, this is almost all I do with my personal packs [/QUOTE] now do you understand?

Shortman -> NiMH Cycle Weirdness - What's going on here? (8/2/2003 12:43:59 PM)
BTW, with a wall wart charger your 1800mah NiMh batteries are going to take 25.2 hours to charge... i highly doubt the Dymond Super Turbo took that long to trickle charge your packs

RickVB -> NiMH Cycle Weirdness - What's going on here? (8/2/2003 12:44:21 PM)
IronZ: OK, one more time. If you go back and read my earlier postings to this thread, you'll see this is all there. 1) EVERY pack charges to more than rated capacity (1800mAH) the FIRST time; 2) EVERY pack cycles to significantly less than capacity every charge thereafter, regardless of what rate the discharge and charge are carried out at (everything from 100mA to 1500mA); 3) EVERY charge cycle is allowed at least peak time plus four hours (1800/rate + 4), sometimes a lot more; 4) ALL charging has been done on the ST; 5) yes, I know how to use my ST, the trickle rate is set to 50mA. In the face of all that, I still don't see how you've identified anything in your process that's different from mine, other than the type of charger. You didn't even say what rate your example pack was charged at when it peaked at 284mAH; I said above I've tried about 10 rates between 100mA and 1500mA, all with the same result. Note that these aren't my first NiMH packs; I've formed and used about a dozen other ones before this fiasco. I ALWAYS use my ST. I don't intend to toss these unless they start to regress again; I guess I'm just looking for confirmation that others have seen this behavior or not. One other thing occurs to me about this: could it be the discharge end where the problem is occuring; that is my ST is not fully discharging them for some reason?

Shortman -> NiMH Cycle Weirdness - What's going on here? (8/2/2003 12:47:48 PM)
hmmmmm... well one suggestion, get radical rc battery packs with sayno genuine cells

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