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Old 03-12-2003, 02:04 PM   #1
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Default NiMh Conditioning

Ok. This post is to share my findings, which may be similar to what someone else has found... so any input would be appreciated! I am currently taking a test batch of 6 cell Sanyo 3000 packs and putting them through stress cycles and recording info as i go. I have a resistor bank comprised of 8, 50 watt 10 ohm ceramic resistors assembled with 1/4 inch hollow brass tubing. This was the same resistor bank i used that was part of a conditioning regimen for NiCd cells years ago when i had my own battery company. From the information i was given, this bank of resistors pulls around 85 amps. For the past year or so i have been charging my NiMh with a reverse pulse charge (duration of 16ms) and conditioning these packs with the resistors bi-monthly, instead of linear charging. Curious as to the condition of my packs, i ran them on a friends T-35 with a 6A charge, and a 30A dump (oval profile). Now since i am not used to using the T-35, i was curious as to the numbers i got, and if they were comparative to others of you that may use the same cell and T-35. Resistance was in the mid to low 20's, average voltage of each pack no lower than 7.05 (highest was 7.08), and run time in seconds at a 5.40 cut off was over 410 on every pack. Are these standard numbers? Or better than average? If these were 2000Mah NiCd cells i would know what i was doing, or comparing too! LOL A little more info... When i cycle the cells on the resistor bank, i take them down linear... as in... they are connected directly to the battery bars of the packs by being soldered in place via 12 gauge novak wire. Two 85cfm fans are pointed directly at the pack and the bank of resistors, and left connected till the resistors are cool (95 degrees). Cells come off in the 90 degree region, but reach well over 220 degrees, 2 minutes into the dump cycle. Am i actually doing any good for these cells... and if so... would this work on the new GP line of 3300? Thanks for any input you guys may have!
-Dave
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Old 03-12-2003, 05:54 PM   #2
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That is really, really, really high voltage for a 30 amp discharge....and really really high runtime. Can you send me some of those things you use? LOL. So wait, are you saying your resistor bank pulls down your cells at 85 amps to 0 voltage? Whatever that is...i want one lol...although that 220 temp sure is high....
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Old 03-12-2003, 06:15 PM   #3
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The company i got the resistors from is based in Nebraska. Vishay Dale Electronics is the company name, and at that time i was a dealer with a tax ID and all that. I dont know if they would sell to a regular person... which sucks... cause im a regular person now myself! At the time, i got 20 of them for $2.48 a piece. I am going to call them again, and see if i can get another order from them. I had a hard time locating them in the first place... no other electronics warehouses in the VA area carried them... and it was an old timer behind the local electronics shop counter that gave me Vishay's number. You say the voltage and runtime are high... what is normal? Is the resistance high too? I plan on purchasing some of the new 3300 GP, and if this is something that is working, i would like to duplicate it on them as well. (assuming the chemical make-up is similar from each brand of NiMh) Yes, the cells are dead when removed from the resistor bank...if you take a volt meter and drop it across the battery bars they may read .001 volt, but no higher. Once the bank is removed, the cells recover to the mid 3 volt range across the whole pack. Incidentally, peak volts when charging these packs hover around 9 volts. My oldest pack peaks at 9.310... its almost 10 months old... and loves a 10 turn! Let me know what you guys are getting numbers wise....I dont wanna have to buy a GFX to find out!
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Old 03-13-2003, 12:42 AM   #4
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If I understood you correctly, you are using 8 pcs of 10 Ohm/50Wt resistors? Probably connected in parallel, which makes the total resistance of the resistor bank 1.25 Ohm.
Voltage of a 6-cell pack at the beginning of discharge is ~7.5V, so the current would be 7.5 V/1.25 Ohm = 6 A. That's quite far from 85 amps, so something definitely does not match.
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Old 03-13-2003, 04:04 AM   #5
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Those figures at 30A don't ring true to me. 7.08v (average over the whole discharge) is higher than you would expect from a brand new pack. 410secs is over 50 secs more than my 3000HV's gave when brand new. I don't believe that a high load discharge and reverse pulse charging could improve the cells performance by that much.
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Old 03-13-2003, 06:24 AM   #6
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I can say it does work. A Friend of mine taught me this years ago for nicads and it almost works like a zapper and is much cheaper but I must warn you weak cells Will blow. As far as using it on Nimahs I've not tried it, the older cells were too tempermental but newer cells are almost treated the same as nicads - discharging and traying- so who knows.
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Old 03-13-2003, 07:01 AM   #7
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Olev... i could be wrong about the exact values of the resistors... i have had them for many years. The past few days i have been looking for the invoice to get the exact numbers, i stated the numbers best from my memory. Yes they are connected in parallel, and not in series. The best i can describe them is 5 inches long, 3/4 inch in diameter, and covered in some kind of black material to coat them. You can tell they are ceramic by looking on the sides, where the coating isnt present, and can see the white ceramic that is about 1/4 inch thick. The center is hollow, and there are tabs on each end of the resistors, not wire. These tabs have the 1/4 inch size hole that i have slid the brass tubing through to connect them all. When i ordered the parts, i told them i was lookin for resistors that would yield 80 to 90 amps of load when connected together... that was what they said would do the job. Since they were a reputable electronics warehouse... i took faith in their word.
Sosidge... as mentioned before, these are not new packs. I have been doing this to my 3000 for some time now. I would however like to buy some of the new 3300 and try it on them. It takes an average of 3 minutes for the voltage to drop below 5.4 volts. So i know it is a serious dump on the cells. I will see about some pics so you guys can see what im talkin about. Ill even see if i can get a pack on the T-35 again.. and take pics of that as well.
Overclocked... Thanks for the support... NiCd's really loved this treatment back in the day when combined with a zap (x2) on each cell AFTER the cycle when still warm. My guess was, electrons are most excited when heated, and more willing to take and deliver, and make most use of, a zap from a zapper. But then again... alot of this was all in theory. All i could do was go by what the Turbomatcher 4 was graphing out for me. What looked good and performed well with 2000 cells, may not with NiMh. Again, that is why i started this thread. Im sure there are lots of guys bored like me that spend time doing numbers on their packs! Thanx guys!
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Old 03-13-2003, 03:27 PM   #8
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Dave, the IR on those is actually pretty darn good for Sanyo 3000's. GPs seem to be a really tough cell...so i would like to see what happens.
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Old 03-13-2003, 06:36 PM   #9
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I think you should go back into business if you have 3000HVs with those numbers at thirty amps. I think all you have to do is look at the numbers on new packs in a shop to know the answer to your question, not ask us.... The IR readings are quite normal, but matching new, production zapped 3000HVs at 30 amps generally provides numbers from 330 - 378 seconds, with 1.10 - 1.16 V per cell. 410 seconds is actually really good for 3300mah packs at 30amps

My first reaction would be to check the "profile" of the machine and make sure it is discharging at thirty amps. It is not that I don't believe you, but maybe, since you borrowed it, and are "not used to it" in your own words, you may have missed something. The reason I say this is because the voltage looks very consistent with a 20amp discharge, and the runtime looks very consistent with a pack that has been "trayed" alot then discharged at 20 amps. From my experience, HVs, and Nimh in general for that matter, do not like to be discharged too far. The voltage gain is negligable and the run time drops away by up to 120sec at 20 amp.

Once you have confirmed that you have these numbers at 30 amps, start putting your packs on ebay and see how much people will pay for them!!
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Old 03-13-2003, 08:16 PM   #10
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Ok, so what you are telling me is, the numbers that come off a T-35 are the same as if i had disassembled the packs and run them independently on Turbomatchers and labelled them again? I assumed the software would most likely be similar... but i didnt think it would be relative. I am quite sure when he and i used his T-35 it was set on 30 amps. We used the oval discharge profile, 5.40 cutoff, 6A charge, 100 seconds to repeak at the same amperage as charged. He asked if i wanted to discharge at 35... i told him no... i wanted to compare what everyone elses cells were at 30... and 35 would skew the digits. I was very familiar with the Turbomatcher 4 menus... so scrolling through the T-35 wasnt a hard thing to do. Incidentally, he had some SMH from Trinity on hand and we did a few packs of his, which were ALOT lower in runtime, and the voltage was right at 6.99... but this was w/o the use of the resistors. Just as they were from the hobby shop. NiCd's back in the day with average 5000 runout, 5A charge, 20A discharge, .90 cutoff for 2000's usually yielded 1.14-1.16 at 370-400 seconds of runtime. When the resistors were used along with zapping (at that time i was doing a throttle curve discharge with a speedo and reciever ... the resistors hooked to the speedo in place of a motor... and my transmitter set for 10 second intervals on the lap timer to beep. When the transmitter beeped ... i dropped the throttle to neutral, and got back into it...and so on, till the pack was dead enough for the speedo to make a screaming noise (high frequency whine).....yes i cooked a few Cyclones till i figured the right profile and used no drag brake....) the runtime was raised an average of 20 seconds... resistance dropped to the high teens... and i had cells with 1.18 and 1.19 voltage. (when i matched my own cells i used a slightly different Turbomatcher setup) Incidentally... this treatment seemed to only last for a few cycles... and was maintained only by zapping each cell then charging at 10 amps EVERY use. At a 10 amp charge, peak volts (an indication of resistance) was low to mid 9 volt region. I definitely in no way am claiming this is all my doing... there were a few people in my area at that time (as i am sure they do elsewhere too) that were doing this similar thing to the batteries they owned... mostly oval guys. But i did spend alot of time tweeking how it affected NiCds. I no longer have access to a zapper... so i dont know the role it may play in this situation with NiMh. What i wouldnt do to be able to open a few cases of cells and go through experiments again! >sigh< Thanks for your input guys... when i get those pics (most likely this weekend) i will post them. And as soon as i get some 3300, ill let ya know what happens to them! (they will prolly detonate!)
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Old 03-14-2003, 03:04 AM   #11
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What has been done here by reverse charging, high current discharging, traying, zapping etc. effects heavily the porosity of the cells electrodes. More porous electrodes mean more surface area for the chemical reactions. This leads to more complete reactions and less internal resistance. So yes, it works. This has been known for ages. However, using these methods does not enable us to make the cells much better than what they were when new. Weak old cells can be made much better employing these treatments.
Normal numbers for todays top cells (GP3300) discharged at 30 A are: t=400s, R=18mOhm and V=6.35V.
You said you were dumping your cells after 3 minutes. That means that your discharge current is close to 50A. That is on average more than any class of racing. Thisi leads to the cells performing well the next time they are used. The opposite also holds true. If you discharge your batteries i.e. on a discharge tray I=0.5A or even use them in a 1/12th scale car I<20A means that they will perform badly the next time use use them. Same holds for charging rates also, but not so heavily. Pulse charging is also known to work to some extent. I mean charging with ~50A, having a pause, charging, pause... You get the picture.
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Old 03-14-2003, 06:39 AM   #12
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Quote:
Originally posted by DaveW
We used the oval discharge profile, 5.40 cutoff, 6A charge, 100 seconds to repeak at the same amperage as charged. He asked if i wanted to discharge at 35... i told him no... i wanted to compare what everyone elses cells were at 30... and 35 would skew the digits. I was very familiar with the Turbomatcher 4 menus...

Sorry to jump in here this late...

The "oval" profile on the T-35 is what is messing up your numbers. Neither discharge profile allows you to set the actual discharge current, both profiles vary the discharge current based on their own algorithms. The only way to get the actual discharge current you set on the T-35 is to NOT use either profile and just do a straight discharge. Otherwise, the value you set is ignored and the machine just follows the algorithm for whichever profile you've chosen.

Hope that helps,

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Old 03-14-2003, 10:37 AM   #13
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Yes Trips. That does make sense. So does what Jesse was saying. So i guess the only way of knowing is actually busting them down and running them on matchers. Man i hate grindin solder off the ends of cells! Aight guys... thanks for the input.
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Old 03-14-2003, 05:53 PM   #14
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Dave, you can just use the normal discharge mode in the T-35. No need to tear the packs down to run them on the Turbomatcher.
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Old 03-15-2003, 09:16 AM   #15
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Dave, GKC is correct, you can just run a straight 30 amp discharge on the pack with the T35, just don't choose the oval or offroad profiles and you'll get true numbers for whatever amp rate you specify. No need to tear your packs down.

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