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Nimh/nicd ponderings...
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lincpimp
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Nimh/nicd ponderings... - 12.25.2010, 11:47 PM

Ok not for my electric rc but I do have a bunch of nimh 2000mah cells that I plan to make some cordless tool packs out of. That should be pretty easy so I will get to my actual questions.

With most tools they have something like sub c 2400mah nicd cells. Was wonder what the best way is to condition these packs? I came in on the tail end of nicd/nimh and never really fooled with them. I could cycle the packs with my hyperion 610i/1210i chargers.

I recently got a dead pack with a used tool purchase. The hyperion did not want to charge it, but I "jumped it off" with a 3s pack till the voltage got up a bit. The charger did charge it up somewhat. Then I put it in the craftsman "intelligent" charger and it seems to be ok? I am letting it sit to see if it self discharges really fast...

I do remember reading some sort of conditioning sequence for nicds. Also remember reading that it is good to occasionally charge a pack at .3amp as it helps the cell "self balance"...

Not sure if any of that is true or not, and some help would be greatly appreciated.
   
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12.25.2010, 11:53 PM

Found this, interesting...

http://blog.holyscraphotsprings.com/...batteries.html
   
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12.26.2010, 01:11 AM

Ok, so seeing that the mig welder puts out somewhere between 16-30v, and he said to max the voltage. Read somewhere else that a good rule of thumb was double the rated pack voltage, so a single nicd cell would require 3v or so.

Guessing that whipping up a nice high C rated large capacity 1s lithium cell to some heavy gauge wires with some sort of tip to do the pack cells 1 by 1 would work? Or do I need some sort of forced pulse, ala the welder? I have a nice big mig welder, and a few dead packs that I could experiment with.

I understand the basics of what they are doing, with the reverse pulse the effect is to remove the anode material from the cathode. (might have got the 2 terms switched there, been a while since basic physics) So why does he then swap over and recharge it with the welder? I am guessing this is similar to what the "matched and zapped" packs had done to them back in the day of nicds.

I did read elsewhere that doing each cell individually would provide better results, as not all of the cells may be as bad as others...
   
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12.26.2010, 01:47 AM

wait...


stop...



WTF are you talking about???





edit: OMG I watched the vid... this guy is ____ _____ _____ ____ crazy... yes the idea(of zaping batts) is true but what he is doing is the equivalent of amputating an arm/leg with a hacksaw


IMO its not realy worth it, pick up some used 3300nimh cells, and do a few low amp cycles, then a few high amp cycles and call it good...



damn I'm tired....
   
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12.26.2010, 02:41 AM

You could always pick up a charger that is specific for nicd, with the reverse pulse option. I have a Tekin bc112c (not for sale as i use it for tool packs also) which works very well. Here is one on ebay.
   
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12.26.2010, 02:47 AM

Quote:
Originally Posted by bdebde View Post
You could always pick up a charger that is specific for nicd, with the reverse pulse option. I have a Tekin bc112c (not for sale as i use it for tool packs also) which works very well. Here is one on ebay.
Very interesting. No idea this existed. What exactly does the reverse pulse do? Similar to the welder method?

Not sure I completely understand why the welder method is used with both reverse and normal polarity. Semms like the reversed polarity would discharge the pack, and the pos would recharge it... Not quite understanding which way breaks up the crystals... Need someone with more knowledge of dc to explain this to me...
   
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12.26.2010, 02:59 AM

Quote:
Originally Posted by lincpimp View Post
Very interesting. No idea this existed. What exactly does the reverse pulse do? Similar to the welder method?

Not sure I completely understand why the welder method is used with both reverse and normal polarity. Semms like the reversed polarity would discharge the pack, and the pos would recharge it... Not quite understanding which way breaks up the crystals... Need someone with more knowledge of dc to explain this to me...
From the Tekin manual

Normally a cell will noticeably begin to lose its edge and crispness to throttle
response after just a few hard runs. This is caused by a gradual buildup of impurity
nd crystal formation inside the cell, which is unavoidable. With each run the impuries
increase, resulting in increasing internal resistance, and therefore reduced voltage
nd power output. Discharging the battery fully after each run will help reduce this to
certain extent, but the only way to totally minimize this deterioration, and even actuly
reverse any previous deterioration, is to use the TEKIN Power-Flex process.
wer-Flex makes your batteries perform like no other charge process can, and
creases horsepower beyond what even a new fresh cell could deliver.
The Power-Flex circuit is a refined version of the Pro-Flex circuit introduced by
EKIN in 1989. Power-Flex works by periodically turning off the charge current, and
pplying a short-duration, high-amperage discharge pulse of negative current to the
attery. This so called “burping”of the battery acts to relieve the pressure buildup which
ccurs inside a cell during charging, and to restore its chemical balance. The net result
that the cell stays cooler during the charging process, and delivers more voltage and
apacity under a load. With the BC112, the amount of Power-Flex conditioning that
ccurs is computer controlled.There are three user-settable levels.
   
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hoober
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12.26.2010, 09:54 AM

Usually the very best you can do for the pack is a c/10 charge for 15 hrs. My experience is that all this other "stuff" doesn't work to restore any NI type cells.
   
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12.26.2010, 01:03 PM

Quote:
Originally Posted by bdebde View Post
You could always pick up a charger that is specific for nicd, with the reverse pulse option. I have a Tekin bc112c (not for sale as i use it for tool packs also) which works very well. Here is one on ebay.
Only issue I am seeing with this charger is that it is only good for 12cells... Need something that does at least 16. I guess I could use some sort of alligator clips to "break up" the packs to less than 12 cells.
   
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12.26.2010, 01:27 PM

I think you should first try a simple cycling process, before worrying about zapping, etc.

The voodoo tricks and zapping was going out of style somewhat with the later generations of nickel cells. The internal resistance and capacities were better with every new batch it seemed. I think only the on road and boat guys were still obsessed with battery voodoo.

The FLEX charging was for the nicd... IIRC it was not recommended so much for Nimh. Same with dead short storage... that was great for the old 2000 cells but nobody was still doing it with the 3700, 4200, 4600 etc.

To bring old pack back to life... best thing to do is cycle it... over and over. I recently cycled an 11 cell pack that I had not used in a couple years. It's not for an rc... it was for "overclocking" my 12v ultraviolet fluorescent cure lights (I do windshield repair... thus the "glassdoctor"). Did the same with a black and decker "wizard" 3.6v tool battery.

I used my Hyperion charger and cycled them both several times. The first cycle of the B&D battery was only like 150mah... second one was about 2x that.... and after 4-5 cycles it was putting out over 1500mah.... about 80% of a fresh pack. Not bad.

Sometimes old cells are just junk... and you won't get much out of them. And it may not matter how much they were used. I've had brand new cells that were never used.... but would barely take any charge after sitting a few years. Others were fine. Same with well used rc packs...


Jammin CRT MM/Neu 1515 1700kv
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glassdoctor
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12.26.2010, 01:30 PM

Short answer... cycle them 2-3 times and see what you get. If results keep improving, keep cycling.

1-2c charge.... discharge however high your charger will do if these are good sub-c cells. 10 amps if your charger can do it.... or 20+A if you can get your hands on a Turbo30


Jammin CRT MM/Neu 1515 1700kv
Losi 8IGHT MM/Neu 1512 1900kv
Kyosho 777
T4 MM 5700
B4 LRP
XX4 MM 7700
old losi xxcr, MM4600 4s lipo 70mph+
   
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12.26.2010, 04:08 PM

yep. just gotta slow charge (.25c) and slow discharge (.25c) over and over.(cycle)

if mah's go up shes got life left, if not dispose of it properly.


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It's "Dr. _paralyzed_" actually. Not like with a PhD, but Doctor like in Dr. Pepper.
   
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hoober
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12.26.2010, 04:19 PM

Generally no amount of "cycling" will help any pack. It will simply use up 1 more life cycle. Many are deceived into thinking that the "cycling" directly increased the capacity since the capacity continued to rise at every subsequent cycle.

It usually stems directly form the forced overcharge that is hung on the tail end of the "full mark" and is rather from the cells being "balanced" rather than from the cells being "cycled"

Try it, you'll like "cycling" once better than many times over. Here's the best that one can do:

Take the discharged pack and allow it to set for a long time (it can be dead shorted for prolonged periods as well) Charge it at c/10 for 15 hrs +. The pack is at it's fullest and best balance already. Use normally. OR simply do a c/10 charge for 15 hrs and use or test.
   
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glassdoctor
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12.26.2010, 05:51 PM

Quote:
Originally Posted by hoober View Post
Generally no amount of "cycling" will help any pack. It will simply use up 1 more life cycle. Many are deceived into thinking that the "cycling" directly increased the capacity since the capacity continued to rise at every subsequent cycle.

It usually stems directly form the forced overcharge that is hung on the tail end of the "full mark" and is rather from the cells being "balanced" rather than from the cells being "cycled"

Try it, you'll like "cycling" once better than many times over. Here's the best that one can do:

Take the discharged pack and allow it to set for a long time (it can be dead shorted for prolonged periods as well) Charge it at c/10 for 15 hrs +. The pack is at it's fullest and best balance already. Use normally. OR simply do a c/10 charge for 15 hrs and use or test.
This would only apply with packs that are in good condition and have been in service.

One charge/discharge cycle on an old cell or pack may only yield 10% capacity. Sure, the capacity and performance will increase with each use... but who wants to waste time trying to "use" a battery that's working like crap. It's better to let a cycling charger do it's thing automatically and then you can use the battery once the performance has improved.

And it's not a myth... cycling can and does yield increased performance in some circumstances and it has nothing to do with the cells being balanced. We used to "balance" the cells in our packs after each use by discharging each cell independently.

Cycling at higher rates (charging at 1-2c and discharging at 20-30A) did increase performance with nickel cell packs.

Sure, there were some practices that may have been merely snake oil... or maybe even detrimental... but plenty of our battery care 101 was real and effective.


Jammin CRT MM/Neu 1515 1700kv
Losi 8IGHT MM/Neu 1512 1900kv
Kyosho 777
T4 MM 5700
B4 LRP
XX4 MM 7700
old losi xxcr, MM4600 4s lipo 70mph+
   
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hoober
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12.26.2010, 08:03 PM

We need some old cells to test, I have some that have set for 2 years.

We can separate the cycling from the forced overcharge and see which actually provide benefit. My experience is that the first "wake up cycle" is always the best and then declines from there.

But, I never do a "regular cycle" like most do. I do a c/10 "charge cycle" and a very deep discharge. If one does automatic cycling by a charger one is being fooled since it is cutting off way too early at both ends.

Who would like to take the time doing a few cells? or packs? I sure wouldn't It is really time consuming and a waste of time.

It's too bad I didn't save more graphs , but here is two such AA cells that were given to me to "fix". A graph before and after just one deadshort and formation cycle. This is as good as it ever will get. Unfortunately I do not have any pics of subsequent "cycles"
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Last edited by hoober; 12.26.2010 at 08:14 PM.
   
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