CONDITIONING NIMH'S WHY HOW??

CONDITIONING NIMH'S WHY HOW??
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All Forums >> Radios, Batteries, Clubhouse and more >> Batteries & Chargers >> CONDITIONING NIMH'S WHY HOW??

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CONDITIONING NIMH'S WHY HOW?? - 6/7/2006 6:35:08 PM

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From: tolland, CT, USA
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Ive got some 7.2v 3000 mah NIMH stick packs that I have probably charged 12-15 times since new. The run times are getting less and less. I do not have a discharger and honestly dont understand the contradiction of discharging a battery and then recharging it when Ive read that NIMH's shouldnt be run until they are fully discharged.
I have been fast charging them at 3 amps and have read that to "reform" them I should charge at 300 amps slow charge (which i am going to do)
Another question is ..do I need to buy a discharger or can I somewhat suitably discharge the batterys by running it until it dies?

Thanks-

RE: CONDITIONING NIMH'S WHY HOW?? - 6/7/2006 6:48:58 PM

guver

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It's too late for a formation charge, but a 300 ma charge for 15 hrs will insure that the cells are equalised or balanced. It is not necessary to discharge completely, but may be beneficial right after the c/10 charge. Then do another c/10 charge. I think that if you notice the run-time is gettting shorter then you must be dischargeing to a point at which you can tell and there's probably no useable capacity left.

3 or 4 other things that may be contributing to lower run-time is dimished battery capacity due to stress/abuse. You are not doing that using 3 amps charge. Dirty , worn driveline or motor getting worn, dirty.

The only real way to tell is to test battery and compare to when new or compare to the label.

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RE: CONDITIONING NIMH'S WHY HOW?? - 6/7/2006 7:15:26 PM

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From: tolland, CT, USA
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Thanks for the info- Can I use my peak charger set to 300 milliamps and have it charge until it reaches 3000 ? At 3 amps it takes about an hour to fully charge so I am thinking at 300 MA it will take less than 15 hours, maybe 10. Im using them in multiple vehicles and it is noticeable in all so its got to be the batteries-
Thanks-

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RE: CONDITIONING NIMH'S WHY HOW?? - 6/7/2006 7:32:26 PM

guver

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Probably not, it isn't the rate that equalises the cells. It is the "forced" overcharge of some of the cells and the ability of the cell to disipate that rate that will allow the other cells to get full. The peak charger will not do this unless pehaps you can disable the peak detect function. Even setting it very high will probably not disable it. The best charger is to use a dumb wall-charger of 200 - 500 ma. even i the voltage doesn't match up.

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RE: CONDITIONING NIMH'S WHY HOW?? - 6/7/2006 8:09:57 PM

Rodney

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Yes, the battery will no doubt improve after a slow charge. Slow charge is defined as charging at 0.1C for 16 hours. Yes, the better cells (or those with higher capacity) will be overcharged at this rate but; charging this slowly allows the recombination of oxygen at the positive plate to occur without excessive heating and the corresponding increase in internal pressure which could blow the seals if overcharged at a higher rate. Cells do tend to degrade with age, especially if they have been subjected to high temperature or very high charge or discharge rates. To get the most life--and capacity--from your battery, do as few fast charges as possible and if you must fast charge, limit to a 1C rate. After every 10 to 20 of these fast charges, do a slow charge for 16 hours to bring the cells back into as close a balance as you can.

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RE: CONDITIONING NIMH'S WHY HOW?? - 6/9/2006 7:59:43 PM

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From: hamilton, ON, CANADA
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So your saying you can still slow charge batteries with like 2700mAh with the charger that comes with the radio?

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RE: CONDITIONING NIMH'S WHY HOW?? - 6/9/2006 9:43:36 PM

Rodney

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So your saying you can still slow charge batteries with like 2700mAh with the charger that comes with the radio?

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Depends on the rate it charges at. For 2700 mah battery, slow charge would be at 270 milliamperes for 16 hours. You could probably get by with any charge rate from 200 to 300 and adjust time accordingly. Anything lower will take a very long time and anything faster risks overheating/ over pressurising the cells.

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RE: CONDITIONING NIMH'S WHY HOW?? - 6/9/2006 11:18:21 PM

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i found a 350 ma dumb charger- and have some 3000 mah packs and some 3300 mah packs to charge-- so Im thinking 14 hours for the 3300's and 13 hours for the 3000's-- is there a formula or calculator that you know of that can be used to calc the correct time?

Thanks-

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RE: CONDITIONING NIMH'S WHY HOW?? - 6/10/2006 1:20:07 AM

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My Radio charger says it charges at 150mAh so could I use it on a 2700mAh pack?, so can I charge it for 18 hours?

< Message edited by Young-RCPilot -- 6/10/2006 1:27:21 AM >

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RE: CONDITIONING NIMH'S WHY HOW?? - 6/10/2006 8:21:10 AM

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The formula is capacity divided by charge rate times 1.4.
So if you charge at 1/10th of capacity (1/10C) you end up with the often mentioned 12-14 hours.

The cells (NiMh) will be warm at the end of that time. If you are able to, check them and if they are getting hot stop charging. The formula above assumes you are starting with a fully discharged set of cells and you are probably not, s it may take less time. It really is a worthwhile process and does wonders for jaded packs.

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RE: CONDITIONING NIMH'S WHY HOW?? - 6/10/2006 1:49:51 PM

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From: tolland, CT, USA
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there ya go- thats the # i was looking for- 3000 mah pack/ 350 ma charge * 1.4= 12 hours charge time- of course i just charged it for 14.5 hours but it never got hot-

i noticed the charger i used said nicads only but it worked nonetheless-- can anyone tell me if i am screwing up using this charger?

thanks .

< Message edited by bkdarch -- 6/10/2006 3:56:02 PM >

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RE: CONDITIONING NIMH'S WHY HOW?? - 6/10/2006 4:39:35 PM

Rodney

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Your batteries should not get warm at athe 0.1C charge rate even if you overshoot the 16 hours recommended charge time for forming charge. The batteries should be designed to allow that much overcharge with the accompanying recombination of oxygen at the positive terminal will not cause excessive heat or pressure. If your batteries are getting hot, that is a definate sign to stop the charge as you have already exceeded recommended limits.

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RE: CONDITIONING NIMH'S WHY HOW?? - 6/10/2006 5:17:54 PM

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Almost every charger says 'NiCds only!' I think they mean 'rechargable only' - don't charge dry cells and use the word like 'Hoover' was used before we started to call 'em vacuum cleaners..... A Futaba wall charger says it even when they supply the kit with NiMh packs. It does confuse people as I've seen the same question asked several times on this forum.

Charger suppliers please note!

When you use peak detection chargers it is an issue as they peak at different voltages.

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RE: CONDITIONING NIMH'S WHY HOW?? - 6/10/2006 11:40:43 PM

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Just jumping in here... Today I bought a 6.0V NIMH RX pack. For the initial charge can I use the 4.8V wall charger that came with my radio? I've got a Triton charger and tried charging it at 150mah thinking it would take 14-16 hrs, but it finished in about 20 min.. Does anyone know how to set the Triton up to do a slow charge for NIMH batteries?

Thanks

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RE: CONDITIONING NIMH'S WHY HOW?? - 6/11/2006 11:23:07 AM

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Think I'll jump in here also...Have be conditioning my batteries for about a year now..am using a "Sirius Pro Former" unit.. A very good, simple unit that does the job...Easy to use and the instructions are not hard to follow ...Check out thier website: www.siriuselectronics.com........................Good luck

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RE: CONDITIONING NIMH'S WHY HOW?? - 6/11/2006 5:16:59 PM

guver

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quote:

ORIGINAL: Tym1_Me0

Just jumping in here... Today I bought a 6.0V NIMH RX pack. For the initial charge can I use the 4.8V wall charger that came with my radio? I've got a Triton charger and tried charging it at 150mah thinking it would take 14-16 hrs, but it finished in about 20 min.. Does anyone know how to set the Triton up to do a slow charge for NIMH batteries?

Thanks

I would use the wall charger and do the math to figure out how long to charge. The Triton )and any peak charger) will have fits trying to do a first slow charge. You can set the setting on the highest nicad mv and set the max timer to 990 minutes of none and set the peak delay at highest value, but it will still shut off early as a result of the peak detection and open volt check.

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