Battery and IR Explanation

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Battery and IR Explanation

Post by Wolfwood » Thu Jul 28, 2005 1:22 pm

I'm going to submit this to Airsoft Quarterly, and I figured I'd give you guys a chance to once it over first. Feel free to ask any questions, give corrections, and offer advice. I believe guges was going to supply some market research on this as well to give some good cells for people.

Batteries and what their characteristics mean

Most Airsoft players should know a good battery is as important as anything else in your AEG. Running a cheap and often inferior battery makes little sense. Why spend 300 dollars on a new AEG and then try and save 15 bucks buying an inferior battery? If you owned a top of the line sports car would you try and save a few bucks by putting the wrong gas into it?

We all know about voltage. More volts mean more rate of fire, right? And we all know about mAH, 3000 mAH will last longer than 2000 mAH right? Well the answer is a resounding "sort of"! What?s actually going on is a chemical reaction within the battery. Batteries are composed of two diametric plates, a cathode and an anode. The actual "power" that comes from a battery comes from the flow of electrons from the anode to the cathode where it converts from NickelIC(Ni+3) into NickelOUS (Ni+2) hydride. So the actual chemical reaction is important.

The mAH stands for milli-Amp Hours. So 3000mAH is 3000 milli-Amp Hours or 3 Amp Hours. That means you can draw 3 amps out of it for 1 hour, or 1 Amp for 3 Hours, or half an Amp for 6 hours, etc. Its important to note that this is just an estimate based on a sampling of the cells, and can vary.

Whenever you run a load across the battery, there is a voltage drop. Always. Since AEGs are high load, that voltage drop is significant. Your 8.4 or 9.6v battery will drop quite a bit. As the battery works harder to chemically react to produce enough power, the drop will become higher. Notice your rate of fire slows down before you battery finally poops out? That?s because the chemical reaction is more difficult as there is not much Ni+3 left. And do you notice that your 3000 mAH 8.4 gives a higher ROF than your 600mAH 8.4 even when both are fully charged? That?s because their is quite a lot more of Ni+3 and its a lot easier for the chemical reaction to take place. Thus there is less of a voltage drop.

Internal Resistance (IR): The Hidden Attribute
Ok, so we think we have everything in place. Voltage and Amp Hours makes sense, we understand about the voltage drop. Perfect, all done. Except for one thing, and this one is significant. Internal Resistance of the battery. Everything short of superconductors in electronics has resistance. It's a shame, but it?s true. Resistance basically turns useful electricity into troublesome heat. Somethings (heating coils) have lots of resistance; other things (speaker wire) are sold because they do NOT have a lot of resistance. In the case of batteries, it is something that makes a huge difference and something retailers will rarely let you know about.
Batteries with a high internal resistance have more of their power turned to heat, thus you will not get the performance from your battery that you really want.

Let?s take two batteries, both 3000 mAH. One has a very good IR of 2mOhms, the other has an IR of 15. Both these batteries can be found on any airsoft field, and have the same dimensions.

Beginning of play: They both have a very high ROF. In fact, they are both identical. Our 15IR is using a bit more power each shot, but it?s not noticeable to our player.

1000 rounds in: Our 2mOhm battery is still performing like it did at the beginning of play. The 15 IR has its ROF slowed some, but it?s still fairly strong. This means 15IR guy's voltage is dropping a bit more under load.

4000 rounds in: Mr. 2mOhm has seen his ROF decrease slightly as his battery is well over half drained. However it?s still working well as the low resistance makes it easy for the chemical reaction to keep up with the drain of the motor. His Voltage has just dropped a tiny bit. However, Mr. 15mOhm has seen his ROF languish. His battery is able to just barely turn the motor over. He has watched his rate of fire slow down the last hour of play, and has already missed some kills because of it. He is experiencing moderate voltage drop.

Even Later: Mr. 2mOhm ROF has definitely slowed, but it is still firing faster than his friend's from a thousand rounds ago. Our 15mOhm player is sitting on the sidelines. See, he made a brilliant charge on the fortification, but nothing happened when he pulled the trigger. Instead he got the business end of a half dozen AEGs. Now he is out of juice, out of the game, shamed, and will probably lose sleep over it. A high price to pay.

Later still: 2mOhm guy's battery finally died. Unlike the higher mOhm guy, his battery does not drop as much voltage until it is almost out of juice. When he notices his gun firing slowly, he knows it?s almost out. On some batteries there is hardly any warning at all!

So you need to do some outside research on your cells to find out the IR of them. Lower is always better!
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Post by Guges Mk3 » Thu Jul 28, 2005 3:13 pm

Very good airsoft cells are:

2/3A Size - Mini Packs

KAN 1050mah, IR 5, slightly larger then a real 2/3 by about 15%.
GP1100 1100mah, IR3, perfect 2/3A cells

Sub-C - Large Packs

GP3300 3300mah IR3
GP3800 3800mah IR3

Sanyo NIMH 3000mah IR6

KAN in 1800mah are also good. IR 5
+++++++++++++++++++++++++++++++++++++++++++++++

Oh a question for you Wolfwood.

I am in disagreement with R22 from AA in the UK and I need your opinion.

If one fully charged a NICD and a NIMH pack. And you let them sit for say a month. Which one "will" lose more power over that time? the NICD or the NIMH.

I say the NIMH, because I was told somewhere that this is true. NIMH are terrible at holding charges for a long period of time.
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Post by Wolfwood » Thu Jul 28, 2005 3:32 pm

NiMH have a natural "bleed" rate that is usually somewhere between 3%-10% daily after a high initial loss in the first 24 hours. NiCDs bleed rate is in the sub 1% typically, after a loss of about 10% in the first 24 hours. Now this is under optimal conditions. If a battery has been damaged it can bleed much much faster. People accidently damage NiCDs often, so he may have observed a NiCD that had a high bleed rate. It also varies from cell to cell. I notice those KANs have a fairly low bleed rate, and have heard from people with the GPs that say that same thing. But I have had NiCDs keep a charge for over a year (oops!) so they typically are the king in that regard. I have one NiMH that loses almost 30% of its charge in one day!

The fact that NiMH have a bleed rate helps with the fact that they rarely develop a memory. A memory develops when a charge sits in a battery and causes the NI+3 to form into crystals, which are reluctant to break down. These crystals spend enough time to get too big, then you no longer have access to that charge.

Some sources for the discharge thing:
http://www.repairfaq.org/ELE/F_NiCd_Bat ... ATTERY_024

http://ibet.asttbc.org/batterys.htm (look under NiMH for "high self discharge")

http://www.buchmann.ca/chap2-page4.asp
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Post by Guges Mk3 » Thu Jul 28, 2005 3:46 pm

Good stuff Wolfwood we should keep modifying the main article to reflect the new stuff.

And just got more comfirmation that NIMH have a higher bleed rate...

Also we should mention that one has to match voltage when charging batteries. You hsoul dnot charge a 8.4v battery with a 12v trickle charge...ahem...Infinity Airsoft!
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Post by Gingerbreadman » Thu Jul 28, 2005 8:11 pm

Two cold weather-related questions:
1) Why does the battery life shorten so much on cold weather?
2) Should the heat generated by internal resistance keep a battery fresh longer in cold weather?
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Post by Digital » Thu Jul 28, 2005 8:20 pm

Molecules slow down at lower tempatures. So since they are not bouncing around so much they create less engery.
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Post by Lacetorous » Thu Jul 28, 2005 8:26 pm

To answer your second question gingerbreadman, I do not believe so. The battery would just be affected by both factors (resistance, and cold), making a battery die out sooner.

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Post by Wolfwood » Thu Jul 28, 2005 8:43 pm

Gingerbreadman-
Yeah, digital hit it on the head. In cold weather chemical reactions typically go slower, so its harder for the battery's to convert NI+3 to NI+2

Higher IR in cold weather will still mean the battery has to work hard to do what it needs to do, and then you have the cold weather to add on to it. Turning energy into eat is easy, heat into energy is a lot harder, its the law of entropy. Basically the heat generated by the higher IR will not get to be turned back into potential energy.
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Post by Turtle Bird » Sat Jul 30, 2005 2:42 pm

Okay I have a question, is there anyway to test IR with say a regular fluke meter? I know that some batteries you can check spec sheets etc, but it would be nice to be able to test it myself.

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Post by Wolfwood » Sat Jul 30, 2005 2:59 pm

Don't just hook an Ohm Meter to the battery. What you'll need to do is measure the battery under load, and use the change in voltage over the change in current. Basically your using the fact that R=V/I. Here is a website that will help walk you through it

http://www.buchmann.ca/Chap9-page2.asp

Now, thats pretty much a college-level electronics lab right there. If you don't have the background for it, it may not be worth doing. Here is something you can do yourself with a multimeter and about 2 bucks worth of stuff from radio shack:

Take your battery and make a circuit with, say, a 10 ohm resistor in it. This should be a load of about an Amp, a significant amount of power. Measure the voltage drop. If its an 8.4 battery, the drop should be about .8 volts or less. If its a 9.6 volt, the drop should be less than a volt. Its a good way to compare batteries to see which is performing the best under that circumstance. Now if you see no drop, or see a very high drop, don't think that you have the world's best battery or that your battery sucks. I've never done tests on these size cells, so they might act differently than I am predicting. If you don't see much of a drop, you can also try it with 7 ohms, or maybe even 5 ohms. Don't go less than 5 ohms.

Monitor your battery while you are doing this. If it starts getting hot, pull it immediatly. The less resistance you use, the more likely you are of damaging your battery.
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Post by Guges Mk3 » Mon Aug 08, 2005 1:13 pm

Wolfwood,

Can you please sum up the reason why charging a 8.4v charger with a 12v charger is bad.

I know its bad, you know its bad...but I have to explain it to a dweeb on another board...

Thanks much...
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Post by AustSiannodel228 » Mon Aug 08, 2005 1:41 pm

I'm a dweeb! I'm on another board! Explain please.
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Post by Guges Mk3 » Mon Aug 08, 2005 1:51 pm

Your not the dweeb...but yes...could you put it out in mild tech speak...
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Post by Wolfwood » Mon Aug 08, 2005 5:32 pm

The answer I am going to give you isn't quite the one you're looking for, but here goes:

Basically, the voltage of the charger HAS TO BE higher than the battery, otherwise you stopped charging the battery and started charging the charger. And you are actually using more voltage when you quick charge. Since V=IR if you want to put more current into the battery, resistance is more or less equal (until it starts getting charged) so you increase your V.

The reason you do not want to use a 12v battery charger on a 8.4 battery is the charger will not step down correctly. The charging phase looks like this:

http://www.pacificpowerbatteries.com/ab ... cfaq6.html
(They use a golf cart charger for this to give a nice wide line, but all batteries are similar, just without so much of a drop)

and if the charger thinks its filling up a 12v it will not decrease its current load correctly and overheat the battery or overfill it. This is doubly true of "intelligent" chargers. Those things will think they are doing the right thing by throwing more charge in there. The way intelligent chargers work is they look for voltage drops and voltage fluctuations. These are greater with a 12V battery than with a 8.4. So you're 8.4 can be sitting there signalling that its full but the 12v "smart charger" will not recognize that as enough of a signal and keep right on feeding the poor battery.

You could use a 12v charger as long as you watch your battery carefully and avoid overheating. Overall your risking your battery.
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Post by Blackcat » Thu Dec 01, 2005 1:55 pm

I am looking at a GP 3700 cell, is that the one Guges said is IR3?

Also, will this fit in a full stock on an m16? I have never used large batteries before. Normally I thought they had 7 cells... this only has 6?
Image

Are there any other retail places to get the good gp 3700 packs for airsoft use?
For that pack above, i found it on http://www.maxamps.com.
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Post by Wolfwood » Thu Dec 01, 2005 6:08 pm

6 cells=7.2 volt.

These batteries are great, but you need a 7 cell guy. I don't have any issue fitting mine into standard large battery compartments.

I bought mine from guges... Might wanna give him a PM
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Post by Porthos » Mon Jun 19, 2006 11:46 am

From what I read, It never really says if higher voltage = higher rate of fire, That could be discussed in much greater detail.
Last edited by Porthos on Mon Jun 19, 2006 12:03 pm, edited 2 times in total.

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Post by Wolfwood » Mon Jun 19, 2006 11:48 am

Higher Voltage nominally means higher ROF, but it depends on the batteries. Some 9.6volt batteries will not give as high of an ROF as some 8.4s given the same motor/spring combination. Thats why it is important to pay attention to what kind of cells you have, not just voltage and mAH.

What parts need work and what regs are you refering to?
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Post by Porthos » Mon Jun 19, 2006 12:00 pm

I ment I saw how some people seemed to be giving you advice about stuff to add to it. I never said I knew anyone that had specific advice for it. Sorry about the mis-communication there.

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Post by Wolfwood » Mon Jun 19, 2006 12:19 pm

No problem. Some advice I don't necessarily want to add since it really depends. The most important thing is to get good cells, which is the point of this topic.
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Post by Predator08 » Sat Aug 05, 2006 10:36 pm

I have a Ni-Cd 8.4v 1300mAh battery. How long does it take for the battery to form crystals or become ruined? Because I have had my gun for about a year now and I have never discharged it. I also have a wall charger that pulgs into the wall and all it is is a black square with no lights, switches, indicators or cut-off features. I just plug it in and leave it charging over night. The battery still works fine and it has never run out of charge or anything on me.
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Post by Miker » Sat Aug 05, 2006 10:49 pm

My 1300mah NICD ran out after about 1500 shots I think and it is a year old. So I am gonning to use that as a last resort battery.

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Post by Wolfwood » Sat Aug 05, 2006 11:32 pm

Predator08 wrote:I have a Ni-Cd 8.4v 1300mAh battery. How long does it take for the battery to form crystals or become ruined? Because I have had my gun for about a year now and I have never discharged it. I also have a wall charger that pulgs into the wall and all it is is a black square with no lights, switches, indicators or cut-off features. I just plug it in and leave it charging over night. The battery still works fine and it has never run out of charge or anything on me.
It depends greatly battery to battery.
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Post by Miker » Sat Aug 05, 2006 11:40 pm

Is it bad to over charge a battery or run it at a half charge if you don't have time to fully charge it and is it good to discharge?

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Post by Wolfwood » Sun Aug 06, 2006 12:04 am

Your ok running at half charge, and you should discharge NiCDs if you will not be using them for a while.
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Post by Miker » Sun Aug 06, 2006 12:11 am

That probably why I only get 1500 shots off before it dies never discharged it and left it charged for days before I played again

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Post by DonkeyPunch28 » Sun Aug 06, 2006 1:14 am

Simple Electronics math

E=I*R

E is voltage
I is current
R is resistance

I love reading about electricity posts. This is the 2 years of school I had to go to in order to play with my big gun in the navy. Research well done Wolf.

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Post by mensk88 » Mon Dec 18, 2006 6:37 pm

I've been wondering if I should discharge my NiCd battery. And where I could possibly buy a better one.

My Current Battery: (Please don't laugh... It came with the gun...)

NiCd 700mAh "AA" 9.6v

I've heard places like Batteries Plus can make you one but it is worth it? or should I buy one off the internet?
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Post by Wolfwood » Mon Dec 18, 2006 6:39 pm

Order one from Olympus Airsoft or if K9troop has any left.

You'll want to get one made for airsoft. Airsoft has demands that require batteries with low IR and high output, not something that batteries plus will likely be great at.
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Post by mensk88 » Mon Dec 18, 2006 6:41 pm

:D spectacular :D , thanks
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Post by K9Troop » Mon Dec 18, 2006 10:15 pm

Shoot me a PM, we have multiple "mini" packs.
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Post by Faust » Fri Aug 10, 2007 6:39 pm

Wolfwood wrote:Order one from Olympus Airsoft or if K9troop has any left.

You'll want to get one made for airsoft. Airsoft has demands that require batteries with low IR and high output, not something that batteries plus will likely be great at.
Can you explain what you mean by 'high output'? Is that the same as 'discharge rate'?

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Post by Wolfwood » Fri Aug 10, 2007 9:44 pm

Right. Output would be the same as discharge.
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Post by Faust » Sat Aug 11, 2007 10:40 am

I have read through both Wolfwood and Guges articles on batteries and the threads that follow multiple times, and found the IR ratings of many batteries, but what are the IR ratings of "Elite" brand cells and "Intellect" brand cells? Those are the cells in most of the packs that I see Guges and Skunksquatch are selling.

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Post by Guges Mk3 » Sat Aug 11, 2007 10:49 am

IB are a varying lot...factory specs are not specific but are listed as IR6-9, and Elites are coming in at IR 7-10
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Post by Faust » Sat Aug 11, 2007 10:57 am

Guges Mk3 wrote:IB are a varying lot...factory specs are not specific but are listed as IR6-9, and Elites are coming in at IR 7-10
Alright, thanks Guges. I was under the impression that these batteries were superior to the KAN's and GP's. I guess not.

Guges Mk3 wrote:KAN 1050mah, IR 5, slightly larger then a real 2/3 by about 15%.
GP1100 1100mah, IR3, perfect 2/3A cells
Are those NIMH cells or NICAD cells? Is there anywhere you would recommend to buy either of those cells and/or packs of either brand of cell?

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Post by Guges Mk3 » Sat Aug 11, 2007 11:12 am

They are all NIMH's....there are no suitable 2/3A cells for High Discharge needs that are over 600mah in capacity or price efficient.
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Post by Faust » Sat Aug 11, 2007 11:18 am

Guges Mk3 wrote:They are all NIMH's....there are no suitable 2/3A cells for High Discharge needs that are over 600mah in capacity or price efficient.
What amp discharge rate do you consider "high discharge needs"?

What are the amp discharge rates of Intellects, Elites, GP's, and KAN's?

Does higher discharge rate mean lower mAH?

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Post by Guges Mk3 » Sat Aug 11, 2007 1:58 pm

What amp discharge rate do you consider "high discharge needs"?
Items that draw a lot of power to function. Think of the "work" it has to do. Lighting up 15 LED's is not a High Discharge requirement. Pushing a spring in an out 15's a second is. And in the case of a Stock TM...its draw is 12amps.
What are the amp discharge rates of Intellects, Elites, GP's, and KAN's?
Roughly:
Intellects 30-35amps
Elites 30-35amps
GP's 35-40amps
KAN 35-40amps
Does higher discharge rate mean lower mAH?
No not necessarily.
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Re: Battery and IR Explanation

Post by Sunny » Sun May 11, 2008 5:10 pm

From my many years experience in R/C Cars which use batteries of a similar nature. Generally speaking a auto sensing digital peak charger will tailor its output to the pack connected to it based on the calculations it does when you start the charging process. I have noticed that the voltage applied to the packs is generally 40 percent higher than the voltage output of the pack itself. I have also experimented with programmable peak chargers and have found out (by damaging packs) that it is best to tailor the charge rate yourself, start out with a low amperage charge rate and work up to one that charges the battery in the time you want but doesn't over heat the cells in the pack. Overheating in either charging or discharging is an instant killer for NiMh batteries. I have built myself a battery discharger for the small packs by connecting two 1157 tail light bulbs in parallel and connecting a matching connector for the packs. I keep an eye on it and disconnect the discharger as soon as the lights go out. Seems to work alright for me, battery stays cool and it takes nearly a full capacity charge according to the display on the charger.
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Re: Battery and IR Explanation

Post by Digital » Tue Aug 05, 2008 8:51 am

Ok so heres an intersting question. For the first time ever I read the side of one of my batteries. It a sanyo 1100 mAh 8.4v. On the battery it states that you should charge the battery for 16 hours at 110 mAh. However if you do a fast charge you will only get a 650 mAh battery use. Can you explain? To me 16 hours is a long ass time to charge any battery. I don't think I have every charged any of my batteries for that amount of time. So ahh....yeah. Do I really need to do the 16 hour charge to my batteries all the time? If so I guess I better get started so I can atleast have two batteries charged for thunder....
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Re: Battery and IR Explanation

Post by Wolfwood » Tue Aug 05, 2008 3:12 pm

Well, batteries have a lifespan, and Sanyo's are not well tailored for airsoft. It sounds like it has a higher Internal Resistance, which is why they want you to charge it at a lower amperage for a longer amount of time. By fast charging, you have probably cut down the life of the battery to about half of what it would be normally. I'm not sure if taking longer to charge it would fix this. It might.

I tell people all the time, you wouldn't put cheap gas into your nice car, why put cheap batteries into your nice AEG? I would recommend some better cells.

To compare, some KAN 1100s that I have get 1050-1250 charge each time. KANs are well suited for airsoft and fast charging in general, and these are OLD cells! Newer cells work even better. Those Sanyos are meant to be slow charged, those you are ending up with such low capacity.
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Re: Battery and IR Explanation

Post by uRizen » Sun May 02, 2010 10:17 pm

I have a question on proper care during the off season, I ran into some trouble at BATC because almost all of my batteries crapped out in multiple AEGs after about 1200-2000 rounds, this included both my newer Elite 8.4v 1500mah pack and my previously trusty 9.6v 3600mah Intellect. All of my packs were running very well until I had to take a break for a year during which I charged all of them twice, I never ran a discharge cycle on them since they are all NiMH packs. I have (what I thought) is a pretty decent charger, a SuperBrain 960 and am fairly certain my charger isn't at fault since I had the same problem after charging a couple of batteries with Judge Viper's identical charger.

Is it possibly that they got screwed up by not being cycled for an extended period of time? Was charging them during the break a bad idea? Am I inadvertently cooking them with my charger?

I did run another charge cycle on the 9.6v 3600mah pack and it took almost 1,000mah and turns my AEGs over perfectly, perhaps they just need to be cycled a few times to work out the kinks? For reference I'm charging all my 7-cell packs at 35mv@1.5amps.
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Guges Mk3
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Re: Battery and IR Explanation

Post by Guges Mk3 » Mon May 03, 2010 7:57 am

1.5amps???

1500mah? on the 2/3A Elites?

Way, way, to high...for a quick charge to dump some power in to get it running...yeah that okay...but it heats them up and heat is VERY BAD for NIMH.

You won't fill the pack with quick charges...but you can get 75% capacity in...roughly.

Ideally, you should be putting in 1/10 of the rated capacity in a slow charge. 1500mah....should be 150-200mah...

You can circumvent the low rate by keeping your pack cool. I put the cooling fan of the charger the battery when I charge them...2 in 1 deal. I knew a guy that stuck the pack in the refrigerator with an extended cord as he charged them...
I rather use a "nightmare" that shoots like a dream over something that looks like a "dream" but shoots like a nightmare.

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Re: Battery and IR Explanation

Post by uRizen » Mon May 03, 2010 10:08 am

Oops, I guess I smoked that battery, I thought it was normal that they got a bit warm (never burning hot though.) :oops: So you'd recommend dropping that charger to ~0.2amps for a good, solid charge and ~0.4amps for my 3600mah pack? What are your recommendations for off-season storage?
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