Battery question

[Rumpel Felt]

Ok, number two in my series of things that have been bugging me for a while....

I've got a few Ni-Mh batteries I've left sitting fully charged since about the end of August 2006. When I got them I game them all 3x a charge and discharge cycle.

So, are these things screwed or what? Should I give them another few cycles or just drain them totally once and charge them again? My charger (once I get the intructions for it again) is can do most anything it needs....

Thanks for any info....

[ringsted]

if you discarge a nimh pack you may break it so dont do that.

cells you have not used for a while should be charged at 1/10 C for 16 hours.

after that you can charge them at 1 C no problem.

and again DO NOT DISCHARGE YOUR NIMH'S

[Ibby]

Originally Posted by ringsted

if you discarge a nimh pack you may break it so dont do that.

Erm, no. You can discharge NiMh just fine, as long as it's done properly. It takes longer than Nicads as NiMh are prone to failure when they get hot. If you discharge them at a slow rate it's quite fine. Same goes for charging them. Fast charging is a bad idea.

[Kos-Mos]

Hmmm

just above your tread is a sticky called "Battery FAQ" It is all in there.

Here is a link if you lost it (how could you anyways):

http://www.airsoftcanada.com/showthread.php?t=25656

You can discharge Ni-Mh pack up to 0.9v per cell, while Ni-Cd packs CAN be discharged fully. It is NOT recomended and will damage the pack to fully drain it. The reason is that the pack will degenerate to compesate for the discharge, so slow discharge will actually be deeper than fast one.

If you have a good charger with cycle capacity, it will not let the pack go below 0.9v

A normal pack (I mean not the crappy no brand ones) will be fuctionning properly up to 120°F/50°C. Above that it might fail. A good pack can go higher with less risks (I already ran a pack up to 75°C...Pack was worth 160$)

Oh and it's better to discharge packs faster tant too slow. A mini type pack can be drained at 10A while a Large pack can be done at 25-30A.

Same apply for charging, 1st time in a while should be max. 1c (a 2000mAh should be charged at or less).

[ringsted]

how do you make sure the cells dont go below 0,9 volts when they are in this configuration. ------ it is impossible since all cells dicharge differently when you shoot with it, some will go below 0,9 volts and some be above and this will damage your pack in the long run. if you have a special dicharger which discharge them seperatly you can discarge them, but then they need to be in this configuration !!!!!!!

[Kos-Mos]

Second. This 0.9v value takes that in consideration. If you have a really good pack and have them side by side (like we do in R/C cars) you can drop it up to 0.5v.

This 0.9v value is just to let you calculate up to where you can discharge a pack.

9.6v pack:

8cells -> 0.9v*8 = 7.2v

Should discharge up to one of the following:

7.2v onload voltage
OR
120°F/50°C

And you must check voltage when the pack is connected on the discharging circuit. Or else voltage reading will be higher than reallity since the pack will recover quickly.

If there is a single cell of the pack heating up very fast, this means your pack is near the en of it's life. Nothing can be done about it.

Now for the question we are talking about: Get your good charger you are talking about, and set if for 3 full cycle starting with dicharging. At the end, your pack should be OK to go play.

*edit*
Oh and BTW I just charged my packs today and looked at the values...

In a stock gun (mine is stock, can't talk about an heavily upgraded one) I shot around 2000 bb's in 4 hours. Charged my pack... and only 940 mAh was spent in 4 hour. I really doubt that the pack will be discharged soo fast that the voltage will vary for more than 0.3v for one cell to an other. Hell we drain a 1400mAh pack in under 5 mins when we race!!! Never had any problem of overdischarge! Kinda more than 900 in 4 hours!

Oh and when a stock AEG stop firing, completly depleted, The pack is still around 1.1v per cell.

In short, get a good hobby grade charger with discharge capacity. Buy some good packs, not some chinese no brand shit. Try no to force your packs drained. And you don't need to cycle everytime you charge.

*reedit*

if you discarge a nimh pack you may break it so dont do that.

cells you have not used for a while should be charged at 1/10 C for 16 hours.

Since you said that, means you must have done a lot of research. Then my 4200mAh matched pack should be charged at only 420mAh for a wakeup, then never discharged.

How come the makers of the pack tell me to Completly drain the pack using a 35A discharger up to 0.5v/cell, then charge it at 6A using a peak detect charger set at 6mV neg. delta-peak???

Means that the world best battery pack distributor is wrong??

Oh btw I am talking about SMC, Short for "Superior Matching Concept", Principal distributor of race grade battery packs.

[Ibby]

Originally Posted by Kos-Mos

If there is a single cell of the pack heating up very fast, this means your pack is near the en of it's life. Nothing can be done about it.

Not exactly. You can dismantle the pack, pick out the good cells, ditch the bad ones and make a new pack. It's much easier to do with NiCad than it is with NiMh, as they're a more robust chemistry. Right now I'm building new packs out of old Panasonic KR1700 cells I had lying around. I took a bunch of packs apart, tested the individual cells and am putting new packs together out of what's still useable.

[Nova316]

How do u test cells if there good or bad?
Trying to find out there NiMH cells

[Ibby]

I have a Cadex 4000 battery analyzer. It's an older unit compared to the 7400 the company now puts out, but it's plenty fine for RC and airsoft stuff. I've even reconditioned a couple of car batteries with it.

[Rumpel Felt]

Ok, the info is helpful but my question was a little more focused on the fact that I left them-at a full charge- for many months.

Anyway, I decided to give them a 3 x fuzzy logic charge. 8.4v 1400mah......they were discharge at 4A/H and charged at 500mah right after with a 2 minute slow charge in between.