Anyone know about 'hobby' batteries (custom NiMH packs)? Also; eBay batteries?

[phucheneh]

edit: question about Chinese rechargeable AA's in post three if someone wants to skip my rambling.


Airsoft is pretty big in middle TN. Actually playing it, that is, not just plinking with toy guns. It's similar to the 'woodsball' version of paintball, generally (although we've played CQB stuff- someone used to host games at an abandoned hospital; that was pretty awesome).

Anyhoosits, my buddy and I didn't play for like two years. So our stuff is a BIT neglected. I can tune up the guns themselves just fine, but I was wondering if someone with some experience with batteries could help me out.

Some of our batteries managed to hold a partial charge, and seem to have charged up just fine with a 7.2-12v NiMH/NiCD 'smart' charger. It has 1a and 2a settings...I always use 1a.

While they will charge for what seems like an appropriate amount of time, if you give them a bit (maybe an hour) and hook them back up, they seem to take quite a bit more charge before the light on the charger goes green. Enough to get the battery warm. These are smaller batteries, got a couple 9.6v 1600mAh and some 8.4v's that I think are are about the same; maybe as low as 1200mAh. I've done a few cycles of this, and they keep taking charge.

I was thinking this might just be surface charge causing the charger to turn off (then it dissipates and will charge some more)...but being for multiple voltages, the 'smart' part can't be voltage-based, can it? When are these batteries 'done' charging?

My most important battery is a big ol' 9.6v brick that's over 4000mAh...it would not charge. Checked it with a voltmeter...zero volts. So on a whim, I took an old NiCD battery that WOULD take a charge and hooked it to this big NiMH batt...got it up to 8v or so, then I hooked it up to the mentioned smart charger.....viola, it's charging. Can I trust this thing? NiMH batteries aren't like lithium batts in that complete discharge = toasted, right?

Any way to test this stuff before I take it out to a field ~45 mins away? Aside from just running the guns...some of them are a bit modified and I'd rather not just cram mags through them to drain the batteries.

Other random question: How does one go about building these batteries? I'd like to be able to do custom voltages, and also not pay prices that I know are well above the cost of the batt's cells. But I'd like 'em to be a bit more sturdy than something cobbled together with wire and duct tape.

 

[phucheneh]

You know what...I'm wondering why the hell I can't just use AA NiMH cells, since size is often not a factor.

Anyone know where I can find a flat, sealed enclosure for eight AA batteries? All I can find are the standard 'open' type for use inside project boxes.

 

[phucheneh]

Nobody does RC cars/planes/doomsday devices or something?

I did find some AAx8 closed boxes on eBay for like $5 shipped from China...for cheap crap, it honestly seems kinda pricey. I'm actually considering designing a box of my own with an optical picatinny mount (big batteries either go in full M16-style stock or people mount them on RIS front ends) and seeing how much I can get them made for via some good ol' Chinese injection molding.

Could make some good money selling a product like that, since pre-made battery packs are NOT cheap...3500-4000mAh pack: ~$60. Smaller format batteries at about 1500mAh, about $35. And one bad cell...hell, for most, just damaging the wrapping that holds the cells together...it gets pitched.

Now the question of them all: How the HELL can you get 3000mAh AA's on eBay for under a dollar a piece? I understood the ruse of old cheap alkalines...they had no capacity. But since a rechargable generally writes it on the cell...are they just lying? Or do they simply have shitty, failure-prone build quality, like the famous Chinese electrolytic caps?

 

[PottedMeat]

Now the question of them all: How the HELL can you get 3000mAh AA's on eBay for under a dollar a piece? I understood the ruse of old cheap alkalines...they had no capacity. But since a rechargable generally writes it on the cell...are they just lying? Or do they simply have shitty, failure-prone build quality, like the famous Chinese electrolytic caps?

they're a hell of a lot lighter than they should be and the actual capacity i'd guess is 1/4 or less. i bought some AA nimh batteries off ebay and they feel lighter than AAA alkalines. three or four cheap chinese AA nimhs weigh about the same as one japanese duracell 2450mah AA cell.

 

[dud]

OP, where you located in Tennessee? I am considering retiring in the area.

As for batteries ... you get what you pay for. Lithium Ion has the highest power density of the 3 main battery types. You can go a little higher by going Lithium Polymer ... used mostly for RC planes (and somewhat expensive). Nicads last a few years and suffer from the "memory" effect. Nickel Metal Hydride has a higher E density and (for the most part) does not have the memory issue.

 

[Paladin3]

I did a bunch of research on those high capacity Chinese NiMH batteries being offered on eBay. Most (all?) of them are a garbage, don't have half the capacity they are rated at, or just don't hold a charge. Avoid. If you google the brand name you will see reports.

 

[phucheneh]

they're a hell of a lot lighter than they should be and the actual capacity i'd guess is 1/4 or less. i bought some AA nimh batteries off ebay and they feel lighter than AAA alkalines. three or four cheap chinese AA nimhs weigh about the same as one japanese duracell 2450mah AA cell.

OK...so basically, the 'lying' thing. I dunno why I would've even thought otherwise, really. I guess it's just that alkalines never seemed to have their ratings printed on them, hence the not-terribly-observant had no way of discerning what was 'good.' I remember three levels of battery: Duracell/Energizer; generally the best, but pricey and could still vary widely in capacity. Chinese crap; felt like they were filled with confetti. And then the stuff in the middle, which is what I usually bought.

I guess I expected some vague honesty in NiMH labelling. I mean, if it wasn't the labeled voltage, I'm sure someone could be held legally accountable...does buying straight from China (no importer/reseller) avoid fraud liabilities?

 

[Leros]

Don't forget to look at the maximum discharge rate. A lot of these expensive RC batteries have relatively high discharge rates compared to something like a standard AA battery.

 

[phucheneh]

OP, where you located in Tennessee? I am considering retiring in the area.

As for batteries ... you get what you pay for. Lithium Ion has the highest power density of the 3 main battery types. You can go a little higher by going Lithium Polymer ... used mostly for RC planes (and somewhat expensive). Nicads last a few years and suffer from the "memory" effect. Nickel Metal Hydride has a higher E density and (for the most part) does not have the memory issue.

I'm in Nashville. Nashville zip code, but I'm right on the southeast edge. If you follow 24E (south, really), I'm right before Lavergne, Smyrna, and Murfreesboro (that's Rutherford county, I'm in Metro/Davidson).

If you've gotta be in TN, it would be my choice. I can't live in the more remote cities/towns...and that pretty much leaves Knoxville (no), Chattanooga (god no), and Memphis (hell no).

I work all over town and have been here most of my life, so I'm pretty familiar with it. If you have any questions about the city, including its various suburban areas and outlying towns (still kinda just commuter suburbs), feel free to ask me.

On the batteries, I know Lithium Polymer (same as Lithium Ion, IIRC?) is becoming popular with hobbyists. People run 11v LiPo batteries through these guns to get crazy rates of fire. Not sure why, though. In addition to being cheaper, NiMH seems to be much more forgiving. I dunno why they only sell 9.6v NiMH's...I cobbled together one 12v out of a couple packs with bad cells...worked fine...was nuts.

And to anyone who wants to ask: Yep, airsoft is basically LARPing mixed with Call of Duty. I find it fun and don't take it too seriously (unlike the guys that squad up, wear actual Army gear...and are usually terrible).

 

[phucheneh]

Don't forget to look at the maximum discharge rate. A lot of these expensive RC batteries have relatively high discharge rates compared to something like a standard AA battery.

I don't ever see that given? But shit, I think you're spot-on as to why we have to use special cells. It strikes me that I've briefly shorted stuff before, and these batteries will freakin' weld stuff...okay, not 'weld,' but you know what I mean...they spark like shorting a car battery and will transfer metal between shorted contacts. I guess a bunch of AA's in series probably don't do that so much.

That leads to another random electricity question...there's no way to figure draw just by reading the resistance of an electric motor, is there? As in, a motor at rest will be different than a motor doing work?

 

[_Rick_]

At work, I have an electronics guy in my office.
He recently ordered a batch of fancy form factor batteries for some projectm via eBay, from Chinese sources.
He had them tested in-house for capacity, and got between 50mAh to 500mAh out of them.
I think they were all labeled at or above 3Ah (in a slightly bigger than AA- form factor).

Not worth the trouble, and not worth even the low prices they're demanding. Stick to stuff with a warranty and somewhere with an address.

 

[arkcom]

Here's some good quality chinese LiPos. They also have chargers.

http://www.hobbyking.com/hobbyking/store/__476__85__Batteries_Accessories-Airsoft.html

 

[Jeff7]

Based on my own testing, a 2250mAh China-special Powerizer brand AA will likely have about the same capacity as a 1700mAh made-in-Japan Sanyo AA, and it will also have a lower terminal voltage under load, and a sketchy discharge curve. You'll also probably be replacing somewhere around 25% of the cells within a year when they develop some kind of internal short, giving you a terminal voltage of somewhere around 0.09V.

That's from my own experience with them. Results may vary.

Japanese-made Sanyo Eneloops are my NiMH of choice now. Unfortunately, they only make them in AA and AAA sizes, at least for sale in the US. :\

 

[MWink]

Just to echo what everyone else has said, it does seem like many generic Chinese batteries are garbage. I bought a pair of AA's from Deal Extreme that were rated 1800mAh. After letting my LaCrosse BC-900 refresh them they ended up with a capacity of 80mAh and 180mAh. In other words, utterly useless. They also self discharge in a few days.

 

[phucheneh]

So what the hell do Chinese people use for batteries?

The realization that Chinese sellers are pretty much untouchable via eBay is kinda scary. They can sell us whatever they want with whatever label they want to put on it. Since they're mailing it directly to you, rather than, say sending it to Walmart for resale, our consumer protections are pretty much moot, aren't they?

eBay becomes the law. D: