what lithium battery replaces 8 AA alkalines?

[DJFuji]

Hey guys,

So I have an electronics project where i have an 8 AA battery pack from radio shack (http://www.radioshack.com/sm-8...lder--pi-2062251.html) and i'd like to replace it with a lithium battery pack so it's lighter to carry and lasts longer.

I assume that I can just strip the wires and splice them together with the battery pack.

Question is, what battery pack am I looking for? Do i just need to worry about it being 12v? (1.5v x 8)? Or do i have to worry about MAHs and other stuff?

Appreciate the help in advance.

 

[PottedMeat]

What is the input voltage range and maximum current on the device and the type of load ( how long does it normally last? ) - that will determine if you can replace the battery pack.

Do you need it to fit in that 8 pack size slot?

A quick google/wikipedia search says AA Alkaline batteries are usually 1000mAh, so you would need to find a pack that is rated 12V with at least 1000mAh. If you fill that slot with a 12V LiIon pack, it will probably be rated way more than 1000mAh and will really really extend the life of the devices - however you're gonna pay a lot ( battery + special charger ).

Kinda like this:
http://www.batteryspace.com/in...VIEWCATS&Category=1069

I'd just try some high mAh rated AA batteries - if the devices doesn't work at the slightly lower voltage, you can just return 'em.

 

[DJFuji]

well, i guess the thing is that i dont want to carry around that huge 8-battery pack with me and then have to worry about individual batteries. I'd rather just carry around a tiny Li-Ion, cell-phone-sized battery that i can charge when i need to.

Not sure what the max current is, but it's not a huge battery drainer. The 8-pack battery pack lasts for quite a while. The other thing i'd like with the lith ion pack is the ability to check the charge. Like maybe a mini battery meter or something.

 

[DJFuji]

^

 

[DJFuji]

Can anyone help?

 

[DJFuji]

would this work?

http://www.supercircuits.com/Power-Supplies/MVLBCS-7

Or maybe something smaller? I don't need that much power...

Just looked at the device it's powering. It says Power DC12V, 100 mA.

 

[Jeff7]

Rubycon would probably be able to help out, but it looks like she's been away for over a month now. I think sometimes her job can take her away from reliable Internet access; hopefully that's all it is, and nothing serious.

I'm pretty sure lithium ion cells are 3.7V these days; older ones were 3.6V.
So that pack you linked to is probably 11.1V, which your device should be able to use.
Unless they now have 4.0V Lithium cells, which I guess is possible.

Rubycon did mention that you always want to have some kind of monitoring circuitry with Li-ion cells, which protects the cells from overcharging, deep discharging, and short circuits. Some may also monitor temperature.
Packs like these include such circuitry within the pack.
And you'll definitely need a charger that is specifically made to charge Li-ion batteries. Use a Nicad/NiMH charger, and at best, you'll have dead batteries; at worst, a fire.


Now the catch - BatterySpace seems to be a major Powerizer distributor. I've never had good luck with any of Powerizer's stuff, namely their AA NiMH cells. They tend to lose capacity very quickly, to the point where they will only put out about 20% of their original rated capacity.
Lithium-ion's inherent volatility makes it something that I wouldn't want to go cheap on.
I'll look around and see if I can find somewhere that sells something non-Powerizer. I've had good experiences with Sanyo stuff, made in Japan.


Capacity: You mention that you use AA's in it. What kind? "Heavy duty," regular alkaline, or NiMH?

 

[Cogman]

You aren't going to find a lithium rechargable battery out there to replace a double AA pack or anything, and for good reason.

Do you remember all the hassle Sony got for exploding batteries? Well, you will run into the same problem if you allow Li-Ion batteries in the hands of consumers without checks. Most people are too stupid to unplug anything that is recharging when it is full, instead they leave it charging for hours on end. NIMH and NICD batteries can take the abuse, but Li-Ion batteries can't. They will explode if overcharged for too long.

So how does that work for cellphones, laptops, ect that have Li-Ion? Simple. Each device that uses it will have a chip installed to check the charge level (and sometime the tempurature) of the battery. These chips will keep the battery from overcharging and potentially causeing damage.

Bottom line, No Li-Ion batteries exists to replace the NIMH batteries. I do suggest though, that you give NIMH batteries a try. They have fairly good power density and less problems exploding.

 

[Jeff7]

Originally posted by: Cogman
You aren't going to find a lithium rechargable battery out there to replace a double AA pack or anything, and for good reason.

Do you remember all the hassle Sony got for exploding batteries? Well, you will run into the same problem if you allow Li-Ion batteries in the hands of consumers without checks. Most people are too stupid to unplug anything that is recharging when it is full, instead they leave it charging for hours on end. NIMH and NICD batteries can take the abuse, but Li-Ion batteries can't. They will explode if overcharged for too long.

So how does that work for cellphones, laptops, ect that have Li-Ion? Simple. Each device that uses it will have a chip installed to check the charge level (and sometime the tempurature) of the battery. These chips will keep the battery from overcharging and potentially causeing damage.

Bottom line, No Li-Ion batteries exists to replace the NIMH batteries. I do suggest though, that you give NIMH batteries a try. They have fairly good power density and less problems exploding.

Well, you won't find li-ion cells to replace regular AA cells. For one, the voltage is all wrong, and as you mention, without proper protection circuitry for the pack, you could be looking at bad news when charging or discharging. A charger though should be smart enough to be able to safely charge a li-ion cell without some kind of circuitry in the middle.

But getting technical/nit-picky, a battery is a collection of cells, and it's fairly easy to find li-ion battery packs, and they come with the protection circuitry already wired in and securely wrapped up with the whole assembly.



Anyhow, moral of the story: Lithium ion cells can be nasty if they are mistreated at all.
Lithium ion cells need protection circuitry to keep them safe.
Lithium ion cells need a charger designed specifically to charge lithium ion cells.

 

[DJFuji]

Hey guys,

Thanks for the quick replies. Cogman, i think you're misinterpreting what i'm looking for. I don't want replacement Li-Ion batteries to fit into the 8-AA radio shack holder, I want a tiny Li-Ion battery pack that outputs the equivalent of the 8-AA holder so that a) i dont have to drag that thing around with me, and b) i dont have to mess with tons of AA batteries all over the place.

Jeff, I'm using alkalines at the moment but i just bought a bunch of powerex NiMH 2700mAH AAs for this and some other equipment. Ultimately i don't even want to have to deal with AAs though. I'd LOVE to just have a tiny battery pack which can power this device without the bulk.

This one (http://www.batteryspace.com/in...=VIEWPROD&ProdID=2464) looks like it would work, as long as this thing supports 11.1V.

 

[Jeff7]

Originally posted by: DJFuji
Jeff, I'm using alkalines at the moment but i just bought a bunch of powerex NiMH 2700mAH AAs for this and some other equipment. Ultimately i don't even want to have to deal with AAs though. I'd LOVE to just have a tiny battery pack which can power this device without the bulk.

This one (http://www.batteryspace.com/in...=VIEWPROD&ProdID=2464) looks like it would work, as long as this thing supports 11.1V.

12 NiMH cells will give you about 9.6V. If they can power it, then you'll be just fine with 11.1V.
You can also do another test with the alkalines - try 7 instead of 8, for 10.5V.


That li-ion pack there should do just fine. All the protection circuitry is built right in, and they link to a suitable charger. I'd prefer a non-Powerizer brand, but I don't know of any other good battery sellers that stock lots of li-ion packs.

 

[DJFuji]

Crap i hate that NiMHs aren't actual replacements for alkalines. I just keep assuming that i can use them wherever i normally use alkalines. I'll test it out. Thanks for the great info.

 

[DJFuji]

I'm tempted to get the one i originally found (http://www.supercircuits.com/Power-Supplies/MVLBCS-7) because it has the connector already setup (the device power connector looks just like the one here) and includes the charger. The problem with the batteryspace one is that i have to splice the connections into another connector, and then i have to UNsplice it in order to charge it with the banana clips. Is there a more elegant solution to this?

Do you see any problem with the 12v battery from supercircuits?

 

[Modelworks]

LiFePO4 batteries would be perfect for your situation.
Unfortunately they are really expensive right now .

http://www.iloveebikes.com/batteries.html

 

[Jeff7]

Originally posted by: DJFuji
Crap i hate that NiMHs aren't actual replacements for alkalines. I just keep assuming that i can use them wherever i normally use alkalines. I'll test it out. Thanks for the great info.

They're pretty close though, and the new low self-discharge NiMH cells really help close the gap between alkaline and rechargeables.


Possible problems with the Supercircuits pack:
1) It's 4.5A, so it's probably going to be fairly large, possibly to the point where it would rival the AA's you're already using. On the plus side, it would give you lots of runtime.

2) The specs are pretty sparse. It's probably not really 12V, since lithium cells are 3.7V each. 3 in series would be 11.1V. And it doesn't list the dimensions or weight.

3) Protection circuitry. I would hope that li-ion packs come standard with some kind of protection circuitry, but that part isn't specified in the description.



All this splicing you mention - what all connectors are you using? What is the device? Can the device be modified in any way?

 

[DJFuji]

It's a spy camera that has a power connector which looks exactly like the connector in the supercircuits pic. Right now we splice the red/black cables into the radio shack adapter but it's a pain. I'm wondering if maybe the supercircuits one isn't as small as it looks in the picture. That thing looks like a cordless phone battery. ANd you're right, 4.5A would probably be huge.

I guess with the battery space one, i could cut the charging terminal clips and permanently connect it to a connector that would plug into my camera power connector. I just want the smallest battery pack possible at this point.

 

[Jeff7]

It'll cost a bit more in shipping, but here's all you'll ever need for battery connectors:

Female

Male

Get those, and some heat shrink tubing, and you're on your way to some excellent spliced connectors.