High current batteries

[Pontiacg5]

I need some 12v batteries that have some decent Ah ratings. Size really doesn't matter so long as they don't weigh 100 pounds! I was thinking some lead acid batteries but I was wondering if anyone else had any better ideas. I need a current draw of around 40 amps

 

[charliebruce]

SLA will probably be the cheapest, but to get high current output, you could also (carefully - make sure they're all equally charged!) put several batteries in parallel, or perhaps investigate LiFePO4 batteries.

 

[Eudaimonium]

Lithium polymer battery packs are designed for high current applications.
They are usually several cells connected in series for higher voltage, and packs are typically used in RC models of planes/boats/helis whatever.

I think I saw a 5000mAh 14.4 V li-po battery pack , rated discharge - 25 C.
Yup, that is 125 A of current.

Price was just under $140 I think.


You can ofcourse find much cheaper and more suitable battey packs.

 

[Pontiacg5]

11.1v is within my range, so I think I'll stick with those (I'm cheap )

Does anyone have experience buying batteries on ebay? I'm looking at these but I don't want to buy 5Ah and only get 1. I guess what I'm trying to say is are they legit?

11.1v 5000mAh 30C LiPo 3-Cell 11.1 RC Wif Akku Battery - eBay (item 120557583864 end time May-16-10 00:33:03 PDT)

I plan on running 4 in parallel which is 20000mAh at 30c which would give me 600A right? not bad for $140 while only weighing ~4 pounds. Those will be easier to tote around than a lead acid battery too

 

[HaloBlu]

In case you go for Lead Acid I would recommend against buying batteries from ebay. Buy from reputable dealer only cause Lead Acids have a certain life span & you don't want to get one thats used, old or worse has been damaged from improper maintenance.
Lead Acid Deep Cycle Battery FAQ
What do you plan on using it for?

 

[Pontiacg5]

A portable 40-60W co2 laser, I plan on putting the tube in a pvc holder then making some sort of umbilical cord to attach it to a backpack.

I had a 20W tube running off of a 300W power inverter, my car battery, and a 17"(IIRC) CRT monitor. I could drive around and lase things. I want a more portable version now though

 

[brando132]

Something like this? http://laserpointerforums.com/f43/starwarz-co2-power-47504.html

 

[Pontiacg5]

Pretty much, but a whole lot bigger and a little bit stronger. I'm going to need some serious battery power, a water tank (I think I can get away with 1 gallon,) a water pump, a radiator, a power supply, and the tube.

 

[pullbangdead]

Check out these guys: Common Sense RC

They have some great big LiPo packs, even single packs that can pump out 90+ amps continuously. They are also very reputable from all of my reading on RC forums while I was looking for a LiPo pack for my WhiteFusion build. And for such applications, I would definitely go for a high-quality battery over saving a few bucks for a battery with any question marks.

The 35C high discharge packs can push some major current per cell, and their 15C Big Packs are, of course, very high capacity. For instance, they have an 11.1V 5Ah cell that can put out 150A continuous, and it's only 4.7x3.8x13.8cm in size. Of course it's $200, but it's available. They also have a 11.1V 8Ah cell that can do 95A continuous, but it is bigger, but also cheaper. Lots of options around.

And this can't be overstated: Be Careful. The packs have whole other dangers besides the high currents. There's a lot of energy stored in these things, and it can come out in several dangerous ways. Charging is not trivial, either, these things are a big fire hazard. In the scale you're talking about, NOTHING is trivial, don't take a single thing for granted. I'm sure you're aware, but it can't be said too many times.


ETA: Oh, just re-read and saw you need 40A, oops, sorry about that. You don't need anywhere near the outputs I listed above, but you can see from those examples that they have a LOT of options that will satisfy your 40A needs without any trouble at all. http://www.commonsenserc.com/product_info.php?cPath=37_35&products_id=242 <---This is an "8C Budget Pack", it's 11.1V 6Ah, and can do 48A continuous, at only $100. Lots of options.

 

[HaloBlu]

A portable 40-60W co2 laser
........
I could drive around and lase things. I want a more portable version now though

Just glad I don't live near you or where ever you might drive past. :tinfoil:

 

[Pontiacg5]

Check out these guys: Common Sense RC

They have some great big LiPo packs, even single packs that can pump out 90+ amps continuously. They are also very reputable from all of my reading on RC forums while I was looking for a LiPo pack for my WhiteFusion build. And for such applications, I would definitely go for a high-quality battery over saving a few bucks for a battery with any question marks.

The 35C high discharge packs can push some major current per cell, and their 15C Big Packs are, of course, very high capacity. For instance, they have an 11.1V 5Ah cell that can put out 150A continuous, and it's only 4.7x3.8x13.8cm in size. Of course it's $200, but it's available. They also have a 11.1V 8Ah cell that can do 95A continuous, but it is bigger, but also cheaper. Lots of options around.

And this can't be overstated: Be Careful. The packs have whole other dangers besides the high currents. There's a lot of energy stored in these things, and it can come out in several dangerous ways. Charging is not trivial, either, these things are a big fire hazard. In the scale you're talking about, NOTHING is trivial, don't take a single thing for granted. I'm sure you're aware, but it can't be said too many times.


ETA: Oh, just re-read and saw you need 40A, oops, sorry about that. You don't need anywhere near the outputs I listed above, but you can see from those examples that they have a LOT of options that will satisfy your 40A needs without any trouble at all. Common Sense RC <---This is an "8C Budget Pack", it's 11.1V 6Ah, and can do 48A continuous, at only $100. Lots of options.

I might just go with one of these, and add another if I need more runtime.

I was thinking of a deep cycle car audio battery too, one like this.
Stinger SPV44 Car Audio Deep Cell High Amperage Replacement Battery

I don't really need the peak amp draw that this battery could provide, but I like the capacity and weight, not to mention its dry so it won't spill. I would like to have some decent runtime!

 

[HaloBlu]

If your going lead acid definitely get AGM absorbed glass mat like that one.

 

[BShanahan14rulz]

Apple Macbook Pro battery packs that I've opened come with Sony LiPo's.

 

[bootleg2go]

11.1v is within my range, so I think I'll stick with those (I'm cheap )

Does anyone have experience buying batteries on ebay? I'm looking at these but I don't want to buy 5Ah and only get 1. I guess what I'm trying to say is are they legit?

11.1v 5000mAh 30C LiPo 3-Cell 11.1 RC Wif Akku Battery - eBay (item 120557583864 end time May-16-10 00:33:03 PDT)

I plan on running 4 in parallel which is 20000mAh at 30c which would give me 600A right? not bad for $140 while only weighing ~4 pounds. Those will be easier to tote around than a lead acid battery too

So how long do you need to supply 40Amps of current from the battery you need?
The battery you described above with 4 in parallel can supply 20Amp hours (20 Amps for 1 hour) or (40 Amps for 30 minutes), so at 40 Amps will only power your device for 30 minutes. The C rating is not that important, it's the mAhr rating that's most important; sure you can say 600 amps, but at 600amps the battery would be fully drained in 2 minutes so at 600A calling it continuous would be kind of a misnomer as that continuous period is pretty short....not to mention the need for a hugh diameter wire (about 1/2 inch diameter), with a 40 Amp load only needing about 1/4" conductor (about the diameter of a pencil).
I would go with a deep cycle marine battery as their capacity rating is probably in hundreds of Amp hours and couple probably supply 40Amps for several hours or more rather than just 30 minutes.

 

[Pontiacg5]

I wanted 30 to hour long runtime and figure I'll be pulling 40-60A continuous. The thing is I don't think that the eBay mAh ratings are legit, I've bought 1000mAh AAA batteries that last about 10 minutes in my laser while duracell 800mAhs run for a good 30 minutes. I guess what I am trying to say is that the quality scares me

I think I'm going to go with a AGM battery, I think I can get more capacity per dollar that way.

Thanks for the tips!