Ożga
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Grom Petukhi!
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Post by Ożga on Dec 29, 2013 23:00:14 GMT -5
I've been having trouble finding the perfect battery for my DBoys AK. What I want is a 1200mAh+ 11.1v lipo with a 20c+ discharge rate. Bonus points if they are already soldered to Deans connectors. I've order a Turnigy Nano-Tech 1300mAh 25c 11.1v battery from HobbyKing, but alas it did not fit in the rear sight block/upper handguard area. The bottleneck in my gun's upper handguard is a 19mm wide circular hole. Having the battery be rounded will maximize it's ability to fit as well as capacity. So good people of MiA, does such a wonderful battery exist?
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ctres
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Post by ctres on Dec 29, 2013 23:24:45 GMT -5
Lipos seem to come exclusively in brick/stick form. Other types of lithium ion batteries do come in round cells and I remember seeing them on wgc but I think they don't usually have a very high discharge rate. Lithium ion is a very general term and I think lipos actually fall under that umbrella but whatever the chemistry of the cylindrical cells is, it did seem to be available with a decent discharge rate when I researched them a couple years ago. I remember being able to fit a 7.4v 1200 mah stick in a dboys AK, so something like that may be your best bet.
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Post by Tank on Dec 30, 2013 2:34:42 GMT -5
I know that the LiFePO4 cells made by A123 systems had a discharge rate of 60C, we were researching these cells for one of our company's products. I believe the individual cells were 1100mAH. There may now exist better cells than that, in the same cylindrical package, being that my reference point was about 3 years ago. This battery technology was developed for use in electric vehicles, so they definitely have every bit of their discharge ability. They are also a lot more safe than your typical LiPO batteries. When they fail, they just stop working, as opposed to the catastrophic failure that LiPOs can potentially have. Edit: I did a little research again on it. They look to be actually not continuous at 60C, but of course I also don't really trust the figures I see in this link either. m.ebay.com/itm/190889197226?cmd=VIDESC&gxo=trueI'm also not entirely certain about buying from them, but you could give it shot.  One thing to note with these cells is that they are not 3.7V per cell, rather they are 3.3V per cell. So figure that in as well. You could do a 9.9V pack, or a 13.2V pack. |
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ctres
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Post by ctres on Dec 30, 2013 10:42:49 GMT -5
Good thought on A123 actually, I think when I looked I was mainly looking at hobby stuff. Here is the 18650 on A123's site www.buya123batteries.com/APR18650M1A_Lithium_Ion_Cylindrical_Cell_p/300030-001.htmLooks like a 30A continuous discharge which isn't bad for a cell that size. C rating*Amp hours=discharge current, so these look like about 27C continuous but I'm not seeing a peak rating on A123's site. They do have a nice spec sheet though. assets.buya123batteries.com/images/a123/18650_data_sheet.pdfObviously these would require you to build your own battery pack, which is an idea I have toyed with but never tried. You'd definitely have to know what you are doing to make sure you don't wreck the cells when soldering onto the terminals but the wiring itself would not be too complicated. On an AK where length isn't really an issue you could build a pack with a nice voltage, but unfortunately these cells are too long for buffer tube applications. |
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Post by Tank on Dec 30, 2013 11:02:48 GMT -5
There are places that will custom make battery packs for you, and don't charge a fortune. I know there is one in Livonia, or at least there use to be, I'm sure they still exist. It was on Schoolcraft. That place dabbled in custom electronics projects and also made battery packs. I'm sure you could buy the cells and have them construct them. Some places will weld on the solder tabs, if you want to build the packs yourself, you just have to solder the other side. This does require having a really nice soldering iron though. You really should have a battery spot welder, but I know from experience that you can solder it yourself with a nice iron, without any noticeable damage to the cells.
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Ożga
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Grom Petukhi!
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Post by Ożga on Dec 30, 2013 14:36:21 GMT -5
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ctres
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Post by ctres on Dec 30, 2013 15:30:42 GMT -5
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Ożga
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Grom Petukhi!
Posts: 158
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Post by Ożga on Dec 30, 2013 15:51:00 GMT -5
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ctres
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Post by ctres on Dec 30, 2013 16:30:20 GMT -5
Man, if 20 RPS is all you want then there are tons of ways to get there. A 7.4 can easily get you up to 40 RPS if you felt like it but I still think the best option is probably to go with the last battery I linked to. Since the cells are each separate it should fit fine as long as you have enough space end to end. The one I linked to will put out more amps and is a higher quality pack and is half the price. As long as you have 232mm of space in the top tray and gas tube then you should be able to make it work.
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One thing to note with these cells is that they are not 3.7V per cell, rather they are 3.3V per cell. So figure that in as well. You could do a 9.9V pack, or a 13.2V pack.