Parallel Battery Pack

[soupdragon]

I'm currently weighing up options for a battery pack to be used in a mag. I fancied a bit more runtime so my plan was to use 18 Elite 1500 2/3A in a 3x6 pack giving 7.2v and a capacity of 4500mah

This should fit into a Tri-bore 3D mag without too many problems

But after reading this thread http://www.candlepowerforums.com/vb/showthread.php?t=159764 I'm not so sure about a parallel pack now

One option I thought could be to have the batteries made into 3 sticks 6 cells long and charge em seperately but its a less convinient option

Anyhow some opinions on what will/wont work would be appreciated

 

[mdocod]

what about a 6x17670 pack, (3 parallel, 2 series), that would be a ~7.4V 4800mAH pack. You'd only have to deal with 1/3rd the number of cells. Make 3 charging "taps" from the pack (one on each end and one in the middle between the 2 banks). Charge half the pack at a time to insure proper balancing of the cells. (charging 3 cells in parallel). Use protected cells Like AWs.

Only problem with this is I'm not 100% sure they will fit in a tri-bore, I *think* they will, but I think this option is worth a look as it reduces the complexity of the pack substantially.

 

[soupdragon]

17670's were another option i thought about and iy would reduce the pack length although i think they are a little too long long for a 2d which is a shame

But the reason for the 2/3a nimhs is their ability to handle large current drain without stressing out too much as they are a size used in rc a fair bit

Heres the data i've been looking at from CheapBatteryPacks http://www.cheapbatterypacks.com/cellinfo.asp?invid=ELITE1500A. I've not found any data for AW 17670's

The bulb i was planning on is the phillips 5761 which draws 5.5a at 7.2v so it would be about 1.8a from each cell

D Li-ions would be really nice but it seems any feeler threads get close then hit a wall and fizzle out

 

[LuxLuthor]

...But after reading this thread http://www.candlepowerforums.com/vb/showthread.php?t=159764 I'm not so sure about a parallel pack now

This would work with the Elites, but you need to periodically deliver a 0.1C charge so the cells all get fully charged and thereby balanced. Many of the universal NiMH chargers go into a trickle mode which should also accomplish that.

If you use Lithium, you will need a way to put them in parallel & series. Not sure what details you are looking for, but AW's listing of his cells and their mAh capacity is here.

 

[soupdragon]

Sorry i was being a bit vague when i said info on the 17670s. I was refering to a runtime graph i've seen the one for the 17500s based on that the 17670s should do the trick quite happily, plus I already have a couple knocking about somewhere

If i went with 17670s id prob leave them loose and charge em seperately but i didnt fancy doing that with 18 2/3a cells

Now the trick is to find some extra space in a 2d mag and i'm set

 

[mdocod]

a stack of 3 17670s in parallel could theoretically deliver upwards of around 8-9 amps safely, you already pointed out the 5761 at around 5.5A, I don't know of any "6-7.4V" bulb that draws much more than that anyways.