Electric Launcher Batteries

Before I can upgrade to a rechargeable gel cell or a car battery, I'm stuck with alkaline.
According to a data sheet I have, alkaline D cells have a capacity of
20.5 Ah, whereas alkaline lantern batteries have a capacity of 18.0 Ah.
Moreover, eight D cells are cheaper than two lantern batteries.
However, some earlier postings I've seen here on the matter recommended lantern batteries when converting to higher-current launchers. Is there any reason why I should go with lantern batteries (as opposed to D cells) that I'm not seeing?
Thanks in advance for any advice you might have on the matter.
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The problem is that the D cell does not lend itself to high current outputs because the connections betweeen cells,and between cell and holder,is only pressure-contact,suitable for only moderate currents. You would get heating across the cell connections,that means voltage drop.
NiCd packs are welded with straps so they can better handle high currents. SLA batteries also have good between-cell connections.
I doubt lantern batteries are any better than D cells WRT internal connections;the high amp-hour rating is more for long periods of moderate current draws,not brief very high current draws.
for example;20 AH does not always mean you can draw 20 amps for one hour,but more likely one amp for 20 hours,or 2A for 10 hours.
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It's not the welded straps that make the difference, its the lower internal resistance of each cell, which is a function of battery chemistry, not pack construction.
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Bob Kaplow NAR # 18L >>> To reply, there's no internet on Mars (yet)! <<<
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Bob Kaplow wrote:

True, to a point, but a battery is only as strong as its weakest link. The contact or ultrasonic welded tags allow the low internal resistance to be fully used.
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I wouldn't use either one. The AH rating really means very little with these batteries. The real question is how much current can they dump under a direct short, and how many times can they do so. Which is a direct function of the internal resistance of the battery technology. AA sized NiCads rated at 0.6AH can dump over 20A. Larger NiCads, like those used in RC electric models can dump even more. So can lead acid, gell or regular. D cells and lantern batteries can not.
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My comments regarding using lantern batteries have always been comparing the standard Estes 4 x AA batteries which give you 6 volts and very little amps or amp-hours to a 6 volt alkaline lantern battery. Same voltage, more amperage and amp-hours. The voltage will not drop as much with the lantern battery when you fire the igniter, so the power delivered to the igniter will be higher.
Think of it in simple "light bulb" terms. If you light up the same 6 volt light bulb with 4 AA batteries or 1 6 volt lantern battery, which will light up stronger and stay lighted longer?
Or you can try a Quest controller with a 9 volt alkaline battery: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item `35468719
-Fred Shecter NAR 20117
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addams013 wrote:

really? the cost of two sets of 8x D cells is close to the cost of a small lead-acid battery. save your pennies and get the good stuff.
check around at garage sales for old computer UPS. often you can get one with a good 12v battery for $5 or so. bonus - comes with a build-in charger! and an inverter so you can run 120v stuff at your launch site.

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What you should look for are batteries that have a high discharge rate. Thes are purpose-made for jobs like a launcher.
Check out: www.batteriesamerica.com
If I remember correctly, they have them. I have bought many a battery from them and they have great service.
Jeff R.
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You may want to look for one of those automotive Jumpstart devices. I bought one from this place for $20.00. http://www.homier.com/detail.asp?SessionKey=INx3EljwtycwMKnPL0RzfRuPMUW16%2fDdZZc313gxHwhPvBUI4Tq%2bquhMZvcXkV%2badcxRag6D1R6A&dpt=&cat=&sku 134
I lucked out and have one in town so I didn't have to pay shipping, but I see similar product on sale for around $25 all the time.
It has a 17AH lead acid battery inside and built in batter charger to boot. For the price you can't beat it since you get a really nice carrying case to hold everything also. All you need to do is add a relay and a few other parts to make a really nice and powerful launcher. I removed the clamps that would have connected to the battery for jumping a car and use what left to hold the wire for my remote. I don't have any pics, but will take some and post if your interested.
I used the plans from ROL to build mine.
http://www.info-central.org/index.cgi?support

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