battery life

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Instead of spending 18 or so bucks on a one time lantern battery. I'd strongly suggest checking at your local hobby shop in the R/C area for a Hobbico 12v 7amp/hr rechargable Gel-Cell battery for about 20 to 24 bucks. buy a 500ma or 1000ma radio shack 12v adapter and a par of small alligatro clips. cut off the adaptor plug, solder on the alligator clips making sure you locate the positive lead (the side of the wire with the white strip) make that your Red lead. You now have an 8 hr trickle charger for the gel-cell. I replaced a hobbico battery this spring, that I'd been using constantly for 8 years to launch everything for micro's to 3 D12 clusters. The replacement is exactly the same size and shape. I can't recommend them any higher as a small personal launch system long use battery. I've Never drained these batteries in a full days launch..up to 30 or so single motor flights or 5 3 motor clusters is about the max I've actually done on a fresh charge.
hope this helps
thanks for your suggestion! problem is though, my pops has about 10 of these batteries. would one most likely last a summer? are they rechargable?

Lantern batteries are not rechargeable, and $18 is a lot of money for a rather wimpy non-rechargable battery.

Below is a link to the Radio Shack lantern battery data sheet. It is rated at 7.5 AH, however it has a very high internal resistance of 2 ohms, and the greatest current draw shown on the data sheet is only 2 amps. If you short it out, you can only get I=V/R=12/2=6 amps out of it in a 1 second pulse (a measly 72 watts). That enough to fire 1or 2 Estes ignitors but probably not a copperhead. (If you only want to fire Estes ignitors, 4 AA Alkalines in series delivering 6 volts work just fine.) This battery will not last very long as a launch battery, and once it's dead, you have to throw it out. It can't be recharged.

As Micromister said, 12 volt lead acid gell cells used of emergency lighting and computer UPS applications are inexpensive and rechargeable.

Below is a typical 7 AH Gell Cell data sheet that you can purchase for $18-$25 at a good electronics supply store or from a number of on-lines sources.

The internal resistance of the battery is listed as 0.040 ohms, so it can theoretically deliver I=V/R=12/0.040=300 amps on a dead short (for a short time anyway). This is much more appropriate for firing ignitors. With the potential of delivering 300 amps, (3.6 KW) it's not a toy, so you won't find one in your local department store.

Note that the gell cell actually has a curve at 23 amp current drain, and it will actually deliver that current for 8 minutes. If you look at a typical copperhead igintor, it will typical ignitor consumes 0.005 AH of the battery capacity (~20 amps for ~1 Second), so you could expect ~700 firings from this battery before you have to recharge it, however it will last a lot longer if you trickle charge it for a day or so after each use.

Any automotive trickle charger will top off the battery. Well maintained and stored around 70 F, the battery will last about 5 years. If you charge it and disconnect the charger, it will last even longer.

Bob Krech
Home Depot has a Jumper/Charger 12 volt pack for $29 that has a 400 cold cranking amp battery. I may get one myself.
at a neighbor's garage sale, for free, I got an old 400W computer UPS which is basically a nice battery and charger ... and an inverter ... in a convenient package.

open it up and tap in to the battery posts for the 12v, and there's your launch power.

the inverter can run 120v AC appliances you might carry with you to the range, like maybe a TV/VCR for your Boostervision camera, laptop computer for running Rocksim, etc.

even if you pay $10 or whatever it's still cheaper than a lead-acid battery and charger.

hope that helps!