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chalinaty
08-22-2017, 09:10 PM
Hey Folks!
My club has a great launch system that we purchased last year. We had been using a car battery with it but it needs to be replaced. The system is a relay-type with 10 Low-Medium Power pads and 10 High Power pads. We only use about 4 Low-Med pads currently but we do launch up to G engines and some clusters. We also have the occasional drag race. My question is: What do I look for in a replacement battery? I can get a cheaper, small lawn and garden battery with 250 cold-cranking amps, a regular car battery with 500 CCA, or a battery with 710 CCA. Any recommendations?
Thanks!

jetlag
08-23-2017, 07:52 AM
Spend the extra $ and get a sealed battery. Then you won't have to worry about acid leakage if it turns over and as it charges. Amperage is your friend, so get a battery with capacity to spare. Keep it trickle charged between launches, and it should last a long time. Interstate and Duracell make great sealed batteries. You can get Duracell sealed batteries at Sam's. You want reliability and safety.
Allen

tbzep
08-23-2017, 09:34 AM
To give you an idea, a little 7Ah gel cell (sealed lead acid) will fire off a large cluster with solar igniters easily. I've routinely done 4 and 5 engine clusters with solars, and I used to do crappy copperheads and tiger tails with 100% reliability. In other words, you don't need 250 cold cranking amps much less a 710 cca car battery assuming your system uses relays and you aren't running ignition current 500 ft to an away cell and you pay a little bit of attention to igniter installation.

stefanj
08-23-2017, 11:55 AM
Oregon Rocketry uses, for its low-power launch system, an emergency car battery charging system.

I bought a a near-identical model for myself, at Harbor Freight. It cost about $40.

The unit has a handle, a very sturdy plastic case, a meter, an emergency light (for changing tires or other repairs), and two heavy-duty battery clips. It charges overnight with AC.

I've never, ever seen a case where it runs out of "juice" during a launch. There have been cases where I forgot to charge the unit, and it maintains enough charge from the previous month to run a launch. (Say, 50 - 75 launches.)

These units are certainly larger than a small sealed battery, but they have multiple uses and are readilby available.

BEC
08-23-2017, 04:06 PM
...and they contain a small sealed lead-acid battery about the size of the one tbzep mentions.

I fly with a couple of clubs who use these jump starter devices to power their launch systems and their PAs.

PaulK
08-26-2017, 09:45 AM
I fly with a couple of clubs who use these jump starter devices to power their launch systems and their PAs.Our club uses the same. Look at the amp-hour capacity, though, they're not all created equal. We had some cheapo ones that would barely last a full day's launch. Our newer ones go the whole weekend.

ghrocketman
08-28-2017, 01:34 AM
I use a jump-starter box to launch as well. It contains a 7.2Ah 12V Gel Cell.
Same battery for use in my R/C glow-engine flight/starter box as well.
Will fire hundreds of rocket igniters on a single charge.