Choosing a rechargeable battery for a launch controller

[brewster_rockit]

Hello all,

I've been looking into getting a rechargeable battery for a homemade launch controller that I've built. My requirement is that the controller should be able to ignite single AP motors with copperhead igniters, or clusters of up to four BP motors. My original design used a cigarette plug to connect to an automotive jump-start battery pack, but the cigarette ports on those jump-start batteries are usually limited to 5A of current. (I've seen ports rated for up to 10A inside the car.)

It would seem that I wouldn't want to go any lower than 12V for my battery, but are there any other factors I should consider based on the requirement to ignite copperheads? I've looked into 12V, 7AH batteries used for scooters and alarm systems. Do those seem like acceptable batteries? Might I be able to get by with a battery that's rated for fewer amp-hours? I've already read about using Harbor Freight trickle chargers to keep the battery charged.

 

[astrowolf67]

If the 12 volt port on the jump battery won't allow enough current, what about hooking directly to the jumper cables off of it?

I've always had good luck just using the cheap lawn and garden batteries available at W.Mart for 20-30 bucks. They have plenty of juice to last a full day, and, will last a few years if properly maintained.

 

[rharshberger]

If the 12 volt port on the jump battery won't allow enough current, what about hooking directly to the jumper cables off of it?

I've always had good luck just using the cheap lawn and garden batteries available at W.Mart for 20-30 bucks. They have plenty of juice to last a full day, and, will last a few years if properly maintained.

Our club uses jump boxes for all our launchers and we always hook directly to the alligator clips.

 

[Donnie]

I'd think you'd be ok with a smaller SLA battery. I've used / seen these used all over the place in the fireworks world: https://remotefiringsystems.com/12-volt-sla-battery/

They will surely last all day, no problems. Plus, I've used a firing system with one of these exact batteries (this system: https://remotefiringsystems.com/s32i-32-cue-remote-wireless-firing-system/) to ignite 20 "talon" clip igniters (which use a nichrome wire to light a fuse: https://remotefiringsystems.com/3-meter-non-pyrogen-fireworks-clip-igniters-80-igniters/) in parallel, at the same time: [video=youtube;e9d71G6uQ-8]https://www.youtube.com/watch?v=e9d71G6uQ-8[/video] .

Plenty of current sourcing ability, no realistic temperature limitations, lots of standby time. I could literally leave that firing system on overnight and it didn't care, would work just as well the next day, even when having the radio receiver powered, some led's, the voltmeter, etc.

I have since moved onto Cobra Firing Systems for scripting ability for pyromusicals, but that Dewey system was a tank!

 

[KennB]

CMASS has used "retired" alarm system batteries for years. One of our club members has an alarm service and codes require that batteries be replaced yearly or biennially, so we always had a supply of slightly used ones. We've launched hundreds of rockets in a day with very little voltage drop in that time and they take well to recharging between launch dates. To ensure copperheads and clusters light reliably, we use relays to dump lots of juice into them. Each relay uses it's own battery.

In the MMMSC, we started with portable jumper packs that could be plugged in to recharge between launch dates. We work with their large clips directly to get our systems - launch controller, PA and relays - powered. They've been okay for a few years but we are starting to see their weaker components breakdown, primarily the charger. We are looking to harvest the batteries out of them, attach Anderson connectors and use them more like the CMASS system. The president of MMMSC just moved his parents into his condo and had chairlifts installed in all the stairways. The company installed fresh batteries in them and let Scott keep the old ones; we're going to send those batteries to a nice sod farm downstate to help us with out launches, too.

It doesn't hurt that we have the same people working on the systems from both clubs; the goal is to have equipment that is compatible with both clubs' launch controllers.

 

[mkadams001]

For years I would just pop the hood and touch the wires to the battery.

Then, I built a relay controller and used a 12v 7 or 8 amp sla battery and it worked great. I think I bought it from Interstate along with a charger.

 

[Space Oddity]

I made a controller about 18 months ago. I bought a 12v 7AH Yuasa battery through Amazon. At the time it cost £12 (I guess around $18). I also installed a digital voltmeter on the controller (also Amazon around $6). It should be adequate to provide all the current you need to launch BP motors.
I've launched around 40 motors over the period. Less now because I've joined a club and fly with their controller. I've charged it once this spring. Having been stored in the shed over winter (-5C) it had only lost 3v charge.

I don't know what the battery life is, I guess 5 or 6 years. That equates to $3 a year. Far cheaper and more certain than constantly changing AA's.

SO.

Edit PS: I also installed lots of flashing "standby", "ready", and "continuity" lamps to impress and instill safety for my grandson. They were live many more times than for rocket launches.

 

[Suborbital Maniac]

I've been toying with using a R/C LiPo battery (3S, ~2800mAh) but haven't had a chance to test it. Smaller, much lighter but a bit more expensive (of course).

 

[Micromeister]

For the last 23+ years our club and Myself personally have been using re-claimed Emergency light 12v -26Amp/hr Batteries on our club and personal launchers...Particularly on our Clustered BP launchers.

I purchased a 12v -7amp/hr rechargable Gel-Cell in 1986, I used it at least twice monthly until 2008. When that particular battery failed to hold a charge I purchased another from Hobbico for under 19 bucks.

You have an excellent Gel-Cell charger in the Harbor Freight float charger. I use as many as 8 charging our Club and personal 26amp and 7 amp launcher batteries. They work just fine. They also work very well on 12V wet cells and higher Amp/hr Gel-Cells they just take a little longer.

As several have posted you'll not get much current from the cigarette plug port, Connect directly to the heavy duty battery clips. you'll get all the current needed.
As a Rule of Thumb- keep in mind 2amps per igniter. you won't go wrong with this formula

 

[KenRico]

I've been toying with using a R/C LiPo battery (3S, ~2800mAh) but haven't had a chance to test it. Smaller, much lighter but a bit more expensive (of course).

My full size harbor freight jumper batt is not holding a full charge now..

Did an impromptu LPR launch a few monthes ago and didn't feel like lugging out the HF jump batt and used my 2300mah 3S with CJs Interlock controller ..worked great!

Kenny

 

[bobkrech]

If you want to use a LiPo pack you can. They are lighter than an equivalent PbAc gel cell battery by considerable amount and much smaller. If you're not planning to launch more than 100 igniters (10 amps for 5 seconds per launch maximum) or so in a day, a 2 AH battery is more than adequate.

https://www.allelectronics.com/make-a-store/item/gc-1223/12v-2.3ah-battery-sealed-lead-acid/1.html is a 2.4 AH gel cell that costs $15, weighs 2.07 pounds, is 7"x1.35"x2.37" in size and is rated to deliver 35 amps. https://www.bb-battery.com/productpages/bp/bp2.3-12.pdf

https://www.hobbyking.com/hobbyking/store/__8934__Turnigy_2200mAh_3S_25C_Lipo_Pack.html is a comparable $12 3S 11.1 volt LiPo battery pack rated to deliver 55 amps, weighs less than 7 ounces, and is 4"x1"x1.5" in size. The equivalent 12 volt gel cell above weights ~ 5 times more, and is ~25% of the volume of the gel cell. A controller will require a smaller case, and be much lighter in weight.

You also need a LiPo charger. https://www.hobbyking.com/hobbyking/store/__7637__Turnigy_12v_2_3S_Basic_Balance_Charger.html is a cheap balancing charger that costs $4.50 that can be powered by a car battery, auto powerport with adapter, or by a 12 volt DC wallwart.

Bob

 

[Handeman]

I've been using a car starter battery pack to power launch controllers and even the new winch on our trailer launcher until we got the battery box in place. The car starter is charged by plugging in a standard extension cord into the charger and the wall. It has a work light and USB port. It has the power to turn over most car engines so it has plenty of power for launching rockets and is light and portable, easily recharged and can be used as a charging source for other items like cell phones, tablets, lipo battery chargers, etc.

If you don't need a dedicated battery for you launch system, you might want to consider a car starter unit. Mine is 8 years old or so and I recently used it to power the winch on our trailer launcher. We ran the mast up and down at least a dozen times it still showed a full charge.

 

[bobkrech]

They will work but they will weigh about 1 pound per amp-hr of battery inside the unit or so most weight between 8 to 20 pounds.

You probably have a larger unit with a 12-18 AH battery. 1 HP is ~ 60 amps so a 12 AH battery will supply 1 HP for 12 minutes = (12AH/60amps) x 60 min/H. Most electric winches are 1/3 HP to 1/4 HP so they will run a winch for 36 to 48 minutes.

Cars need ~ 1 amp per cubic inch or 60 amps per liter engine size in the summer and 2 times that on a cold winter night and diesels require twice the gasoline motor current. You could crank a 2 liter 4 cylinder for 6 minutes in the summer, and 3 minutes in the winter. A 3 liter diesel or a 6 liter gas motor could crank for 2 minutes in the summer or 1 minute in the winter. It wouldn't do too well on a 7 liter diesel, but truck with this size motor usually have 24 volt systems with dual batteries....

Bob