Beginner launch battery question

[darryn]

Hi all.
I am new to rocketry and need some advice on launch batteries.
I am looking at building my own launch controller system.
I will be started off with C class motors.
Will a 12V 7aH battery be sufficient for my needs?
How many launches would i get from this capacity battery? Basically what I am wanting to find out is if this battery will last a whole day of launching.
Any advice would be appreciated.
TIA.

 

[Marlin523]

If you are launching by yourself or just a few others, you might consider making some cables that attach to your car's battery and then input to your launch controller. The 12V in your car will last all day and is easily transported. to the launch site. I made one like this and used phone plug jacks to input the box and an additional jack to output to the launch pad. That means two cables one has clips for the car battery on one end and a phone plug on the other. The second cable uses a phone plug at one end and alligator clips on the other.

 

[Trident]

Hi all.
I am new to rocketry and need some advice on launch batteries.
I am looking at building my own launch controller system.
I will be started off with C class motors.
Will a 12V 7aH battery be sufficient for my needs?
How many launches would i get from this capacity battery? Basically what I am wanting to find out is if this battery will last a whole day of launching.
Any advice would be appreciated.
TIA.

That battery (assuming it is a gel cell) wil give you more launches than you're likely to do in one day. I used to do elementary school rocketry programs, and I never ran one down, not even when we had two classes go on the same day, and had 60+ launches. I do not recall that max current they can source, but for a simple example, assuming it can source a pretty healthy current, that 7Ah rating means it can nominally deliver 7A for one hour (3.5A for 2 hours, 10A for .7 hours, etc.). Regardless, that is a bunch of ignitions!

 

[Zeus-cat]

The power needed to fire an igniter is quite small. A well charged 12V 7aH battery will have plenty of power to fire a very large number of igniters. As a matter of fact I use a 12V 7aH battery for my rockets. Someone at work had six of them and was going to throw them away. I took them several years ago and have launched probably 100 rockets in that time. I switch back and forth between two of the batteries. Ignition is always instantaneous.

I always take two of theses batteries as I really don't know how much power these batteries have. They may have been sitting around for years before I got them.

If you r battery is new you will get a lot of use out of it before you need to charge it or replace it.

 

[jpbell]

The power needed to fire an igniter is quite small. A well charged 12V 7aH battery will have plenty of power to fire a very large number of igniters. As a matter of fact I use a 12V 7aH battery for my rockets. Someone at work had six of them and was going to throw them away. I took them several years ago and have launched probably 100 rockets in that time. I switch back and forth between two of the batteries. Ignition is always instantaneous.

I always take two of theses batteries as I really don't know how much power these batteries have. They may have been sitting around for years before I got them.

If you r battery is new you will get a lot of use out of it before you need to charge it or replace it.

A simple voltmeter/multimeter would tell you how much juice each battery has... then you would know if it worth lugging both batteries around or not, or how many launches you could expect to get from one....

 

[Zeus-cat]

A simple voltmeter/multimeter would tell you how much juice each battery has... then you would know if it worth lugging both batteries around or not, or how many launches you could expect to get from one....

The sad thing is I am an electrical engineer and I have a voltmeter. I am just to lazy to check it. The batteries are fairly small so I just throw two in the back of the car whenever I launch. :bangpan:

 

[MarkII]

If you are launching by yourself or just a few others, you might consider making some cables that attach to your car's battery and then input to your launch controller. The 12V in your car will last all day and is easily transported. to the launch site.

Not all launch sites are drivable, though. And removing a 40 lb. battery from your car and lugging it 1/4 mi. out to the middle of a field is a a real PITA.

For LPR, the 4 AA's in my Estes Electron Beam launch controller seem to last forever. My favorite external power source, though, is a 6 lb., 12 volt emergency car starter battery. I can get an entire summer's worth of launches out of a single charge.

 

[RimfireJim]

The sad thing is I am an electrical engineer

In that case, I'm not going to let you off easy for using the term "power" instead of "energy". Units, man, units! :gavel:

 

[Zeus-cat]

In that case, I'm not going to let you off easy for using the term "power" instead of "energy". Units, man, units! :gavel:

D'oh!

 

[Micromeister]

Personally I can't recommend the Hobbico 12V 7amp/hr Gel-Cell any higher! it's a fantastic small footprint battery that provided more then enough power for even small club size launchers. For less then 20 bucks it'll power you LPR MPR models and small Clusters with no problem. Properly cared for it'll last for years. I bought one in the early 80's that lasted until 2004. they are Great little batteries. and can be charged with either a quicky converted 12V 500 to 1000ma wall pack or on of those little Harbor Freight Trickle chargers also under 9 bucks.
For the money I don't beleive they can be beat.

 

[WillMarchant]

We got tired of lugging car batteries around our site and have switched over to 12V "lawn tractor" batteries with no issues...

 

[txaggie08]

I'd recomned this charger to anyone. I've used them for almost every kind of commercially available battery, and they will charge them all.


Plus if you ever go into RC or something requiring LiPo or NIMH charging, you're good to go. It'll even charge the batteries in most kids toys, and do it faster to boot.

 

[Trident]

Personally I can't recommend the Hobbico 12V 7amp/hr Gel-Cell any higher! it's a fantastic small footprint battery that provided more then enough power for even small club size launchers. For less then 20 bucks it'll power you LPR MPR models and small Clusters with no problem. Properly cared for it'll last for years. I bought one in the early 80's that lasted until 2004. they are Great little batteries. and can be charged with either a quicky converted 12V 500 to 1000ma wall pack or on of those little Harbor Freight Trickle chargers also under 9 bucks.
For the money I don't beleive they can be beat.

The Harbor Freight trickle charger is excellent. I've had my 7Ah gel cell on one for years. It will not overcharge a battery, so you can keep it plugged in 24/7. I removed the big battery clips, since I knew this one was going to be dedicated to the gel cell battery. I soldered on push-on connectors to match the gel cell terminals, so there was no worry that they would get bumped off the battery while sitting in my shop.