Securing Batteries

[sailmike]

I just bought the MAWD from Perfectflite. Now I am looking for methods of securing the 9V battery in the electronics bay. I thought of using a couple velcro ties, but I don't know if that will be strong enough. I use velcro to secure a battery larger than a 9V in my 3D plane and never had a problem with the batter coming loose, but I imagine that the battery in a rocket will experience much higher G forces. What methods do you guys use to secure the battery?

Thanks a lot,
Mike

 

[MarkM]

I just bought the MAWD from Perfectflite. Now I am looking for methods of securing the 9V battery in the electronics bay. I thought of using a couple velcro ties, but I don't know if that will be strong enough. I use velcro to secure a battery larger than a 9V in my 3D plane and never had a problem with the batter coming loose, but I imagine that the battery in a rocket will experience much higher G forces. What methods do you guys use to secure the battery?

Thanks a lot,
Mike

I use a combination of zip ties and electrical tape.

 

[jcsalem]

Two things:
1) A cable tie to hold it to the altimeter sled
2) Screws sticking up from the sled to keep it from sliding out from under the cable tie

Never had a problem with this.

 

[quickburst]

I just bought the MAWD from Perfectflite. Now I am looking for methods of securing the 9V battery in the electronics bay. I thought of using a couple velcro ties, but I don't know if that will be strong enough. I use velcro to secure a battery larger than a 9V in my 3D plane and never had a problem with the batter coming loose, but I imagine that the battery in a rocket will experience much higher G forces. What methods do you guys use to secure the battery?

Thanks a lot,
Mike

Never use Velcro. It is a static electricity nightmare. Use tie wraps, tape or anything but velcro.

 

[JDcluster]

Zip ties & duct tape......



JD

 

[LarryC]

I normally mount instrumentation on plastic from a kitchen cutting mat. The method is described in a thread in the section on techniques.

Neglected to mention battery mounting. I'll reply and add it. Very simple.

 

[kandsrockets]

I use zip ties. Here is a pic of how the batteries are secured on my L3 sled.

 

[quickburst]

I use zip ties. Here is a pic of how the batteries are secured on my L3 sled.

Exact method I use. Works great.

 

[Pantherjon]

And I presume the contacts on the AFT end so the G forces shove the battery into the contacts, correct?

 

[kandsrockets]

And I presume the contacts on the AFT end so the G forces shove the battery into the contacts, correct?

Yup

 

[Adrian A]

And I presume the contacts on the AFT end so the G forces shove the battery into the contacts, correct?

In the accel data I've seen, the Gs you get from the deployment usually put the motor Gs to shame. Depending on how the av bay is located relative to the deployment charges, you may get an acceleration in the anti-motor direction that's much larger than the motor Gs, so a battery setup that assumes that the only acceleration is coming from the motor could cause an unwelcome surprise. Even if the drogue deployment is behind the Av bay, the shock of Kevlar shock cord reaching the end of its length often causes a higher G load than the motor, and in the opposite direction from the motor thrust.

If you're using a battery holder that could be affected by G loading, my recommendation would be to orient it sideways. The largest lateral accelerations are always much smaller than the biggest axial ones. But the setup shown in the picture looks great. The zip ties would have to break in order to let the connector come off, no matter which way the G's are pointed.

 

[sailmike]

Cool! Thanks for all the replies guys.

Good point Adrian.

I was trying to think of a way to hold the battery securely while making it easy to unplug. In my experience in my RC aircraft, if the battery is left connected when the switch is turned off, the battery power is still drained. So, the lesson I learned was, always unplug. I don't know if this rule applies here though.

I guess it's zip ties then.

Thanks again,
Mike

 

[MarkM]

If you're using a battery holder that could be affected by G loading, my recommendation would be to orient it sideways.

This is how I mount mine.

Cool! Thanks for all the replies guys.
In my experience in my RC aircraft, if the battery is left connected when the switch is turned off, the battery power is still drained. So, the lesson I learned was, always unplug. I don't know if this rule applies here though.

I use an altimeter battery once, then discard it. IIRC, there was a thread about this some time ago. I know many may disagree with this and some may even fly all "season" with one battery. For me, I feel safer knowing I have a fresh battery for every flight. When I might be spending up to $150 for a large K motor, what's $2 extra for my piece of mind.

 

[ben]

This is how I mount mine.



I use an altimeter battery once, then discard it. IIRC, there was a thread about this some time ago. I know many may disagree with this and some may even fly all "season" with one battery. For me, I feel safer knowing I have a fresh battery for every flight. When I might be spending up to $150 for a large K motor, what's $2 extra for my piece of mind.

Very true. I stick true to the "one shot" theary.

Another thing I do in my larger rockets is use NIHM batteries. I usually get 9.6V ones with a high amperage rating. I then get one of those Futaba charging jacks and cut off the plugs. Then hook the battery up and mount the switch on the board. I then can leave my batteries and altimeters on and pull it out and give them a quick on field charge to make sure they are topped off. The batteries are only like $20-25 and one of them I have has enough Amps to power my MAWD and HA 45 easily (its 10V) so its not to bad. Plus they pay for themselves after a while. I do replace the batteries after 2-3 years depending on how much I fly it.

Ben

 

[sailmike]

That's an interesting idea. The MAWD instructions says it uses about 27 A peak, but doesn't say for how long. I would think it uses that much only for 2-3 seconds. I don't know how many mAh a standard 9V has, so I can't calculate how long it would last. Anybody know?

Mike

 

[Sailorbill]

Cool! Thanks for all the replies guys.

Good point Adrian.

I was trying to think of a way to hold the battery securely while making it easy to unplug. In my experience in my RC aircraft, if the battery is left connected when the switch is turned off, the battery power is still drained. So, the lesson I learned was, always unplug. I don't know if this rule applies here though.

I guess it's zip ties then.

Thanks again,
Mike

Mike since you were/are an RC guy get som Futaba style connectors from the hobby store and splice them into your wiring harness. I always use solder and heat shrink tubing for a good connection.
When you are done with the flight pull the connector apart and you are disconnected. If you decide to use rechargeable batteries you can put the same connector on the charger.

 

[sailmike]

I am thinking of using Deans plugs.

Mike

 

[bobkrech]

That's an interesting idea. The MAWD instructions says it uses about 27 A peak, but doesn't say for how long. I would think it uses that much only for 2-3 seconds. I don't know how many mAh a standard 9V has, so I can't calculate how long it would last. Anybody know?

Mike

Mike

The MAWD has a capacitor discharge pyro circuit. It stores 190 millijoules of energy and when discharged will support a peak current of 27 amps for a few milliseconds only which is plenty of time to ignite the pyrogen on a well designed e-match or low current igniter. It's been discussed here. https://www.rocketryforum.com/showthread.php?t=39715

The standard Duracell MN1604 transistor battery has a capacity of ~0.45 AHr @ ~10 ma-20 ma current draw. The MAWD draws ~ 10 ma current in operation and and additional 20 ma for 1 second to recharge the discharge cap. The MAWD will run for a busy launch weekend before you have to replace the battery.

https://www.duracell.com/oem/Pdf/new/MN1604_US_CT.pdf

This does not apply to the HA45 which does not employ a CD pyro circuit.

Bob

 

[cjl]

I am thinking of using Deans plugs.

Mike

That's what I use, and it works beautifully. If you're comfortable with them, by all means go ahead.

 

[jadebox]

I use zip ties. Here is a pic of how the batteries are secured on my L3 sled.

It also appears you are using heavy-duty 9V connectors. I like them. They definitely feel as though they hold onto the battery better than regular snaps.

-- Roger

 

[ben]

Lee does such good work. I couldn't help but post this

https://www.rocketryforum.com/showpost.php?p=514834&postcount=35

Look at how nice his sled is! I am going to try that with some flat rechargable batteries I have. Mount them in a wooden "enclosure" with some foam.

Ben

 

[BAR0051]

I use these from Newtons 3rd Rocketry;
https://www.newtons3rdrocketry.com/shop/product_info.php?cPath=23&products_id=38
I put a tie around the battery to hold it in the holder and I only use the battery once, not because I am worried about it running down but I worry about how well the internal cells hold up under the G's of launch and recovery. I have read that some 9v batteries do not do well, the intercell connections come apart under high G's and why risk a $300+ rocket (with alt.) on a $2 battery.

 

[sailmike]

Ben, I thought of securing my batteries that way too, but then realized that all that extra wood would add more weight than I want. I just need a way to easily disconnect/connect the battery (ies) without adding too much weight. I'm going to use the red micro Deans so I can't connect it the wrong way.

Mike

 

[ben]

Ben, I thought of securing my batteries that way too, but then realized that all that extra wood would add more weight than I want. I just need a way to easily disconnect/connect the battery (ies) without adding too much weight. I'm going to use the red micro Deans so I can't connect it the wrong way.

Mike

Well where weight isn't an issue I like that design. I am using Dean's on all my rockets now. From my 3" 29mm Deuce to an HPR 8" Patriot. They really are nice connectord

Ben