Quantcast

A Launch Battery problem to learn from

The Rocketry Forum

Help Support The Rocketry Forum:

georgegassaway

Lifetime Supporter
TRF Lifetime Supporter
Joined
Jan 18, 2009
Messages
4,558
Reaction score
401
I'm cross-posting a message I put on the NAR sections list.

I forgot to mention that the launch panel also had two circuit breakers (one as a switched parallel back-up for the first), which were part of what I suspected and checked. But they were not the problem, only part of the dead-ends that were being chased.

---------------

This could happen to you, in some way, so I'm posting what happened to us (BRB) last week so you could hopefully avoid or at least detect the real problem very quickly.

Imagine your section is holding it's biggest launch of the year, and after a dozen or so flights, your main launch system stops working? Well, fortunately we use a hybrid range with a centralized launch system plus "Misfire Alley", so we were not 100% down. But we did not have the misfire alley individual pad capacity to make up for the central panel (with its two racks and 5-pad HPR box) being down.

It could not be the car battery, since this is a new one bought 2 months ago.

And the battery clips are hooked up, so the always-on "power incoming from battery clips" status Blue LED is on.

So you open the panel, to try to see why it's not going. Even the built-in LCD voltmeter is not going. Every once in awhile the panel starts to run again (it beeps and of course lights up when armed), but you had not been touching anything at the moment that it came back. Yet every time you press the launch button, instead of launching a rocket, it stops running, for awhile.

This goes on for about 20-30 very frustrating minutes.

So, you get out a VOM (thank goodness Kim Mitchell had one!) and start checking voltages inside the panel, but they seem very low.

OK, maybe the new battery that was charged last night somehow lost its charge? So, you touch the VOM leads to the battery clips on the battery, and the instant you nudge a battery clip, the panel comes to life!

It turns out, the battery clips were not getting good contact with the battery. Wiggled the clips onto the posts to get a nice GOOD bite into the battery posts, and we flew the rest of the day just fine.

It was NEVER the panel!

So it seems when it was coming back on, then going back off, the clips had a very tenuous electrical contact that went away every time it tried to pass a lot of current to launch something. Then after a few minutes, it regained some weak electrical contact to let the panel run again.

Also, even when the panel was "dead", the blue LED showing it was getting power, did light. But, once the clips were seated securely, that LED was MUCH brighter. So, when it was dim before when the panel was dead, it was not actually getting good power from the battery as "assumed".

Now, I mention this for a special reason. I told a club member I wondered if there was some sort of coating on the posts of that new battery. And he said, yep, they do that these days to prevent corrosion. When installed into a car, the posts should be roughed up with some sandpaper or something before attaching the cables (and after a secure connection is made, some places
then spray an anti-corrosive over it).

Or in the case of a rocket launch battery.... wiggle the clips to seat them for a good "bite", or sand off the coating first.

So, in case you too are at a launch some day and the launch system "mysteriously" stops working (or maybe seems dead from the start), make sure it is not something as simple as that battery clips not getting a good connection with the battery. And if it is a new battery, consider it may have an anti-corrosion coating on the posts that you may want to remove with sandpaper.

- George Gassaway
 

Handeman

Well-Known Member
TRF Supporter
Joined
Jan 18, 2009
Messages
7,727
Reaction score
323
Location
Stafford, VA
George,

Checking the contacts with the battery seems like such a basic thing, that you shouldn't have to even mention it. Obviously when small things change, like coatings where there never used to be any, our basic assumptions can be completely wrong. Some times we also start looking for the difficult problem and overlook the very simple causes. Reminds me of tech I worked with that spent several hours troubleshooting why a control circuit that wouldn't work when the adjustment knob was turned. When the next shift came on and took over fixing the problem, the first thing they did was tighten the set screw in the control knob so it would turn the control. Problem fixed.
Glad you brought this up. It should remind all of us not to overlook the simple things when trying to fix something.
 

sj_h1

Well-Known Member
Joined
Mar 21, 2009
Messages
218
Reaction score
0
I'm cross-posting a message I put on the NAR sections list.

I forgot to mention that the launch panel also had two circuit breakers (one as a switched parallel back-up for the first), which were part of what I suspected and checked. But they were not the problem, only part of the dead-ends that were being chased.

---------------

This could happen to you, in some way, so I'm posting what happened to us (BRB) last week so you could hopefully avoid or at least detect the real problem very quickly.

Imagine your section is holding it's biggest launch of the year, and after a dozen or so flights, your main launch system stops working? Well, fortunately we use a hybrid range with a centralized launch system plus "Misfire Alley", so we were not 100% down. But we did not have the misfire alley individual pad capacity to make up for the central panel (with its two racks and 5-pad HPR box) being down.

It could not be the car battery, since this is a new one bought 2 months ago.

And the battery clips are hooked up, so the always-on "power incoming from battery clips" status Blue LED is on.

So you open the panel, to try to see why it's not going. Even the built-in LCD voltmeter is not going. Every once in awhile the panel starts to run again (it beeps and of course lights up when armed), but you had not been touching anything at the moment that it came back. Yet every time you press the launch button, instead of launching a rocket, it stops running, for awhile.

This goes on for about 20-30 very frustrating minutes.

So, you get out a VOM (thank goodness Kim Mitchell had one!) and start checking voltages inside the panel, but they seem very low.

OK, maybe the new battery that was charged last night somehow lost its charge? So, you touch the VOM leads to the battery clips on the battery, and the instant you nudge a battery clip, the panel comes to life!

It turns out, the battery clips were not getting good contact with the battery. Wiggled the clips onto the posts to get a nice GOOD bite into the battery posts, and we flew the rest of the day just fine.

It was NEVER the panel!

So it seems when it was coming back on, then going back off, the clips had a very tenuous electrical contact that went away every time it tried to pass a lot of current to launch something. Then after a few minutes, it regained some weak electrical contact to let the panel run again.

Also, even when the panel was "dead", the blue LED showing it was getting power, did light. But, once the clips were seated securely, that LED was MUCH brighter. So, when it was dim before when the panel was dead, it was not actually getting good power from the battery as "assumed".

Now, I mention this for a special reason. I told a club member I wondered if there was some sort of coating on the posts of that new battery. And he said, yep, they do that these days to prevent corrosion. When installed into a car, the posts should be roughed up with some sandpaper or something before attaching the cables (and after a secure connection is made, some places
then spray an anti-corrosive over it).

Or in the case of a rocket launch battery.... wiggle the clips to seat them for a good "bite", or sand off the coating first.

So, in case you too are at a launch some day and the launch system "mysteriously" stops working (or maybe seems dead from the start), make sure it is not something as simple as that battery clips not getting a good connection with the battery. And if it is a new battery, consider it may have an anti-corrosion coating on the posts that you may want to remove with sandpaper.

- George Gassaway
Been there done that!!! But it still a good idea to remind people.:headbang:
 

georgegassaway

Lifetime Supporter
TRF Lifetime Supporter
Joined
Jan 18, 2009
Messages
4,558
Reaction score
401
Checking the contacts with the battery seems like such a basic thing, that you shouldn't have to even mention it. Obviously when small things change, like coatings where there never used to be any, our basic assumptions can be completely wrong.
A big reason why I did not think it was the battery contacts was the lighted blue LED in the back of the panel. The only thing that LED is for, is to show that there is power and that it is of the correct polarity (there are electronics inside the panel that need the correct polarity). There is no switch or anything involving that LED, it (plus its dropping resistor) is literally the first thing inside of the panel, electronically speaking.

With the rest of thep anel "dead", but seeing that blue LED lit up, it gave the impression that there was power coming in, so it "had" to be some serious problem inside the panel. I had also forgotten to mention that when this cropped up, there was a 4-model drag race going on. Which, again seeing the blue LED was lit, caused me to think at first that the primary circuit breaker had popped out, but then nothing happened when I switched in the back-up breaker. And that had me concerned that something was SERIOUSLY screwed up inside of the panel.

So, yes, it might seem that it would be a basic thing to check the clip connections with the battery, but wow, all these years of flying, including lots of systems using a car battery, this is the first time that sort of thing has happened with a system running fine at first, then intermittently after awhile. And the first system I ever built to provide an "incoming power status" indicator (the blue LED) and it led me astray that it was getting some "voltage", but not much "power".

FWIW - below is a photo showing the back of the panel. The blue LED is visible as being lit blue, under the "12V" label. That LED is inside of a clear housing, so it is visible as being "on" when it appears blue in color (the LED itself is clear when not lit). Above there, the big red switch swaps the circuit breakers. Above that, the primary breaker, which pops out a short white post when tripped. The other breaker is internal, an automotive thermal-type circuit breaker(It trips due to heat then as it cools it resets itself in 30-60 seconds).

OK, while I am at it, also a photo of the front view of the panel. Three red lights on top show which rack is selected (or shows HPR Junction box is selected). Big rotary switch to select racks or HPR. Upper row of LED housings, for green LED's to show continuity. Lower row for red LED's to show which pad (or pads) is armed. Pad arming switches. Arming key, launch button, and panel armed (green) light. Plus voltage meter at the bottom. Youtube movie of the system in use:

http://www.youtube.com/watch?v=FizWJ518XHI&feature=channel_page

- George Gassaway

IMG_3227.jpg


IMG_3225.JPG
 

n5wd

Well-Known Member
Joined
Jan 18, 2009
Messages
1,030
Reaction score
2
A big reason why I did not think it was the battery contacts was the lighted blue LED in the back of the panel. The only thing that LED is for, is to show that there is power and that it is of the correct polarity ...
Maybe it's not as common in cooler parts of the nation, but I've had the experience where battery terminals have worked loose enough (through contraction and expansion over a period of time) to develop some oxidation between the post and the connector - you get in the car, turn on the ignition switch and all appears good with the correct idiot lights appearing, until you turn the ignition switch to crank, and poof, what appears to be a dead battery. That's why a metal post cleaning brush and an open ended wrench of the proper size for the battery connectors is the first thing I grab whenever that happens. Fixes things up almost 100% of the time.

Or, as one of my computer repair gurus used to tell me --- first, you check the power plug! ;)

Good pix of a nicely built controller, but I gotta ask... what gauge is the power wire? Looks like a bit smallish, to me... 12, 14 ga?
 
Last edited:

RimfireJim

Well-Known Member
Joined
Jan 20, 2009
Messages
988
Reaction score
0
Good lesson, George. Thanks for sharing the story.

As n5wd says, the symptoms are a perfect match those caused by bad connections in automotive wiring, which often show up on older vehicles (I have a number of collector, vintage, vehicles). I remember troubleshooting a non-working brake light once. First, replaced the bulb. Didn't fix it. Maybe the new bulb was bad (wouldn't be the first time). Check both bulbs on a test battery - fine. Check the socket with a volt meter - 12V. Try the bulbs again - still no light. Eventually traced the cause to a poor connection, can't remember if it was the +12V or ground, that was capable of conducting the minute current required for the high-impedance volt meter but not for the much higher current of the light filament.

Close observation of the blue LED probably would have revealed that it went out as soon as the launch button was pressed, indicating a drop in voltage, but, of course, one would be looking at the rocket to be launched instead of the power LED, wouldn't they? :)
 

georgegassaway

Lifetime Supporter
TRF Lifetime Supporter
Joined
Jan 18, 2009
Messages
4,558
Reaction score
401
Close observation of the blue LED probably would have revealed that it went out as soon as the launch button was pressed, indicating a drop in voltage, but, of course, one would be looking at the rocket to be launched instead of the power LED, wouldn't they? :)
Well, I admit I was not looking at the blue "incoming power" LED when the button was pressed. But, that blue LED was lit up when the panel was "dead". The one thing that might have been noticed when pushing the button was perhaps the intensity of that blue LED might have been seen to drop from pretty bright (good connection) to some lower amount of brightness (when the panel went "dead"). But judging the intensity of that LED was never part of the criteria of using it, it was put in there as a Pass/Fail indicator that power is coming in and that the polarity is correct. If it lights up "blue" (otherwise it stays clear), then it's "on" and power is coming in. But as I found out the hard way, that did not mean GOOD power was coming in, due to the poor contact of the battery clips and that new battery's posts due to the unsuspected anti-corrosion coating on the posts.

There are other LED's in the Panel (continuity and pad select), but those did not light up because a flasher circuit drives those. And the flasher circuit was not getting the current/voltage it needed to drive those other LED's.

On previous occasions when we did have power issues (car battery going dead), those were easy to confirm (not only did the voltmeter indicate it, but the beepers/buzzers sounded "wrong")

- George Gassaway
 
Top