9-Volt Batteries - Part 1 : The Tear Down - Battery No.1 thru No. 5

[DAllen]

i HEAR YA - POOR SWITCH SELECTION CAN BE BAD.
However those screw switches violate my personal rule requiring a tool-less and obvious disarm capability.
Another hard pass here - and another thread.

So what is your go-to switch for arming electronics then?

 

[waltr]

That is a great question Dave.

Two measurements come to mind:
1- Open circuit Voltage- This is just measuring the Battery Voltage and comparing to above chart or to previous measurements kept in a logbook. The initial open circuit Voltage MUST be measured and recorded when the battery in NEW. Refer to lower graph in Post #74. This would tell you which of the three 'types' of battery of have.
Note in the lower graph that after three tests the open circuit Voltage drops. This could be the critia to say - time to replace.

2- High current discharge measurement. Similar to the OP's Shorted test but use a low value, high wattage resistor and a Voltmeter. Looking at the Current graph (upper) in Post #74 of the batteries that do 5amp. Note that after a while they only do 4amps. Lets pick this as the 'cut-off' for replacement.
I would use a 1.0 Ohm, 100Watt resistor. Connect Voltmeter across resistor. Connect resistor and meter across battery for just long enough to get a reading, about 1 second. By Ohms Law Voltage measured equals the Current ( E/R = I with R = 1 then E = I).
Now compare to previous measurement and refer to graph. If Current has dropped to below 4.5A (for the 5A batteries in graph) then replace.

Last-
This may still not be perfect in determining the total charge state of the battery as has been mentioned in other posts.
Also, one must make the measurements on the new battery to determine starting Voltage and Current capability so later measurements can be compared.

This has been a very interesting thread. The OP seems to have a way for us to determine which type of battery one has.
My conclusion is: If open circuit Voltage is low AND output Current is high then one has the better battery.

I would use a 1Ohm resistor for the Current measurement instead of a dead short on the battery.

I use LiPo but am not saying 9V batteries can not be use. Fact is the OP proved to me that there are 9V batteries that will reliably fire multiple ematchs without all the fuss of maintaining rechargeables.

 

[tfish]

So what is your go-to switch for arming electronics then?

They make flexible face plates.



Tony

 

[mh9162013]

Charge before.
Charge after.
Check over the off season.
Too many touch points required.

I swap a battery once per season and never think about it again.
That's often the ONLY time I open a rocket's EBAY for the season.

How long does it take you to open the Ebay, swap/charge the battery and re-assemble?
With a rechargeable, you need to do that before and after every flight.....screw that.

If you only want to touch the battery once every season, then that changes almost EVERYTHING about which battery to use. This is the first time I've heard of that being a consideration when choosing which battery to use on a rocket.

 

[user 30299]

Soooo...I haven't read the entire thread but has someone come up with a standard for when to switch out 9v's? Switching out the 9v every flight seems ridiculously wasteful. Yes, I do have other things I can use 9v's for like smoke detectors but I mean...come on there has to be a better way to handle this. I'm not a electrical engineer nor did I sleep at a Holiday Inn Express last night but there has to be a simple quantifiable way to determine if a 9v is still good for flight.

If you go read post #74 you will have probably the most basic and pertinent information you need for the 9-volt batteries.

• First, use a battery that is in the high-amp group and has the 6LR61 stamped on the battery's packaging and casing.
• The results show that after 14 tests, and 28 "shortings" of each battery in the 6LR61 group, there was substantial voltage and amperage remaining.
• You just have to keep tabs on the number of times you fired deployment charges; launches and pop tests.
• Then it comes down to your personal cutoff on the battery's voltage.

Just about every altimeter with deployment controls beeps out the voltage when you first turn it on.
So you will know if you have hit your personal cutoff. Personally I think you could take the voltage
to as low as 8 volts. But it all starts with a quality battery.

 

[Johnly]

I'm not a electrical engineer nor did I sleep at a Holiday Inn Express last night but there has to be a simple quantifiable way to determine if a 9v is still good for flight.

Just measuring the battery voltage is a poor method as it could have what is called plate voltage which can be far different that the battery voltage under load.

 

[user 30299]

Just measuring the battery voltage is a poor method as it could have what is called plate voltage which can be far different that the battery voltage under load.

I'm not familiar with "plate voltage". I looked it up on the internet. But if you had the battery hooked to the flight controller (altimeter),
and then turned it on, wouldn't the inrush to the capacitor and all the system checks dissipate a plate voltage? So when the flight
controller finally "beeps out" the battery voltage - wouldn't you have a true (reliable) voltage condition?

 

[mh9162013]

I'm not familiar with "plate voltage". I looked it up on the internet. But if you had the battery hooked to the flight controller (altimeter),
and then turned it on, wouldn't the inrush to the capacitor and all the system checks dissipate a plate voltage? So when the flight
controller finally "beeps out" the battery voltage - wouldn't you have a true (reliable) voltage condition?

No, because you don't use the battery to make a beep. You use the battery to trigger the e-match(es), which (presumably) requires far more current than a simple voltage check process.

Unless the voltage check process simulates the current draw of an e-match deployment?

 

[user 30299]

No, because you don't use the battery to make a beep. You use the battery to trigger the e-match(es), which (presumably) requires far more current than a simple voltage check process.

Unless the voltage check process simulates the current draw of an e-match deployment?

So is plate voltage an issue with 9-volt batteries?

 

[mh9162013]

So is plate voltage an issue with 9-volt batteries?

I don't know what plate voltage is. But I do know that to predict what a battery will do under load, you have to test it under load. So unless the "battery is good beep" actually simulates an actual load the battery will have to provide for deployment, the reassurance provided by that beep has to be taken with a few grains of salt. In other words, measuring cell or battery's voltage with no load (or only a very small load) is a poor way of trying to predict how the battery will perform in its actual application.

This concept applies to most (if not all) consumer batteries that we use.

 

[waltr]

Correct, Open cell Voltage is not a good method to determine battery condition in most cases. LiPo is an exception and the open cell Voltage is a good method to determine total remaining charge.

For these 9V batteries I did recommend doing a Voltage measurement with a resistor across the battery. I suggested a 1 Ohm resistor to find max output current (instead of dead short as per the OP's testing). A 10-100 Ohm resistor (900 - 90mA @ 9V) could also be a ok test.

For those that do not open the ebay the Altimeter's Battery measurement may be ok if calibrated. At least there is some loading (not open cell). This may also require experience with the particular altimeter and batteries used to make a good determination of battery charge remaining.

 

[cls]

I suggested a 1 Ohm resistor to find max output current (instead of dead short as per the OP's testing).

Yeah, I did too. The only way to verify battery performance.

 

[user 30299]

For these 9V batteries I did recommend doing a Voltage measurement with a resistor across the battery. I suggested a 1 Ohm resistor to find max output current (instead of dead short as per the OP's testing).

I'll have to give it a try in the coming weeks.

The "dead short" method through the multimeter is not a fun thing. Luckily my meter is rated to 20A - but no fuse.

 

[FredA]

OK - enough side debate - back to the great work from QFactor.

 

[Handeman]

... For those that do not open the ebay the Altimeter's Battery measurement may be ok if calibrated. At least there is some loading (not open cell). This may also require experience with the particular altimeter and batteries used to make a good determination of battery charge remaining.

I don't open my av-bays and have found that my Perfectflite altimeters measure 0.1 V less than the multimeter does on the same battery without a load. I leave the batteries in the av-bay until the Altimeter reports less than 8.9 volts. I suspect they battery would operate and fire ematches fine all the way down to about 7 volts but have never tested that.

I did hang a rocket in a tree on a Sunday and the chainsaw recovery was on Friday. After 5 days, both the StratoLoggerCF and HiAlt45 were beeping out altitude. The StratoLoggerCF battery was down to 4.8 volts and the HiAlt45 was down to 7.6 volts. Both batteries were the old style Duracell 9V with the six AAAA cells inside.

 

[Rocketjunkie]

Back on Post #74 the graphs & chart show three distinct groups. What is interesting is to see how "tight" the numbers
appear to be within a group yet maintained across the manufacturers. With so little data there is no way to look at this
with a statistical analysis (which would take the fun out of this), but there appears to be little to no variations across
the manufacturers.

Top group, internal 6 AAAA cylindrical cells. About 5A current.
Middle group, stack of retangular alkaline cells. About 2A current.
Bottom group, carbon zinc cells. Less than 1A current.

 

[dpower]

TRF limits you to 25 attachments - so I was not able to put all the battery pictures in one thread.
There are two threads for the battery pictures.

Anyway, I wanted to highlight the four batteries that have the (6) welded cells.

Please note that the PK Cell Ultra Alkaline (No. 6) has a fused plastic case surrounding the cells. All the other batteries
have the traditional metal case. I used a coping saw to cut open the the PK's case. It has a solid construction to it.

I looked at the PK Cell batteries because PK Cell makes many of the Lipo batteries we use in other electronics.
You will find many of their Lipos on the Sparkfun and Adafruit webstores, and also Digikey and Mouser.


View attachment 556436 View attachment 556437

Excellent work! For the PK Ultra Alkaline, they advertise that there's an internal steel shell, can you confirm this?

 

[FredA]

Explosion-proof? Really? I bet if you charge them hard enough they will grenade.

 

[dpower]

If you go read post #74 you will have probably the most basic and pertinent information you need for the 9-volt batteries.

• First, use a battery that is in the high-amp group and has the 6LR61 stamped on the battery's packaging and casing.
• The results show that after 14 tests, and 28 "shortings" of each battery in the 6LR61 group, there was substantial voltage and amperage remaining.
• You just have to keep tabs on the number of times you fired deployment charges; launches and pop tests.
• Then it comes down to your personal cutoff on the battery's voltage.

Just about every altimeter with deployment controls beeps out the voltage when you first turn it on.
So you will know if you have hit your personal cutoff. Personally I think you could take the voltage
to as low as 8 volts. But it all starts with a quality battery.

Well, I learned something today. The 6LR61 refers to a set of (6) LR61 batteries. Cool, and thanks for your effort!

 

[user 30299]

Here is the full tear down of the PK Cell Ultra Alkaline. No steel shell. The case label is just an adhesive wrap.

It has a very durable plastic casing. Took some work to crack it open.

I don't think I found any real "truthful" advertising for any of the batteries.

The industry codes are the key to the battery selection.

 

[Rocketjunkie]

I ordered 24 Amazon Basic 9V batteries for $28 and free shipping. Got them today. They do only have a 5 year shelf life guarantee. Tested at 7A best of any. Repeated about 2 sec shorts. Still provided 7A even when open cell was 8.9V, just not as long to get to 6A. Tear down showed 6 AAAA cells, even had the polarity marked

 

[user 30299]

I ordered 24 Amazon Basic 9V batteries for $28 and free shipping. Got them today. They do only have a 5 year shelf life guarantee. Tested at 7A best of any. Repeated about 2 sec shorts. Still provided 7A even when open cell was 8.9V, just not as long to get to 6A. Tear down showed 6 AAAA cells, even had the polarity marked
View attachment 560019 View attachment 560020 View attachment 560021 View attachment 560022

(sell them for $2 a battery at your next launch event . . . )

 

[Zman1961]

This is great information! So what brand/type of multimeter is recommended for all of this testing? I have seen a brief discussion of this in another TRF thread a while ago, but it was more bantering about analog vs. digital than it was helpful. It seems like a good practice to test your e-matches for proper resistance (and every other component) before a flight. Also, I might be missing something, but when you have $300 to $500 worth of rocket (or more) on the pad, and maybe a $100 motor +/-, why short-change yourself with anything other than a new $2 battery? I ask these questions as I am just now starting to get into dual deploy with altimeters. Have been using a Jolly Logic chute release very successfully, but I want to get into more of the traditional dual deploy.

 

[user 30299]

This is great information! So what brand/type of multimeter is recommended for all of this testing? I have seen a brief discussion of this in another TRF thread a while ago, but it was more bantering about analog vs. digital than it was helpful. It seems like a good practice to test your e-matches for proper resistance (and every other component) before a flight. Also, I might be missing something, but when you have $300 to $500 worth of rocket (or more) on the pad, and maybe a $100 motor +/-, why short-change yourself with anything other than a new $2 battery? I ask these questions as I am just now starting to get into dual deploy with altimeters. Have been using a Jolly Logic chute release very successfully, but I want to get into more of the traditional dual deploy.

You're short-changing yourself if you take out a perfectly good battery. What is the reason for taking out a
perfectly good battery? You end up with a bunch of good batteries on the shelf at the end of a launch season.

Do some people change the battery after one launch? Yes. But how many do that because of an old rule of thumb?
It would be cool to find someone that knows when, how and why this "one use" rule came about. Someone out
there knows the history.

Before I did my testing I regularly put 4 or 5 launches on a single battery. I wanted to know how far I could go,
based on voltage, with a well-made battery - and what was a well-made battery. The "one use" rule never
quite made sense to me. I now know I can go way more than 4 or 5. Now it's a personal choice as to the
cutoff point, but with some better data behind the decision. I can confidently zip tie a battery into the av-bay
and leave it there for the launch season.

You can check the voltage before the launch, and most of the altimeters beep out the battery voltage when you
arm them. So if the voltage is too low for your liking - then you can change the battery or scrub the launch.

No matter what, you need to select a quality battery.

 

[Buckeye]

You're short-changing yourself if you take out a perfectly good battery. What is the reason for taking out a
perfectly good battery? You end up with a bunch of good batteries on the shelf at the end of a launch season.

Do some people change the battery after one launch? Yes. But how many do that because of an old rule of thumb?
It would be cool to find someone that knows when, how and why this "one use" rule came about. Someone out
there knows the history.

Before I did my testing I regularly put 4 or 5 launches on a single battery. I wanted to know how far I could go,
based on voltage, with a well-made battery - and what was a well-made battery. The "one use" rule never
quite made sense to me. I now know I can go way more than 4 or 5. Now it's a personal choice as to the
cutoff point, but with some better data behind the decision. I can confidently zip tie a battery into the av-bay
and leave it there for the launch season.

You can check the voltage before the launch, and most of the altimeters beep out the battery voltage when you
arm them. So if the voltage is too low for your liking - then you can change the battery or scrub the launch.

No matter what, you need to select a quality battery.

Totally agree. The use once rule for the battery is probably another one of those over-building myths built up on TRF. Use once seems so wasteful.

I have a couple Perfectflight MAWD altimeters with the big capacitor for firing the events. I can get 10-12 flights with one 9V battery.

 

[FredA]

Realize that the number of flights/battery is a function of "ON" time - time sensing and beeping and burning power. A quick up & down and a quick shag will go a long way toward using a single battery over many flights.
If your rocket sits on the pad for long wait times and/or you can't get to it quickly after the flight, then you might want to consider more frequent replacement.

What might be a good "next level" set of tests and discussion could be to survey the current demands of the favorite FC's in their various modes. Knowing the power while waiting for launch and power while waiting for recovery would go a long way toward being able to predict the battery state.

 

[Handeman]

You're short-changing yourself if you take out a perfectly good battery. What is the reason for taking out a
perfectly good battery? You end up with a bunch of good batteries on the shelf at the end of a launch season.

Do some people change the battery after one launch? Yes. But how many do that because of an old rule of thumb?
It would be cool to find someone that knows when, how and why this "one use" rule came about. Someone out
there knows the history.

Before I did my testing I regularly put 4 or 5 launches on a single battery. I wanted to know how far I could go,
based on voltage, with a well-made battery - and what was a well-made battery. The "one use" rule never
quite made sense to me. I now know I can go way more than 4 or 5. Now it's a personal choice as to the
cutoff point, but with some better data behind the decision. I can confidently zip tie a battery into the av-bay
and leave it there for the launch season.

You can check the voltage before the launch, and most of the altimeters beep out the battery voltage when you
arm them. So if the voltage is too low for your liking - then you can change the battery or scrub the launch.

No matter what, you need to select a quality battery.

Well said, I totally agree with this.

I trust a flight proven battery more than a new one. As @FredA said, the type of altimeter, wait time on the pad, recovery time until it's turned off, all affects the battery life. I've had some that lasted 3 seasons, some only one, and a couple that hung in a tree for 5 days and were still beeping the altitude when the rocket was finally recovered but couldn't be flown again.

I install them with the contacts down so thrust moves any internals toward the top of the battery. I've only had flights a little over 80G, but the batteries worked fine. I don't know if that really makes any difference or not, it's just the way I mount them.

I lost one rocket from what I suspect was a broken internal connection in the old style Duracell 9V with the 6 AAAA internal cells. It had been in a rocket where the main failed to deploy and the rocket came down on drogue only. It was installed in another rocket and flown. The boot up, beep sequence, etc. all worked perfectly, and was beeping continuity for both matches when left on the pad. Neither match fired and there was no data stored for the flight. I suspect the thrust caused a broken, but touching internal contact in the battery, to open and reset the altimeter during flight. I could be wrong about the battery causing the issue, but now, I replace the batteries when the altimeter reported voltage goes below 8.9V (up to +20 flights and 3 years) or if there is some recovery anomaly that causes a hard impact on landing. That is also when I started making sure the contacts are installed downward. YMMV.

 

[user 30299]

Well said, I totally agree with this.

I trust a flight proven battery more than a new one. As @FredA said, the type of altimeter, wait time on the pad, recovery time until it's turned off, all affects the battery life. I've had some that lasted 3 seasons, some only one, and a couple that hung in a tree for 5 days and were still beeping the altitude when the rocket was finally recovered but couldn't be flown again.

I install them with the contacts down so thrust moves any internals toward the top of the battery. I've only had flights a little over 80G, but the batteries worked fine. I don't know if that really makes any difference or not, it's just the way I mount them.

I lost one rocket from what I suspect was a broken internal connection in the old style Duracell 9V with the 6 AAAA internal cells. It had been in a rocket where the main failed to deploy and the rocket came down on drogue only. It was installed in another rocket and flown. The boot up, beep sequence, etc. all worked perfectly, and was beeping continuity for both matches when left on the pad. Neither match fired and there was no data stored for the flight. I suspect the thrust caused a broken, but touching internal contact in the battery, to open and reset the altimeter during flight. I could be wrong about the battery causing the issue, but now, I replace the batteries when the altimeter reported voltage goes below 8.9V (up to +20 flights and 3 years) or if there is some recovery anomaly that causes a hard impact on landing. That is also when I started making sure the contacts are installed downward. YMMV.

That's some pretty good info.

This is the way . . . .

 

[OzHybrid]

Well said, I totally agree with this.

I trust a flight proven battery more than a new one. As @FredA said, the type of altimeter, wait time on the pad, recovery time until it's turned off, all affects the battery life. I've had some that lasted 3 seasons, some only one, and a couple that hung in a tree for 5 days and were still beeping the altitude when the rocket was finally recovered but couldn't be flown again.

I install them with the contacts down so thrust moves any internals toward the top of the battery. I've only had flights a little over 80G, but the batteries worked fine. I don't know if that really makes any difference or not, it's just the way I mount them.

I lost one rocket from what I suspect was a broken internal connection in the old style Duracell 9V with the 6 AAAA internal cells. It had been in a rocket where the main failed to deploy and the rocket came down on drogue only. It was installed in another rocket and flown. The boot up, beep sequence, etc. all worked perfectly, and was beeping continuity for both matches when left on the pad. Neither match fired and there was no data stored for the flight. I suspect the thrust caused a broken, but touching internal contact in the battery, to open and reset the altimeter during flight. I could be wrong about the battery causing the issue, but now, I replace the batteries when the altimeter reported voltage goes below 8.9V (up to +20 flights and 3 years) or if there is some recovery anomaly that causes a hard impact on landing. That is also when I started making sure the contacts are installed downward. YMMV.

The problem with a flight-proven battery is that you cannot see internally what damage may have been done to it from the previous flight. Going the other way with a new battery, the manufacturers change both the chemistry and construction without ANY notification to anyone. The only way you know what you have is to buy a bunch of new stock, test one and tear it apart to make sure the correct power will be supplied and the construction will be up to the loading you'll expose it to. You're then faced with your stock running out or reaching end of storage life before you have to do it all over again.
This is why I prefer to use single cell lithium and inverter voltage converters. I can visually inspect and test all parts. Some systems will run off a single cell.
But that's my choice. You have to make yours. YMMV

 

[FredA]

The problem with a flight-proven battery is that you cannot see internally what damage may have been done to it from the previous flight.

This is why I prefer to use single cell lithium

Just FYI - Pouch-type Lithium's are the MOST sensitive to shock induced internal damage.
So if those are the single-cell's you are using, I'm not sure you plan is as solid as you think.