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

DAllen

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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

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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.
 
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mh9162013

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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.
 

QFactor

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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

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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.
 

QFactor

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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

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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?
 

QFactor

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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

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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

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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.
 

QFactor

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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

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

Handeman

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... 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.
 

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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

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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?

PkCellUltraAlkaline.jpg
 
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FredA

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

dpower

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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!
 

QFactor

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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.

IMG_6927.JPG IMG_6931.JPG

IMG_6932.JPG IMG_6935.JPG IMG_6941.JPG IMG_6945.JPG IMG_6947.JPG IMG_6951.JPG
 

Rocketjunkie

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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 :)
Amazon 9V 1.jpg Amazon 9V 2.jpg Amazon 9V 3.jpg Amazon 9V 4.jpg
 
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QFactor

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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 . . . )
 
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