StratologgerCF Battery Options

[kevinkal]

My Stratologger CFs just arrived (thanks Perfectflite), so this was a good read

I never trust batteries straight out of the box - always give them a quick test on a multimeter. I've always got a cheap one in my range box, similar to this one:

I note someone mentioned that twist and tuck 'seems so archaic' - It is the simplest, cheapest and IMHO most reliable 'switch' that I know of :wink:

I was waiting for the guy in the video to use the new DMM he had.. with the battery test function that puts a "load' on the battery. But he didn't... bah. That's a good idea for batteries that might have a surface charge.. showing voltage that they cannot supply under load. I suppose that's what gets me with the 9V alkaline batteries that I test after the smoke alarm is beeping. I get the unloaded value.. which appears to be ok. but there's no muscle behind it and the smoke alarm knows it. Perhaps I'll use a low ohm power resistor inline with my DMM next time I test. I found some 10 watt 50 Ohm resistors in the garage. they might be a good test load.

Aside, I just finished my StratologgerCF testing with a 1S LiPo. I'll post the results in a short while.

 

[kevinkal]

Since I didn't have any 1S LiPos beyond the very small "gumstick" sized units, I decided I could make one out of the parts from a failed 3S 850mAh LiPo I had salvaged last year.
So, I carefully extracted a single Cell, verified it was still healthy, then proceded to construct a pack that would be the same size at the 2S LiPo I needed to replace. After some careful soldering, hot glue and clear shrink wrap, I had a replacement ready to go with a JST connector to match what I had for my 2S LiPo.
I then reassembled my altimeter bay, and did the Shop Vac test with both the drogue and main terminals connected to a single inexpensive Ematch. I measured each Ematch befor I installed them.. and they were both only 1.0 ohms.. a certain overcurrent event if I were to use a 2S LiPo. I then ran the test and both Ematches fired as expected. I restarted the StratologgerCF to see if it threw an alarm warning of overcurrent. I did not. I downloaded the data, and as expected the currents during ematch firing were within safe tolerances. The drogue spike to 4A and the main spiked to 3A when firing. I'm feeling pretty good about this battery. It held a constant 4.1 V during each firing event, with no measured dip in voltage. Here's a plot of the data, and a shot of my new battery specifically fabbed for use with my StratologgerCF and these inexpensive Ematches.

 

[Dave A]

My Stratologger CFs just arrived (thanks Perfectflite), so this was a good read

I never trust batteries straight out of the box - always give them a quick test on a multimeter. I've always got a cheap one in my range box, similar to this one:

[video=youtube;W38x9RJs29I]https://www.youtube.com/watch?v=W38x9RJs29I[/video]

I note someone mentioned that twist and tuck 'seems so archaic' - It is the simplest, cheapest and IMHO most reliable 'switch' that I know of :wink:

Agreed. I have used Duracell 9v batteries for the longest time, no failures. You fly it all day on one battery.

If room is tight I use this>


Look at the battery pack at the left. Perfectflite used to sell this setup I still use in tight spaces.
6 - 357 silver oxide batteries. Slide them in a piece of the right size of heat shrink, I think it fits in a A23 battery holder.
12v all day long

I'm using it in my 29mm timer module.

 

[dhbarr]

Agreed. I have used Duracell 9v batteries for the longest time, no failures. You fly it all day on one battery.

If room is tight I use this>
View attachment 290623

Look at the battery pack at the left. Perfectflite used to sell this setup I still use in tight spaces.
6 - 357 silver oxide batteries. Slide them in a piece of the right size of heat shrink, I think it fits in a A23 battery holder.
12v all day long

I'm using it in my 29mm timer module.

Is that a telemini in an 18mm sled? Neat.

Edit: I see that it is not.

 

[bobkrech]

I'm not sure why you are soldering up your LiPo. Just go to hobbyking.com and purchase a 1S LiPo with connector and buy a mating wired commector and connected the wires to the altimeter.....

Digital volt meters have a 1 Meg ohm input impedance. A practically dead 9v battery will still read 9 volts if you don't pull current from the battery.

Get the datasheet for your battery and get a load resistor that will draw a known current from the battery and compare the voltage you measure across the resistor with the % lifetime of the battery.

https://cdn-shop.adafruit.com/datasheets/MN1604_US_CT.pdf is the Duracell datasheet. Referring to 2 ma load line on the top right graph, if you put a R=V/I=8.6/0.002=4300 ohm resistor across the battery and the voltage is ~8.6 volts, the battery has ~80% of its capacity remaining and will work fine. If you use a R=V/I=7.8/0.002=3900 ohm resistor and the voltage is ~7.8 volts, the battery has ~50% of it useful capacity remaining and should not be used.

https://ecee.colorado.edu/~mcclurel/resistorsandcaps.pdf is a table of standard 5% resistors. https://www.brannonelectronics.com/images/STANDARD VALUE.pdf is the same for 1% resistor if you want better lifetime resolution.

To determine the test voltage at 2 ma, V = R ohms from table / 0.002 amps. and refer to the discharge chart to estimate lifetime. I consider end of useful life at 7 volts so you don't want to go that far.

Bob

 

[Dave A]

That's Landru's 29mm nose cone sled, I modified it to work in a 29mm blue tube coupler. It fits like a 29mm motor would in my 29mm tubes at the aft of the rocket

 

[bobkrech]

Agreed. I have used Duracell 9v batteries for the longest time, no failures. You fly it all day on one battery.

If room is tight I use this>
View attachment 290623

Look at the battery pack at the left. Perfectflite used to sell this setup I still use in tight spaces.
6 - 357 silver oxide batteries. Slide them in a piece of the right size of heat shrink, I think it fits in a A23 battery holder.
12v all day long

I'm using it in my 29mm timer module.

Dave

I've designed medical electronic devices using AgO batteries. They are excellent current sources for ma level currents, however these small buttons cells will not provide fractional amps.

I can understand how you can use (6) 357 AgO batteries (which are 9 volts in series not 12 volts) will operate the StratoLogger that draws 1.5 ma for a day or more, but I do not understand how it can fire an e-match. These batteries can not source enough current to activate an e-match.

Here are 3 datasheets for various versions of these batteries.

https://data.energizer.com/PDFs/357-303ZB.pdf

https://www.farnell.com/datasheets/60308.pdf

https://www.jameco.com/jameco/products/prodds/140783.pdf

Bob

 

[Steve Shannon]

I note someone mentioned that twist and tuck 'seems so archaic' - It is the simplest, cheapest and IMHO most reliable 'switch' that I know of :wink:

I have no problem with twist and tape, but twist and tuck allows you no means of disarming your electronics in case of a problem. That could be a safety issue.

 

[FredA]

I have no problem with twist and tape, but twist and tuck allows you no means of disarming your electronics in case of a problem. That could be a safety issue.[/B]

That IS a safety issue.

 

[kevinkal]

I'm not sure why you are soldering up your LiPo. Just go to hobbyking.com and purchase a 1S LiPo with connector and buy a mating wired commector and connected the wires to the altimeter.....

Digital volt meters have a 1 Meg ohm input impedance. A practically dead 9v battery will still read 9 volts if you don't pull current from the battery.

Get the datasheet for your battery and get a load resistor that will draw a known current from the battery and compare the voltage you measure across the resistor with the % lifetime of the battery.

https://cdn-shop.adafruit.com/datasheets/MN1604_US_CT.pdf is the Duracell datasheet. Referring to 2 ma load line on the top right graph, if you put a R=V/I=8.6/0.002=4300 ohm resistor across the battery and the voltage is ~8.6 volts, the battery has ~80% of its capacity remaining and will work fine. If you use a R=V/I=7.8/0.002=3900 ohm resistor and the voltage is ~7.8 volts, the battery has ~50% of it useful capacity remaining and should not be used.

https://ecee.colorado.edu/~mcclurel/resistorsandcaps.pdf is a table of standard 5% resistors. https://www.brannonelectronics.com/images/STANDARD VALUE.pdf is the same for 1% resistor if you want better lifetime resolution.

To determine the test voltage at 2 ma, V = R ohms from table / 0.002 amps. and refer to the discharge chart to estimate lifetime. I consider end of useful life at 7 volts so you don't want to go that far.

Bob

Thanks Bob, you are a wealth of knowledge! That's excellent useful information for the 9V batts, not to mention you took the time to link resistors. Wow. Thank you. I often find your gems of information when I'm searching this site.

Aside, I soldered up the LiPo for a number of reasons vs. ordering new. First, I am in a time crunch... I need to get my bird all ready for May 20th, and I have never fired test deployment yet. Second, I have more Hobby King Nano Tech LiPos that I care to admit, just nothing substantial in a 1S package.... buying more LiPos is something that I'm trying to cut down on. Third, I salvaged that LiPo cell a while back, and always intended to put it back into use rather than toss it. Finally, for me at least, I get satisfaction in doing it myself if I think I can do it.

I managed a single main charge test fire that shot the nosecone and chute out with gusto tonight. 1.4 G BP in a 4" FG tube 14" long held with 4 2-56 shear pins (screws). That's a first for me and my new DD rocket. I hope to finish charge testing during the next few nights after work.

 

[astrojase]

Totally agree With Kevin above - excellent information re 9V batteries thanks Bob.

Re: twist and tuck - 'switches' coming out of one hole, tucked into a different hole and taped to the air frame = no problem. You can still disarm if you need to. YES - Don't twist and tuck back into the same hole with no access... Always 'insulate' the 'twisted' bit too... I guess that would be Twist, Tuck & Tape :wink: