StratologgerCF Battery Options

This is time sensitive. I've got a launch Saturday. I'm attempting my first DD flight.

I just finished my a/v bay tonight. I'll post pictures tomorrow. My SLCF is mounted. The switch is wired. All that is left is the battery. And I've got limited space.

I COULD fit a 9v in there, but it's gonna be tight. I'm looking at the mini 12v. I think it's called an A23. Would this work? How reliable is it? The SLCF says it's 4v-16v input. Seems it CAN handle the battery. But will the battery last for a couple of flights? Or even reliable for one?

No. An A23 battery will not supply enough current to fire the ematches. Do not use.

You can use a 1S or 2S lipo battery in the 200-300 mah range however. Either should work fine. The altimeter works fine on a 1S lipo and non-deployment variants are supplied with one, however depending on the resistance of your e-matches you might want to opt for a 2S lipo.

Bob

Well, I had a pending email in to Perfectflite. Options are a bit interesting for small spaces. Being inside the coupler of a 2.5" OD rocket does not give much space. When I asked the same info of Perfectflite, this was his response

"The A23 will run the altimeter just fine. The altimeter has a very low current drain, so an A23 will run it for a relatively long time (10 - 20 hours), BUT the A23 has limited ability to provide a high current "surge" to fire the ematch. A good quality, fresh A23 will run the altimeter and fire a single (at a time) low current ematch but generally will not fire two redundant matches connected in parallel. As long as you are using one ematch for each channel (drogue and main) and since they will not be firing at the same time, it should work.

If you use an off-brand A23, or one with a "use by" date that is coming up soon, you could have a problem. Also -- the ematches that you provided a link to are Chinese -- the quality and consistency may be variable, and the exact firing current isn't specd by the seller. You should ground test them with the A23 brand that you plan to use before flight. If you can connect two in parallel to one of the altimeter's outputs (drogue or main) and the altimeter will fire two at once during testing, you should be OK to use a single match on each channel in flight.

(Unless the single match that you use during your flight happens to be defective -- that's why using a more powerful battery that can fire several at once, and using the two in parallel for the actual flight, is a better idea. But you won't be able to do this with the A23.)

Those ematches are cheap -- do a bunch of ground testing before you decide on whether your matches and battery are OK. Those ematches are cheap, failed deployment isn't....

If you have the USB data download kit, you can do some vacuum ground tests with a shop vac (described in the altimeter manual) and then download the data and look at the voltage plot. If the battery voltage drops a bit while the ematches are firing, and recovers quickly, that is a good sign. If the battery voltage drops by several volts or more, and doesn't recover to near-original levels after firing, then that's showing a sign that the battery isn't really up to the job.

Also -- common "N" cell holders don't really fit the A23 properly, so if you are using this kind of holder make sure you tape it in or it may pop out during flight (not good).

If you can somehow cobble together a reliable way of holding 2 or 3 "CR2" lithium cells in series, that would be a better bet, able to provide more current. You may be able to force two of them into a single "AA" battery holder if the holder is somewhat flexible. If it doesn't seem robust, don't fly it....


We have a 2 cell LiPo battery that is about the size of an A23 and is rechargeable and can supply more current than the A23, but the charger is not yet in production so that won't help you right now if you are in a hurry."

Not the worst news, but not sure I want to rest the fate of my rocket on the battery. I may do some testing with a Lithium A23 just to see the ground results. The 9v is not impossible, just a little snugger than I'd prefer. More info in a few hours.

See my recent thread on this. Lots of good battery info in there.

Too many "If's" in Perfectflites reply for my money. I'd explore alternatives... or just listen to bobkrech ! It ain't the volts, it's the amps (... and the volts. :blush.

I ran three dual deploy flights last week with a Stratologger CF and two staged flights with an R/C switch on a 300mAh 2S lipo all with Firewire "Initiators". Can't beat them for size or power.

I run both the StratoLogger CF and the old StratoLogger SL100, with dual e matches in parallel using a 1S 350mAh 25C Li-Po and have never had a failure due to low current or low voltage. I have even bench tested several e-match manufacturers all performing back to back tests just to see how many concurrent charges the battery will fire and a 1S is plenty of Li-Po for these altimeters. If you search and read through the postings you will see that a lot of fliers seem to prefer the 2S option, which I am guessing provides them some comfort. However I would encourage you and anyone else to run the tests that I have and I am confident that you will come to the same result. I will eventually test the same model line of Li-Po I tested but the 250mAh version instead of the 350mAh...I would not be surprised that it will yield the same result. Here is a link the the specific Li-Po I ran all the tests with https://www.thunderpowerrc.com/Products/350ProlitePlusPower/TP350-1SP25J_2

So here it is. My first a/v bay. As you can see it's a very tight fit. But I managed to get it all in. Full assembled it's about 236g not including powder or matches. All it needs now is the static sample port / switch port. I'm having issues in that category.

I still wish there had been a smaller battery option at this time but ya gotta do what it takes I guess.

This is an excellent 300 maH LiPo 1S battery from HobbyKing. Costs $2 each and weighs 8 grams including the wire and connector. Hard to be the quality or the price. Rated for 10.5 amps continuous and 21 amps for 5 seconds without reducing the battery capacity. You will use not more that 2% of battery capacity per dual deployment recovery cycle or 0.5% per hour of on time so you have plenty of reserve capacity for a weekend launch. So if you launch 6 time a day on both weekend days you use ~ 1/3 of the battery capacity. That's a good reserve power capacity ratio.

https://www.hobbyking.com/hobbyking...Lipo_Pack_Fits_Nine_Eagles_Solo_Pro_100_.html

Bob

bobkrech said:

This is an excellent 300 maH LiPo 1S battery from HobbyKing. Costs $2 each and weighs 8 grams including the wire and connector. Hard to be the quality or the price. Rated for 10.5 amps continuous and 21 amps for 5 seconds without reducing the battery capacity. You will use not more that 2% of battery capacity per dual deployment recovery cycle or 0.5% per hour of on time so you have plenty of reserve capacity for a weekend launch. So if you launch 6 time a day on both weekend days you use ~ 1/3 of the battery capacity. That's a good reserve power capacity ratio.

https://www.hobbyking.com/hobbyking...Lipo_Pack_Fits_Nine_Eagles_Solo_Pro_100_.html

Bob

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I've been considering the Lipo option. Still have to get one AND a charger. I understand that gets quite expensive fast. Plus I was on a short schedule. My launch is Saturday. Just 2 days away.

The rocket should be assembled by bedtime tomorrow. Odds are she'll be flying without paint this time. If I only had 2 more days this week, she'd at least get primer. My first DD flight. Why do I have a feeling I'll be bringing the rocket back in a small box this time?

bobkrech said:

This is an excellent 300 maH LiPo 1S battery from HobbyKing. Costs $2 each and weighs 8 grams including the wire and connector. Hard to be the quality or the price. Rated for 10.5 amps continuous and 21 amps for 5 seconds without reducing the battery capacity. You will use not more that 2% of battery capacity per dual deployment recovery cycle or 0.5% per hour of on time so you have plenty of reserve capacity for a weekend launch. So if you launch 6 time a day on both weekend days you use ~ 1/3 of the battery capacity. That's a good reserve power capacity ratio.

https://www.hobbyking.com/hobbyking...Lipo_Pack_Fits_Nine_Eagles_Solo_Pro_100_.html

Bob

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Nice find Bob, @ $2.00 I may pick a couple of these up

Where can we find the chargers and the other half of the connector for these?

Here is a Madcow Frenzy I am making into a dual deploy. I used the Missle Works sled with 9 volt battery. He has LiPo sleds now.

nmartin said:

Here is a Madcow Frenzy I am making into a dual deploy. I used the Missle Works sled with 9 volt battery. He has LiPo sleds.

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What's the diameter of the Frenzy?

To the OP: this won't help you this time but think outside the box next time ...

1) Don't center your threaded rods on small diameter av bays. Off center by just a bit and you have plenty of room for a 9v battery.
2) Eschew the huge battery holder. In a small diameter av bay I use the 9v battery connector on the end of a wire plus electrical tape. The battery has no where to go in that small space.
3) That huge switch is costing you a lot of space and aggravation. Rocket people have been using twist and tape for years. It works and is reliable.

Your set up looks fine, just get creative and weigh more options next time.

--Lance.

timbucktoo said:

What's the diameter of the Frenzy?

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Judging by the grid on the mats in his pictures its a 1.6" Mini Frenzy.

llickteig1 said:

To the OP: this won't help you this time but think outside the box next time ...

1) Don't center your threaded rods on small diameter av bays. Off center by just a bit and you have plenty of room for a 9v battery.
2) Eschew the huge battery holder. In a small diameter av bay I use the 9v battery connector on the end of a wire plus electrical tape. The battery has no where to go in that small space.
3) That huge switch is costing you a lot of space and aggravation. Rocket people have been using twist and tape for years. It works and is reliable.

Your set up looks fine, just get creative and weigh more options next time.

--Lance.

Click to expand...

Well, it was a first bay. I've learned a lot with this one.

I never saw an offset sled until AFTER I had already drilled my bulkheads. That would definitely have helped.

I went with the battery holder for the comfort of the connections. Lesson learned. It doesn't look like much, but it does make a noticeable difference in overall space.

The switch may be a bit bulky, but I like it a lot. Twist and tape just seems so archaic when everything else is so technologically advanced in out builds. I am considering a lever switch and pull pin for my next bay.

I'm also looking hard at Lipo batteries for my small builds. Money and time played too big a factor this go round. I'm currently looking at a DD cosmic interceptor that I may be able to get more creative with. My future sleds will definitely be cleaner. It's my learning curve. And one I plan to advance quickly. I've got a DD scion about to go into construction. I'll work on my bay design before assembling it.

Thanks all for the input. Now just wish me luck tomorrow.

It is a 1.6 mini frenzy.

So the battery preformed admirably. The bay functioned perfectly. The entire setup was a success. I now have my L1 cert in the bag. Time to look at a smaller battery and a 2" a/v bay. It's time to go DD nuts.

I've been test firing my StratoLoggerCF with some cheap Ematches from Amazon. These have the orange wire and a red plastic tube over an e-match. I'm using a 2S 450mAh 25C LiPo. However, I keep triggering the channel current warnings even with a single match.
I looked at the log data, and I see peak drogue and main currents of 6A to 8A. The Battery voltage remains a solid 8.2, with no perceivable drop in voltage in the 20Hz data.
If I keep using it and pulling 6 to 8A for 1 second to fire a charge.. will my Stratologger fail, or deal with it?

I certainly wouldn't go whoosh-up with an equipment arrangement that's giving such a clear warning.

kevinkal said:

I've been test firing my StratoLoggerCF with some cheap Ematches from Amazon. These have the orange wire and a red plastic tube over an e-match. I'm using a 2S 450mAh 25C LiPo. However, I keep triggering the channel current warnings even with a single match.
I looked at the log data, and I see peak drogue and main currents of 6A to 8A. The Battery voltage remains a solid 8.2, with no perceivable drop in voltage in the 20Hz data.
If I keep using it and pulling 6 to 8A for 1 second to fire a charge.. will my Stratologger fail, or deal with it?

Click to expand...

Read your manual. It says that the maximum current thru the pyrocircuit should not exceed 5 amps!

Your igniters are following ohms law. V/I=R 8.2/6=1.37 ohms >= R >= 8.2/8=1.03 ohms.

You should not exceed 5 amps: so for V = 8.2 and I = 5 amps R must be not less than Rmin V/I = 8.2/5 = 1.64 ohms so you need to add minimum of 0.5 ohms in series with your e-matches or change to e-matchs that have a higher resistance. To totally protect the FETs, you should use a 1.5 ohm resistor in series with the battery to limit the current flowing into the altimeter to ~5 amps on a short. The wattage rating should be P = V^2/R = 8.2^2/1.5=45 watts.

Another option is a PTC self resetting thermal fuze.

or switch to a 1S LiPo battery. Then V = 4.1, I = 5 amps so Rmin V/I = 4.1/5 = 0.82 ohms. Since your e-matches range from 1 to 1.3 ohm and are above the minimum resistance.

BTW: When the battery has a 25C current rating and a .45 Amp-hour capacity, it will source 25 x .45 amps = 11.25 amps continuously without dropping the voltage significantly. In 5 second bursts, they will usually deliver twice that current or 22.5 amps! If your igniter shorts, it will take out the output FETs.

Bob

Tis the nice thing about 9V alkaline batteries - output current tops out at ~4A so you pretty much can NOT fry your FETs.

As Bob points out -- LiPoly's while small and light can really dump the current into the [near] short of an igniter.

Thanks for the replies. I should have added more detail in my post. but it was late. I ran a half dozen ematch ignitions through the ammeter of my Fluke 117 multimeter, I set the min/max feature of the multimeter and captured maximum current. The current it measured was between 40mA and 130mA. The output event is fast, the StratologgerCF only sources current to the Drogue and Main outputs for 1 second. I don't know if my multimeter is fast enough to see the true peak or not.. but it would seem that these matches fire in a fraction of a second.. and thus only draw current for that short duration. (I keep telling myself to buy one of those cheap o-scopes .. I think they'd be faster and capture the even data.)
I am aware of the stated 5A current limit, as well as what the peak currents reported by the StratologgerCF were. I was hoping there was an experience base for use of this setup, as it seems that it would be common and the current is relatively close to the limit. Some of these cheap matches don't trigger the current warning.

Thanks for the 9V recommendation. My plywood battery mount will cradle a 9V Alkaline just fine as the dimensions are close to my current 2S LiPo. I can fall back to that.. but I trust LiPo batties more than I do 9V Alkaline, and I have a good number of LiPo batteries floating around my house to choose from. It's somewhat funny that one of the reasons I'm using a LiPo is that they are very good current sources.. however the reason I'm having trouble with the StratologgerCF is that they are very good sources of current! Perhaps I need to relax my LiPo preference and go with a 9V alkaline.

I plan to look into tapping the balance lead of my 2S lipo to access a single cell. Thus, I'll try a 1S 450mAh Lipo. I should be able to fire single cheap ematches without warnings, and peak around 4A.

The other thought I had was to put 2 of these cheap ematches in series, not parallel. This would double their resistance and thus drop the current demand In half. I would then not have to change out my battery and mounting system.

The rocket that this altimeter will be installed in, will have dual redundant altimeters. It will run along side an Eggtimer Quantum.

I just ran a test using 2 of the cheap ematches connected in series. I measured their individual resistances at 1.1 and 1.1 ohms, and as expected the series connected pair measured 2.2 Ohms. Thus, using a 2S LiPo battery, I would expect 8.2V/2.2Ohms = 3.7 Amps peak, assuming the ematch resistance snaps up to the K-ohm range immediately after firing.
The test seemd to run fine, and both ematches fired simultaneously. I downloaded the StratologgerCF data and found that the current it measured was right at the 5A limit. Here's a plot of the data:



I find it hard to believe that there's no measured battery voltage drop when the ematches are fired.

I suppose this could be a work-around for me so that I can keep my existing setup using the low resistance cheap ematches with a 2S LiPo. Downsides might be the potential for one of the two ematches to open circuit, and the minimal added expense of using 2 cheap ematches.

kevinkal said:

I've been test firing my StratoLoggerCF with some cheap Ematches from Amazon. These have the orange wire and a red plastic tube over an e-match. I'm using a 2S 450mAh 25C LiPo. However, I keep triggering the channel current warnings even with a single match.
I looked at the log data, and I see peak drogue and main currents of 6A to 8A. The Battery voltage remains a solid 8.2, with no perceivable drop in voltage in the 20Hz data.
If I keep using it and pulling 6 to 8A for 1 second to fire a charge.. will my Stratologger fail, or deal with it?

Click to expand...

I think a 1s might be a better choice, or switch to a nine volt alkaline.

markkoelsch said:

I think a 1s might be a better choice, or switch to a nine volt alkaline.

Click to expand...

I think you're right. Thank you. I supposed I'm being somewhat stubborn given that I build this side of the av bay around the darn 2S LiPo. It is all setup.. then testing found this over current issue.
However, inline with your suggestion, I've just salvaged an 800mAh liPo cell from a 3S pack that had a bad cell. I'm in the process of soldering on a JST connector to this single cell now. It should be a drop in replacement into the mounting provision I built into my plywood sled.

Believe I = V/R. It's Ohms law! :kill:

The typical action time of an e-match ranges from <0.001 to ~0.003 seconds for 2 times the all-fire current or more. This is the time for the pyrogen to ignite. Once you have pyrogen ignition, it doesn't matter if the bridgewire breaks or not, and the bp charge will ignite in a few milliseconds or less later.

Your meter measurements do not have the temporal response to measure the current. You need to have a time resolution of at least 10-4 second and preferably 10 times that to get an accurate peak value.

You certainly can use 2 e-matches in series if you use a 2S LiPo. We discussed this earlier in the electronics forum. When used in series, the altimeter continuity is valid and will let you know the e-matches are good. If one e-match does not ignite, the other one will set of the bp so you gain a degree of redundancy with 2 e-matches in series. Another way the altimeter can draw more than expected current is if the bridgewire breaks and arcs in the hot plasma generated when the bp burns. With 2 e-matches in series, the probability that both bridgewire break is quite low so the probability of an arc current overload goes way down.

Alternatively you can use a Duracell Alkaline 9 volt battery with the StratoLogger and not have to worry about exceeding the 5 amp current limit using 1 e-match per channel as it will only source 4 amps when new. The StratoLogger draws 1.5 ma when running unless you are firing an e-match. Being conservative you can rate the battery life as 100 maH at this current draw. (life to 8.5 volt, a very conservative rating based on the battery datasheet). Every time you fire an e-match consumes 1 maH which is 2 maH per flight. If you go to a weekend launch and have your altimeter on 12 hours per a day for 2 days, you consume 2 days x 12 hr/day x 1.5 maH = 36 maH and if you launched the rocket 12 times each day you would consume another 2 days x 12 flights/day x 2 mah/flight = 48 maH. Adding both you consume 36 maH + 48 maH = 94 maH per weekend. So it's ok to use one fresh Duracell 9 volt alkaline battery for a weekend of launching.

The battery will still have useful life afterwards for toys, but get a fresh one for the next launch.

Bob

Thanks Bob. I appreciate the insight backed with experience.
So, I'm in the middle of ginning up a 1S LiPo.. I'm in "lack of proper connector hell" at the moment.. but I think I've got a path to goal. I'll post the findings after I fire a couple of matches with it.

I suppose my distrust of 9V alkalines is related to the damn things reading more than 9V on my meter, but the smoke alarms and CO2 alarms going off with the battery warning in the middle of the night anyways. I think they frustrate me for that reason! I have one sitting here in front of me.. it's staring at me wondering why I'm soldering up a 1S LiPo instead of hooking it up. After the 1S LiPo tests, I likely will hook up the standard 9V Duracell and fire some more tests. At that point, I hope to have a better vantage point for the 3 viable options you all have been so helpful with...
1. 1S LiPo, single inexpensive Ematch
2. 2S LiPo, 2 inexpensive Ematches in series, verify >2 ohms before installing
3. 9V Duracell Alkaline, single inexpensive Ematch

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: