LiPo Help - Stratologger CF

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jenget

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Hello,

Any recommendations for what LiPo I should use to power a PerfectFlite Stratologger CF?

Thanks
 

jenget

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Can I ask why? I have almost no experience with LiPos. Everything I've bought that needed them told me exactly which one to use
 

timbucktoo

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PerfectFlight recommends not exceeding 5 amps as you can damage the FET so you need a Lipo with a peak or "burst" current discharge rating less than 5 amps.
 

ttabbal

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PerfectFlight recommends not exceeding 5 amps as you can damage the FET so you need a Lipo with a peak or "burst" current discharge rating less than 5 amps.
Just to put it out there, most lipos will not limit the current. If you put a resistance across it that is low enough, it will destroy itself trying to do it, and possibly catch fire.

I suspect you know that and meant that you don't need a battery that is rated to source any more than 5A, but just in case is gives a new lipo user the wrong idea..

jenget: To select a lipo, you need to know what voltage and current levels you want to use. 2S refers to the number of cells in series. A 2S has 2 cells, for 7.4V. The altimeter manufacturer will tell you what voltage and current levels you need to aim for. You get the current rating by combining capacity (180 mAh) with the "C" rating. So if you have a 20C battery, that's 0.180*20 = 3.6A max rated. Note that "C" ratings are a bit of a guess and in some cases just plain made up. :) I like to get them with a little higher rating than I actually need. Once you know number of cells, capacity, and "C" you want, just look for one with the right size/shape/connector. How much capacity you want depends on how much current the electronics draw and how long you want to be able to power them. Other users of those altimeters can generally give you a good idea what to go with, as can the manufacturer. I like to try to have enough capacity so I can arm on the pad, wait about 15 minutes, fly with deployment and have about 50% left. Giving me time to find the rocket before the battery drains so much it damages itself. More than that is just dead weight.

It sounds more complex than it is really.
 

Buckeye

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Can I ask why? I have almost no experience with LiPos. Everything I've bought that needed them told me exactly which one to use
Welcome to rocketry electronics where the manufacturers are afraid to suggest anything other than a 9v Duracell for their products. If you want a different battery, you are on your own to figure it out.

I'd dare say at least one half of altimeter buyers are now using LiPos. Would be nice for the manufacturers to support this trend, make recommendations, and avoid confusion.

BTW, there are many threads on this topic.
 

sl98

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Welcome to rocketry electronics where the manufacturers are afraid to suggest anything other than a 9v Duracell for their products. If you want a different battery, you are on your own to figure it out.

I'd dare say at least one half of altimeter buyers are now using LiPos. Would be nice for the manufacturers to support this trend, make recommendations, and avoid confusion.

BTW, there are many threads on this topic.
There is at least one exception ... Eggtimer. Cris recommends LiPo and gives recommendations in his instructions.
 

patelldp

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You cannot beat the Altus Metrum 160mAh battery. It doesn't have a protection circuit and it has a nice form factor. Here's what you need:

Battery: https://shop.gag.com/parts-and-accessories/160mah-lipo-battery.html

Charger: https://www.sparkfun.com/products/10217

Female plug (no wires, just connector that goes straight into the terminals): https://www.sparkfun.com/products/9914

Female plug with wires: https://www.adafruit.com/products/1131

I can also make you a battery holder that captures the battery, much like this:

ImageUploadedByRocketry Forum1490741157.356815.jpg
 

patelldp

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Here is the sled I printed for a Stratologger or a Raven with Simple Circuit inside of a 54mm coupler and using the above mentioned battery and peripherals. Total sled length is 3.5".

ImageUploadedByRocketry Forum1490741338.607245.jpg

ImageUploadedByRocketry Forum1490741367.485866.jpg
 

jderimig

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crossfire

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For most flyers a 9 volt will work out fine. If its the price of the 9 volt you are in the wrong hobby.
 

FredA

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For most flyers a 9 volt will work out fine. If its the price of the 9 volt you are in the wrong hobby.

I actually prefer 9V batteries.
One flies ALL SEASON - which is about 6 flights max.
That battery won't kill itself with self-discharge when I don't remove it and keep it charged in the off season...which is longer than the flying season here.
Nor do current 9V alkaline leak, so no problem there.
Plus they self-limit the current output so no worries of blowing FETs in some altimeters.*

So - I can put a new battery in at the beginning of the season and never think about it again.

* Note: some newer altimeters PWM their outputs when current is too high to protect the FETS - MARSA and Telemetrum are two that I know do this.
 

ttabbal

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It's funny, when I was using 9V I always heard one flight per battery. I would re-use them for smoke alarms or ground testing, but never for flights. But I never flew less than a I on electronics, and the motor was far more expensive than the battery.

You don't need to keep lipos charged, it's better if you don't. If you bring them to "storage charge", they will sit a really long time there. Most chargers have a storage mode. Once there, you can disconnect them and store them. Holding them at 100% all the time is hard of them, letting them drain below 3.0V or so is worse.

That's not to say they are perfect, they aren't. But I do like the higher current capability, particularly for altimeters like the Quantum that can use it. They are lighter, but again, a couple grams is probably not an issue for HPR flights. The biggest reason I'm switching everything to lipo is just to standardize. Everything uses the same connector and battery type, so I don't have to remember to grab the right one, any of them will work. And since the Quantum specifies that 9V is a no-go, lipo it is.
 

FredA

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I'm quite aware of the "storage charge" but that's still "charging" .... as in I need to disassemble the Ebay and mess with the battery.
 

crossfire

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Fred I do the same thing as you do. The lipos just seem to be a pain.
 

Exactimator

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jderimig

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Instructions suggest 4-16V.
Yes. 1S LiPo are nominal 3.7V They will come off the charger a little over 4V but the cell chemistry is 3.7-3.8V. We don't round up when it comes to batteries and manufacturers recommmended voltage range.
 

Buckeye

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Not for a Stratologger. It needs a 2S battery not a 1S.
Several forum members use 1S. I am sure they will chime in.

I like Perfectflite, but the lack of LiPo info is very annoying. Missleworks, too. Hence the emergence of this same thread every couple of weeks.
 

GregGleason

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I used 6 x 1.5V silver oxide batteries for the PerfectFlite MAWD because it is what they recommended. They are small and lighter than a standard 9V and I have 2 flights on the same set of batteries and plan at least 2 more. Not much of a hassle for me to pop them in and fly.

Greg
 

jderimig

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Several forum members use 1S. I am sure they will chime in.

I like Perfectflite, but the lack of LiPo info is very annoying. Missleworks, too. Hence the emergence of this same thread every couple of weeks.
They may (use 1S), but if the manufacturer specs the supply voltage as 4-16v and you choose to use a 3.7V nominal battery then you are operating against the manufacturers specifications. Battery chemistry is not a factor. If you can supply the required voltage and current over the devices operating loads it doesn't matter whether you use alkaline, lithium, lead-acid or a series of potatoes. The electronics will not know the difference.
 

patelldp

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Direct from Perfectflite:

Below you will find some general information about using a LiPo with the StratoLoggers. I believe it answers your questions, but if anything isn't clear please ask.


You can use LiPos, but they have a number of issues that you have to be concerned about. If not charged properly, they can burst into flame and/or explode, so you need to make sure you are using exactly the right charger (current, voltage, and cutoff) and you should never charge them unattended.

Also, if you lose a rocket for a couple of days running on a LiPo so that the battery is run down to less than 3 volts per cell (3 volts for a 1S single cell, 6 volts for a 2S two-cell battery) you need to resist the urge to try to recharge and re-use it -- throw it away instead. In addition to diminishing the capacity of the cells to an unpredictable state, trying to recharge a severely discharged cell can result in fire or explosion.

Choosing a LiPo:

A large LiPo (> 300 mAh) can put out over 30 amps of current when shorted. The altimeter has a max current rating of 5 amps. It will PWM the signal to try to reduce the current to this level, but if you use a large LiPo and fire into a shorted ematch it could fry the altimeter before the PWM can come into play. We'd recommend 125 - 150 mAh maximum. Anything more will not net you any benefit anyway, will be larger and heavier, and could damage the altimeter if you have a shorted ematch. A 150 mAh LiPo will run the altimeter for several days on a single charge and is smaller, lighter, and less expensive.

If your LiPo has a small PCB attached to it (usually wrapped in yellow Kapton tape) it probably has current limiting built in. If so, and the current limiter detects an overcurrent situation, it will shut down the power from the battery permanently until all load is removed. If your drogue ematch triggers the overcurrent limiter, the altimeter will lose power and will shut down, and you will not get any events fired and will crash your rocket. If you have this PCB installed on your battery, you should remove it.


Choosing 1S (one cell, 3.7V nominal, 4.2V full charge) or 2S (two cells, 7.4V nominal, 8.4V full charge):

The altimeter has built-in brownout protection that will allow it to function through brief disruptions of power (but not the permanent power loss scenario described above). If your battery does not cut out altogether (the preceding scenario) but the voltage drops significantly when the ematch is pulling current, the brownout protection serves to keep things running properly and the altimeter will ride out the momentary voltage dip. With a 9V battery, you get 2 to 3 seconds of brownout protection. With a single cell 1S LiPo in the 4 volt range you will get much less protection (less than 1 second) -- If the ematch is shorted and kills power from the battery for 1 second the altimeter would likely shut down and your rocket would crash.

Also, the beeper is louder with higher voltage, it will not be as loud with 4V.

If you want to use a LiPo, we would suggest a two cell 2S 125 to 150 mAh LiPo battery which will have plenty of power to fire your ematch, will run the altimeter for several days, will be louder, and will be much less likely to burn out the altimeter in the event of a shorted ematch or shorted ematch wiring.
 

kevinkal

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I've been using 1S LiPos in two rockets using a StratologgerCF. With 2S 450mAh 25C lipos, I had problems with too much current draw with the StratologgerCF and ematches with 1.2 ohms resistance. Rather than drop the battery capacity or C rating, I used the 1S LiPos that I had at home. To make sure the voltage doesn't go below 4.0V, I make certain the LiPo voltage is 4.1 or 4.2 V, else I charge them to 4.2V before leaving for launch. The 350mAh pack lasts multiple flights/flight days and does not drop below 4.1V, the 850mAh will last even longer.. probably overkill capacity. I have come to trust them in over a dozen successful flights.
Below are some flight data plots including voltage over time. The voltage is generally constant at 4.1 or 4.0 V during flight and deployment. Occasionally, I see a 0.1V voltage dip when the drogue or main charge fires. As the Ematches I have vary in resistance, when I connect a lower resistance Ematch, roughly 0.8 to 1.0 ohms, the current draw will go up to 4 or 5A... but not over.

1S 350mAh 45-90C Nanotech LiPo
2017-04-04.jpg

1S 850mAh 20C Generic LiPo
2017-04-04 (1).jpg
 

mpitfield

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I've been using 1S LiPos in two rockets using a StratologgerCF. With 2S 450mAh 25C lipos, I had problems with too much current draw with the StratologgerCF and ematches with 1.2 ohms resistance. Rather than drop the battery capacity or C rating, I used the 1S LiPos that I had at home. To make sure the voltage doesn't go below 4.0V, I make certain the LiPo voltage is 4.1 or 4.2 V, else I charge them to 4.2V before leaving for launch. The 350mAh pack lasts multiple flights/flight days and does not drop below 4.1V, the 850mAh will last even longer.. probably overkill capacity. I have come to trust them in over a dozen successful flights.
Below are some flight data plots including voltage over time. The voltage is generally constant at 4.1 or 4.0 V during flight and deployment. Occasionally, I see a 0.1V voltage dip when the drogue or main charge fires. As the Ematches I have vary in resistance, when I connect a lower resistance Ematch, roughly 0.8 to 1.0 ohms, the current draw will go up to 4 or 5A... but not over.

1S 350mAh 45-90C Nanotech LiPo
View attachment 316523

1S 850mAh 20C Generic LiPo
View attachment 316524
I run a half dozen StratoLogger CF and 100s using a 1S 25C 350mAh LiPo and have for three years, no issues. On top of this I have done several non-real world bench tests firing dual e-matches several times in a row and no issue, never dipped below 4 volts for bench tests and 4.1 for real world. From what I have read when a 1S LiPo is @ 3.7 volts it is somewhere around a 50% charge and when it is at 4.2 volts it is 100% charged.

However I would also use a 2S 20C 150-250mAh LiPo.

This topic has been discussed and debated many times, and I have come to the conclusion that either choice has its risks. The 1S could dip below the 4volt range if not fully charged, and although the 2S provides a greater margin of error it also carries an increased risk of damaging the StratoLogger. In the end PerfectFlight needs to add some protection circuitry, then the 2S would the best choice.
 
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