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rocketcharlie

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Hello Forum-

At a launch a while back I believe I saw a guy powering his electronics with several (6?) button type batteries stacked in series in a holder, as an alternative to the traditional heavy 9V battery. Does anyone know of this?

Thanks as always, this forum is a huge help.
 

GregGleason

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They were probably SR44 silver oxide (like the Energizer 357/303) batteries. When 6 are in series they are at 9V. This is the recommended battery type to use in lieu of the typical 9V box battery for Perfectflite's MAWD altimeter (which has been superseded by the Stratologger).

Greg
 

manixFan

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Of course with some altimeters you can use LiPo batteries as a 9 volt replacement. I'm doing that with both several Featherweight Raven's and Perfectflite Strataloggers. The big advantage is size and weight reduction. The LiPo batteries are much smaller and lighter so they work better in smaller rockets like a 38mm minimum diameter. However you do need a charger of course and it does complicate prep a bit. The LiPo batteries aren't as robust as a 9 volt physically so mounting is different.

Also important to understand is that many altimeters have a wide input range for supply voltage so something like the Raven can use a 1S cell that only supplies about 4 volts while the Perfectflite can use a 2S battery. Other altimeters may not have that flexibility.

Here are a couple of good threads that got me going:

http://www.rocketryforum.com/showthread.php?63873-LiPo-Batteries-for-my-StratoLogger-PerfectFlite

http://www.rocketryforum.com/showthread.php?62105-Wildman-mini-dual-deploy-kit&p=657980#post657980

Those talk mostly about the Strataloggers but you can do a similar search for other altimeters. It is important not to use a battery with too high capacity or it can fry the altimeter. For the Raven Adrian sells a couple of really cool mounts that that incorporate a connector for a LiPo battery and even a charger.

Good luck,


Tony
 
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KenRico

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I like that the Lipos have a variety of phsical sizes. . It has been easier once i standardized on the JST connector for mounting and charging.

Most often using a 2s 7.4v .

Kenny
 

thomas

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I use Lipos for everything unless the manufacturer says 9V only. I want to have a battery which will run the altimeter several hours.
It is best to buy "bad" lipos which can deliver only a low current, so you do not risk burning the mosfet on your altimeter.

Some guys here use 11A batteries which have 6V and very low in weight, but their capacity is very limited.
 

rocketcharlie

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I am going to be using a stratalogger. It looks as though the LiPo 2S would be the correct choice. Tony, you say that charging is a problem because at a launch you may not have a power source?

Charlie
 

thomas

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Most Lipo chargers use 12V, so as long as you have a car you are fine.
There are also versions for USB ports. The Telemetrum charges the lipo over the usb.

I never charge altimeter batteries on the field.
The stratologger consumes 1.5mA/h so even with a tiny 100 mAh Lipo you will have several days.

Some people think Lipos are to dangerous to put them in a rocket, because they can start a fire if the rocket crashes.
I think the risk is acceptable, especially since modern Lipos are way less sensitive to mechanical damage.

I can recommend the Imax B6 charger, which works with almost every battery. But pay attention not to buy a fake version.
 
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manixFan

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I am going to be using a stratalogger. It looks as though the LiPo 2S would be the correct choice. Tony, you say that charging is a problem because at a launch you may not have a power source?...
Actually most chargers are designed to work off 12 volts like a car battery out at the field. I had to look a bit harder to find one that was A/C powered. But as Thomas mentions I would not charge at the field - I have enough batteries with spares so I can have them charged and ready to go once I am at the field.

I am a big fan of regular 9 volt Duracells and use them in my bigger rockets where space and weight are not a concern. But at BALLS this year I am flying 2 min dia 38mm rockets and for that the LiPos are a great choice, or anywhere space and weight are overriding concerns.


Tony
 

blackjack2564

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rocketcharlie

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Since I know zero about RC. Please recommend a source for LiPo batteries, charger etc. It looks as though many have used Hobbyking. They don't seem to have very good reviews though. Is this the place to go for batteries, charger, etc? I will be needing this stuff in about a week.

Charlie
 

timbucktoo

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I buy most of my Lipo's from HobbyKing, never a problem & pretty quick shipping. Just make sure you order from one of the 2 US warehouses.
 

FredA

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Watch the max CURRENT you are dumping with anything other than a 9V.
Alkaline 9V batteries are internally current limited to ~4Amps.
This matches the outputs of MANY altimeters.

The smallest LiPo's can dump 25-50X their current rating.
Any LiPo rate much above 100maHr could destroy your output FETs .

Watch your FET and LiPo ratings!
 

mpitfield

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I have been using single cell 3.7 v 750Mah Lipo's on all my Strato's .....link to those, clips & a very good AC/DC charger

Here:http://www.rocketryforum.com/showthread.php?126340-Missile-Works-RTx&p=1608019#post1608019
X2

I use both the SL100 and newer SLCF all with a 1S 325Mah 25C and I have seen guys run them with 1S 250Mah 10C Lipos which is what I am going to eventually replace mine with as I think they are a better match and provide a bit more protection against over current and blowing the FETs. Hopefully the altimeter manufacturers will follow Marsa in designing their altimeter to safely handle a Lipo.

There is no reason or need to use a 2S. Simply put the bigger the battery in all aspects, number of cells, Mah and C rating, the more damage it can cause if you have a short, there are several threads on the topic.

The problem as I see it is that people can't get their heads around the idea because they think a Lipo is 3.7 volts and they read the Stratologger specs as 4-16volts...if I remember correctly. This I get because it took some convincing to me along with a lot of testing. Keep in mind that Lipos are very different that a 9 volt alkaline in that they hold their charge for a very long time and you see almost no voltage drop on the events, they also have a much lower internal resistance so they can deliver whatever they have, which can be a problem if you have too much to give. I say almost no voltage drop because the altimeter does not even record it or if it does it is because it was close to dropping to the next increment.

Also remember when a Lipo is at 3.7 volts it is just below it's ideal storage voltage of 3.8, which is roughly a 50% charge. A 100% charge is about 4.2 volts and that .2 volts although seems like too small a margin, in reality it has proven to be quite a big margin. I know if does not sound like much but I have done extensive and unrealistic bench testing firing multiple charges off, even dual e-matches per channel to load them up, with back to back firings (as fast as I can reload them) and I have never had a failure due to a low Lipo.

So long as you charge them to 100% before you hit the field you could easily fly the same batteries 5 or 6 times before you get down to the 4volt range, assuming your recovery time and waiting on the pad time is reasonable. For me this number is unrealistic as I am usually only good to get two electronic flights in, with some MPR slow and lows in between. I also have a few batteries with me all fully charged.
 

Tonimus

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For those that do HAVE to use a 9V battery, use the Energizer Advanced Lithium. They weigh about 25% less than a quality alkaline 9V and last a lot longer.
 

rharshberger

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For those that do HAVE to use a 9V battery, use the Energizer Advanced Lithium. They weigh about 25% less than a quality alkaline 9V and last a lot longer.
iirc the Enegizer Advanced Lithium batteries have a PTC which limits there output to 5A. I have used them myself and they definitely weigh less than regular alkaline 9v.
 

dhbarr

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iirc the Enegizer Advanced Lithium batteries have a PTC which limits there output to 5A. I have used them myself and they definitely weigh less than regular alkaline 9v.
Is this the part where we talk about Duracell being soldered / welded internally? Has anyone disassembled the EAL, or possibly seen the Energizer Ultimate Lithium in the wild yet?
 

NateLowrie

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I only use Lipos nowadays.

If weight is not an issue, I recommend using these:
  1. For 1S 3.7V batteries - https://www.amazon.com/dp/B01B4EUP6Y/?tag=skimlinks_replacement-20
  2. For 2S 7.4V batteries - https://www.amazon.com/dp/HOBBYTIGER/?tag=skimlinks_replacement-20

I've used them and they have a ton of capacity so if you have to sit on the pad for hours you don't need to worry about it. The battery would last all day for flying.

If you want the lightest possible av bay there are smaller capacity versions that will work too.
 
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mpitfield

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I only use Lipos nowadays.

If weight is not an issue, I recommend using these:
  1. For 1S 3.7V batteries - https://www.amazon.com/dp/B01B4EUP6Y/?tag=skimlinks_replacement-20
The StratoLogger CF has an output rating of 5A per channel. The battery you recommended has a 25C rating which if my math is correct 25 x 500mAh = 12500 / 1000 = a max burst rate of 12.5 A. This means that using this battery has a greater potential of damaging the FETs vs, something with a lower mAh or a lower C rating. If this was a 10C battery then it would be perfect (5A) for the StratoLogger as well as giving you lots of run-time, days if that was a goal.

The 25C rating is not apparent on the Amazon ad but someone who did some testing mentions it in the reviews.

Bottom line is there are a few things to keep in mind when selecting LiPos for this application.
 
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NateLowrie

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I only use Lipos nowadays.

If weight is not an issue, I recommend using these:
  1. For 1S 3.7V batteries - https://www.amazon.com/dp/B01B4EUP6Y/?tag=skimlinks_replacement-20
The StratoLogger CF has an output rating of 5A per channel. The battery you recommended has a 25C rating which if my math is correct 25 x 500mAh = 12500 / 1000 = a max burst rate of 12.5 A. This means that using this battery has a greater potential of damaging the FETs vs, something with a lower mAh or a lower C rating. If this was a 10C battery then it would be perfect (5A) for the StratoLogger as well as giving you lots of run-time, days if that was a goal.

The 25C rating is not apparent on the Amazon ad but someone who did some testing mentions it in the reviews.

Bottom line is there are a few things to keep in mind when selecting LiPos for this application.
This is true with the Stratologger, though not with other Altimeters. The Eggtimers don't have this limitation and have functioned fine on those. I use the 1200mah 2S lipos because the eggtimer units use 80ma from the WIFI. They are overkill for the stratologger though. The OP did not mention a specific altimeter, so I gave a general recommendation.

For the Stratologger in particular, 10C 500mah batteries are hard to come by. A 250mah 20C battery like https://www.amazon.com/dp/B00W9F6VAC/?tag=skimlinks_replacement-20 will do well. Max current is 5A and it has 2.5 times the current capacity of a normal 9V. Given the stratologgers minimal consumption of 3ma it would run for days.
 
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mpitfield

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This is true with the Stratologger, though not with other Altimeters. The Eggtimers don't have this limitation and have functioned fine on those.
Hey Nate, I hate to come over as argumentative so please forgive me. The Eggtimer has a rating of 8A and as far as I know most of the altimeters actually are not designed for the type of current that LiPos can deliver.

That is except for the Marsa products, which John designed for LiPos, below is a cut and paste from his site.

"Battery recommendation: MarsaSystems recommends the use of 2S Lithium Polymer (LiPo) batteries with the Marsa54L and Marsa54LHD altimeters. Do not be concerned with battery capacity and C rating, the Marsa54L/LHD has current protected outputs in flight mode."
 

NateLowrie

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Hey Nate, I hate to come over as argumentative so please forgive me. The Eggtimer has a rating of 8A and as far as I know most of the altimeters actually are not designed for the type of current that LiPos can deliver.

That is except for the Marsa products, which John designed for LiPos, below is a cut and paste from his site.

"Battery recommendation: MarsaSystems recommends the use of 2S Lithium Polymer (LiPo) batteries with the Marsa54L and Marsa54LHD altimeters. Do not be concerned with battery capacity and C rating, the Marsa54L/LHD has current protected outputs in flight mode."

It's a healthy debate. My other thought on this is that the all fire current on ematches is not going to come close to 5A. In reality, once the igniter fires you should burn the bridge wire and open the circuit. The only thing you would need to worry about is an short circuit, but even then the fire time of the FET is probably not going to be enough to overheat it.

I do know that Cris didn't mention anything when we talked about lipo sizing. He didn't have any concerns with the 1200mah 25C lipos and I haven't had any issues with the eggtimer units I have so far. Maybe he can chime in on the capacity as he recommends lipos for the TRS units.
 

Rocketjunkie

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A 1 ohm (1S) or 1.5 ohm (2S) resistor in series with the ematch will eliminate overcurrent concerns with any battery size.
 

cerving

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It's a healthy debate. My other thought on this is that the all fire current on ematches is not going to come close to 5A. In reality, once the igniter fires you should burn the bridge wire and open the circuit. The only thing you would need to worry about is an short circuit, but even then the fire time of the FET is probably not going to be enough to overheat it.

I do know that Cris didn't mention anything when we talked about lipo sizing. He didn't have any concerns with the 1200mah 25C lipos and I haven't had any issues with the eggtimer units I have so far. Maybe he can chime in on the capacity as he recommends lipos for the TRS units.
The difference between Eggtimer altimeters and most of the others is that the deployment transistors are bipolar transistors (BJT's) instead of FET's. They have a natural current-limiting ability since they basically act as a resistor between the power and the load. FET's will happily pass as much current through them as you can push, until they short out. That's why you have to be more careful with them than with BJT's, but FET's do take somewhat less real estate on the board for a given amount of allowable power. Like just about everything in electronic design, there's more than one way to do things, and there are pluses and minuses for each possible choice.

Just about any battery you can think of flying will be OK with any of the Eggtimer altimeters. I've only seen one Eggtimer altimeter with a blown transistor... the owner did a continuity test with a fairly large piece of wire, and there was a loose strand underneath one of the optoisolators so when he powered it up it dead-shorted. Big bang...
 

bobkrech

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I only use Lipos nowadays.

If weight is not an issue, I recommend using these:
  1. For 1S 3.7V batteries - https://www.amazon.com/dp/B01B4EUP6Y/?tag=skimlinks_replacement-20


This is true with the Stratologger, though not with other Altimeters. The Eggtimers don't have this limitation and have functioned fine on those. I use the 1200mah 2S lipos because the eggtimer units use 80ma from the WIFI. They are overkill for the stratologger though. The OP did not mention a specific altimeter, so I gave a general recommendation.

For the Stratologger in particular, 10C 500mah batteries are hard to come by. A 250mah 20C battery like https://www.amazon.com/dp/B00W9F6VAC/?tag=skimlinks_replacement-20 will do well. Max current is 5A and it has 2.5 times the current capacity of a normal 9V. Given the stratologgers minimal consumption of 3ma it would run for days.
Nate

A 10C 500 mah cell or a 20C 250 mah battery will deliver way more than 5 amps. In reality the short circuit is likely to be 25 to 50 amps!

What the C rating means for these batteries is that you can draw 5 amps continuously from the battery without significant loss in capacity due to internal resistive heating of the cell due to internal IR drop. Alternate interpretation is the higher internal conductance of the cell, the higher the C rating, and the lower the I^2 R heating.

Ohm's law of series resistance always applies. I = V/R where R = R battery + R wires + R FET + R e-match.

The R battery is 1.8 ohms for a 9 volt alkaline battery, but below 0.1 ohms for many LiPo batteries. R wires is typically less than 0.1 ohms, R FET is usually below 0.1 ohms, and the resistance of the e-match is ~ 1.5 ohms if good, less than 0.1 ohm if shorted, and infinite if open unless there is a plasma arc and then the resistance of the plasma will be less than 0.1 ohms.

When you use an 9 volt alkaline battery, I < 9/(1.8+1.5) = 2.7 amps under normal conditions and I < 9/1.8 = 5 amps there is a dead short.

If you use a single 4.2 LiPo cell, then I < 4.2/(1.5 + 0.1) = 2.6 amps but if the e-match shorts then the current could be as high as I ~ 4.2/0.1 = 42 amps if the battery and FET resistance is really low! The only simple remedy is to put a resistor in series with the e-match return to the -side of the battery. A wire would ~1.6 ohm resistor with 2S battery pack should work: I < 8.4 /(1.5 + 1.6 + 0.1 ) = 8.4/3.2 = 2.6 amps under normal conditions and I = 8.4/(1.6+0.1)=5 amps with a shorted e-match.
 
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NateLowrie

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Nate

A 10C 500 mah cell or a 20C 250 mah battery will deliver way more than 5 amps. In reality the short circuit is likely to be 25 to 50 amps!

What the C rating means for these batteries is that you can draw 5 amps continuously from the battery without significant loss in capacity due to internal resistive heating of the cell due to internal IR drop. Alternate interpretation is the higher internal conductance of the cell, the higher the C rating, and the lower the I^2 R heating.

Ohm's law of series resistance always applies. I = V/R where R = R battery + R wires + R FET + R e-match.

The R battery is 1.8 ohms for a 9 volt alkaline battery, but below 0.1 ohms for many LiPo batteries. R wires is typically less than 0.1 ohms, R FET is usually below 0.1 ohms, and the resistance of the e-match is ~ 1.5 ohms if good, less than 0.1 ohm if shorted, and infinite if open unless there is a plasma arc and then the resistance of the plasma will be less than 0.1 ohms.

When you use an 9 volt alkaline battery, I < 9/(1.8+1.5) = 2.7 amps under normal conditions and I < 9/1.8 = 5 amps there is a dead short.

If you use a single 4.2 LiPo cell, then I < 4.2/(1.5 + 0.1) = 2.6 amps but if the e-match shorts then the current could be as high as I ~ 4.2/0.1 = 42 amps if the battery and FET resistance is really low! The only simple remedy is to put a resistor in series with the e-match return to the -side of the battery. A wire would ~1.6 ohm resistor with 2S battery pack should work: I < 8.4 /(1.5 + 1.6 + 0.1 ) = 8.4/3.2 = 2.6 amps under normal conditions and I = 8.4/(1.6+0.1)=5 amps with a shorted e-match.
Bob,

I stand corrected. In looking over my notes I do see where that is the continuous current rating, not the peak current rating. In practice, I have always designed systems to stay under the continuous current rating and over time just assumed it was the peak rating. Thanks for the clarification.
 
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