TeleMega Battery

[Richardx]

First time trying to use TeleMega and am little unclear on its battery configuration. It comes with an option for dual battery (avionics and pyro). I am not doing anything fancy. Just a standard dual deploy. Should I use 2 separate battery or a single battery good enough? I can see pyro battery being useful if I am doing multi stage, but for a basic dual deploy, not so sure.
Also, I am planning to transition from 9V battery to 3.7v 900mAh Lipo . Will this work for TeleMega and RRC3?
My standard build have been RRC3/RRC2L with fresh 9V. This build is for my L3 cert and planning to use TeleMega as a backup GPS for Featherweight.
Thank you!

 

[Voyager1]

While both altimeters operate on a 3.7V LiPo, you are probably better off using a 7.4V one on the RRC3 to provide a little more supply voltage headroom. Be aware that the RRC3 outputs are limited to 3A and are optimised for 9V batteries.
I also use a RRC3/RRC2L redundant combination with 9V batteries in one of my rockets.

Edit: The TeleMega is designed to use a 1S LiPo and using a higher voltage may damage it.

 

[Ben Murdock]

Throwing my two cents out here:

I use AltusMetrum products pretty heavily, including a TeleMega for standard dual deploy and staging flights. I have always run it with a single 1S lipo. For your lipo, do you plan on using one of the AltusMetrum ones/ones sold by other vendors that come from them? That is what I use, but I wanted to make sure you knew that they have their overcurrent protection circuit taken out of the battery. This is intentional because the pyro channels can draw a lot of current, even for the default 0.1 second firing time. If you are using a different battery and still want to do this, they have directions for how to remove the circuit on their website. The polarity of the jst connector on the board is reverse from some used for RC cars, so if you use a different battery just be aware of that. Of course, the TeleMega also has the battery screw terminals you can use for another battery, this is just something to be aware of if you ever use like a TeleMetrum or TeleGPS that require you to use the jst connector.

I was curious what would happen if you used something beside a 1S on the TeleMega, so I took a peek at the open source schematic: https://altusmetrum.org/TeleMega/v5.0/telemega-sch.pdf. At least the v5.0 Megas have a voltage regulator rated for a max input voltage of 6V.

I've used RRC3s as well, my experience has been with 9Vs on them. I have seen people run 2S lipos with them, so either option is valid. At the end of the day, choose whatever makes you feel the most confident in your avionics.

 

[user 30299]

While both altimeters could operate on a 3.7V LiPo, you are probably better off using a 7.4V one to provide a little more supply voltage headroom. Be aware that the RRC3 outputs are limited to 3A and are optimised for 9V batteries.
I also use a RRC3/RRC2L redundant combination with 9V batteries in one of my rockets.

Here are pictures of 2S LiPos I am currently using with some of my RRC2's. They get you the 7.4 volts, which you want.
And they won't generate more than 4.8 amp discharge. The RRC2's and C3's can actually handle up to 5 amps.

You can see they are noticeably smaller than the standard 9-volt battery. This Blade LiPo comes with a Spade
connector, not the usual JST connector. I purchased spade connectors, from Amazon, to wire them in.

 

[Titan II]

Stick with a 9V or a 2S LiPo for the MissleWorks altimeters.

 

[Titan II]

And they won't generate more than 4.8 amp discharge.

I would like to clarify that point if you do not mind.

Your 320mAh 15C battery will output 4.8A continuous. However, LiPo batteries have another rating they typically do not talk about. There is also a burst rating, which is the output they can achieve over a short period of time. It is frequently 50% - 100% the C rating, and can occur if the match shorts out, for example. Here is an example of a battery that shows the burst rating.

 

[user 30299]

I would like to clarify that point if you do not mind.

Your 320mAh 15C battery will output 4.8A continuous. However, LiPo batteries have another rating they typically do not talk about. There is also a burst rating, which is the output they can achieve over a short period of time. It is frequently 50% - 100% the C rating, and can occur if the match shorts out, for example. Here is an example of a battery that shows the burst rating.

View attachment 626503

Yes, you are correct that some LiPos have a burst factor. But that is not the case for the
specific battery I show. It does not have a burst factor feature.

For those of you researching LiPos you can calculate the Amp discharge by knowing
the mAh and the "C" rating.

In the case of my battery the Amp Discharge = (320 mAh x 15C) / 1000 = 4.8 amps.

If it had a burst factor of 30C, then the math is (320 x 30) / 1000 = 9.6 amps.

When swapping out LiPos for 9-volt batteries - always do the math and check for the burst factor.


Small addendum to my burst factor statement on the Blade LiPo. The 15C rating
is this battery's burst factor.

 

[Richardx]

Throwing my two cents out here:

I use AltusMetrum products pretty heavily, including a TeleMega for standard dual deploy and staging flights. I have always run it with a single 1S lipo. For your lipo, do you plan on using one of the AltusMetrum ones/ones sold by other vendors that come from them? That is what I use, but I wanted to make sure you knew that they have their overcurrent protection circuit taken out of the battery. This is intentional because the pyro channels can draw a lot of current, even for the default 0.1 second firing time. If you are using a different battery and still want to do this, they have directions for how to remove the circuit on their website. The polarity of the jst connector on the board is reverse from some used for RC cars, so if you use a different battery just be aware of that. Of course, the TeleMega also has the battery screw terminals you can use for another battery, this is just something to be aware of if you ever use like a TeleMetrum or TeleGPS that require you to use the jst connector.

I was curious what would happen if you used something beside a 1S on the TeleMega, so I took a peek at the open source schematic: https://altusmetrum.org/TeleMega/v5.0/telemega-sch.pdf. At least the v5.0 Megas have a voltage regulator rated for a max input voltage of 6V.

I've used RRC3s as well, my experience has been with 9Vs on them. I have seen people run 2S lipos with them, so either option is valid. At the end of the day, choose whatever makes you feel the most confident in your avionics.

Thank you for the reply. Yes, the plan is to use the battery sold from Altus Metrum. I was thinking about buying one off Amazon and remove the overcurrent protector, but Since I only need to buy a few, I will just get them directly from the vendor.

 

[Richardx]

Here are pictures of 2S LiPos I am currently using with some of my RRC2's. They get you the 7.4 volts, which you want.
And they won't generate more than 4.8 amp discharge. The RRC2's and C3's can actually handle up to 5 amps.

You can see they are noticeably smaller than the standard 9-volt battery. This Blade LiPo comes with a Spade
connector, not the usual JST connector. I purchased spade connectors, from Amazon, to wire them in.


View attachment 626480 View attachment 626481


View attachment 626482

Thanks for the reply. I will definitely use this method for secondary controller going forward. Looks like there are small 2S battery with JST plugs too.

 

[Handeman]

I've been using the standard 9V batteries for all of my DD flights, L1 - L3. I make sure I have the 6LR61 type with the six AAAA cells, welded connections and +4Amp discharge rate. I have had some of these last for 20+ DD launches over 3 years before dropping down to 9V where I actually change them out.

Most ematches do NOT open during flight. They fire and come back reading the same .8 to 1.0 Ohms they did when tested before flight. So even though the 9V battery had 20+ 1/2 second discharges through the ematch, they still last a LONG time.

If you are going to start using WiFi switches or comms to your altimeter, you'll have to go to LiPo batteries and recharge them for every flight.