9v, Lipo's and RRC2 Minis

Hi all,

I have searched threads and, while many have referred to using Lipos in lieu of 9v for deployment controllers, I haven't found any definitive threads on specifics.

I have obtained two, new RRC2 Minis at a price I couldn't refuse. Down the road I would like to use them in a redundant, dual-deploy system sequenced so that they are firing only one match at any given time.

Weight is a consideration, and at 45.5g 9v are outside of the range I would like (especially two of them).

I know that the literature states the RRC2's are optimized for 9v, but that falls neatly between two and three cell Lipos (of course) and three cells exceed the 10.5 suggested max for the controllers.

Will a MW RRC2 fire reliably on a fully charged two cell, 20C Lipo? (I have a decent charger and can top off easily in the field). Are 9v A10's (@ 56mAh) a viable alternative (I'm concerned about connections with these).

The RRC2 has a low draw at 'idle' and if you sequence the charges can you use one battery to power two controllers in parallel?

Any experienced comments would be appreciated!

C

As an aside, i wonder why capacitive discharge systems aren't being used, as even large caps are so much lighter than batteries...?

The usual problem is with the 5V regulator that powers the micro-controller. While low drop out regulators are common now many altimeters used the 7805 or similar regulator that require at least 7V to maintain regulation. I tested one of my AltAcc altimeters it was good down to 6.7V.

This will work with a 2 cell LiPo but cannot use the full capacity of the battery. But that shouldn't be a big problem.

The problem with capacitive discharge systems is that the energy available is very limited. While the RDAS (2,200uF @ 9V) works well with the Daveyfire N28B it didn't work with the Firewire when I tested it.

Theoretically a 2-cell can max out to something like 8.4v (I believe), but that can vary with batch, etc.. And how it would hold up after 15-minutes idling on the pad and setting off four matches would have to be seen after a plugs-in test, but at 27g (vs. 45g) a $4.25 370mAh 2-cell Lipo at 20C(40C burst) should supply 14.8 Ah in a burst (if my math is correct). Sounds like a viable alternative.

I use Turnigy nano-tech 2S 180 mah lipos on my perfect flight SLC’s all the time & they hold up great. I might go 3 flights before ever recharging.

Mini's & RRC3's [internally they are same] will work with 3.7 1cell lipo's...but must be fully charged to 4.1- 4.2
They get wonky around 3.7 ish, but a fully charged battery will go 2 days.
I did all the testing using Turnigy Graphenes'.
Flew all weekend with one.

9v is great as well as a 7.4 2 cell. These 2 are best.

The RTX {GPS} has a 3v clock and works best with 3.7 A 9v will only last 60-70 minutes.

I did hook 2 altimeters [RRC3 and Strato] to one battery during testing. Works fine just be sure to set one with 1 second delay at apogee fire. Battery was 3.7 750ma. So a 7.4 would be fine.
I really don't recommend that, as if switch malfunctions you lose redundancy. But yes is works.

I also use 2 matches per charge, so that was 8 total and all functions perfectly.
All this was covered in original RRC3 thread but it was many pages long and buried somewhere in past around 2012-13.

I frequently use 2s 120 mAh or 2s 180 mAh Lipos with RRC2s and RRC3s. I also frequently use two igniters in parallel per channel. As Jim said, using one battery for two altimeters is not a good idea.

Thanks, everyone, for your thoughtful inputs; I very much appreciate it.

While everyone here has experience with the type of set up I am considering, what are your thoughts on reliable e-match brands that you use? Are there any I should stay away from? (Feel free to PM me on that, if you prefer). Also, what type of locking switches do you like? I have seen a great many of the black rotary switches that seem to be very popular, but have yet to find the make/model/name.

Thanks, again!

Lipos work just fine. Get a good charger, a car adapter, and make sure they're topped off before the flight and you're golden.....even with pad wait times. There's so many threads here with so many of us using the same batteries that if there would have been a problem and word would be out by now. Also, they're so super cheap and available they're seasonal throw aways. If they check good at the end of season, relegate them to bench/ground testing.

I've used the Firewire initiators, never had a single failure. I've also used 110 of the chinese ematches, also not a single failure. Of the 300 that I purchased initially, only 1 failed continuity tests.

Most will tell you to stick with the firewire, no real good reason not to. $1 each is cheap insurance.

I have a pretty nice Hobby King charger from my R/C toys with auto adapter, so I am good to go. No Lipos small enough to put in a rocket, tho!

Just a little tip, but most people aren't aware that Lipos should be stored with a 50% charge (that's why when you get something with a Lipo it is only half-charged). Then they should last for a great many cycles.

I see CJ's matches are very popular here...? and what are the 'Chinese matches'? I don't have issues with imports as long as the quality is good.

Thanks!

C

https://www.ebay.com/itm/0-3M-50PCS...234198&hash=item3f9c2a0452:g:eckAAOSwrhBZEBtc

There's some debate as to their legality, but no denying that they work. Several dozen debate threads here over the last few years. Plenty of 'domestic' sources, ebay or Amazon.

These are the two more popular batteries for flight computers, currently.
https://www.ebay.com/itm/1-New-Turn...e=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649

https://www.ebay.com/itm/Turnigy-Na...e=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649

Here is some information on the rotary switches:

https://www.mouser.com/datasheet/2/358/typ_SWA1__Frontpl_-22536.pdf

I use the ones labeled 0 and 1 for Off and On.

Just note that these switches were not meant to be used in a high duty cycle environment and have a somewhat limited service life of 300 cycles as noted in the specifications sheet. This short service life is probably not a factor for most people flying these in rockets though.