Rechargeable 9V batteries

Discussion in 'Rocketry Electronics and Software' started by molten_dragon, Sep 9, 2015.

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  1. Sep 9, 2015 #1

    molten_dragon

    molten_dragon

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    So at the moment, I'm using a MissileWorks RRC2+ altimeter for my dual deploy rocket. I'm just using a 9V battery for power. I'd like to buy some rechargeable 9V batteries though, since I don't want to re-use them and risk an e-match not firing, and it's going to get expensive to keep buying disposable ones.

    Are lithium ion rechargeable batteries okay to fly with? I'm thinking of these.
     
    Last edited by a moderator: Oct 24, 2018
  2. Sep 9, 2015 #2

    dixontj93060

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    Traditionally I have used the Maha Energy recharegables (http://www.mahaenergy.com/home/). The ones you point to may be a better solution given the low self-discharge of Li-Ion, but sure seems like the Amazon reviews are pretty bad for the particular listing.
     
    Last edited by a moderator: Oct 24, 2018
  3. Sep 9, 2015 #3

    molten_dragon

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    Hmm, doing some more research on the Li-ions, I see what you mean.

    Do you use the 8.4V or the 9.6V Maha ones?
     
  4. Sep 10, 2015 #4

    COrocket

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  5. Sep 10, 2015 #5

    timbucktoo

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    I use 8.4 Maha in my RRC3.
     
  6. Sep 10, 2015 #6

    dshmel

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    +1 on LiPo's. I was struggling with finding the right rechargeable 9V and decided to buy the IMAX B6 charger and a variety of 2 and 3 cell LiPo batteries. I flew my Entacore AIM Xtra at AirFest using (2) 7.4V batteries that, side by side, both fit in a single 9V battery compartment of my 3D printed sled. One battery powered the computer, the other was wired to the ejection charges. The capacity of each battery is 300 mAh, which is plenty for a flight. They recharge fast. Most altimeters can run on 7.4V or even 3.7V. HobbyKing has good prices and ships fast.
     
  7. Sep 11, 2015 #7

    dixontj93060

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    +1 on the 8.4V Maha.
     
  8. Sep 13, 2015 #8

    bobkrech

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    The only problem with the Maha NiMH batteries are that they are 8.4 volt 7-cell and 9.6 volt 8-cell pancake battery packs. Pancake NiMH batteries have a higher mah capacity due to higher volumetric efficiency, but the 7.2 volt 6 AAAA cylindrical cell battery pack variants have a much lower impedance and source more current.

    The impedance of LiPo pouch cells are even lower, and LiPo battery pack will source much higher current than any equivalent size NiMH battery pack, and the LiPo batteries are lighter and smaller for equivalent capacity than NiMH batteries. And as previously posted they are readily available from hobby king.

    It shouldn't matter much for commercial e-matches, but the Maha batteries will probable not fire many motor starter or homemade e-matches that need many amps of current to function. For that you will need a LiPo battery.

    Bob
     
  9. Sep 14, 2015 #9

    bdureau

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    I have been using li-ion batteries for the last 5-6 years and I am quite happy with them (up to 10 dual deployment flights without recharging) and they are still working fine after several recharging.
    The only issue I have had is when I lost one of my rocket in the wood and found it 6 months later. After 6 months in the wild the batteries were flat and dead.
    Do not expect 9v but 8.4v. Make sure that you use a special charger otherwise you can damage them.
     
    Last edited by a moderator: Oct 24, 2018
  10. Sep 14, 2015 #10

    jderimig

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    A while back I did some testing comparing battery alternatives so there is some data available .

    The summary post can be found here
    http://www.rocketryforum.com/showth...ance-of-9v-NiMH-batteries&p=565033#post565033

    In addition to voltage, current and internal resistance measurements the performance of the batteries were tested over several charge/discharge cycles.

    In short the MAHA8.4 is a pretty robust battery for rocket altimeters. Much better than the 9.6v version. It will safely source ~4A into a load, if you need anywhere close to this current then you are doing it wrong as far as the devices you are choosing to use for your RRC3 pyro duty.

    However, the small lipo's are a better value and have other attractive features like faster recharging than the NiMH, and much lower self-discharge. In my opinion that latter is the biggest risk with rechargeable NiMH. You will forget about them, they will self discharge too much and ruin the energy capacity of the battery.
     
    Last edited: Sep 14, 2015
  11. Sep 15, 2015 #11

    molten_dragon

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    I ended up buying a couple of the Li-Ion batteries I linked in the first post. There were some bad reviews, but they were cheap, and Amazon has a good return policy, so I figured I'd give them a try. I'll let you know how they turn out.
     

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