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1/2A, 9V battery hack

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1/2A, 9V battery hack

Old 03-08-2015, 07:17 PM
  #1  
AndyW
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Default 1/2A, 9V battery hack

I came across this 6V Lantern battery hack https://www.youtube.com/watch?v=nzgDffMcsUU a while ago, and it left me suspicious. First, it's made by GagFilms. That's the first clue. Secondly, the 32 AAs pour out without any evidence of being hooked up together.

This is the real deal for a 9V battery hack for making up 1/2A battery packs.

I tried this many years ago with Ni-cads but inside were these rectangular, plastic cells that were not conducive to hacking. They could not be separated to make up a 4 cell pack.

Enter NiMH, 9V, 175 mAh batteries from Energizer.

The images are self explanatory. The neat thing is that the case is plastic and all you need to do is slice away at the corners until the assembly slips out. Take care here, or slips out could mean a gashed finger.

In any case. you get 7, neat little, 1/3AAA cells that can be made up into various configurations, depending on your aircraft's battery bay.

At first, my Super Cycler would only deliver 5 minutes till it kicked into charge mode. Inspection revealed that 3 of the 7 cells were at .5V while the rest were at 1.1Volts and my pack just happened to get 2 of the bad cells.

Hobbico makes a field charger with two outlets that allow for charging of Ni-Cads, NiMH and Lipo batteries. It has the capacity for detecting and charging, 1 to 8 cells for Ni-Cads and NiMH. This is a major improvement over all other field chargers and this includes having the capacity to adjust the charge rate, from 200 mA all the way to 2 full Amps.

So I took to charging all the cells separately at the lowest rate and then assembled the pack again and just for good measure, I put the whole pack on charge for a final, top up.

I'm pleased to report that this worked great. My Super Cycler delivers 30 minutes and this is just fine. That's 3 ten minute flights. However, I always give myself a good margin of safety and will field charge after two flights. In ANY case, I always use my expanded scale voltmeter before every flight.

What do you do with the 3 remaining cells? You buy two of the little guys, that gives you 14 cells, enough to make 3 packs. The Energizers cost me 16 dollars each, including tax. The neat thing is that you can pick them up locally, you don't have to wait for your order and you can configure the packs just the way you want them.
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Last edited by AndyW; 03-08-2015 at 08:52 PM.
Old 03-08-2015, 10:27 PM
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combatpigg
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That's a good find Andy, because the "sub AAA" cells are losing shelf space with the suppliers I've dealt with .
Old 03-09-2015, 08:16 AM
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AndyW
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Thanks CP. My source for batteries here in Canada is www.onlybatteries.com and they're pretty amazing. But this size, they don't have. They do have 2/3rd AAA and these come with solder tabs. I use these mostly but for those special, very small guys under 10 " span, like my next Ugly Stik, or for small gliders. I've bench run the new packs I've made on my small glider by putting on a good movie and wiggling the sticks in a manner consistent with glider flying and have got some 2.5 hours before the packs reached 1 volt or so. Good enough.
Old 03-09-2015, 08:44 AM
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AndyW
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My mistake. Here, http://www.onlybatteries.com/search....g=tabs&what=kw they show 1/3rd AAA but they're only 120 mAh. They also show, 1/3rd AA at 300 mAh. The latter size is perfect for the typical, 1/2A airplane.

So the 9V NiMH packs must be some kind of special size, made just for the application.

All of this means is that we have more choices than ever. Neat.
Old 03-09-2015, 09:35 AM
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It looks like the batteries have changed over the years. Around 1990 or so, a flying buddy was using the 9v batteries in his single channel plane. I got one to try, and removed one cell. He told me not to bother, but just use it as is, because it would suck the voltage down to something you may want anyway. They were stacked rectangular cells, and there were 6, which totalled 7.2 volts. He only did one flight each, just to be on the safe side. Since you are in Canada, check out the Dollarama, they have an Iphone charger for $3. It contains a LiPo battery (I think) Don't know the C rating, and was kind of hoping to get someone else to experiment a bit for me, as I haven't a clue. I unsoldered the little circuit board that was on the tip of the cell. Had to use a magnifying lamp to see it.
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Old 03-11-2015, 04:00 AM
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Andy - great tip on the batteries. I was able to get a couple on eBay at a good price.
I'll be using these in an upcoming Guillows Stearman build, RC conversion...

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Old 03-11-2015, 05:18 AM
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If you get 2, then you get 3 flight packs, and a couple could be 5 cell.
Old 03-13-2015, 02:52 AM
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Some will be 1/3A's and some will be like the one I pulled apart, full of tiny little long cells, about maybe 3/16" in diameter but the full length of the 9v battery.

These days though I don't tend to use the NiMH packs anymore, I've found that a single lipo works quite well on 2 channel models.
Old 03-13-2015, 09:21 AM
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How has the radio range been like with 3.7v ?
Old 03-13-2015, 05:27 PM
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there is also a 200 MaH LiFe from hobbico that works great, has no memory and last forever.
Old 03-14-2015, 09:09 AM
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Is the 200 mah a two cell or one? I am afraid to use the 6.6 volts with the little 9 gram servos and even the larger old style servos I seem to have a lot of, and also afraid of the low voltage of the single cell.
Old 03-14-2015, 05:13 PM
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I use the Life on every plane I own. now if you have some 10 year old servos you might have an issue but a fully charged niMh is just over 7 volts
Old 03-14-2015, 05:13 PM
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2 cell
Old 03-14-2015, 05:56 PM
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+1 on the 200 mah LiFE from Radical R/C. I'm flying one in a Norvel .074 powered Carl Goldberg Chipmunk electric I converted. It only draws about 25 mah per flight per recharging results with 4 X HS65 servos.

John C
Old 03-15-2015, 10:13 AM
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If one is concerned about the voltage of some of the alternate packs, there is sort of a solution. Diodes are useful devices to drop the voltage of a battery pack. I use 1 or 2 on LiPo packs to lower the 3 cell voltage for use in my transmitters. There are 3 primary types of diodes, silicon, selenium, and germanium. Each has a different voltage drop. Germanium is approx 0.6 to 0.7 volts, Others are around 0.2 to 0.3 volts. So putting 2 germanium diodes in series will drop between 1.2 and 1.4 volts. So a fully charged 4 cell NiMh is 5.76 volts (1.44v / cell) A fully charged 2 cell LiPo is about 8.4 volts. So 3 germanium diodes in series should get the pack down to around 6 volts at full charge.
Old 03-20-2015, 07:56 PM
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The Align 5V "regulator" is a pair of diodes in parallel/reverse polarity, exactly that in bi-directional format.
Old 04-10-2015, 05:32 PM
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How about a voltage regulator and a small 2S LiPo?

Blue Arrow Ultra Micro Automatic Voltage Regulator 5V/1A DC Output

HK for $6.65
[h=3]This ultra lightweight automatic voltage regulator provides a constant and stable 5V/1A DC output. It is perfect for DLG, HLG type gliders and other models where you want a very small lightweight power source for your receiver and servo's.
This unit is supplied with a variety of connectors and adapters to suit most applications.

Spec:
Input Voltage: 7~12V
Output Voltage: 5V
Output Current: 1A
Output Plug: Micro JST 1.50mm pitch
Weight: 1.4g
Dimensions: 20x10x4mm
[/h] [h=3][/h] [h=3]or a[/h] [h=1]Turnigy 5V/6V 5A Heli-UBEC for Lipoly (6~16V)[/h] [h=3]$6.69[/h] [h=3]Features:[/h] [h=3]• Compact in size[/h] [h=3]• 5V/6V selectable output[/h] [h=3]• 5A continuous output current (7.5A burst)[/h] [h=3]• 6~16V input range allowing for use with 2~4S lipoly battery packs[/h] [h=3][/h] [h=3]Specs:[/h] [h=3]Output voltage: 5V/6V (selectable)[/h] [h=3]Continuous output current: 5A[/h] [h=3]Burst output current: 7.5A[/h] [h=3]Input: 6V~16V[/h] [h=3]Size: 39x27x15.5mm[/h] [h=3]Weight: 25g[/h] [h=3][/h]

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