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Could I Use A Y-Harness to Connect 2 600 mAh batteries for longer flights??

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Could I Use A Y-Harness to Connect 2 600 mAh batteries for longer flights??

Old 01-13-2004, 01:29 PM
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iflynething
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Default Could I Use A Y-Harness to Connect 2 600 mAh batteries for longer flights??

Is this possible.....I have on battery that messed up on me about 4 months ago...I was flying my Superstar and the battery went dead.....I just told everyone that I didn't know what happend. Actually I just didnt' charge it overnight, and I didn't tell them that, but didnt' want to look stupid, but I have that battery and I think that it will work fine. So, could I use a y-harness that I was going to use on the Somethin' Extra ailerons and plug one battery into on of the slots and the other in other?? THANKS........I would just like maybe have longer flights.....
Old 01-13-2004, 03:03 PM
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famousdave
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Default RE: Could I Use A Y-Harness to Connect 2 600 mAh batteries for longer flights??

Theoretically this would work and it is a cheap solution for redundant batteries, but you must use diodes in line with BOTH packs and both should always have the same charge, voltage, etc. You can see where this is going.

If one pack went dead, the good pack would "take over" assuming the diode would block its current from going into the dead pack. The diodes would be forward biased and on the positive side of the battery pack(s). When the current starts to flow from the good pack to the weak or dead pack the diode would theoretically "cut off" and block the dead pack.


I have heard this cheapo idea discussed many times, but have not actually seen it work or hear about anyone who had it work. I am an electrical engineer and I would not put anything than rudimentary in my planes! That alone should tell you something. Another issue is that there are many types of diodes at different voltages and cut-off currents, so a trip to Radio Shack is unlikely to provide anything.

On my less expensive gas planes I use two packs and two switches, but it is NOT for redundancy, I have power hogs and even my 2000 mAh packs only last 3-5 flights before going into a marginal charge condition. Rather than force charging packs (reduces life) I discharge two packs during the day and then slow charge them later. On my large plane , I use a redundant battery and receiver system from powerbox (modelbrau - deutsch) .. works great but is expensive - two receivers and four battery packs, plus two ignition packs. $$$

Your best solution for the cost of your plane is a Hobbico Voltwatch. They are about $10 and weigh nothing. You plug them into a spare port on the rx, or use a y-cable. All my small glow planes have had them, not one lost due to a dead battery.


DP
Old 01-13-2004, 04:11 PM
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iflynething
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Default RE: Could I Use A Y-Harness to Connect 2 600 mAh batteries for longer flights??

I will keep that voltwatch thing in mind......it would be pretty good tho have that 'just incase'....
Old 01-13-2004, 06:48 PM
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Stick Jammer
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Default RE: Could I Use A Y-Harness to Connect 2 600 mAh batteries for longer flights??

iflynething,
First off, don't be afraid to admit when you've screwed up. I think you will find that you'll get more respect from your fellow pilots by being honest. No one likes to admit that they were at fault, but trust me, you'll come out looking like a bigger man when you do. As far as putting two packs on a Y, it will work, but not if you forget to charge them. If you have an extra channel open on your receiver you can just plug the second pack into that, no Y connector needed. You also won't need a diode. One pack will not drain into the other enough to notice on one flight. You should always check both packs before each flight with a good Expanded Scale Voltmeter. A second pack is also gonna add 4 to 6 ounces of extra weight to the plane. All of this is usually overkill for a .40-.60 size plane, so a better alternative for longer flight time would be a single pack with a bigger mAh capacity. If your existing pack is a NiCAD, you can switch to a NiMH pack with about twice the capacity and still weigh about the same.
Old 01-14-2004, 10:10 AM
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famousdave
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Default RE: Could I Use A Y-Harness to Connect 2 600 mAh batteries for longer flights??

The diode will prevent a shorted pack from taking out the good pack. It also will prevent pack discharge if for some reason one pack is below 1.1 v per cell ( i.e. vibration in flight creates a shorted or dead cell in an otherwise good pack). This is more common with cheaper NiCds than NiMh.

As far as if one pack is at a lower potential than the other, but both are still good packs, StickJammer is right, there will not be a noticeable cross-charge effect.

DP

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