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using two battery packs

Old 01-13-2007, 02:39 PM
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jeffk464
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Default using two battery packs

I have a cmp extra 300s 72" wing span with HS475's all the way around and a HS645-mg on the rudder. I have the standard 700mah battery back that came with my controller, and am a little worried that it might be too small. To solve this problem, I was thinking about adding a second pack on a Y harness. I'm pretty sure that the plane will have no problem drawing off this set up, but can I use my quick field charger with the Y harness set up.

The other thing is, should I be able to fly off just the one pack and top it off with the field charger after each flight.
Old 01-13-2007, 03:37 PM
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jzinckgra
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Default RE: using two battery packs

I am not familiar with that plane or how many servos it takes, but why not just ditch the 700mAh and get something like 1400-1600 capacity? Adding a wire harness and an additional battery is asking for trouble IMO. Just one more set of wires that could come loose,etc. Also, you'll be adding more weight to the plane with 2 packs.
Old 01-13-2007, 07:55 PM
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khodges
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Default RE: using two battery packs

Using two packs is fine, but the recommended way is to use a switch for each pack. You can plug the second pack into any available Rx channel. The reason for doing it this way is in case one pack goes bad, it won't suck the other one dry, makes the system redundant. You'd charge the packs separately. Higher capacity batteries aren't that expensive, though, I'd try getting something like a 1450 Hydrimax NiMH pack as long as you're not using high torque or digital servos.
Old 01-14-2007, 12:40 PM
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jeffk464
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Default RE: using two battery packs

Only my rudder servo is high torque, its rated at 106.93 oz at 4.8v and none of my servos are digital. I only fly for about 10 minutes at a time, so my main concern is that my 700mah nicad wont be able to handle the max current draw of my servos. I have heard that NiMH cant handle as much current draw as similar NiCads.
Old 01-14-2007, 05:41 PM
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khodges
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Default RE: using two battery packs

What kind of plane is it that you need that big a servo for the rudder? I'd definitely increase the size of your battery, at least 1500mAh.
That's why I was asking about high torque or digital servos, NiMH aren't recommended due to the current drain; if you parallel the packs, though, it halves the internal resistance of the system, and generally NiMH is okay. The newer ones can deliver current better than the older packs could. I have an old beater gas powered plane that has 3010 Futabas (2) and some kind of old 1/4 scale Futaba servos (2) plus a standard servo. I have a 1000mAh NiCd battery in it which needs recharging before I can run a tank of gas through the engine, so I can say for sure that 700mAh ain't enough ('course you know that or you wouldn't be asking about two packs).
Old 01-14-2007, 06:39 PM
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Default RE: using two battery packs

Flying a Funtana 90, YS110, Futaba 3010's everywhere except the throttle. 2 6V 1100mAh Nicads on seperate switches. I can fly all day with those batteries, or 8-10 flights @10 min a flight with plenty to spare.

A side question that I hope someone can answer for me here: Now that I have my first 2 pack system, charging has brought in another equasion. I have Hobbico chargers, and with the single pole's for each RX and TX on it, I wanted to know if I could put a Y or splitter for the bannana plugs to run two leads for each battery out of one charge port?

RED you there? Come back.....?

Greg
Old 01-19-2007, 06:37 PM
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BalsaBob
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Default RE: using two battery packs

JeffK, The added weight of a second battery pack on an airplane with a 72 inch wingspan is insignificant ..... don't worry about it. However, just simply plugging a second pack into any open port on the receiver is not the recommended method. If one of the packs is failing due to a bad cell or short curcuit .... it will probably drain the other pack down with it. I use the Jomar-EMS Ultimate battery backer in most airplanes. Both packs are plugged into it and it has electronics in it to prevent the draining of the second pack I described above. It is not expensive .... and provides the true power redundency you want. Bob
Old 01-20-2007, 11:44 AM
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daveopam
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Default RE: using two battery packs

Bob, do you have a link for the unit you are talking about?

David
Old 01-20-2007, 11:50 AM
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BalsaBob
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Default RE: using two battery packs

Tower Hobbies carries it. Search their site using 'Ultimate Battery Backer'. Bob

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