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HomeAircraftHelicopterBeginners Corner › a123
03-09-2008 01:34 PM  10 years agoPost 21
Frank Bostwick

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Cincinnati Ohio

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I dont think you can get A123s to match the LiPo flight time. To get the same voltage you'll have to add at least 1 cell, 7S A123 but the mAh is only 2300. To get the mAh up youd need to go 7s2P and that gets heavy.
As far as I can tell, the big disadvantage to A123 is flight time, no real way around it. Mild to hard 3D is a 4min flight. When I quoted the $170 price I was talking about "Power Tubes" from MEC. Currently most dewalt 36v on ebay are going for $120 plus shipping. $100-$170 is still way below what a Lipo will run you. If the marketing is just marketing and we dont get 1000s of cycles then we still get over 500 cycles and that still beats the crap out of Lipo.

A123 has some very real advantages, flight time and weight are the real disadvantages and untill they come out with 4600mAh cells that dis advantage will not go away. All in all, for me a guy having to do this hobby on a budget, Im sticking with A123. Ill have 3-4 packs for what a 10s will cost me, charge em in 15-20 mins, not worry about fire or balancing, replace damaged cells easy and live with a 4min flight time. 4mis is OK w/ me cause I cant think too much longer than that any way!!

RIP ROMAN

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03-09-2008 01:43 PM  10 years agoPost 22
Frank Bostwick

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Cincinnati Ohio

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BTW Im gonna run my RX pack on 2s or 3s A123 thru an Arizona regulator. Should get 3-4 flights on a charge and when I crash, and I will crash, my Heli and $$ wont burst into flame. I really like the no fire thing

RIP ROMAN

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03-09-2008 06:23 PM  10 years agoPost 23
wlfk

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uk

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I run 3s1p A123 in my T-rex - the 2300mAh cells. The motor's the stock 430X and I use an Emax 40A ESC. I use the largest pinion (15T as memory serves) and I get a headspeed of 2500rpm. The stock align ESC doesn't work with A123 cells, or nicads for that matter. It's meant to but they seem to have disabled the low-voltage cutout.

I don't see the point of 4600mAh A123 cells - you get this anyway if you use 2p. I would like some slightly smaller cells - perhaps 1800 mAh so that I could run 4s1p.

I don't use the 109 charger, but I read reports of people swapping a resistor in it, which fooled it into charging the cells to a lower voltage.

K

A bit like a kite, but 500 times more expensive

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03-09-2008 08:52 PM  10 years agoPost 24
Invrted1

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Cincinnati, Ohio

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I don't use the 109 charger, but I read reports of people swapping a resistor in it, which fooled it into charging the cells to a lower voltage.
If I knew what resistor that was and what value was being swapped, I could put a switch on it that would allow me to change resistors to match the cell type without making my charger an "A123" only charger.
The stock align ESC doesn't work with A123 cells, or nicads for that matter. It's meant to but they seem to have disabled the low-voltage cutout.
Does this mean that the Align75 ESC will not work with A123, or does it mean that it will work if I disable the low voltage cutoff?

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03-10-2008 12:38 AM  10 years agoPost 25
Frank Bostwick

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Cincinnati Ohio

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Whatever ESC you use for A123 has to have an adjustable low voltage cut off point. 123s start at lower volatage and finish at a lower voltage than Lipo but they give pretty constant volatage till the charge is exhausted (you get almost all the energy out of them till they drop out) with Lipos you need to keep 1/3 of the charge in the pack or damage will result, with 123s you can drain em dry with no ill effects.

RIP ROMAN

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03-10-2008 12:52 AM  10 years agoPost 26
wlfk

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uk

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Sorry,

I was just referring to the 35A ESC that comes with the T-Rex 450. I don't know about the 75A ESC but it might be worth investigating to look for the problem. The 35A ESC would work if you could disable the low-voltage cutoff, but

If you do a google search I'm sure you will find the mod for the 109 charger. The person who did it had exactly the same idea as you: he wired in a switch so that he could choose between A123 and LiPo.

I think there's some debate about whether the equivalent of 6s LiPo is 7sA123 (charges to the same voltage so you don't even need to modify your charger) or 8s LiPo - which might be a better match under load considering the weight/capacity of the pack.

I think there are many people running 7s LiPo on the stock T-Rex 600 with the align regulator, but it's a while since I looked into this so I'd advise you to check to make sure. I'm pretty sure I've heard of people running 8s A123 on the align regulator, with a bit of messing around to fool it into thinking that the pack voltage was slightly lower than is actually the case when they first connected it up (under load the voltage drops and it is apparently safe).

K

A bit like a kite, but 500 times more expensive

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HomeAircraftHelicopterBeginners Corner › a123
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