Originally Posted by RC_Feen

So I have a PS Spektrum 9ch Rx with two Battery connections. I just got these two packs to run the RX for a redundant power source. I'm running a separate 1100mah A123 for the ignition. Is this a good A123 setup for the Rx and Ignition? This is my first gas plane (30cc). Thanks all!

I run 2 A123 2300mah packs on my PS RX, and then the Tech Areo IBEC for the ignition it is an optical kill switch and voltage regulator, no need for a 3rd ignition battery.

I just started a new thread, but should have stumbled across this one first. Sorry! Anyway, I want to run A123's with Futaba 9157 servos which are rated at 6V. If a freshly charged A123 comes off at 7.2 to 7.4 V, am I going to fry my 9157'S? Is regulation necessary? I thought the whole reason to run A123's was to reduce the point falure of a regulator. Thanks to all who respond.

Don't worry, I've been doing this for over a year and 150 flights on my Dalton Extra 300.
Jim

Originally Posted by phoenixjeff123

I just started a new thread, but should have stumbled across this one first. Sorry! Anyway, I want to run A123's with Futaba 9157 servos which are rated at 6V. If a freshly charged A123 comes off at 7.2 to 7.4 V, am I going to fry my 9157'S? Is regulation necessary? I thought the whole reason to run A123's was to reduce the point falure of a regulator. Thanks to all who respond.

Tons of flights with A123's and 9157's unregulated. A123's drop to 6.6 volts pretty quick.

Originally Posted by phoenixjeff123

I just started a new thread, but should have stumbled across this one first. Sorry! Anyway, I want to run A123's with Futaba 9157 servos which are rated at 6V. If a freshly charged A123 comes off at 7.2 to 7.4 V, am I going to fry my 9157'S? Is regulation necessary? I thought the whole reason to run A123's was to reduce the point falure of a regulator. Thanks to all who respond.

This illustrates a key point of common confusion. Yeah the manufacturers specify 6v ratings for servos, but indeed A123's are 7.2v at full charge.

There are a few reasons why the servos will be ok.

1. The 7.2volts wont last long. They drop down to 6.6v very quickly.
2. What other battery pack would you use? 5 cell nicads and nimh which were used exclusively a few years ago have a full charge voltage that's actually higher than A123s. (closer to 7.5volts). The 4 cell packs have a full charge voltage of about 6 volts.

So I believe the manufacturers rated their servos according to the "nominal voltage" of NiMH/NiCD packs. Either 4.8v or 6.0v (which actually translates to full charge of 6v and 7.5v).

8.4v in Lithium Ion and LiPo packs is often a step to far since they will stay above 8 volts for some time.

Anyway, thats how I rationalise it.

Originally Posted by erjpilot

Thanks, I had looked at WrongWay's website as he does have the 2500's. I prefer to build my own receiver packs custom for the application, but Richard only sells packs and not single cells. I guess I will have to bite the bullet and just go with pre-made packs as I have not been able to find the 2500's as single cells anywhere.
Travis

Richard at WrongWay i believe has the 2500 packs, I just spoke with him the other day... call him if you are still looking, and his are indeed OEM A123's from A12 systems!!!

Originally Posted by phoenixjeff123

I just started a new thread, but should have stumbled across this one first. Sorry! Anyway, I want to run A123's with Futaba 9157 servos which are rated at 6V. If a freshly charged A123 comes off at 7.2 to 7.4 V, am I going to fry my 9157'S? Is regulation necessary? I thought the whole reason to run A123's was to reduce the point falure of a regulator. Thanks to all who respond.

Are they for your 3.1M Sukhoi? I am running the exact setup you mentioned. Futaba 9157s all the way around and unregulated A123 packs. over 500 flights and not a problem one.

Hey Robotech, yep, they are, I went back to the Sukhoi build site last night and studied your responses! I believe you are running 2300 mAh. Do you have to cycle those before the first complete charge? Where do you purchase from?

I never cycled mine. Charged them initially and started flying, taking note of how many Ma. I was putting back in. I can fly an IMAC contest with 4 known rounds and an unknown round and use about 50% of capacity.

I have purchased packs from Hangtimes Hobby, Wrongway RC and Taildragger RC. All three of them use GENUINE A123 Systems cells in their packs and that is important.

I charged then discharged mine to find capacity right at the start. Then i just count mah after a few flights and it lets me know when i need to charge. I only run em down to about 40% before recharging.

This thread is incredably long, but here's some "testing" I have done that I don't think has been covered yet. Using a Hanger 9 current/volt meter and 2 trailer light bulbs to drain a full pack, the current draw is steady 3 amps, voltage drop is around .8V. (this makes the JR connector pretty hot, I wouldn't want any of my planes drawing a steady 3 amps!) To get an idea how much load a 30% AJ Slick 540 would draw from a single 2300 A123 & standard JR HD switch, I hooked up the H9 meter for current at the switch, taped some weights on each surface to add some approximate in flight load and did my typical 3-D inputs at the sticks. A rolling harrier was the most draw=spikes to 2Amps momentarily, everything else was less than 2 amps and again, only for a moment. I did the weighted test because for the first time, I planned on flying the 30% Slick with only 1 A123 pack and no power expander, just a single JR HD rcv. switch. I was concerned this would possibly heat up the wires and/or switch but the readings (assuming they are in the ball park)indicated it should be OK. I now have around 30 flights without a hitch and mah usage is around 200-250 per 15 minute flight with some hard core rolling harriers (figure 8's & circles). So far, so good. My other 30% Slick has P.E. & 2 rcv. packs. I also use 2 methods for monitoring the packs remaining capacity, I always calculate the mah usage on new packs and do this for the first 10 cycles or so. Then I also use the H 9 volt meter to check the voltage drop after each flight, I never fly under 6.55V, I usually get 3-4 flights before charging, using around 1000-1200 mah. After a full charge to 7.2V, the A123's can drop to 6.8V after sitting overnight, this seems to be normal as they all drop close to the same. It does'nt seem to affect capacity.

Originally Posted by james.l.hill

This thread is incredably long, but here's some "testing" I have done that I don't think has been covered yet. Using a Hanger 9 current/volt meter and 2 trailer light bulbs to drain a full pack, the current draw is steady 3 amps, voltage drop is around .8V. (this makes the JR connector pretty hot, I wouldn't want any of my planes drawing a steady 3 amps!) To get an idea how much load a 30% AJ Slick 540 would draw from a single 2300 A123 & standard JR HD switch, I hooked up the H9 meter for current at the switch, taped some weights on each surface to add some approximate in flight load and did my typical 3-D inputs at the sticks. A rolling harrier was the most draw=spikes to 2Amps momentarily, everything else was less than 2 amps and again, only for a moment. I did the weighted test because for the first time, I planned on flying the 30% Slick with only 1 A123 pack and no power expander, just a single JR HD rcv. switch. I was concerned this would possibly heat up the wires and/or switch but the readings (assuming they are in the ball park)indicated it should be OK. I now have around 30 flights without a hitch and mah usage is around 200-250 per 15 minute flight with some hard core rolling harriers (figure 8's & circles). So far, so good. My other 30% Slick has P.E. & 2 rcv. packs. I also use 2 methods for monitoring the packs remaining capacity, I always calculate the mah usage on new packs and do this for the first 10 cycles or so. Then I also use the H 9 volt meter to check the voltage drop after each flight, I never fly under 6.55V, I usually get 3-4 flights before charging, using around 1000-1200 mah. After a full charge to 7.2V, the A123's can drop to 6.8V after sitting overnight, this seems to be normal as they all drop close to the same. It does'nt seem to affect capacity.

Great information, thanks for sharing.

DaleD

Originally Posted by james.l.hill

This thread is incredably long, but here's some "testing" I have done that I don't think has been covered yet. Using a Hanger 9 current/volt meter and 2 trailer light bulbs to drain a full pack, the current draw is steady 3 amps, voltage drop is around .8V. (this makes the JR connector pretty hot, I wouldn't want any of my planes drawing a steady 3 amps!) To get an idea how much load a 30% AJ Slick 540 would draw from a single 2300 A123 & standard JR HD switch, I hooked up the H9 meter for current at the switch, taped some weights on each surface to add some approximate in flight load and did my typical 3-D inputs at the sticks. A rolling harrier was the most draw=spikes to 2Amps momentarily, everything else was less than 2 amps and again, only for a moment. I did the weighted test because for the first time, I planned on flying the 30% Slick with only 1 A123 pack and no power expander, just a single JR HD rcv. switch. I was concerned this would possibly heat up the wires and/or switch but the readings (assuming they are in the ball park)indicated it should be OK. I now have around 30 flights without a hitch and mah usage is around 200-250 per 15 minute flight with some hard core rolling harriers (figure 8's & circles). So far, so good. My other 30% Slick has P.E. & 2 rcv. packs. I also use 2 methods for monitoring the packs remaining capacity, I always calculate the mah usage on new packs and do this for the first 10 cycles or so. Then I also use the H 9 volt meter to check the voltage drop after each flight, I never fly under 6.55V, I usually get 3-4 flights before charging, using around 1000-1200 mah. After a full charge to 7.2V, the A123's can drop to 6.8V after sitting overnight, this seems to be normal as they all drop close to the same. It does'nt seem to affect capacity.

That's good information. Can I add something that you might not have thought of?

We often hear talk of redundancy as for the reason to have two packs. The trouble with Lithium 2S packs is that their failure tolerance is much lower than other technologies.

When a Lithium cell dies, it's failure mode is open circuit. So on a 2S pack, you'll go from having 7.2 volts (full charge) to zero if the cell craps itself.

Compare this to Nickel technology packs with fail in a dead short. This means that if one of your 5 cells in your NiCD pack fails, you go from 7.5 volts to 6 volts and the plane keeps flying.

In other words. You need 2 cells to fail in a nickel pack to bring your plane down. With Lithium, *either* cell crapping out will screw you.

But it's all good news.... The weight difference:
5 cell 2500mah NiCD pack: 275 grams.
2 cell 2300 A123 pack : 155 grams.

Other issues. Nickel is not nice for the environment. It's probably already illegal in places.
And I *think* but I am not sure, that your 2 amp test with the weights on the ailerons would probably show that the NiCD packs have a larger voltage drop. They are better than NiMH tho. On a 30% I think it should be fine.

I'm not suggesting that you do this with NiCD instead of A123. Only that you should be aware that the plane would be significantly more fault tolerant with a 5 cell NiCD pack. (Or two A123 packs ;-)

You may say, "But the cells never just die". For the most part that is true. Interestingly enough, today I tried to give a 4S lipo pack it's 5th charge from new. It looks like the first cell is dead for no reason at all. It just happened sometime between when I used it yesterday and tried to charge it today. Glad it wasn't in the air at the time ;-)

Just food for thought since you seem to have been doing some nice work in this area....

You make some good point's.. However the real beauty of the A123 technology is how they react under a load and the lower internal resistance.
NIMH with their high internal resistance can give you false voltage reading under a load (especially fast charging them causes this). A123
A123's 2.3 A cell was rated for a 10A charge for up to 1000 cycles. Fast charging this technology does not hurt them.
A123 can handle a constant 30 amps.. Up to 120 amp burst.SO with that said you get a constant 6.6 Volt's for up to a 30 Amp load.. Thats pretty good Thats why this is the technology of choice for giant scale planes with LARGE control surfaces and HIGH drawing digital servo's..

A lot of good input here in the last couple of days
I was not aware that the failure mode of the A123 cells was open circuit, this makes a dual battery with dual switches a very good plan for larger size models. With the open circuit failure mode of the cells, that seems to eliminate the need for isolating the packs with diodes.
I fly gas, glow and electrics. The only thing I use now that's Nixx powered is a glow plug lighter
I recently added a Hyperion cell checker to my flight box. I'm finding that it is quite accurate for "fuel gauging" my A123 packs. I'm using it as a cross check with my normal procedure, using a Cellpro Multi4 to determine the amount of power consumed per flight.
Pete