A123 Batteries for Dummies.

[dick hanson]

I really don't understand your readings --You and I are somehow, doing this differently--are you using an adjustable load , expanded scale Volt meter ?
You will always get some voltage depression as any load is applied

the packs are good to 6V- and it takes 30 minutes at a constant 3.5 amps to get there - starting at 6.5 volts ---

[dick hanson]

	Quote: Originally Posted by Rolling Thunder
	I have a Aeroworks 35% 260 with 8 8711 servos and a Medusa Research Oracle unit. We were testing the Smart Fly Power Expander Sport to see how hot the voltage regulators got. I also recorded amp draw. I have records of 10 minute flights from basic to Unlimited sequences and also some 3d flight. The only time the amp draw was over 1.5 was in snap rolls. All the ganged servos were matched with equalizers (rudder,ailerons). All the surfaces have 45 degrees of throw at 135 ATV on the 10X.

thanks for the info - I presume you have voltage at 6.something volts? how many amper hours is a typical flight -if you have figured that draw .
One thing - if you swapped the LiIons and reg for A123 --you may use more power from the cells -(actually have more power to the servos)
this would be if the resistance thru the regs gets high. Is it possible to monitor voltage at servo BUSS on rx during flight? I don't know that recording unit or it's capabilities..

[Pale Rider]

	Quote: Originally Posted by dick hanson
	I really don't understand your readings --You and I are somehow, doing this differently--are you using an adjustable load , expanded scale Volt meter ? You will always get some voltage depression as any load is applied the packs are good to 6V- and it takes 30 minutes at a constant 3.5 amps to get there - starting at 6.5 volts ---

Using the Hangar 9 voltmeter--no load read = 6.4---push red button for .5a load--read goes down to 6.1v---

[dick hanson]

	Quote: Originally Posted by dick hanson
	I really don't understand your readings --You and I are somehow, doing this differently--are you using an adjustable load , expanded scale Volt meter ? You will always get some voltage depression as any load is applied the packs are good to 6V- and it takes 30 minutes at a constant 3.5 amps to get there - starting at 6.5 volts ---

I started wondering about your .5 amp load -so I took a A123 pack -hooked it to my Whattmeter and then to my Matchmaker with a JR 8611A servo plugged into it
the batt pack read 3.7 volts-- then I gripped the servo output arm and applied pressure till meter reached and held .5 amp load - the voltage at batt remained constant -
by rapidly cycling the servo -I got .1 V depression at battery- and a one ampere hr load .I did not want to twist and hold servo to develop a higher amp loads ---

[dick hanson]

	Quote: Originally Posted by Pale Rider
	Using the Hangar 9 voltmeter--no load read = 6.4---push red button for .5a load--read goes down to 6.1v---

is anything else hooked up when this is read? that sounds like large AMP load -- for example on my 4 cell battery at 13.6 volts -I add 40 amps and voltage goes to 11

[Rolling Thunder]

	Quote: Originally Posted by dick hanson
	thanks for the info - I presume you have voltage at 6.something volts? how many amper hours is a typical flight -if you have figured that draw . One thing - if you swapped the LiIons and reg for A123 --you may use more power from the cells -(actually have more power to the servos) this would be if the resistance thru the regs gets high. Is it possible to monitor voltage at servo BUSS on rx during flight? I don't know that recording unit or it's capabilities..

I was using 20C 2100mah lipos, the regulator on the power system is set at 6 volts.

This is not a perfect system. The oracle goes between the battery and the power system. It also only takes 5 reading per second, so there could be spikes that are not registered. I may be able to plug it into the power buss output to measure voltage, never though of it. There are plenty of open ports to plug into.

here is a pic of the unit I have been testing on.

[Pale Rider]

	Quote: Originally Posted by dick hanson
	is anything else hooked up when this is read? that sounds like large AMP load -- for example on my 4 cell battery at 13.6 volts -I add 40 amps and voltage goes to 11

No--nothing else this pack in installed in my plane

I took another 2 cell pack

unloaded 6.76

.5A load---6.54

1A--6.30

2A --5.84

[Kiwi]

Dick,

I just chunked out enough change to buy two Eagle tree systems so I can do this measuring both packs at the same time. My intended test rig (God willing) is a 35% Extra with a DA85 in the hole. Twin A123 2300 MaH packs direct to the Power Expander so no regulators. The Eagle Tree system does 10 samples a second which while fast could still miss a lightning fast spike however I doubt it.

With this setup running I can measure.

MaH used in the flight or over a series of flights, peak amps, voltage, watts etc.
Voltage to the servo bus on the RX or in this case the Expander
Battery temp (I wont bother that one)
Engine RPM
Cylinder head temps (x2)

The Eagle tree and the Medusa units are pretty much inflight wattmeters with a data recorder built in.

If you want the Rolls Royce of data logging or at least faster sample rates then there is a company called BNH that has a unit capable of 1000 samples a second.

My biggest battle is waiting for my A123 charger(s) to arrive. I don't expect to see them until mid September so I have two weeks to sit her and tell lies on the web while I wait for them.

[dick hanson]

	Quote: Originally Posted by Pale Rider
	No--nothing else this pack in installed in my plane I took another 2 cell pack unloaded 6.76 .5A load---6.54 1A--6.30 2A --5.84

that is quite different-compared to your earlier reading
I tried doing readings with external meters whilst reading decreasing voltage on Whattmete - got conflicting numbers as resistances in wires skewed the results
also in doing "looky here" comparisons at the field - we found small differences in different brand equipment -nothing serious .

[Pale Rider]

I know its definitely not anything to fret about---I guess Im still trying to figure a "no-go" reading--loaded or unloaded--makes no difference just as long as its consistent---Another guy said at 6.4 unloaded he had just enough for one more 10 min flight based on HIS setup---Really though there isnt a need to get that low since they charge up so fast and easy but its good to have a reference

[dick hanson]

	Quote: Originally Posted by Rolling Thunder
	I was using 20C 2100mah lipos, the regulator on the power system is set at 6 volts. This is not a perfect system. The oracle goes between the battery and the power system. It also only takes 5 reading per second, so there could be spikes that are not registered. I may be able to plug it into the power buss output to measure voltage, never though of it. There are plenty of open ports to plug into. here is a pic of the unit I have been testing on. Attachment 64849

all info is good info when sorting out new stuff. simply the different measuring methods of things can make info seem to conflict.
One thing -
I have wondered how well the 7000 rx would do ,mounted to an expander.
It looks lik it could shroud the short antenna setup.
My own consideration would be to elevate and stand up the rx a much as possible - th system was designed around long antennea and the 2.4 are different animals
but you seem to have no trouble -- obviously using the remote antenna which comes as part of the 7000

[Rolling Thunder]

The picture shown is not the plane that I am working with. I have a 24" extension on the satellite, it is mounted on a cross brace behind the hatch. It has worked well, so far.

[toprudder]

Part of the problem I see with external battery testers/loads that people use is the resistance of the wiring between the battery and the tester. I've seen some people have long leads, sometimes with extensions (male-male adapter, etc). It is ok to have a long lead to the load, but when the voltage measurement is made at the same end of the lead where the load is, the meter is seeing the voltage drop of all the leads and connectors between the battery and the load.

Dick, you said you measure the "voltage at the battery" and I think that may be the reason others are seeing different voltage depressions, they may not be seeing the true battery voltage. This is a problem I noticed a long time ago when using the voltmeter built into my Futaba 9ZAP. When I enabled the load, the voltage reading was low due to the wiring between the battery and transmitter.

I've been considering making a variable load to test flight packs, but will use four wires instead of two. The load will be at the end of two wires, the voltmeter at the end of the other two. The pairs will be joined together at the connector that plugs into the plane. This will eliminate the voltage drop of all the wiring except from the battery to the charge connector.

[dick hanson]

	Quote: Originally Posted by Pale Rider
	I know its definitely not anything to fret about---I guess Im still trying to figure a "no-go" reading--loaded or unloaded--makes no difference just as long as its consistent---Another guy said at 6.4 unloaded he had just enough for one more 10 min flight based on HIS setup---Really though there isnt a need to get that low since they charge up so fast and easy but its good to have a reference

Only one more flight at 6.4??
a rough calc says that means he is going to burn up an amp
out of the two amps available -- so---how many flights does he get BEFORE seeing 6.4? If you know.
the total usable voltage range is as previously mentioned -- down to 6 volts rock bottom -then things drop off faster.
I am goingto run some mor looky sees while I assmble stuf tomorrow
and see how the time (roughly 35 minutes ) and the volt readings align. unde the 3.5 amp load I get with the two tail light bulbs .
If I start at 6.7- then go to 3.0 (no load)- somewhere around 17 minutes - I expect to see 6.3-6.4 (no load )
I will have to pop the load off at various times to see.
I will also run the test again- loaded- and read while loaded - as I did before .
this results in reading into the 5 volt range under this load. I have three packs all wired th same so I should soon see if there is much difference in packs
On my 3 other 4 cell power packs -they are now like peas in a pod - all the same - all charge up with no balance needed etc..

[Pale Rider]

	Quote: Originally Posted by dick hanson
	Only one more flight at 6.4??

Ok here is the post---my mistake though--voltage was 6.34 NOT 6.4

---On a two cell 23oo mAh pack with a starting voltage of 6.7 volts I did get 15 flights. Most of the flights were in the 10 minute range and a couple were actually closer to 14. This was over the course of three outings.

I have purposefully not charged to see where the bottom of the well is, and in after though.... I cut it close. I flew the last 5 flights tonight and on the last flight the starting voltage was 6.34 after exactly 10 minutes of flight I landed and checked to find it was down to 5.74 volts. Usually with these batteries you check a voltage and a week later it exactly the same to .01 but after sitting a few minutes it came up to 5.9 volts.

That is were it could prove fatal to the unaware. When I got home I set my Futaba 9C in servo test mode and ran the timer to see if I could get another flight. Out of pure laziness I did not hook up the wing servos so was just running the two elevators, rudder and throttle.

After 8 minutes the noise changed and when I looked over the rudder had stopped and the elevators were not in sync. At this point the battery voltage was at 3.0 v.

So from 5.74 volts to crash without the aileron servos and flight loads was 8 minutes. To me that means a flight begining at this level is a certainty not to complete.