6V Nimh and 2.4 Ghz Spekrum reciever?

[bmoney69]

i was wondering if anyone had any hard data for peak low voltage (PLV) in a 35% airframe with high torque digital servos during hard 3D on a 6V Nimh pack? i know that's a very specific question but figured someone out there had some data. i know anyone using A123's is going to say "6.5v" because they hold thier voltage under high load. i'm trying to determin if there is a real concern using dual 6v Nimh packs (with a low internal impedance) on a spectrum 2.4 AR9100 reciever with regards to the low voltage cutoff of 3.5v.

[JoeAirPort]

If you're talking about the 1950 FAUP 5-cell, you will have to try really hard to brown out a pair of those even on a 35%. They have a huge amount of discharge current, especially in parallel. Just make sure you have a good power system and those batt's will be just fine. Good power system means using Dean's connectors on the batt's and switches, no regulators !!! Fromeco switches are nice. If no power expander will be used, make sure you have two JR outputs per switch going to the receiver (unless the AR9100 has Dean's battery connectors, don't know). Also remember that the A123's can fall of their voltage cliff too, it just happens a lot sooner, and you never know when. It seems better to charge often with A123. I think the batt's you are using will not be the source of a problem if there is one.

[bmoney69]

ok, thanks joe. i am using a pair of NoBs elite 2000 Nihm batts (internal impedance is about 6) both with EC3 connectors directly to the AR9100 with no switches in between, only the fail safe soft switch that comes with the reciever.

[JoeAirPort]

Oh...I just bought one of those myself for a 50cc Yak. That's a really nice pack. It actually is little better than the FAUP according to the discharge graph I looked at.

[bmoney69]

is your 50cc yak on 2.4?

[wildhare]

	Quote: Originally Posted by JoeAirPort
	Also remember that the A123's can fall of their voltage cliff too, it just happens a lot sooner, and you never know when.

Where does this information come from?

The performance of A123 batteries is well documented and I can predict almost exactly when they will reach the point of falling off due to being fully discharged. It is totally inaccurate to say that you never know when they will fail, you just have to use a different method of measuring them than the traditional volt meter.

As far as happening a lot sooner, a 2300mah Nimh pack will start to drop off when you reach the 2000mah point of discharge. This will NOT be sooner than a 1950mah Nimh pack becomes useless.

TF

[JoeAirPort]

	Quote: Originally Posted by wildhare
	Where does this information come from? The performance of A123 batteries is well documented and I can predict almost exactly when they will reach the point of falling off due to being fully discharged. It is totally inaccurate to say that you never know when they will fail, you just have to use a different method of measuring them than the traditional volt meter. As far as happening a lot sooner, a 2300mah Nimh pack will start to drop off when you reach the 2000mah point of discharge. This will NOT be sooner than a 1950mah Nimh pack becomes useless. TF

Hey Tom, aren't you coming on a little strong?

I was talking more about load testing. You can't load test a A123. Once the voltage drops, it drops. There's no gradual falling off. Relax !!! This is supposed to be a hobby.

[cjcyclesrc]

	Quote: Originally Posted by wildhare
	Where does this information come from? The performance of A123 batteries is well documented and I can predict almost exactly when they will reach the point of falling off due to being fully discharged. It is totally inaccurate to say that you never know when they will fail, you just have to use a different method of measuring them than the traditional volt meter. As far as happening a lot sooner, a 2300mah Nimh pack will start to drop off when you reach the 2000mah point of discharge. This will NOT be sooner than a 1950mah Nimh pack becomes useless. TF

Don't get so worked up. Relax. No one is throwing off on the A123's or K2's you sell.

[cjcyclesrc]

	Quote: Originally Posted by bmoney69
	i was wondering if anyone had any hard data for peak low voltage (PLV) in a 35% airframe with high torque digital servos during hard 3D on a 6V Nimh pack? i know that's a very specific question but figured someone out there had some data. i know anyone using A123's is going to say "6.5v" because they hold thier voltage under high load. i'm trying to determin if there is a real concern using dual 6v Nimh packs (with a low internal impedance) on a spectrum 2.4 AR9100 reciever with regards to the low voltage cutoff of 3.5v.

Here is a little current draw info that might help. I hooked up a Watt meter to my 100cc yak last weekend.

Here is my set-up

• AR9100 RX
• Ailerons 4 5955's
• Elevators 2 5955's
• Rudder 2 7955's
• Throttle 5625

There was no binding at center, full throw, or anywhere in between. If moved all the sticks as fast as I could it would pull 6 amps. So that would be 3 amps per battery.

[JoeAirPort]

Pretty good info there CJ....actual current draw on a similar size air frame.

[bmoney69]

ok, that's good information....thanks charles.

i'll shut this thread down if it turns into an A123 vs Nimh war. that was not my question

[cjcyclesrc]

	Quote: Originally Posted by bmoney69
	ok, that's good information....thanks charles. i'll shut this thread down if it turns into an A123 vs Nimh war. that was not my question

Your Welcome.

[robertp17]

I think the thread was started because Bmoney wanted to make sure he was not going to have a low voltage cutoff problem with using (2) 5cell nickel metal packs on a spektrum 2.4 setup. The thread is about nmh not a123. Can anyone here say yes it is fine to use without a problem with running 5 hi torque servos? What would be the lowest you would want to see the voltage drop to before you would get concerned?

[cjcyclesrc]

Keep in mind the low voltage reset problem was fixed on the Spektrum receivers. So it's now no different than a 72 mhz receivers.

[cjcyclesrc]

	Quote: Originally Posted by cjcyclesrc
	Keep in mind the low voltage reset problem was fixed on the Spektrum receivers. So it's now no different than a 72 mhz receivers.

I'm using 1950 FAUP's in a 50cc w/ 5 5955 with out any problems. Just be sure not bottle neck the current in your connectors.