4.8 NIMH and 2.4 9303

[crashproof]

Hey guys just wanting some opinions. I have my TF P51 GS all set up with the 9303 2.4 system, it is binded and seems to be functioning properly. I was going to fly it in the morning but have become concerned with all this battery power drop info. Is the main issue with the voltage drop with large aerobatic planes with multiple surfaces working together under heavy load. I will be using a fully charged 2700 NIMH 4.8 without regulator to power my system. Basically the usual Warbird stuff loops rolls low passes with Hitec MG 645 100 oz tor. I am really confused on this batt issue. Some ideas would be appreciated. Thanks, Kevin.

[Eagleburger]

I would be concerned. Most importantly check to see if you receiver has quick connect. If it doesnt get a another pack, 5 cell NiMH or 2 cell A123.

[50%plane]

I have the same question. Many of my glow planes are set up using 4.8 volt packs....

[Sin City Jets]

4.8v batteries + Spektrum = potential disaster.

Please don't do it. I'm not just writing this to be an a$$. If you really need reasons, I will post them.

[KIM]

please post the reasons,so i can understand the systems better thanks

[Zeeb]

There's lots of reasons why using five cell batteries is a better choice, especially for the 2.4GHz systems. There are lots of posts referring to those reasons and maybe a bit of time spent reading about them via the search engine would be beneficial.

Basically tho, the low voltage threshold for the rx to quit working is 3.5 volts at which point it will shut down. It will come back on when the power is restored and one of the problems with the earlier Spektrum/JR stuff was that it took 2 to 5 seconds to relink with the tx. Now there is a software update for the rx's which will allow almost instantaneous reconnection with the tx which does help. If your power system is adequate, this shut down should never happen but if you read about the systems and user reports, you'll see that it does occur.

So generally speaking if you're using a 6 volt battery, you have more "room" for the voltage to drop before the rx shuts down. Now that is not in and of itself the final answer as different battery packs can have different impedence, or internal resistance, which affects the ability to deliver the appropriate amperage to the system. Even a 6 volt system with high impedence packs and a possibly large servo load can drop below the threshold voltage.

While we all have our priorities, I've never understood the reasoning behind building a GS size model with all the expense and work involved, then going cheap on the power system/batteries?

Like I said, if you want to know more than that just doing some reading of the posts already made about it as there's way too much to explain in one post...

[crashproof]

Hey Zeeb I appreciate the info but it seems on these forums it comes to often with a personal jab as the caveate. I never said I wanted to run cheap, did I ? I have read the forum and 99 % of the post pertain to giant aerobats with large surfaces doing ungodly things simultaneously. I was inquiring as to the non digital less stressfull Warbird type flying and while I appreciate your concern and taking time to post I wish it would come without the opinion that I must be lazy or somehow cheaper than you must be, because I highly doubt that to be the case. Kevin.

[50%plane]

	Quote: Originally Posted by crashproof
	Hey Zeeb I appreciate the info but it seems on these forums it comes to often with a personal jab as the caveate. I never said I wanted to run cheap, did I ? I have read the forum and 99 % of the post pertain to giant aerobats with large surfaces doing ungodly things simultaneously. I was inquiring as to the non digital less stressfull Warbird type flying and while I appreciate your concern and taking time to post I wish it would come without the opinion that I must be lazy or somehow cheaper than you must be, because I highly doubt that to be the case. Kevin.

Well said!

On my Edge, I run a li-ion/reg setup. On my glow, sport birds, I run Futaba 3003 servos and a 4.8V battery.(which, on 72, is plenty of juice)

[JimC-MD]

The reason that people are going to higher voltage systems is to prevent the supply voltage from dropping below the reboot voltage during a flight. This could happen due to several things. First, the load on the system could be more than the power system can supply. (read high torque and or high servo count) The second would be someone flying the battery down too low on state of charge. The results either way are a reboot of the processor in the RX. Before the latest version of the RX units, this could result in a hold or failsafe until the RX came back on line and control returns that could last several seconds. In an extreme case, if someone has not properly bound the system, the servos could deflect to some very adverse positions resulting in almost certain death. (read about binding and rebinding after model setup for more information) The new RX units will reconnect within 4ms in most cases. This results in nothing more than what we have likely had happen in the past with the old 72 systems. That little, almost instant burp, that makes us say "What was that?" but does not cause any other issue.

That being said, I think these units may have just awakened us to issues we have has for some time with our power supply systems. It all comes down to matching the system correctly. Some chose to go to higher voltage systems to engineer in more of a safety margin. Not a bad idea. If your servos and plane load do not need it, you do not have to go that route, IMO. Spectrum sells 4.8v packs in the 1100 mah range. They are flying a lot of models without issues. My brother in law has a Funtana 100x with a 125 Saito and high torque servos that he is flying on 4.8v. He does 3D and IMAC with it with no issues. He monitors his battery between flights.

If you want the added peace of mind, go with the higher voltage. If you have a system, check it to see how fast it will reconnect when you cycle the power. See if your unit flashes the RX light after this happens. If so, it is a good telltale to chech when you land. Flashing light means you have had an issue during the flight regardless of you "feeling" it or not. Kinda cool to me.

[Zeeb]

	Quote: Originally Posted by crashproof
	Hey Zeeb I appreciate the info but it seems on these forums it comes to often with a personal jab as the caveate. I never said I wanted to run cheap, did I ? I have read the forum and 99 % of the post pertain to giant aerobats with large surfaces doing ungodly things simultaneously. I was inquiring as to the non digital less stressfull Warbird type flying and while I appreciate your concern and taking time to post I wish it would come without the opinion that I must be lazy or somehow cheaper than you must be, because I highly doubt that to be the case. Kevin.

Well my post was directed at the poster "Kim", but if you feel offended enough to verify that your power system is adequate to the job and it may be, then I have no regrets as I just might have saved your plane.

While my primary interest is in IMAC type stuff I do have some scale warbirds I'm working on and have always had an interest in those models. So I pay attention to the threads on them, those models I see at our field, and models at events I attend.

If there is one glaring commonality between all that, it's that virtually everyone of those models I've seen and most everyone I've seen talk about their setups on the forums, almost all have marginal power systems as the builders don't see it as a need, just as you said.

These new 2.4 systems all have more specific power requirements as they are more "computer" than ever before. In the world of computers there are no points for "almost" good enough, it either works or it doesn't. If you undersize the electrical components of these systems, and that includes batteries/switches/extensions etc, you will get bit.

[Flyfalcons]

	Quote: Originally Posted by Sin City Jets
	4.8v batteries + Spektrum = potential disaster. Please don't do it. I'm not just writing this to be an a$$. If you really need reasons, I will post them.

It wouldn't be to sell your batteries would it?

[propchief]

Kevin,Fly your plane and have fun. Just keep track of your battery condition by checking with a voltmeter. You are not using digital servos or flying an aggressive 3d profile. Would I upgrade to a 6 volt pack in the future ... sure because there are a number of benfits to be gained. Such as the voltage supply to the Rx and also increased servo torque and speed, and some redundancy. Would I ground my plane until then - no. We can talk more about this over a cold beer or soda.John