grizzdaddy

My Feedback: (6)

How low should you run the 4,8 down too? I have had as low as 3.5 volts with a load tester and stopped flying, but I only got four to five flight and was wondering if I would be safe to run it down any lower than this.....all help is appreciated

MetallicaJunkie

it depends on the capacity of your battery what size servos you are using and what ind of flying you do... im assuming its a trainer, i wouldnt go lower than 3.8 with a 250mah load....

why not go 6v?

http://www.ebay.com/itm/Tenergy-6V-2...item4160f63b37

JohnBuckner

My Feedback: (1)

The old four cell Nicd's should go no lower than 1.1 volt per cell - 4.4 volts.

At 4.4 the pack is completely discharged and for a safe point I always went to no lower than 4.7 This is what I used as an absolute in flite minimum when I used those old packs for cross country some years ago.

John

grizzdaddy

My Feedback: (6)

It came out of the hangar 9 P-51 pts... I had a bad experience with it and lost the body.LOL so I took all the parts off and put them on the seagull Ultimate Bi .46. I am only using standard hangar 9 servos in it. I guess I need to ck the mah on the battery. I was thinking of just going to a 6V battery with more MAH so I can fly a little longer

JPMacG

My Feedback: (2)

3.5 volts on a 4-cell NiCd or NiMH pack is too low to be flying. If that reading was accurate then you came close to losing the airplane.

Be sure the connections from your charge jack to the loaded meter are good. Wiggle them and see if the voltage reading changes. It's common for those connections to cause the voltage reading to be lower than it really is. Also, the expanded scale meters sold for RC use are often inaccurate.

5 or 6 10-minute flights is typical for a 40-sized glow trainer using standard size analog servos with a 72 MHz receiver. That is with a the 600 mAh NiCd pack like the ones that used to come in the box with 72 MHz radios and with a safe reserve left in the battery at the end. Stuck or binding servos or other issues could run the battery down faster.

JohnBuckner

My Feedback: (1)

Grizzdaddy yes you need to check the capacity of your battery and it is expressed in Mah (milliamphour). Typical batterys included with some radio systems will be a four cell 4.8 volt with a capacity of around 700 mah. Do not fly this type of battery lower than about 4.7 volts.

Now if you want more flying time you purchase Nimh batteries in a four cell with capacities around 1650 to 2000 that will give you greater flying time.

While you certainly do not need to go to five cell 6 volt batteries you can indeed but what the higher voltage buys you is very slightly faster servos not increaed flying time. Many folks including myself choose to do just that and I no longer use any 4.8's except for some unusal controlline applications. When useing 6 volt batteries what most us do is use higher capacity Nimh's and therefore get long flying times.

Enjoy

John

CGRetired

My Feedback: (1)

The picture is of a typical discharge curve for a NiCd battery over time. In this case, the time isn't important, but what IS important is the location of the "knee" of the curve which begins at about 4.6 volts. You do NOT want to be flying when this occurs because it discharges very quickly at that point. Discharge rate is dependent on the load placed on the pack - number of servos, flying style, and other factors, all play a role in the discharge time from full charge to the "time to recharge" time.

Under no circumstances would I fly a 4.8 volt 700 mah NiCd pack more than four flights.

I use Voltwatch2 on all my planes. It gives a visual indication of the LOADED condition of the battery pack. I check it before and after each flight. If it begins to flicker to the yellow, it's time to recharge. This is my down time when I sit back, and enjoy some RC conversation with my fellow pilots as the pack charges.

CGr.

JPMacG

My Feedback: (2)

I agree with CG Retired. Previously I said 5 or 6 flights, but now that I think about it, 4 is a better number of flights for a 600 mAh pack.

Hossfly

I don't know what you're flying or what the load you command, however Energizer and several other suppliers furnish NIMH AA size batteries at 2300Mah, Easy to solder up several packs and keep them on a pulse charger so they are ready when you are if your question is for the radio and not for an electric motor. Now you can get some large packages of them at a rather modest price. There are numerous chargers that you can find at places like Radio Shack, Home Depot or such or with cheap cameras that will keep the batteries charged indefinitely. I have several chargers that will take up to 20 packs with fast pulse or slow pulse or simple regular charge and then go to pulse as you select.
I have found the standard radio shack 4 cell plastic boxes to work very well with the pen cells if soldering is not to your taste. I strongly suggest tape or rubber band to lock them in place and also a good foam pad around non-soldered box-packs.
Now any Naiad or NiMh will charge up to 5.5 volts but will come down to 5.0 pretty fast. It will hold there for a long period then began to drop off. Once I get down to 4.8, on any 4-5 servo airplane, it's time to recharge. Radio shack often has sales on small chargers that have multiple voltages, and changeable polarity. One can use both JR and other standard radios for transmitter charge.
Lots of good stuff around not usually found in the RC trade itself.

CGRetired

My Feedback: (1)

Soldering batteries into packs has been discussed several times here on RCU. Buying batteries with tabs that are designed to be soldered into packs if fine. Buying batteries from Radio Shack that are not designed with tabs is an iffy situation for someone that is not familiar with soldering. Not everyone knows how to properly solder. To much heat can and will destroy batteries. Even batteries with soldering tabs already fixed to the ends of the batteries should be carefully done because, again, to much heat will kill them.

I would not encourage someone to solder batteries together into packs unless they know how to solder and how to properly set the packs up for series operation.

CGr.

goirish

I thought I was pretty good at soldering but guess what, I ruined a couple of batteries so now I buy the ready made 6v packs. BTW, CG, are you going to Toledo this year. April 13,14,15. Hope so.

CGRetired

My Feedback: (1)

Good morning, Gene. How is the Marine doing? Hope all is well.

I don't know if I can make it or not. The company I work for did a re-org and then took a week of vacation time away from everyone. I have to be very careful with my time. If I can make it, I will go. We will see.

Dick.

grizzdaddy

My Feedback: (6)

WOW!! Thank you all for this awesome information.....I was thinking of asctually building/soldering my own packs but thought it might be a little risky. Just to make sure that I am right on this when cking the battery you want to see what the volts are under a load right. I cked my servo's and the averge draw is about .025 to .05 amps. When I normally ck the battery I use the Hangar 9 battery checker at 2amp draw, is this where I might be messing up? Because by what everyone is saying I am only good for one maybe two flights and that sucks

charlie1960

i recommend this one.
http://www3.towerhobbies.com/cgi-bin...?&I=LXNHS4&P=0

6v-2000mah

charges to 7.2 with the standard JR wallwart that came with the PTS

cant beat the price either.
6 ten minute flights easy before it drops into the 4's

jester_s1

Yes, you do want to check your pack under a load, but 2 amps is too much for a pack that size. .5 amp will give you an accurate indication of how much power is left. If you want to get extra safe about it, use a cycling charger after making a few flights to see how much capacity was left in the battery. Do it a couple of times to get an average, then decide to recharge when you've gotten below 50% of capacity. If you amp draw estimate is correct, that should give you 4 flights. Then use the loaded voltmeter to check between flights to make sure your battery and connections are all still good.

grizzdaddy

My Feedback: (6)

the battery is a 4.8volt 1500mah battery.  the voltage show 5.03 but  with a 2.0a draw with tester it went down to 3.5 .

JohnBuckner

My Feedback: (1)

Grizzdaddy 'number of flights' is entirely subjective and is an almost worthless method to try to communicate how long one may want to fly with any setup. What and how long does it take to constitutes a flight? Ask that question among any group of flyers and indeed you will have as many conflicting answers as there are flyers. And that does not even begin to approach starting and testing or even just taxi habits of each of those flyers. Of course all of which directly affect you and your number of flights.

No its better just to keep track of your onboard flight battery and simply do not fly below that 4.7 volts practical minimum that I posted earlier.

How does one do that? Simple here are three methods: One is the on board gizmos that lite up a bar graph to indicate voltage, these were mentioned by one of the privious posters and they will do the job. Mearly look at them before takeoff.

The next method is the most common and what I still suggest to most and that is simply the loaded expanded scale voltmeter or the loaded electronic voltmeter. These are for the purpose and have fixed loads already. They are quite practical and very effective when you check voltages between each and every flight. This is faciltated by using one of the nice combo switch mount charge jacks such as the inexpensive dubro mount.

The last is what I use exclusively and that is because of the mircle of telemtry that is avalible here and now. I use a couple of Aurora 9's and whenever I turn on both the transmitter and the receiver I have an instant visual readout of the exact real time loaded voltage of both the transmitter and the receiver battery packs. This in the air or on the ground. I have found carrying an extra loaded meter no longer neccessary.

John

goirish

Well he is a full Marine now. It was great to have him home for 10 days. He goes back to San Diego for another 8 weeks then gets deployed some place.

JohnBuckner

My Feedback: (1)

Grizzdaddy 3.5 is too low period. The 4.7volt minimum that I use as an absolute minmum is using any commercial sold for our purpose loaded tester and I beleve all will use a load of around 2 to 400 miliamps.

John

charlie1960

firm believer in that onboard gizmo that lights up;D

grizzdaddy

My Feedback: (6)

Thanks John, this helps out alot and I think I am going to look into one of these onboard readers.....only thing that comes to mind about these is; if it shows the voltage under load; does it do this the whole time the battery is turned on or is this meter operated by a switch. If it is on the whole time the the battery is turned on this would cause a draw/ more load on the battery.

Chad

Rodney

Those gizmoes described as light bars are IMHO the best way to go as, if you have them connected and you cycle the sticks rapidly to their extreme positions, you will see the lights flicker up and down the scale. If it is dipping into the red area when you do this, you know you have a problem somewhere as the voltage is being momentarily reduced below acceptable limits. This can be from several causes such as high internal impedance in the battery, a switch with a high impedance contact(s), to small a gage wiring between the battery and receiver, a servo drawing excessive current, a jammed servo at extreme position etc. as well as a low battery. If it flickers into the red area, find your problem before you fly. A loaded voltmeter will not show up those kind of problems. And, no, the current drain of these devices is so low that it has virtually no detrimental effect on flying time.

JohnBuckner

My Feedback: (1)

Grizzdaddy there you have it concerning the "Gizmos" from Rodney and of course I fully concour with their functionality as well as his explination of their use.

I have just never used them and I continue to train all my students however in the use of the loaded meter and the Morning check before transport, morning check before first flight and a check between each flight of the day senario. Here is why:

For the gizmo to work one must be installed in every single aircraft. Now no problem for just your first airplane but a five or six bucks a whack or whatever they are now, it will begin to add up as you add airplanes. Make no mistake if you stay in the hobby you will start adding airplanes. Next thing you know you will have some airplanes with and without the gizmo and ultimately most all peope will eventually just add the very important loaded voltmeter.

In the real world only a small minority of folks will end up with a Gizmo in every airplane in lieu of a good meter.

Now all of the above is only just my opinon and what you need to do here and now though is make sure by whatever method you choose that you do not go any lower than the afformentioned 4.7 volts (with a metered load).

rudder turns

Hi Guys,I converted all of my 24 planes to the Hitec 2.4 conversion,using my futaba 9c and 8u radios. The receiver talks to the transmitter modular,it comes with this telemetry,built into the receivers, at no extra charge,the transmitter modular beeps if your battery is starting to get too low. I have personally tested it and it works great, It automatically reads if you have a 4 or 5 cell battery on board. I also have been using the volt watches,from tower and hobby king,for extra insurance.[8D] It plugs into an extra receiver port or a Y connection.I have been using Battery's America/Mr Nicad battery's with no problem a 700ma pack for $13 assembled,ready to charge,there in all of the magazines.I'm using std servos,digital servos do require allot more power. I wouldn't take a chance soldering your on board battery's. And NEVER spring loaded battery holder. It's not worth saving a few bucks and possible have a fly away or a crash thanks Ed

Hossfly

grizzdaddy, it sounds like you might have one of those Hanger Nine Digital Variable Load Voltmeters. If not I certainly recommend such. I keep one on each of 3 worktables, and one in my flightbox with a couple NIB hanging on the wall. At the field I also suggest that your name and address sticker is on the back.

Personally I don't like the light type switch harnesses as they are very shoddily built. I trust my H-9 Voltmeters.

They have the .5, 1, and 2amp load functions. Going flying without one can be dangerous to the flying machine. Maybe I missed it but do you cycle your battery.

Any 4 cells of Nicads, Nimah will charge to 5.5 or about but drop off to 5.0 or about fairly quickly. 2,0 amp load is a bit much for the basic 4 analog servo airplane. Most of my models are well within the limitations of regular analog servos up to 90 0z. torque, mostly in the 50-75 range. If you have DIGITAL servos, remember that they IDLE at about the same current draw that an anolog works at.

This is one "L" of a difference in how a battery holds up. When the digitals first hit the scene and all those folks that just had to have the latest thing, went out and placed digitals in all positions including throttle and retract landing gear even for air systems, I just stood by and watched the carnage and laughed at the numerous reasons they found to explain their losses. OTOH the 3D and IMAC crowd needs those high output servos, but most quickly learn the ropes. The sport flier does not, but so many just have to keep up with the Jonses. Their choice and it makes "no never mind to me". Just so they crash on the OTHER side of the field. BTW I fly some sport scale up to 101" w/span with gas burner engines. Analog is fine.

Whatever you want someone will sell it to you. Sounds like you also know how to solder. It can be done. Best of luck there young fellow!