jeffsend

My Feedback: (4)

If I charge same day I fly,my 4 cell 1100mah nicad rx pack holds good voltage for at least 3 or 4 ten min. flights(.40 size glow plane with 5 standard servos). On the other hand,I had recently overnight charged,then didn't fly for 3 days. Got to the field expecting to be good for at least one quick evening flight,and the voltage was showing low under load(I use a voltwatch and move all servos before each flight). So I put it on my Triton charger at 1C(first time I've ever tried a quick charge),and it peaked within 10 minutes and showed good voltage before and after the one flight I was able to get in before the sun went down.
Now this battery is getting kind of old and I plan on replacing it soon,but I'm just curious,is this a sign of a pack going south,or will even a good pack need recharged after sitting around for 3 days? Does the self-discharge rate increase so much on older packs,or is there another explanation?

pilotpete2

How many years have you had those packs. I used to use 5 cell packs made up from Sanyo 1100mAh nicds, but they did seem to deteriorate after 3 seasons. I think the higher capacity in a "AA" cell comes at a cost[&o].
I've since switched to 2S A123 packs for all my gas/glow models. A 1100mAh A123 pack is perfect for the typical sport model. I have one in my 4 Star 60. Five servos and a 90 class four stroke take very little power per 11 minute flight, I've never had to replace more than 1/3rd the capacity of the pack on a typical day. Self discharge? Not anymore
Pete

P-40 DRIVER

You should be able to fly all day on that pack in new condition. It sounds like it needs to be replaced asap. I think if you cycle it you will find its pretty well shot.

jeffsend

My Feedback: (4)

Thanks for the replies. The battery is around 2yrs old. They are the Sanyo cells(I have a couple of them about the same age that act about the same). I don't recall ever getting more than 3 or 4 flights on it,but I'm not the type to push my luck,and also that's generally all the time I have as I don't often get to make a full day of it. I will cycle the battery as soon as I get a chance,and see what I get. I have thought about making the switch to A123,but will have to buy a new charger if I do. I also have a new 5 cell NiMh I can swap it with for the time being.....but it will take some re-arranging to fit it in,as it's a flat pack and the old one is square.

JPMacG

My Feedback: (2)

The 1100 mAh Sanyo AA cells do not seem to hold up for long. My 1100 mAh packs went bad after 2 or 3 years. The 600 mAh and 700 mAh packs last much longer. I have some that are still good after 8 years. If you don't need the extra capacity, I recommend avoiding the 1100 mAh packs.

rockin daddy

My Feedback: (32)

I have a couple of older Thunder Tiger Expanded volt meters. They have always beengreat in pre-flight testing my battery packs in my receivers and transmiters. Lately I purchased several 800 and 1100 ma flight battery packs with 5 cells instead of the usual 4 cell packs. These 5 cell packs cannot be tested on my meter as they "pin" the needle when you test on the 5 volt expanded scale.

What load resistor do I need to use in series when testing these 5 cell NiCad packs when I am plugged into the 5 volt test jack? Hopefully there is an RKI out there! Oh, that's a "reasonably knowledgeable individual" !!!! Any help would be appreciated.

Rockin' Daddy

JPMacG

My Feedback: (2)

A series resistor will not give you the accuracy that you need for testing batteries, as the voltage drop across a series resistor will be dependent upon current draw.

You need a different meter. I recommend a loaded multimeter rather than an expanded scale voltmeter. A loaded multimeter is more versitile and moe accurate.

Lnewqban

Could you explain the difference?

JohnBuckner

My Feedback: (1)

You need to get a Digital loaded meter such as this and it will read any of your packs whatever voltage:

http://www3.towerhobbies.com/cgi-bin...&I=LXWW16&P=RF

John

jeffsend

My Feedback: (4)

Another option would be to use a Voltwatch,for on-board battery monitoring. They now come with a switch for either 4 or 5 cells. I have an older one without the switch(for 4 cell),and before each flight,I move all the servos erratically to their extremes to get a "loaded" reading. If it dips into the red while flopping the sticks around,I don't fly.

Basil Yousif

My Feedback: (3)

A better option is jut to switch to the Reciever Li-poly's they have out now. They are 2 cell 7.4 volt packs. If you reciever can't take the 7.4 volts you can get a regulator but most are okey with that voltage. Hobbypartz has these for $16. 2100mah 2c with a low discharge rate right from LA. You can keep them around without charging for an outragious amount of time. The only thing is you have to remove them from the plane to charge them. The up side is you can have them charged at the field in a few hours. They have ones for the transmitter Li-poly packs also. You can fly for months without having to charge the transmitter battery pack.
Old NIMH battery packs can cause crashes. If you want you can also build your own NIMH packs and get right from the factory cells for $2 each. I bought a brick of NIMH 2200mah batteries and built a few packs when they were .80 each. It was worth it then
For $10 a pack plus shrink covering and lead I would go with the Li-poly hands down.

Link to batteries:
http://www.hobbypartz.com/txrxbatteries.html

pilotpete2

I use lipos for many planes, but I would never, ever put one in a gas/glow powered model. Whilehe receivers will not have a problem at 8.4V, The servos will if used directly with 2S lipos. Very limited choices of lipo compatible servos Adding a regulator only makes the lipo an even worse choice, as they add their own problems and failure modes.
2S A123 have it all over lipo for receiver/servo power. No regulator, and as safe or safer than Nixx when charged in the model.
Pete

Capt Lou

I agree with pilotpete, go for A123 battery technology. I have 4 giant scale planes, all using high torque servos, and use 2300 mah A123 packs in them. You can get plenty of flight time, they charge quickly (about 10 minutes), you don't need a voltage regulator, and they are much safer than lipo's. If you are going to invest in a new flight pack, A123's are the way to go. If you want to learn more about them, go to www.hangtimes.com

JohnBuckner

My Feedback: (1)

Basil it is never a better option to suggest that a lipos are a better idea over the use of a loaded voltmeter. And Lipos old and new can also cause crashs just as much as any other type of battery system with poor or careless operation and use. I too would never use lipos on any installation that did not use a speed control and/or the associated rx voltage regulation.

Jeffsend voltwatchs are great but agine should only be used as an adjunct to careful first flights of the day with a proper loaded expanded scale voltmenter or the more versatile loaded digital reading volt meters which serve well with all our various battery systems and the varying voltages associated with them.

John

mundo330

My Feedback: (3)

I will second the A123 opinion. Lipos will wreck havoc with most servos, but the old 4.8 volt packs are asking for trouble in planes running 2.4 Ghz systems. Unlike our 72mhz receivers that have very simple processors that reboot in milliseconds, 2.4 Ghz receivers can take up to 7 seconds to boot. All receivers will reboot if the voltage drops below 3.7 volts and a hard maneuver with a battery that read 5.0 volts on the ground can send that pack well below the 3.7 volt threshold. We have had several planes go in after a reboot on 2.4ghz. I use 5 cell (6 volt) Sanyo packs built by E.H. Yost and for almost 25 years have found their batteries reliable and of the highest quality. A 123s are a viable option providing you have the charger for them. If you have multiple planes then it can compound the issue. If you are starting out new the A123s are great. Also the eneloop 2000 NiMh batteries work great in the transmitters.

carrellh

It's really easy for us to spend YOUR money.............
Since you have a field charger that will work with NiCad or NiMH packs there is no compelling reason to buy chargers, balancers, etc to change battery technology. I'd just replace the battery packs with something pretty similar.
A few online sources
http://www.cermark.com/categories/Ba...Cd%252dNiMH/Rx
http://www.servocity.com/html/6_0v_batteries.html
http://www.radicalrc.com/category/Re...s-NiMH-NiCd-19
http://www.hangtimes.com/sportrxpacks.html
http://cheapbatterypacks.com/?menu=4...856&sid=661442
Or pick them up at a hobby shop.

Mikecam

If you want to save money in the long run then switch to A123's. I've used them for 3 years now and they still discharge within 10ma of when they were new. I bought 2 hydrimax 2000 ma/h nimh's last year (they are a little cheaper) and after receiving them did 3 cycles and got out 1700 ma/h and 1650 ma/h. This year after 20 charge sessions one is down to 1400ma/h. The only nimh pack that has stood the test of time for me was a Hydrimax 4200ma/h C size pack I bought for a cub. The small nimh packs just don't last. The A123's they say are good for 1000 + charges. After 3 years of use I'm really starting to believe that.

Direct link for the A123 FAQ on Hangtime hobbies site. Steve has been great and will answer any question you might have. The FMA multi4 has been great for me (too bad Steve can't work out the shipping issue) as well and I did the mod for the simple 3 wire switch feed and balance charge right through my charge jack.

http://www.hangtimes.com/a123_batter...iants_faq.html

Look toward the bottom of this link for the Simple 3 Wire Switch Feed For 2nd Generation Chargers


http://www.hangtimes.com/a123rxsetup.html

jeffsend

My Feedback: (4)

Thanks.
I am still flying with the same packs that I posted about in the first post,although I haven't been doing much flying lately. I did cycle one of the packs in question and it hasn't lost much of it's capacity if any. I don't have the numbers in front of me at the moment. I still get good performance out of it as long as I charge it the same day,or overnight the night before. I am considering A123 for the future because I'm also interested in going up to giant scale(30 to 50cc). I also have a new nimh 5 cell that I've only cycled and haven't flown yet,so I've got options.
Anyhow,thanks for all the input.

KB9STD

My Feedback: (1)

Put 2 silicon diodes in series with the meter and the voltage drop will NOT be dependant on current draw.Each diode will drop .6 to .7 volts,giving a 1.2 to 1.4 volt drop(closely equivalent to 1 cell).Test the reading against a good voltmeter,and with maybe a slight "Fudge factor" your meter will be perfectly usable on 5 cell packs(with the 2 diodes in series).

Edit: I tried this myself today,and the voltage drop was too high(almost 2 volts).I then used 1 silicon diode and 1 Schottky diode,and got a drop of 1.2 volts.Making the cut-off point of the 4 cell scale on my ESV exactly right for the 5 cell pack(with the diodes if series).

rockin daddy

My Feedback: (32)

Dear KB9:

Thanks for the input on testing 5-cell Nicd battery packs with my old meters. I looked up Diodes in my electronics catalog. They dhow "Schottky diodes" and "Zener diodes". There is a Schottky diode rated at 3 Amps at 40 volts. The Zener diodes are rated in wattage and voltage. One zener diode is 5w at 10 volts. Would that work??

Thanks so much for your advice.

Best regards,

Rockin Daddy

KB9STD

My Feedback: (1)

Rockin Dad...A silicon "rectifier" diode is what your looking for.You DON'T want either a zener or Schottky diode.Zener diodes only conduct ABOVE the rated voltage,and are used in voltage regulators.Schottky diodes are designed to have a very LOW voltage drop. You want the .7 volt drop of a "Silicon" diode.It's that drop across the diodes that You are using to make a 5 cell pack read (Somewhat close to ) correctly on the 4 cell scale.You "lose" the voltage of one cell through the diodes.Anything like a 1N4001 will do fine.

KB9STD

My Feedback: (1)

If You want to know more.....

Function
Diodes allow electricity to flow in only one direction. The arrow of the circuit symbol shows the direction in which the current can flow. Diodes are the electrical version of a valve and early diodes were actually called valves.

Forward Voltage Drop
Electricity uses up a little energy pushing its way through the diode, rather like a person pushing through a door with a spring. This means that there is a small voltage across a conducting diode, it is called the forward voltage drop and is about 0.7V for all normal diodes which are made from silicon. The forward voltage drop of a diode is almost constant whatever the current passing through the diode so they have a very steep characteristic (current-voltage graph).

Reverse Voltage
When a reverse voltage is applied a perfect diode does not conduct, but all real diodes leak a very tiny current of a few µA or less. This can be ignored in most circuits because it will be very much smaller than the current flowing in the forward direction. However, all diodes have a maximum reverse voltage (usually 50V or more) and if this is exceeded the diode will fail and pass a large current in the reverse direction, this is called breakdown.

Rectifier diodes (large current)
Rectifier diodes are used in power supplies to convert alternating current (AC) to direct current (DC), a process called rectification. They are also used elsewhere in circuits where a large current must pass through the diode.
All rectifier diodes are made from silicon and therefore have a forward voltage drop of 0.7V. The table shows maximum current and maximum reverse voltage for some popular rectifier diodes. The 1N4001 is suitable for most low voltage circuits with a current of less than 1A.

Jazzy

Jeffsend,

Here is a link to some simple drawings and discussions of LVMs (Loaded Volt Meter).

[link]http://www.rcuniverse.com/forum/m_6061222/mpage_1/key_loaded%2Cvolt%2Cmeter/tm.htm[/link]

Without putting a load on the pack a voltmeter cannot be trusted. I've seen 5V floating voltage on a pack but with a load it dropped to or below 4.8. Beware and good luck!!

JPMacG

My Feedback: (2)

Yes, the silicon diode idea is good. Or, if you are so inclined, open up your meter and install a voltage divider resistor circuit in front of the meter movement.

But if you are not into tinkering with electrical stuff it may be best to just purchase a different loaded voltmeter / DMM.