I have a fairly new (used about 15-20 times) 600ma Nicad batt pack I use for my receiver. I have been told "dont fly below 5 volts" and "dont fly below 4.8 volts". My question is this. After I have charged my battery ( i only have the generic wall charger that came with my radio) I get a reading of usually around 5.4 volts or so. ( this is a Hobbico tach/voltmeter so im assuming this is under load). After about one 4 minute flight Im down to 4.8 volts. Being eager and not especially prudent as I am new to the hobby. I flew some more and landed in about 4 minute increments to check the battery and it stayed at 4.8 for about three more flights at which time i decided to not press my luck. Is this normal for the voltage to initially drop so fast? If I listened to the "dont fly below 5.0 volt" advice I would get one flight in. Sorry this is so long. Thanks!

Try cycling the battery Nicads can develop memory.

most Rx shut down at around the 4.0 volt

A properly maintained 600mah pack is usually good for 1-2 hrs

if any of your servos are making a buzzing sound then you are draining the battery at a much higher rate.

getting a battery cycler like the accucycler from hobbico is a good investment this tool will cycle the battery and during the discharge phase show you the capacity in Mah and time it took to bring the cells in the pack to 1.2 volts. During the charrge phase you can see the charged capacity in Mah of the pack. general rule of thumb if the pack will no longer accept more the 75% of its rated capacity it's time for a new one.

It's difficult to get a good idea of the condition of your pack with only a voltmeter and wall charger.

normal volts is 4.8.you need a ESV meter to test the batteries under a load, your piece of equiment does not ,volts and tach,but not volts under load

You have made a good observation there, and are probably devdloping questions about the advice you're getting.

It's possible your battery is just fine. You might run the test you ran (4 minute increments, note voltage, repeat) on the ground instead of in the air. After you have mapped your battery response out to an hour or so, you should see how it acts, and at what point the voltage begins to drop rapidly.

That will tell you a lot about your battery and your meter. It should register a peak voltage after charging, drop rapidly to some level, then provide power at a more constant voltage for the useful duration. Then the voltage will begin to drop fast. It is that point, the voltage at which you see the voltage drop quickly, that you should never reach while in the air.

Your meter reading may be somewhat different from the readings you've been told to expect. Good luck, and keep asking questions!

Dave Olson

--That will tell you a lot about your battery and your meter. It should register a peak voltage after charging, drop rapidly to some level, then provide power at a more constant voltage for the useful duration. Then the voltage will begin to drop fast. It is that point, the voltage at which you see the voltage drop quickly, that you should never reach while in the air.--

So that voltage at which it drops quickly is different for every pack then and I just need to do these tests with each pack I buy?

Also remember that testing the battery pack under load is very important. I believe the meter I have puts a 100mah load on the pack. If yours does not you should get one since the only time they are under a load is when you are using them.

Without a test under load it will be hard to determine if you have a bad cell or a cell going bad.

a NORMAL 4 cell pack can be used down to 4.5 volts with no problem. Right after charge, it will be high like you read but that peak charge comes down very rapidly to a plateau of approximately 4.8 volts and will hold within a few tenths of a volt for a long time. It is easy to make your voltmeter provide a load to the battery when you check it, just parallel a 22 ohm one watt resistor across the leads while you are measuring the voltage. do be little Leary of the accuracy o your voltmeter. If you have a friend with a known calibrated one, compare them. Some of the cheaper ones do not have real good accuracy. Even if they don't compare, as long as you know the offset, you will be safe.

Remember that a triple "A" rechargeable battery is only rated to hold 1.2 volts (not 1.5 like alkaloids do). Therefore a fully charged 4-cell pack =4.8v

Miniflyer, best you check out something like rcbatteryclinic.com or something before making such statements. Not only are they missleading, they are wrong. For instance the alkaloid open circuit voltage is 1.55, not 1.5; and most NiCads will top off well above 1.5 volts per cell. Perhaps I should not even have replied to this post but when gross miss info is put forth, I couldn't refrain.

Look at the gross misinformation that is being put forth by battery companies

This one claims that a 6 cell pack is 7.2 volts. 7.2 / 6 =1.2
http://www.rcbatteries.com/category....0498%7C1105177

This one claims that their single cells carry 1.25v


While their 4 Cell packs hold 4.8v


Or this one from Sanyo's very own website...


Notice Sanyo says "Nominal" voltage... Hmmm acording to the dictionary, "nominal" means: According to plan or design .

I think we have a conspiracy here. It's no wonder I was so misinformed.

I'm sorry, I take back what I said earlier.

Hi MinnFlyer,
now that you know better,why don't you just send me those old junk batteries you've been using,h***, most of in Texas can't read anyway,so using those missprinted labeled batteries wouldn't effect us,we're stuck with the same kind.

Even Red Scholefield says the manufacturer's specs to achieve the rated capacity involves discharging to 0.9 V per cell (3.6V on a 4 cell pack)! However, in order to maintain saftey while flying, it's best to stop before reaching this point. I have always stopped when I reached 1.1V per cell, and I have recently seen Red (I think it was Red) recommend an absolute minimum voltage of 1.0V per cell.

I'm with MinnFlyer on this one as well... 1.2V per cell has been the normal voltage for NiCd batteries for as long as they've been around. Having said that, I have a 6 Cell, 12V battery I can't explain. I picked it up at a surplus center years ago, and I use it for my flight box. I has a warning label that used to read "Energy Hazard - 200 Amps available" (The label is well aged now).

Well, a little research seems to explain my battery - it isn't NiCd, it's a specialized lead cell.

It was sold as a NiCd, and back then I didn't know better. Besides, for $20 (Canadian) it has served me well for about 10 years, and still going strong. The maunufacturer (Gates Energy Products) has evolved into Hawker Energy Products, which specializes in high-end lead batteries. Mine looks like it is made of 2 - 6V "Cyclon Monoblocs" www.hepi.com/monobloc.htm .
It contains 6 "X" size cells (5.0Ah), with a nominal short-circuit current of 570A!. That makes for a good kick on the electric starter... http://www.hepi.com/scprod.htm :boxing: