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LETMEFLY 03-28-2014 08:36 PM

AA batteries
 
Yes I know that this is a total electric group. I fly glow powered parachutes and use 4 Kirkland AA batteries for the receiver. Can anyone out there tell me what the total mAH of these four batteries comes to?

This is just a very simple question so please do not sound off because I am on the wrong group.

Thanks,

Bob

mclarkson 03-28-2014 09:31 PM

Hmmm... I'm not familiar with the brand. AA batteries have between around 500 - 3000 mAh each, depending on the brand, the chemistry, and etc.

DHC Beaver 03-28-2014 10:41 PM

deleted

DHC Beaver 03-28-2014 11:05 PM

Hi Bob,if I unstand you correctly,you're assuming 4 cells have a higher capacity than 1.That is not so.
It's the voltage that multiplies by the number of cells,so a 4-cell pack will be 6 volt for dry batteries,or 4.8volt for nimh/nicad.
If you want to increase the current of your battery,you need to get higher mah cells.
Sorry if I 'm assuming too much,that's just the way i read your question.
I use LiFepo4 receiver packs,which are 2-cell,6.6volts nominal.They come in capacities from 1100mah upwards.The advantage of those is low self-discharge,and lighter weight than nimhs.I charge those about once a month with regular use.
If you want to stay with the AA format,Hobbyking sells 2500 mah AA LSD nimhs for less than $2 a piece.These are great batteries,I use use them in all my household remotes,eg,tv,dvd player etc.
I see they actually sell them as a 4-cell receiver pack now.I would recommend that as a simple upgrade for your receiver power,if that's what you're looking for.
regards.Hans

kyleservicetech 03-29-2014 12:13 AM

Quote:

Originally Posted by LETMEFLY (Post 943871)
Yes I know that this is a total electric group. I fly glow powered parachutes and use 4 Kirkland AA batteries for the receiver. Can anyone out there tell me what the total mAH of these four batteries comes to?

This is just a very simple question so please do not sound off because I am on the wrong group.

Thanks,

Bob

Glow powered models??? What are they??? (My rapidly fading memory vaguely recalls having flown glow engine powered models back in the 1960's! My current 1200 Watt electric models have far more horsepower and performance than those 60 sized glow engines back then. Or, even nowdays. My Hacker A50 series motors turn a 15X10 prop at 7700 RPM))

I just checked for Kirkland batteries, and noted that they are available from Costco. These are apparently one-shot batteries that are not rechargeable.

Checking the Amazon web site, these Kirkland batteries apparently have a very bad habit of leaking, and ruining what ever they are installed in.
http://www.amazon.com/Kirkland-Signa...ews/B0015UVOJU

A real big concern for me, is using a "cheap" AA type battery holder for a glow powered model. Those battery holders often are not very reliable, especially under any vibration levels that may be present.

As for their milliampere hour capacity, that can vary all over the map, depending on the discharge current level, and how low their voltage is allowed to go before deciding the battery is discharged. Even on the same battery cell. Some of those mfg's rate their batteries mah rating on a discharged voltage level of 0.7 or 0.8 Volts per cell. The minimum safe voltage level for receiver power would be around 1.1 Volts DC or so per cell.

I've checked name brand alkaline "AA" batteries on my Western Mountain battery analyzer, and found that they ran about 1200 Mah or so, when discharged to 1.2 Volts DC.

If your radio can tolerate four alkaline cells, that is 6.0 volts DC for the four cells in series. That would make a two cell LiFe battery a direct drop in for the 4 alkaline cells. The price of LiFe receiver battery packs is dropping down to reasonable levels. You'll still need a quality balancing charger for the LiFe batteries. Tower Hobbies has both LiFe and LiFe chargers in their inventory.

Nice thing about those LiFe batteries, they hold their voltage pretty much flat, until just before they are totally discharged.
http://www3.towerhobbies.com/cgi-bin...vers+batteries
http://www3.towerhobbies.com/cgi-bin...?&I=LXCURR&P=7

And, an entry level LiFe charger
http://www3.towerhobbies.com/cgi-bin...?&I=LXZWP0&P=7

You could probably find lower prices in Ebay and similar locations.

LETMEFLY 03-29-2014 03:53 AM

batteries
 
I was referring to the common 'AA' one use battery that is rated at 1.5 volts. I have been using four of these to power a JR RS6UL micro receiver, a standard servo like a Futaba S148 and a Hobbico CS73 1/4 scale servo in my Seabreeze powered parachutes. I have never had battery failure.

Now I want to use four of these 'AA's to handle four standard servos in my Hangar 9 Alpha 40 trainer. I am not a fan of nicads period. I prefer to use the 'AA's.

If four of these come out to around 6.3 volts new then I needed to know what the total Mah would be. Up til now this is the way I wanted to go.

Today I find out that Hobbyking makes a 6.6 volt 1700 Mah lipo that I can use for the powering of my AR600 receiver and four standard servos and not have to worry about running out of power. That is the way I will go as soon as they come in as they are back ordered. Thanks to all of you who chimed in. Bob

LETMEFLY 03-29-2014 04:17 AM

powered parachutes
 
I fly what are called Seabreeze powered parachutes. My friend in Bradenton, Florida makes two models. One is called the QBSE which stands for Quick Build Series Electric and the other is called the QBSG which stands for Quick Build Series Glow.

I am currently fly two of his glow versions with OS LA40 two stroke engines in them. Both swing MAS 10 X 5 GF props. The parachutes are made by him also and I fly four of these which are made to whatever color and letters I want. He makes three sizes, a 24" X 62", a 31" X 82" which are the ones I have and a larger version. These are not fast and cruise along at a speed of around 15 mph. I use JR Sport FM radios on the 72 MHz band and each rig has a JR RS6UL micro receiver. I have never had any trouble with range. I usually fly up to 700 feet and around 800 feet out. I also have a little device called How High that tell me how high I am flying.

If you want to take a look at what is available then go to Troys site, www.seabreezeparachutes.com . He will sew you up a custom parachute with various colors and I think now he is only offering the electric version of his gondola. I also fly one of these with a AXI 2820-10 outrunner and a 40 amp esc. The batteries I use are no longer made, Polyquest enerlands rated at 4350 Mah. I also use a Turnigy Nano tech rated at 5000 Mah which is about as large as one wants to go. Flight time is about 8-9 minutes where as the glow versions give me up to 20 plus minutes using a 12 ounce fuel tank. Take a look at what Troy has to offer. He is top notch and everything he makes is made in the USA. And he offers a super guarantee which no one else anywhere can match.

kyleservicetech 03-29-2014 05:26 AM

2 Attachment(s)
Quote:

Originally Posted by LETMEFLY (Post 943902)
I was referring to the common 'AA' one use battery that is rated at 1.5 volts. I have been using four of these to power a JR RS6UL micro receiver, a standard servo like a Futaba S148 and a Hobbico CS73 1/4 scale servo in my Seabreeze powered parachutes. I have never had battery failure.

Now I want to use four of these 'AA's to handle four standard servos in my Hangar 9 Alpha 40 trainer. I am not a fan of nicads period. I prefer to use the 'AA's.

If four of these come out to around 6.3 volts new then I needed to know what the total Mah would be. Up til now this is the way I wanted to go.

Today I find out that Hobbyking makes a 6.6 volt 1700 Mah lipo that I can use for the powering of my AR600 receiver and four standard servos and not have to worry about running out of power. That is the way I will go as soon as they come in as they are back ordered. Thanks to all of you who chimed in. Bob

Again, the milliampere hour rating of those alkaline battery cells depends on the rate of discharge. Discharge them at one milliampere, and they can have a milliampere hour rating of over 2000 Mah. But, discharge them at two or three Amps, and they can have a milliampere hour rating 500 Mah, or even lower. Those numbers will vary widely depending on mfg of the alkaline cell. (Don't even think of using AA cells that are not alkaline type.)

As for the 6.6 Volt LiPo, that is a contradiction. LiPo batteries go up to 8.4 Volts DC on the charger, enough to blow out most servo electronics. Only servos specifically rated for LiPo use can be used with those LiPo battery packs.

Those LiFe or A123 batteries go up to 7.2 Volts DC right off the charger. But their voltage quickly drops to 6.6 Volts after a minute or three, about the same as a four cell Alkaline battery pack.

Those A123/LiFe batteries can have milliampere hour values ranging from 1100 Mah or so to 3000 Mah or more. AND, their milliampere hour doesn't change much from very low discharge rates over days, to 10 or 20 Amps over minutes of discharge time. I've got a whole bunch of A123 cells that are routinely discharged at 35 Amps, (35000 milliamperes), that only get slightly warm in the process.

OK ************************************************** *******************

Right now, I just ran a discharge test on a cheap Shisu Extra Heavy Duty Carbon Zinc battery. The Western Mountain CBAIII analyzer was programmed for one amp discharge, with a 1.1 Volt cut off. That Shisu battery died instantly at one amp, dropping below 0.5 Volts DC. Then, that same setup was used with a brand new Rayovac AA type Alkaline cell. With a cut off of 1.1 Volts, that Rayovac cell shut down at 0.013 Ampere Hours. That is only 13 mah.

So, the cut off point was dropped to one Volt, bare minimum value for safe operation of your receiver and its servos. At one Amp, the battery put out 0.053 Ampere Hours, or 53 mah before hitting 1.0 Volts DC. The test was restarted with a cut off of 0.8 volts DC. Right now, that battery is at 0.89 Volts DC, with 0.147 Ampere Hours, or 147 mah.

Compare those results to a LiFe cell with 1100 Mah capacity, that will put out 1000 Mah at 5 Amps. Yeah, I've checked many of them on my analyzer.

With that, IMHO, I'd NEVER use any alkaline battery for receiver power on any of my models. In fact, those results surprised the heck out of me. As an example, some of my servos have measured peak current values of 2 Amperes, with the entire giant scale model pulling 14 amps peak current, while just spinning the transmitter sticks around and around. That peak current was measured with my $350 Fluke 87V digital multimeter with its millisecond level peak current hold feature.

Before people chime in, yeah, I'm well aware that servos don't pull those high currents very long. But, this test does show that those alkaline cells don't have anywhere near the momentary high current ability of a comparable size LiFe battery, that will hold 6.0 Volts at a continuous discharge current of 5 Amps.

The attached Western Digital CBA test results are attached. Note the far left portion of the chart that shows tests with a 1.1 Volt DC cut off. The longer test of about 0.286 Amp hours was shut down at 0.849 Volts DC. Compare that to two different LiFe packs on the second chart. One pack had been run dead, and still had 71% of capacity. Discharge test was at 2.5 Amps. Those LiFe packs were three years old.

solentlife 03-29-2014 06:47 AM

I am led to believe by friends in the 'biz' that Dry Cell AA's tend to sit in the 1000 - 1300 mAh range ... higher than the old style rechargeables but less than todays ... But no g'tee that's correct for your cells.

OK - I do not agree with the generalisation that cell holders are bad. It all depends on how you set-them up and install.

I use cell holders and over counter 2300 mAh Grundig NiMH AA's ... and I have used such packs for many years without any problems at all. The only model lost to a Rx pack I have ever had was with a factory JR welded pack that one cell broke it's weld ... a beautiful scale P51 D ...

My packs have springs engaged and then locked with tabs to FORCE contact. The whole is then wrapped TIGHT in self-amalgamating tape to make sure no cell ever moves. The tape also has the lead doubled back to stop any pull / stress on it's soldered tags.
When installing in model - foam sponge is wrapped round to protect.

Total cost ? About $15 all in ....
Life expectancy ? I have packs years old and still delivering reliable power.

Models used in ? Example : 61 powered aerobatic biplane, gasoline powered Cessna with 2 identical packs (4.8v 4 cell) ... 1 for ignition, other for Rx.

Nigel

kyleservicetech 03-30-2014 01:28 AM

2 Attachment(s)
Quote:

Originally Posted by solentlife (Post 943908)
I am led to believe by friends in the 'biz' that Dry Cell AA's tend to sit in the 1000 - 1300 mAh range ... higher than the old style rechargeables but less than todays ... But no g'tee that's correct for your cells.

OK - I do not agree with the generalisation that cell holders are bad. It all depends on how you set-them up and install.

I use cell holders and over counter 2300 mAh Grundig NiMH AA's ... and I have used such packs for many years without any problems at all. The only model lost to a Rx pack I have ever had was with a factory JR welded pack that one cell broke it's weld ... a beautiful scale P51 D ...

My packs have springs engaged and then locked with tabs to FORCE contact. The whole is then wrapped TIGHT in self-amalgamating tape to make sure no cell ever moves. The tape also has the lead doubled back to stop any pull / stress on it's soldered tags.
When installing in model - foam sponge is wrapped round to protect.

Total cost ? About $15 all in ....
Life expectancy ? I have packs years old and still delivering reliable power.

Models used in ? Example : 61 powered aerobatic biplane, gasoline powered Cessna with 2 identical packs (4.8v 4 cell) ... 1 for ignition, other for Rx.

Nigel

Hi Nigel

I've checked some quality alkaline batteries at low currents. At a few milliamperes, these cells can approach 2000 Mah. Even a low cost AA size Nih cell can exceed that Mah value. But, most of my club members are going to the LiFe or A123 battery packs on their more expensive models. These LiFe or A123 packs work, and work well. Add to that, what you take out is almost identical to what you put back in with your charger. So a club member can perform perhaps five flights, top of the battery at the field, and see exactly how much battery capacity was used. Using my [personal rule of NEVER using more than 50% of the battery capacity during any flying day without topping it off, you've got a very safe situation.

Guess there are some cheap battery holders, and some not quite as cheap battery holders. Here in the USA we have a store by the Name of Radio Shack that sells both types.

IMHO, the real cheap units have steel springs with riveted connections between the steel springs the plastic housing, and the battery plus terminals. I've seen those riveted connections between the steel spring, the rivet, and the plastic housing develop high resistance, more than once. On top of that, the plastic housing can yield over several years, allowing the cells to simply pop out.

The not quite as cheap battery holders have the spring and battery plus terminal permanently bonded, metal to metal crimping. And, they have screw on lids. The Radio Shack unit also has an internal on-off switch though, something I'd rather not have in radio control use.

If you look at the battery holders in the Spektrum DX6i transmitters, those are well made units.

Here is the Radio Shack unit with a screw on lid:
http://www.radioshack.com/product/in...ductId=2062253

And, attached are the two different styles of battery holders. At least with the better battery holder, you don't need to resort to duct tape to provide good battery security. :D :D

As for me, I'm using two cell 2300 Mah A123 batteries for backup power on my giant scale models. Those packs are built up in my workshop, and proper wire security is made with shrink tubing over all wiring, and over the entire battery pack.

hayofstacks 03-30-2014 06:53 AM

Man, too bad none of the 50+ nitro's flew with the 4 cell double a batteries. those were all full sized servo's.

all joking aside, batteries have really advanced. i think you would be crazy to not update them, but I've seen a .40 sized trainer fly four several hours on 4 double aa's and four full sized servo's. Grandpa's old phil craft ugly stick flew fine on the spectrum pack that came with the transmitter. not sure what its rated at, but i only had to plug it in.

solentlife 03-30-2014 08:35 AM

I agree that there are new technology solutions out now ... but they are limited to those applications where the voltages incurred can be used. I have models that I cannot use 6V or higher ... so if I went LiFE or LiPo - I would need to use a uBEC anyway.

My NiMH AA packs sit in my models with recharge plug accessible so I can recharge without need to extract pack. No need to go balance method ... simple and works.

I can fly my 61 Bipe with 3 40gr and 1 12gr servo on the 2300 NiMH 4 cell AA pack ... at a weekend meeting with no recharge needed at end of first day. OK - for safety sake - I do plug in to top-up, but I admit I have forgotten odd times and had no trouble at all.

My gasoline job with 2 such packs - same ... no problem.

When I replace / upgrade my servo set-ups - then I will look at other power packs ... but till then - I fly without problem.

Nigel

kyleservicetech 03-31-2014 05:12 AM

Quote:

Originally Posted by hayofstacks (Post 944007)
Man, too bad none of the 50+ nitro's flew with the 4 cell double a batteries. those were all full sized servo's.

all joking aside, batteries have really advanced. i think you would be crazy to not update them, but I've seen a .40 sized trainer fly four several hours on 4 double aa's and four full sized servo's. Grandpa's old phil craft ugly stick flew fine on the spectrum pack that came with the transmitter. not sure what its rated at, but i only had to plug it in.

Yeah, those old Nicads did do a pretty good job with the 72 Mhz radios we used. Now, we've gone from 500 Mah Nicad battery "AA" Nicad battery packs to 2700 Mah "AA" Nickel Hydride battery packs. And with the 500% increase in battery Mah capacity came thinner plates for the internal battery construction.

Thinner plates equals higher internal battery resistance. Still not really a problem, but with 2.4 Ghz radios, it can be an issue.

If my fading memory is correct, when Spektrum first came out with their 2.4 Ghz radio, a Spektrum factory team buried a big model airplane in front of a lot of spectators in a demonstration flight. The cause was the undersized 4 cell Nih battery pack that Spektrum provided with the radio.

With the old 72 Mhz radios, if the power supply dropped to, say, 3.0 Volts DC briefly, when the battery voltage returned to normal 4.8 Volts DC, that receiver was all ready tuned to the proper channel, and it linked up to the transmitter instantly.

Not so with 2.4 Ghz. Any 2.4 Ghz receiver can pickup every 2.4 Ghz transmitter within range, each transmitting its own modulation pattern. Be it the original two frequency wide bandwidth of the original Spektrums, or the DSMX transmission of the newer Spektrum radios. Or, it might find the frequency hopping Futaba series of radios.

Now, that receiver has to select the proper transmitter, out of perhaps 50 or 100 that are turned on, and synchronize its self to your transmitter. The original Spektrums took several seconds to do it. The later Spektrum radios re-sync in about 1/2 second.

So, IMHO, for the 2.4 Ghz radios, it is wise to use batteries that will do the job for just about any airborne radio, that includes the LiFe and A123 packs.

We just underwent one of the coldest winters in recent years in Wisconsin. Nice thing about those A123 batteries for receiver power, they will work very well down to minus 40 degrees F. (:censor:)

solentlife 03-31-2014 06:12 AM

Denny is talking about Voltage sag under load ... and todays radios losing lock.

Spektrum was notorious for it's too high a base line voltage - where it lose lock, take too long to recover. A lesson they later rectified.

One of the problems of today - and I'm serious about this :

Peoples lack of understanding of load on servos and making installations as free moving as possible.

How many people realise that models that use foam hinge are subject to stiffening action as temp drops ?

How many people realise that servos' with silicon grease in stiffen up when temp. drops ?

How many people realise that control runs that do not sit cleanly have significant increase in load to move ?

How many people realise that any control connection that is not correctly aligned needs more force ?

There are so many factors that add up and can lead to voltage sag and drop out of lock.

Older FM radios were able to keep going even when voltage dropped to levels that only 2.4 can dream about ... agreed that the servos may have been very slow and operating at extreme low capability - but often a twitch amount of movement was enough to keep model alive for the second or so voltage sagged. Now you don't have that option ... even failsafe will not work.

And something I have never seen anyone mention but is a fact : Digital servos have a characteristic that you should be aware of .... unlike analogue they do not like voltage sag. Digital are like Digital radio - it's either on or off. The digital suffers drop so far and then STOPS. There is no low level gradient as in analogue. Analogue will keep moving as long as it can physically, it has no STOP like a digital.

Nigel

hayofstacks 03-31-2014 06:07 PM

What is the actual differance between a digital and analog servo?

In my opinion, nothing I've used has changed, except it.breaks easier.

solentlife 03-31-2014 06:17 PM

Quote:

Originally Posted by hayofstacks (Post 944130)
What is the actual differance between a digital and analog servo?

In my opinion, nothing I've used has changed, except it.breaks easier.

They say that a Digital is more precise and also expected to be quicker in response.
What I have found is that they can draw more A than a similar rated analogue.

I don't use them even in my Heli's ...

Breaking - yep - all the Digi's I used all broke easily. The Corona MG Digitals I had once were worst servo's I ever used ...

Nigel

rcers 03-31-2014 06:44 PM

Quote:

Originally Posted by hayofstacks (Post 944130)
What is the actual differance between a digital and analog servo?

In my opinion, nothing I've used has changed, except it.breaks easier.

This is a good read although a bit fluffy (marketing wise)... While digital is generally better they have a their place as does analog. That said - high quality digital servos are pretty spectacular. Speed, holding and accuracy are unmatched.

http://www.futaba-rc.com/servos/digitalservos.pdf



Mike

hayofstacks 03-31-2014 08:30 PM

Sorry to run the thread off of course. thanks for the link and replies.

on a side note, the lemon receivers claim to be good down to really low voltages, and can handle up to 10v's as well. id like to do a side by side comparison of fm and these to see what the differances in performance are.

kyleservicetech 04-01-2014 12:50 AM

Quote:

Originally Posted by hayofstacks (Post 944142)
Sorry to run the thread off of course. thanks for the link and replies.

on a side note, the lemon receivers claim to be good down to really low voltages, and can handle up to 10v's as well. id like to do a side by side comparison of fm and these to see what the differances in performance are.

Any idea of how low in voltage those lemon receivers can go before they reboot?

In comparison to the Spektrum series that reboot right around 3.2 Volts DC. At least with the dozen of various models that I have in my airplane models.


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