Topic: Battery Questions

I'm quite surprised that no ones yet mentioned the servo installation. If there's one thing that will drain a freshly charged battery in no time at all it's a 'binding' or 'stalled' servo! 
You should make sure that all control linkages are smoooth, and none of the servos are buzzing, which is usually what happens when they bind and can't find their centre.

I think the reason for servos/servo installations not being mentioned was the title of the thread being Battery Questions EssJay.

However, this hasn't prevented threads going in all directions previously!

Brian, I think that's a bit harsh to imply that I was 'hijacking/deviating from' the thread when the only intention was to inform the OP that having a "dodgy nicad" is not the only reason for it going flat suddenly, but to also consider your servo installation.
Perhaps I should have alluded to the above in my post. If it was taken to be 'hijacking/deviating' then it was not meant to be so.  

Apologies

Straight forward here, go with the vapextech batteries, the 'instant' batteries are very good, use 5 cells if you're flying 2.4GHz, make sure you have a good quality switch harness and a decent charger then you can forget this potential issue.

J

use 5 cells if you're flying 2.4GHz,

Not true, not necessary and highly misleading especially to a beginner.

BrianB, if your 'Instant' LSD's were discharging in 3 or 4 days I'd suspect you have something wrong, a corroded switch, some leakage current somewhere, poss a duff charger? ... I'm sure you're aware an LSD should keep its charge for months unless something is drawing current from it. Disregarding mine or any individuals anecdotal experience, Eneloops and Instants have been extensively tested and found to uphold the manufacturers claims... 3 or 4 days indicates a problem IMHO.
Cheers
Phil

Not true, not necessary and highly misleading especially to a beginner.

You could also argue it could make things worse  By using a higher voltage you will increase the maximum current draw from the system and if the cells where struggling to deliver the current on a 4 cell pack they wouldn't stand a chance on 5.

You could also argue it could make things worse  By using a higher voltage you will increase the maximum current draw from the system and if the cells where struggling to deliver the current on a 4 cell pack they wouldn't stand a chance on 5.

Not to mention the detail that there are many servos which are not rated for 6+ volt operation. The experienced modeller can select the servos; the beginner cannot.

PDR

so 4 cell premade packs it is for you dear sir,get a load tester and a good charger and you should have no issues,but remember if you commit it to the air ,you must be prepared to commit it to the ground !

Phil G

I've no idea what was wrong with the Vapextech packs I had, apart from the fact that they weren't doing what a lot of users on here claimed they ought to be doing.

Dodgy switch?      Nope. Wasn't using a switch harness. I charged them, then plugged my battery meter(s) in to check them periodically.

Dodgy charger?     I doubt it.  I used 3 different chargers specifically to eliminate that possibility. Firstly, a Graupner Ultra Duo Plus 30, second, a Mainlink Systems Delta 6, and third, an X Peak 3 small field type charger.

The fact that the Vapextech packs rapidly discharged over just a few days, and the Eneloop packs I now have do not, would suggest to me the Vapaxtech packs (or at least the packs I had) were of inferior quality.

Not true, not necessary and highly misleading especially to a beginner.

Not really, IF he's using 2.4 (I did mention that) then theres a good chance he will be using new (ish) servos but as others have pointed out it would be wise to check, then 5 cells is a good safety margine to stop the Rx's restarting. Yes ultimately a little more current is taken and therefore the duration is reduced but having made the switch myself from 4 to 5 cells I haven't noticed any difference in duration.

I could argue that the supporters of 4 cells are being misleading by not mentioning potential brownout issues on Rx's including 35MHz PCM systems.

J

John, the idea that 2.4ghz sets need 5 cells is just plain wrong.  Early Spektrum rx had a design flaw that exaggerated the effect of weak electrical systems.  We are talking here of a beginner with a 4 servo plane, not some 12 digi servo monster. 

Phil G

I've no idea what was wrong with the Vapextech packs I had, apart from the fact that they weren't doing what a lot of users on here claimed they ought to be doing.

Dodgy switch?      Nope. Wasn't using a switch harness. I charged them, then plugged my battery meter(s) in to check them periodically.

Dodgy charger?     I doubt it.  I used 3 different chargers specifically to eliminate that possibility. Firstly, a Graupner Ultra Duo Plus 30, second, a Mainlink Systems Delta 6, and third, an X Peak 3 small field type charger.

The fact that the Vapextech packs rapidly discharged over just a few days, and the Eneloop packs I now have do not, would suggest to me the Vapaxtech packs (or at least the packs I had) were of inferior quality.

Just to put all my cards on the table from the start. I actually sell the Vapextech range of battery packs on ebay to subsidise my addiction to moulded gliders!

I discovered Vapextech batteries many years ago and found them to be so good that I started selling them too. I can honestly say that I've personally never had any problems with any that I've used and quite happily use them in my expensive F3F gliders. Sure, out of the thousands that I've sold I do occasionally get a return and generally the problem has been caused by incorrect charging. Sometimes too the problem is just that the battery is faulty however these are very rare occurences. In all cases (provided the customer is reasonable and not abusive) I readily replace the battery and inform the customer how they can charge it correctly in future.

It is odd about your Instants self discharging as they have done. Again I've been using them since they were first launched and again not had any problems with them. I would however never rely on any battery pack being safe to use without charging it just before use. Yes, Instants do have a low self discharge but the main benefit of that is that the pre flight charging will be a lot shorter than if using standard Nimhs. If I was to be honest I'd say that the Instants are actually a more robust battery than the standard Nimhs of capacity 2600mAh which is why I only use them now.

Hope that helps a little.

Dave

Just to put all my cards on the table from the start. I actually sell the Vapextech range of battery packs on ebay

Are you "vapextech" on ebay?

Are you "vapextech" on ebay?

I'm sailplaneworld. I originally started selling moulded gliders (hence the name) but it became just too much hassle so I now just sell batteries which is an easy little mail order business to run from home.

Vapextech are the main UK importer/distributor who I get my packs from. Unfortunately due to mark ups I have to sell at a higher cost however I do try and give as good service as possible to make up for that.

For some unfathomable reason I find myself distressed that someone is unhappy with their Vapex Instants!  The only other possibility I can think of is that maybe they weren't actually flat after a few days - I wonder how were you assessing them as 'flat' Brian?   By discharging via mAH meter or by cell voltage?  Sorry to harp on but its just way, way contrary to all expectations...
Cheers
Phil

For some unfathomable reason I find myself distressed that someone is unhappy with their Vapex Instants!  The only other possibility I can think of is that maybe they weren't actually flat after a few days - I wonder how were you assessing them as 'flat' Brian?   By discharging via mAH meter or by cell voltage?  Sorry to harp on but its just way, way contrary to all expectations...
Cheers
Phil

Me too, top cells. I have a 3 year old Tx pack and having left the Tx on for several days - twice, I cycled and found the capacity to be about 85% of the usual max.

Fitted a new set in the Tx and popped the old fully charged set in a pocket of my flying rucksack a couple of months ago, maybe 3, as a spare.

On reading this thread I gave them a top up peak charge and they had only self discharged 175 mA in that time.

Cycled pack and they still achieved 1950 mA. These cells are rock solid.....

John, the idea that 2.4ghz sets need 5 cells is just plain wrong.  Early Spektrum rx had a design flaw that exaggerated the effect of weak electrical systems.  We are talking here of a beginner with a 4 servo plane, not some 12 digi servo monster. 

I do understand fully the ins and outs of Spektrum and Futaba systems, no matter whether it's a 4 servo trainer or not I personally would still opt for the 5 cell packs IF the servo's were suitable for 5 cell operation to give a little more headroom on the days when it's cold and the pack voltage is a little down etc.

The op is at liberty to make his own choice and in my view neither 4 cell or 5 cell advice is wrong, simply that 5 cell *may* save the day under certain conditions.

J

I can not see what extra headroom a 5 cell pack would give you  . In the cold isn't it the capacity that reduces and not the voltage? In which case it would make no difference.

I actually use 5 cell packs alot but purely for the additional speed and torque but they do discharge quicker but that maybe because I am working my servos quite hard so drawing a higher current. I have though in the past saved a 4 cell model because I could feel the servos slow down, I had just enough time to land it before the pack died. You wouldn't get this on 5 cells as the drop off would be greater.

There are benefits to 5 cells but I don't think they are safer   

I can not see what extra headroom a 5 cell pack would give you  . In the cold isn't it the capacity that reduces and not the voltage? In which case it would make no difference.

OK, consider a switch harness / connectors that aren't quite as good as they should be, add to the scenario a partially discharged pack and throw in a linkage thats binding. Sufficient load could be placed on the system to cause the Rx to restart (Futaba, Spektrum and the others, any Rx that has processing on board). Go to a 5 cell pack and that situation has gone away.

J

OK, consider a switch harness / connectors that aren't quite as good as they should be, add to the scenario a partially discharged pack and throw in a linkage thats binding. Sufficient load could be placed on the system to cause the Rx to restart (Futaba, Spektrum and the others, any Rx that has processing on board). Go to a 5 cell pack and that situation has gone away.

J

I'm not sure that would be the case though, I would like someone with a little more electrical knowledge than me to comment. If using the desribed situation above firstly the model shouldn't be flying but also by using 5 cells and having the servos binding the stall current will be considerably higher putting a higher current on a very poor setup.

The most important thing is to use a switch,cells & wire that is capable of deliverying the current the system requires. Anything above that is an attempt to cover up a poor setup that shouldn't be flying and is just a likely to have problems on 5 cells as it would on 4.

The other thing I have just thought of is you must be more careful not to have any binding on any servos on 5 cells as it is far more likely to burn a servo out. This with the expected shorter life of servos on 5 cells really negates any other benefits that I'm yet to be convinced of 

As I said I do use 5 cells but I did on 35 mhz but purly for the power and speed gains for 3D but I accept I am working my servos harder and therfore I should not be surprised if I suffer shorter life.

buy new packs every year,they are so cheap compared to a model ... I buy new packs every year.

I recommend nicads,...  We have been using that method for 35 years or more ...

New packs every year?   I still use my original 40 year old 500mah DEAC nicd cells, not for flying but in domestic radios etc, they hold their charge very well and still deliver close to full capacity. Ditching them annually is just a waste!

I have a horrible suspicion that this has become one of those fashion things. People started to use 5-cell packs to achieve specific objectives and before you know it people believe that anything less than a 5-cell pack is dangerous (which is of course utter rubbish). Once upon a time PCM was introduced, and soon modellers believed that PPM was dangerous (which of course it isn't). Then digital servos came along which give significant advantages in specific applications, but joe public is being led to believe that analogue servos are now unfit for anything - more patent bollox. Then is was 2.4GHz - a good system, but please stop telling everyone that 35MHz suddenly became dangerously unusable 2 years ago.

"Nice" does NOT equal "Essential".

PDR
(who uses 5-volt systems with single-conversion PPM receivers on 35MHz driving analogue servos, mostly with electric powered models that the uninformed buffoon element insist require 2.4GHz to avoid continuous glitching - I've sent the gear back under warranty many times because it fails to glitch like it's supposed to...)

I'm not sure that would be the case though, I would like someone with a little more electrical knowledge than me to comment. If using the desribed situation above firstly the model shouldn't be flying but also by using 5 cells and having the servos binding the stall current will be considerably higher putting a higher current on a very poor setup.

The most important thing is to use a switch,cells & wire that is capable of deliverying the current the system requires. Anything above that is an attempt to cover up a poor setup that shouldn't be flying and is just a likely to have problems on 5 cells as it would on 4.

No problem, you fly how you like, I'll install what I know works, no problem.

I have no hesitation in recommending 5 cells for the exact reasons stated, it does give a little extra safety margin.

J

I have no hesitation in recommending 5 cells for the exact reasons stated, it does give a little extra safety margin.

So does using a correctly sized, (mAh rating), 4 cell pack

The only reason I can see for using a 5 cell pack, is to allow for voltage drop over very long extension leads.


Mark

Hi again BB-Q

As already mentioned, never use loose cells in a model aircraft installation.

Below in the first pic is a pack of Sanyo Eneloop cells, which are currently some of the better rechargeable AA size cells on the market. As you will see, the pack is assembled at manufacture with the cells welded together. They cannot and will not move or rotate under all normal operating conditions. Although I use mainly 2 x 5 cell (6volt) packs in many of my models, a 4 cell 4.8volt pack is ample for most smaller models.

The second photo shows two safety switch harnesses. These gadgets operate in exactly the same way as a "normal" switch harness, but do not allow the current from the main battery to the receiver and servos to pass through the on/off switch. This completely eliminates the switch contacts as a possible source of problems.

If you need any more help, just ask.

Brian
where did you get these safety switches from please
Regards
Styk

I have no hesitation in recommending 5 cells for the exact reasons stated, it does give a little extra safety margin.

I stated how I fly because I draw higher current loads than some others which causes the quicker discharge on 5 cells. I have no problem with using 5 cells for increased speed and power of servos but the user must understand they will reduce the number of flights they get if they use the same mha cells as a 4 cell pack.

The extra headroom and saftey you speak of is as far as I can tell is a myth. I have some basic understanding of electronics but if I had been talking out of my backside I'm sure PDR or someone else would have pointed this out to me. If you had a system where the current loads did not increase on 5 cells I would agree that 5 cells was safer but we don't. The stall and work current will increase and this as a result gives no advantage when using poor cells that are not up to the current requirments. These same cells are no good on a 4 cell pack but will hold there voltage better as you will be drawing less current from them. By telling people that using 5 cells gives them extra headroom could give them false confidence in system that is not up to the requirments.

If you have ever used high capacity fully charged AA Nihm cells on just five high current servos and watched the voltage drop when you just waggle the sticks it is shocking. If just using an onboard checker it will go from full green to bottom red or off off the scale, this is worse on 5 cells I have done it and bined the pack in question as it could not deliver the current required. It dropped below 4 volts and this was on the ground but a PCM RX. The quality of cell choice is far more important than the number of cells. I had been sold this pack by a reputable shop as well up to running the servos I had also bought from them so I can understand how people can get into trouble when trusting the Carp they are told by some shops and not testing the equipment. It is these same people that are telling us 5 cells must be safer 

Styk

The safety switches in my earlier pic are standard Multiplex stock items. Several types are available. May I refer you to Punkies website? I see no reason why they couldn't be adapted for use with other makes of radio.

Punctilio Modelspot Online! A real model shop! - radio control model aircraft, radio control model boats

Click on the white Multiplex banner below the main heading, then look for the RC Accessories tag.  

P.S. PDR, I have also yet to see a single glitch on my IPD equipped Ripmax e*ectr*c Spitfire. Mega motor, Jeti 40amp, 8 nimh cells. I wonder what's wrong with it?

Thanks a lot Brian Most appreciated
Regards
Styk

P.S. PDR, I have also yet to see a single glitch on my IPD equipped Ripmax e*ectr*c Spitfire. Mega motor, Jeti 40amp, 8 nimh cells. I wonder what's wrong with it?

I guess it must the the NiMH cells. As everyone knows, electric models CAN'T FLY unless they have lipos...

PDR

But I don't own any LiPos.

So that explains everything. I must have totally imagined the last 50 or so flights.