Which Battery.

[David Barker 2]

Hi, I'm new to this hobby, and would like to know if there is a preferred battery type to power receiver and plane control surfaces. Don't know which is best Lipo or Nimh. My model is a ugly stik with a sc .61 2 stroke engine. Thanks Dave B.

[Engine Doctor]

Hello David. Use the kiss principle (keep it simple st___d) and use NiMh .They are simple to maintain ,don't need special chargers, wont burst into flames if abused and inexpensive. Make sure to use good quality packs with ample capacity but avoid the AA cells claiming very high capacity. 2200 may is typically as high as I would go with AA cells.

If you have the room then sub "c"cells would be good .

JMO. This will no doubt start a heated debate about which batteries to use but to get you going NiMh is easiest option.

Edited By Engine Doctor on 22/06/2016 10:12:24

[Peter Beeney]

Yes indeed, although this is hopefully not that heated, ED…

With the greatest respect we’ve long been advocating the use of LiFe receiver packs due to what what we see as their big advantages, namely ease of charging, also very little maintenance required, greater voltage limit excursion tolerance as compared to Lipo; considerably better specific energy values than nickel cells; this simply means you get more energy out for a given unit weight. Also I believe there is little or no evidence to suggest that LiFe cells will spontaneously burst into flames; and extremely easy to fast charge into the bargain! So far they have a good longevity record too, it seems in general they have a long working life.

Having meddled with many batteries due to their foibles over the years, I do think is is possible to sometimes get in a tangle with nickel cells, particularly NiMhs; often when they’ve lain dormant for a while. They do need some care, I know for a certain fact this has resulted in a splintered model on at least two occasions.

So with this in mind a very important accessory, in my view bordering on mandatory, is the on-board voltage monitor, again a certain sure definite model saver on at least two more occasions.

Hope this is of some help.

PB

[Masher]

I have also started migrating to LiFe from NiMh and am very pleased with them. I have yet to find a disadvantage but the advantages are listed by Peter. I had a few issues with NiMh including the charger detecting false peaks and terminating - this isn't necessarily picked up by an on-board voltage monitor.

Only thing to watch is that your receiver and servos are happy working from 6.6volts which is the output from a 2s LiFe battery. (This is also true if using a 5 cell NiMh)

[iqon]

here goes - ive started taking life out. stick to nimh, get a 6v over the 4.8v.

[MattyB]

Personally I prefer LiFe to NiMH - they are more resilient in the long term in terms of cycle life and storage charge, especially at the smaller capacity end of things. I have still had one of my cheap HK LiFe packs swell up when left fully charged which they aren't supposed to do.

The other disadvantages of LiFe are that some servos cannot take the extra 0.6V at full charge (Futaba digitals and MKS are among them), and the flat discharge curve means measuring capacity left is much harder; in general you are better off speccing a higher capacity battery (1.5-2x the max you think you will need) then measuring the mah you put back in after each of the first few flying sessions. With LiFe telemetry alarms don't really help much I'm afraid!

Edited By MattyB on 22/06/2016 11:59:58

[IanN]

Posted by iqon on 22/06/2016 11:51:19:

here goes - ive started taking life out. stick to nimh, get a 6v over the 4.8v.

I moved to LiFe a while back and prefer them by far- though use of OBVM is imo, as Peter suggests pretty essential

Interested in why you're going back to NiMH?

[Denis Watkins]

David, make sure that your flight electronics, Rx and servos have the ability to use 6v, otherwise 4.8v is safe on any flight array.

[Former Member]

[This posting has been removed]

[Bob Cotsford]

LiFe all the way for me, they retain their charge better than any form of Ni cell and I've yet to use a servo that can't handle them. I'd avoid LiPo because fo teh need for a regulator and having to remove them from the model to charge them.

I lied - I have some HS645MGs that don't like fully charged LiFe 2S packs, here I just used a 6v regulator between switch and receiver as you would with LiPo but with LiFe I leave them in the model permanently.

[Peter Beeney]

Matty,

Are you saying that these servos are playing up even though the specification is for (nominal) 6V use? Or should that be 4.8V? I’d have thought that if a 2S LiFe causes problems then a 5 cell NiMh might also do the same, when fully charged the voltage is slightly higher then the LiFe.

With regard to the monitor, as I reported in a thread long ago, these things are pretty good. It’s easy and cheap to very accurately monitor voltage nowadays. I forget the actual figures I recorded when I did some checking, but I paralleled 4 together and by using a variable bench supply and a high spec. voltmeter I identified when each led was illuminated. They were slightly out of step at the top end, but that’s of little consequence as it happens, I’m not that interested when the pack is full, but at about the half way mark they got in sync. and stayed there. All the red leds lit simultaneously, and as an extra the last led was very bright, almost dazzling close up. I agree, the discharge curve is very flat, but nevertheless it does progressively descend and the monitor faithfully follows it, if only in millivolt increments. Just a quick glance at the end of each flight and I know the exact state of the pack. One little trait to observe is that the the pack quickly loses it’s very top fully charged voltage but then settles down.

Back then these were Hextronik, now they are TowerPro, but still essentially the same unit I would think. They look exactly the same.

When I started flying everything used 500mAh Nickel Cadmium packs because that’s all that was available; or sometimes Deacs, the blue button cells; later I always made my own packs, UniRoss triple A, (for lightness), 800mAh size. Joined together with heavyish solid wire to make the pack really secure, with silver loaded solder for lowest resistance, they performed faultlessly for many years. I could have a long session and quite often the monitor would not even fall off the top led. So with that in mind I now tend to use 700mAh or 1000mAh packs.

In the end really I guess it’s all just horses for courses so to speak, the system is flexible enough to cater for most tastes anyway…

PB

[Masher]

As part of the change to LiFe, I have started monitoring current consumption of a typical flight (out of interest more than anything)

For a 57" IC MX2 with 5 standard analogue servos, FrySky X8R Rx (which has telemetry so also Tx's) running off a 2s LiFe for 12 minutes consumes about 75mA for 'non-relaxed' aerobatic style flying.

I like to use 2100mA packs because I'm greedy so should be Ok for over 20 flights on one charge

[MattyB]

Posted by Peter Beeney on 22/06/2016 13:41:01:

Matty,

Are you saying that these servos are playing up even though the specification is for (nominal) 6V use? Or should that be 4.8V? I’d have thought that if a 2S LiFe causes problems then a 5 cell NiMh might also do the same, when fully charged the voltage is slightly higher then the LiFe.

All I am saying is that some manufacturers are very clear in their manuals for certain servos - they say you should not use more than 6V or the warranty will be voided. Futaba 3150/3155s for example are not even rated for 6V use. MKS even make tiny linear per servo regulators to allow you to use a Li chemistry battery of >6V.

Edited By MattyB on 22/06/2016 15:03:28

[iqon]

Posted by IanN on 22/06/2016 12:15:18:

Posted by iqon on 22/06/2016 11:51:19:

here goes - ive started taking life out. stick to nimh, get a 6v over the 4.8v.

I moved to LiFe a while back and prefer them by far- though use of OBVM is imo, as Peter suggests pretty essential

Interested in why you're going back to NiMH?

had one swell up, was on ignition.

[gangster]

As already pointed out use the correct voltage as recommended by your radio manufacturer. There seems to be a blanket trend these days by a lot of people to think that if your radio manufacturer recommends 4.8 to automatically think that 6volts must be better as already pointed out 6v will destroy some servos. Destroyed servos destroy models.

I am however wary of very high capacity cells in little packages. ie AA cells of over 2AH I am open to debate on this one but am not convinced that bigger is better in this respect . I am not convinced that a high capacity

nimh can cope with high peak current demands. It is possibly that which had triggered the 6 volt bandwaggon . Fuel has been added to that debate by some 2.4 receivers disliking sudden volt drops

Back in the day we used 500mA hr nicads and happily flew all

day.

must admit I do lament the passing of the nicad . Give me a 600 nicad over a 2100 nimh any day. I have finally sadly retired my last Nicd rx pack

[The Wright Stuff]

Posted by gangster on 22/06/2016 17:05:14:

must admit I do lament the passing of the nicad . Give me a 600 nicad over a 2100 nimh any day. I have finally sadly retired my last Nicd rx pack

I'm with you on this one, but... dare I say it? Dare I say it?

There's a chance to get NiCads back tomorrow!

There. Said it!

[Running away to hide!]

[Bob Cotsford]

Posted by gangster on 22/06/2016 17:05:14:

Back in the day we used 500mA hr nicads and happily flew all

day.

must admit I do lament the passing of the nicad . Give me a 600 nicad over a 2100 nimh any day. I have finally sadly retired my last Nicd rx pack

'back in the day' we were only using 4 Futaba FD16s or 128s on 95% of models!

[Mike Blandford]

I would go for slightly lower capacity, but using cells capable of high current. I madeup a 4-cell pack of 25 Amp rated AA cells (from Component Shop) I use for the radio/servo supply in my Black Horse Mosquito. This handles 2 aileron servos, 2 flap servos, elevator and rudder servos and 2 retract servos.

They are not low discharge, so do need to be charged properly before going flying, but easily handle large currents.

The specific cells I have are not listed anymore, but there are some others with the same rating: **LINK**

Mike.

[gangster]

'back in the day' we were only using 4 Futaba FD16s or 128s on 95% of models!

not sure how much has changed there although I can accept that the% might be lower because so more of the everyday hacks are electric with BEC ! Oh and don't use a Futaba 128 on 6 volts

[Don Fry]

A very very complicated pontificate to a fairly simple task. As a beginner, you will forget to switch the model off, which will destroy a Lipo or Life battery. Put a good brand 1200 Nimh, 4 or 5 cell, and you will be good. And will survive a memory lapse.

50 years in, many planes destroyed.

[ChrisB]

Been using Nimhs for years. Check them regularly and use a load tester and all will be well. 6V and Sub c if possible, but i'm also using 2200 AA 4 cell packs in models up to 120 size and 60"

[Denis Watkins]

A consideration for longevity of cells is their internal construction. AA is a nominal accepted size that we all use. To fit the electrolytes within a standard ce has always been a challenge for chemists. The best that they could do at one time was 500mah, then 800mah and now we have 2200mah as almost standard. But, guess what? they rol up the electrolyte to fit it within the AA cell, and how thick, or should be say how thin does the 2200 neen to be to fit where an 800 did before?

You are right, the 2200mah electrolyte is half as thin as the 800mah, or should be say that the 800mah is twice as thick as the 2200mah.

This is one of the reasons eaqually useful regular packs of 1000mah usually last twice as long

I use 300mah through a flying day and others I have seen use up to 400mah from a 4.8v Rx pack. Make up your own minds which suits

[Peter Beeney]

Thanks for that, Matty, I have to admit I’ve never had any dealings with those servos but I would consider that anyone who does choose to use them will get the message ok from the instructions first. I’m guessing these are designed for some sort of specialist purpose? For general modellers most of the standard types of servos seem to be labelled both 4.8 and 6 volts and I suspect will run happily on either 5 cell NiMh or 2S LiFe. Surely it’s quite a simple matter just to check the spec? I used 5 cells for many years and I’ve never had any problems with servos; or at least any voltage clash type of issues anyway.

It’s possible to still buy nicads ok, up until recently even our local Maplins had them on the shelf. But after a complete store rearrangement a while back they seemed to have disappeared so maybe that’s now finished. But there are other sources, although you’d have to glue them together yourself. And I also liked the nicad compared to the NiMh, too, but I think it’s highly unlikely I’ll ever be going back there…

The monitor can be quite useful when used a crude testing tool as well. It is after all just an expanded scale volt meter that’s sensitive and reasonably fast acting. Wait until the pack has started to become a little discharged and then rattle the sicks about; if the leds run up and down the scale in sympathy that could well be a sign that trouble is starting to brew. It might be the case that there could be a higher resistance point somewhere else, but in my experience it’s invariably the battery pack; and cells going high resistance is generally how they fail. This might well be worth investigating if it happens in normal usage, too, which it can, but my packs in good condition never budged from the one led that was lit. Same with the LiFe packs.

I’d also agree about the ‘only 4 servos’ angle but even back then there was some large models flying. Meaning that the servo had some heavier loads so slightly more drain on the battery perhaps. I flew a PFM Zlin for a long time, from memory late seventies early eighties, and there was no readily available means of checking the battery, either. The first such device I remember was the Skyleader Bat Stat, so at least it was a start. The reason I became interested in the battery mysteries in the first instance back in those ancient days was because there were a couple of mysterious crashes, (no change there, then!), which caused some puzzlement until I checked the power supplies which were flat on the ground along with the models, and the respective pilots insisted that they’d fully charged, which I’m also sure was perfectly true. I’ve been copping the occasional faulty pack ever since, fortunately before they manage to create a spot of disaster!

Going back to the OP, then, I’d settle, as with others, for a LiFe receiver pack, but would also hang a monitor on it for total peace of mind.

Two points to note, the switch can be a trifle misleading, it needs to be fully up for LiFe; and even when the battery is right in the red there are still some mAh’s left, so a margin of safety!

PB

[MattyB]

Posted by Peter Beeney on 23/06/2016 16:28:50:

Thanks for that, Matty, I have to admit I’ve never had any dealings with those servos but I would consider that anyone who does choose to use them will get the message ok from the instructions first. I’m guessing these are designed for some sort of specialist purpose? For general modellers most of the standard types of servos seem to be labelled both 4.8 and 6 volts and I suspect will run happily on either 5 cell NiMh or 2S LiFe. Surely it’s quite a simple matter just to check the spec? I used 5 cells for many years and I’ve never had any

If by specialist purpose you mean gliders and large models, then yes, I suppose so. But frankly many modellers are branching out from the Futaba 148s and HS-300s of old; just look how popular the 20-30cc size is these days, and almost all of their buyers are using decent digitals in them; as was noted by an earlier poster some of the Hitec servos like the HS645MG don't like >6V either, and nor do many of the extremely cheap 9-15g digitals available from HK et al. All I am suggesting is that you cannot just assume your servo will work on 6V any more - you have read the instructions before you plug a LiFe in, otherwise you may blow them up or (more likely) reduce their useful life.

Posted by Peter Beeney on 23/06/2016 16:28:50:

Two points to note, the switch can be a trifle misleading, it needs to be fully up for LiFe; and even when the battery is right in the red there are still some mAh’s left, so a margin of safety!

Surely you are not espousing running down LiFes to low levels? Their flat discharge curve means they tend to drop off a cliff at the low end, so doing so is much more dangerous for the health of your model than with NiMHs. Personally I always size LiFe RX packs to be double my maximum expected daily use, that way I know from a full charge no checking on the day is needed.

[Former Member]

[This posting has been removed]