Topic: Battery Questions

Having just watched a friend's Irvine trainer do a 200ft nose dive due to dodgy Nicads (engine was about 5" into the ground), I was wondering what the general consensus is for Rx/servo battery packs?

I noticed when I ordered my servos that they had ratings for both 4.8v & 6v, so would it be more prudent to use a 6v battery pack to get a little bit more life/warning when things go wrong?

What level of power does a 4ch standard servo setup require?

How long should one get from a battery pack? Is there a voltage regulator available that would allow the use of Lipo's, or are they overkill in this situation?

Why isn't there a parachute back up as is now being fitted to some light aircraft (I'm actually serious about that bit too!)?

Sorry for so many questions, but being a newbie I really don't want to see such a violent and swift end to my first plane. I accept I'll have crashes, but the one I just witnessed detroyed everything up to and including the wings!

"dodgy" nicads will still be dodgy if you use a 5 cell pack.  Actually the nicad is imo still the best battery by far but like all things the quality varies enormously.  The only one I will let in my models is Sanyo brand, and from a reputable source so thay are welded/soldered properly together.  I also refuse to use cheap switches as these can cause you trouble.

For your purposes a 4 cell, 4.8V battery is fine.  A 6V battery just weighs more, takes up more space, and will actually flatten faster for the same capacity because the higher voltage pushes more current out of it.  So you have to fit a higher capacity or accept shorter usage time if you fit a 5 cell 6v battery.  

Was the nicad dodgy?  It is amazing how many people won't charge them and then complain when the model crashes!  I have seen it time after time!  I have seen someone crash and blame the nicad which he was going to take back to the shop and demand they refund the cost of the model.  He told me he had charged it up 4 weeks beforehand and only used it a bit in the workshop to set up the radio.  Incredible but true, and he was a very experienced modeller.  They must be charged shortly before use (batteries that is, not experienced modellers though I begin to wonder...).  A beginner turned up with his trainer for its first flight, I checked it over and whilst range testing it, the radio went off.  I asked how much he had charged it, oh this morning, 2 hours!  Never mind the radio manual that said charge 14 hours.  I reinforced the point.  A few weeks later while flying him on the buddy box the model stopped responding and disappeared over the horizon.  Guess what, he had charged it that morning for 2 hours.  Some people refuse to listen or to learn!  Then there was the experienced modeller whose model crashed, yet again, it was becoming almost a weekly habit and on trawling the wreckage another flier spotted that he plugged the switch harness into the rx the wrong way so that when he thought it was off, it was on and by the time he got to the airfield the radio had been on for a few hours flattening the battery.  He lost several models to "dodgy batteries" before that error was spotted.  So, it's not always the nicad that is "dodgy"!

lipos and regulator would be overkill at the moment!

parachute back up would require it's own power system since it couldn't rely on the flat nicad to release it, the normal size model simply doesn't have the space or payload to carry all the extra gubbins.

A good quality 4.8V nicad of around 800mah and a decent switch, properly charged, occasionally discharge cycled, is amazingly reliable year after year and will give you an afternoon's flying of a trainer.

Hi mark most trainers will be quite happy with a 4.8 volt battery and a 2000 Mh capacity will be fine for a good 6 or 7 10 minute or so flights . If i recal there is a parachute failsafe that is available but that only works when you lose the signal not when the rx battery goes flat . The thing to do is keep a check on the rx battery before it goes flat ! Hope that helps a little ? Mickey

Hi mark most trainers will be quite happy with a 4.8 volt battery and a 2000 Mh capacity will be fine for a good 6 or 7 10 minute or so flights .

It certainly will, and some more.  I get that much flying from 6V 2200mah on an 11 servo jet model with some digital servos!

I used to fly a whole day session (probably 20 5-10 minute flights) with a 60-powered Wot4 that had a single 4-cell 500mAh nicad - you don't need anything like 2000mAh unless it's a Carp cell-type. And that's the point - decent cells cost three times the price of crappy ones, but have less than 1% of the whole-life cost.

They must be charged shortly before use (batteries that is, not experienced modellers though I begin to wonder...). 

There's a choice. Either the modeller charges the batteries before use, or the model trade charges the modeller after use. It's a binary solution set.

PDR

Ok, so do I get some branded batteries and stick them in a Maplins case or buy from a model shop?

If buying from the model shop what brands should I look for?

I'd rather go for the former as I already have a household charger

Get a purpose-made battery pack - something like this.  Using loose cells in a Maplins (or any) battery case is just asking for trouble.

Get them from a model shop pre-soldered into a pack , as Mpx and pdr said sanyo cells are blinding ! When you get your tx if you go for spectrum you will have to buy a charger as it dont come with one . If you buy a wall charger  normally the tx and rx are charged off the same charger as it has two out puts one tx and one rx . But these only trickle charge and do not cycle the batteries . Other wise you will have to buy a cycler charger these are far more expensive but well worth it ! Any good model shop will be able to advise you . Mickey

Get a purpose-made battery pack - something like this.  Using loose cells in a Maplins (or any) battery case is just asking for trouble.

Loose? Loose? Have you never heard of insulting tape?!

Ok, so do I get some branded batteries and stick them in a Maplins case or buy from a model shop?

If buying from the model shop what brands should I look for?

I'd rather go for the former as I already have a household charger

NO NO NO and once again NO.

Do not use loose cells in your airborne packs this is asking for trouble as the contacts in the holder WILL eventually fail with the reult seen by your pal!

What MPX says is spot on (he usually is by the way though he was wrong once however that was because he thought he was wrong but was actually correct )

Sure you will pay more buying premade packs especially Sanyo, buy good quality (i.e. JR,FUTABA branded) switches and extention leads and you will SAVE in the long run.

BUY cheap buy twice! or even several times, is your model only worth batteries that cost £2 from £saver? to say nothing of the safety of those around you when the inevitable happens.

BB-Q

You wrap insulating tape around loose cells, and use them in a model aircraft?    And may I ask what is the "case" you're putting them in please?

Oh dear. We still have some way to go here I feel.

PLEASE DO NOT USE LOOSE CELLS.
You can get good quality packs from Vapextech at a reasonable cost. The ones you want are the Instants. They are the green ones in this link: Vapextech Batteries
They, unlike normal Nicads and NiMh ones, have a very slow self discharge and are 2100mah.



  Tom

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.

Eneloop and Instants are the same chemistry, both come ready charged and have a slow self discharge.


  Tom


   

Hi Tom

The Vapextech cells I had weren't anything like as good as the Eneloop packs I now have Tom. Without exception, all the packs I bought (7 packs) seemed to flatten themselves after 4 days or so. No amount of cycling on the Mainlink changed this. I gave them all away.

In complete contrast, the Sanyo Eneloops I now have stay charged for much longer.

Hi Tom

The Vapextech cells I had weren't anything like as good as the Eneloop packs I now have Tom. Without exception, all the packs I bought (7 packs) seemed to flatten themselves after 4 days or so. No amount of cycling on the Mainlink changed this. I gave them all away.

In complete contrast, the Sanyo Eneloops I now have stay charged for much longer.

Were they the green instants? I even have some of the standard orange ones that hold a reasonable charge for weeks.

   Tom

Hi Tom

They were definately the green packs. I bought 3 or 4 packs all in one go a while back purely on recommendation from the forum. However, they turned out to be no better than the cells they were replacing. I won't buy anymore, or recommend them to anyone.

I'm now 3 months or so into Eneloop usage, and so far they're holding up brilliantly.  

So, loose cells is a no-no then?

Thanks for the advice.

One things that strikes me as odd, though (I'm probably missing something here- I'm a newbie, remember?). If the battery packs discharge themselves over time then does it really matter if they do it in four days or four months? Surely you're going to charge them before use?

Or is there a battery conditioner (like I have for car batteries) that will condition them and ensure they remain topped up?

Hi BB-Q,

I don't know if you are a member of the BMFA yet but i think in the hand book there is something about "loose cells" being used in the model to power it, and that it will invalidate your insurance. If that is the case then saving £10 now could cost you thousands later if the insurance company doesn't pay out.

Sorry to bring such a downer on it, its just if they shake loose or the plastic tabs break off the end (happend to me in a model car) then you will not have any control and it might go in to a house or someones car.

I'm not the sort of person to be picky, enjoy the hobby and keep asking questions. A question on here will save you a trip to the field when you want to start flying. All the people (that i have found) on here are good and are willing to help new members.

Gareth

Sorry you posted before me, you can ignore this post if you wish

BB-Q, either go to a model shop in person or on line such as Inwood Models The Home Of Radio Control Modelling and buy a 4.8V nicad with a label from JR or Futaba or Multiplex or Spektrum, these are usually Sanyo.  A 500mAh to 800mAh is plenty. At any website or shop do not be tempted by the cheaper cells or any cells with labels such as “Super Mega Lightning Bolt King Kong Godzilla Turbo Power”.  I recommend nicads, not nimh and you must not be tempted to buy very high capacity nimh AA cells thinking it is better – they are poor at delivering power.

Just stick to a properly made pack of 500-800mAh Sanyo nicad, or same with a brand label as mentioned above and all will be hunky dory.  We have been using that method for 35 years or more and we know it works very very well.  Don't be distracted by anything else. As a beginner with no experience this is not a time for you to be experimenting!

BB-Q, either go to a model shop in person or on line such as Inwood Models The Home Of Radio Control Modelling and buy a 4.8V nicad with a label from JR or Futaba or Multiplex or Spektrum,

Have Futaba changed the supplier? They used to be unmarked packs that were Carp.

I second the comment about going Sanyo, I walways try too. They tend to come out at a higher capacity than quoted and hold up very well over time. I would also recomend getting a peak charger as the additional functionality of knowing how many mha you are putting back into a pack can be a good indication of the condition of that pack. These wall chargers just because the light is on does not mean the pack is accepting a charge.

One things that strikes me as odd, though (I'm probably missing something here- I'm a newbie, remember?). If the battery packs discharge themselves over time then does it really matter if they do it in four days or four months? Surely you're going to charge them before use?

A very astute point that many people in this hobby seem to miss. Get in the habit of charging all your batteries not earlier than the night before you fly, and you won't go far wrong, whatever the battery type.

I've used the vapex packs you were linked to earlier, and i can't fault them at all- who cares if they're low-self-discharge or not, they're a good price for a decent capacity, decent quality pack.

Or is there a battery conditioner (like I have for car batteries) that will condition them and ensure they remain topped up?

Most modern computer chargers will have NiCd/NiMH cycler programs, which condition cells. Not really necessary to do it too often though. A good cheapo-chinese computer charger would be a good investment if you're serious about this hobby. Something like this would be good (although that model doesn't actually have a cycle program iirc. but i'd still get it anyway).

Trouble is Harry, ni-cad packs are now a little harder to get hold of. I was down at Overlander just a couple of weeks back, and noticed stocks of ni-cads in the main storeroom were no longer abundant.

In fact Overlander are now marketing some nicad packs on a "get them while you still can" basis.

Ni-Cads are no longer supposed to be stocked and or sold for the purpose of modeling.

There was a big thing about 3 months back in the BMFA Mag about this.

Gareth

Have Futaba changed the supplier? They used to be unmarked packs that were Carp.

Genuine Futaba packs are OK. The Carp unmarked ones were Ripmax substitutes. I think Ripmax have stopped doing this now.


   Tom

That's what I'd heard too Gareth.

BB-Q,

I know in one of your other threads you are talking about getting a radio, if you get a Spectrum radio (as a bundle) you will get a charger and a flight pack with it. This will cover the transmitter, charging and will give you a good flight pack for your first model.

Gareth

Genuine Futaba packs are OK. The Carp unmarked ones were Ripmax substitutes. I think Ripmax have stopped doing this now.


   Tom

Ripmax used to use what they were told to, the unmarked cells were genuine Futaba packs. I know it took Ripmax years of hasseling Futaba for the battery cases for the 9ZAP so they could supply packs of better quality because they used to get so many complaints. They still were not allowed to supply the cases on there own. For a long time they were only allowed to sell the sealed units with Futabas cells 

Genuine Futaba packs are OK. The Carp unmarked ones were Ripmax substitutes. I think Ripmax have stopped doing this now.

Indeed, the link I supplied back in reply #6 was the Ripmax pack with Sanyo cells.

And as previously mentioned by Brian and Gareth, NiCds are on the way out.  Existing stocks can be sold but once they've gone there will be no more.

Ah yes, poor old nicad RIP.  I guess we will have to look for high quality alternatives, perhaps eneloops or Vapex instants when we can no longer get a suitable nicad.  Inwood Models The Home Of Radio Control Modelling is still listing JR 1100mah nicads and Sanwa 600mah nicads, and sussex model centre still had a very few when I last looked.

at the moment a lipo and regulator seems overkill on technology, cost, and lots of bits to fail, for a standard model.

I don't know if you are a member of the BMFA yet but i think in the hand book there is something about "loose cells" being used in the model to power it, and that it will invalidate your insurance.

But not after the July corrections to your BMFA handbook?

The modifications to the handbook say "It is strongly recommended .......They must never be used in the airborne pack if you have four or more servos operating.


   Tom

The modifications to the handbook say "It is strongly recommended .......They must never be used in the airborne pack if you have four or more servos operating.

That's to do with dry cells  and presumably their voltage drop under high current.
We're discussing rechargeables    

That's to do with dry cells  and presumably their voltage drop under high current.
We're discussing rechargeables    

I think the relevant bit is the existing paragraph in the batteries section;

(f) When fitting Nickel Cadmium (Ni-Cd) or Nickel
Metal Hydride (Ni-Mh) rechargeable batteries to
equipment designed and sold to take dry batteries,
always ensure that the cells are soldered or welded
into packs and that the packs are either hard wired
or wired through a plug and socket into your
transmitter and receiver systems. NEVER rely on
the spring type battery contacts in battery boxes.

Notice the final sentence - and the word in bold, upper case (that's not my emphasis,  it's as it appears in the handbook.)
 

always charge you batterys the night before/overnight on a decent charger,by new packs every year,they are so cheap compared to a model,
I use vapextech packs and have no issues,I buy new packs every year.
I use 2s2p lipos and a regulator in my bigger petrol models but that is because they have large high power servos and a large current draw.
on a trainer you will be fine with a nice new 4 cell pack and a decent cahrger,for piece of mind also buy a battery checker,the type that puts a load on the battery and check before each flight.
if a battery goes so will your plane !,at best it will smash to bits,at worst it will kill someone

rotaxman

Buying new packs every year will not ensure battery reliability! You could, in theory, be replacing a perfectly good pack with a dud using this method.

What you really need to know is just how good are your packs after a year? To do this you'd need to cycle charge your packs on a fairly regular basis. You'll soon spot a dud this way. Otherwise you're just shooting in the dark, and probably throwing perfectly servicable packs away.

fair comment,but a new pack correctly charged is my favourite flavour,and they are so cheap these days

But that's my point. You could be buying a new pack with a defective cell in it. Why replace what's performing perfectly well?

You can "correctly" charge a pack with a dicky cell until your a$$ heals up, but it'll never be any good. How much charge goes into a battery isn't in the least bit important. It's how much charge the battery retains once its in there!

I think the relevant bit is the existing paragraph in the batteries section;

(f) When fitting Nickel Cadmium (Ni-Cd) or Nickel
Metal Hydride (Ni-Mh) rechargeable batteries to
equipment designed and sold to take dry batteries,
always ensure that the cells are soldered or welded
into packs and that the packs are either hard wired
or wired through a plug and socket into your
transmitter and receiver systems. NEVER rely on
the spring type battery contacts in battery boxes.

Notice the final sentence - and the word in bold, upper case (that's not my emphasis,  it's as it appears in the handbook.)
 

Am I the only person who has the July 2009 corrections and amendments to the 2007 handbook? 
There's a new section (g) that begins " There are however exceptions to this advice..."

No doubt the Spektrum DX6i is what they are thinking of, and sensible advice is given. Its battery case has quite good contacts, but that's unusual, and normally the use of individual cells is asking for trouble.

Am I the only person who has the July 2009 corrections and amendments to the 2007 handbook? 

No you're not the only one with the corrections and additions - though I do wish they'd just issue a new handbook rather than multiple sets of corrections and additions of which this claims to be the third.

There's a new section (g) that begins " There are however exceptions to this advice..."

The exception they mention refer to transmitters.  The original post was asking about receiver batteries for which I feel the advice in section f) is still valid.

No doubt the Spektrum DX6i is what they are thinking of, and sensible advice is given. Its battery case has quite good contacts, but that's unusual, and normally the use of individual cells is asking for trouble.

Indeed.