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what type of battery pack for i/c engine trainer

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Richard Elvin 101/12/2019 22:34:01
11 forum posts

I was recently given a well worn i/c engined trainer aircraft minus battery pack and engine, which I am currently restoring over the Winter months. I now have an OS Max 46 to go in it, but I have no idea what type of battery system to put into it to power the receiver and 5 servo's. Any help in this matter would would be appreciated,

Richard.

Martin Harris01/12/2019 23:03:54
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8968 forum posts
221 photos

If the servos are rated for 6v then I would use a 2S LiFe battery through a series silicon diode. If you must use a 4 cell NiMH then go for an Eneloop type.

Old Geezer01/12/2019 23:29:18
640 forum posts

I tend to follow the KISS principle - in other words, avoid the LiFe batteries & diodes for now, so get a 4s 2000 Eneloop Rx battery - if there's a switch harness already fitted in the airframe, take it out and replace it! Contacts corrode, wires & insulation crack etc.etc.. Whilst you're in a buying frame of mind, an Rx battery checker - which will tell you whether the Rx battery voltage under load is adequate, and use it before each and every flight.

cymaz02/12/2019 06:12:00
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8817 forum posts
1195 photos

New switch, something like this

4a097d2f-fc65-430d-9623-0fecdfc43107.jpeg

And a new 4.8 or 6v eneloop depending on the servo. With any airframe , these two essential items that must perform faultlessly

David Davis02/12/2019 06:50:56
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3472 forum posts
622 photos

+1 for a 4.8v Eneloop if using Futaba equipment, that's four cells,or 6v, five cells, if using a Spektrum radio. 1600-2000 maH should do fine.

Where did you get that switch from Cymaz?

Edited By David Davis on 02/12/2019 06:52:21

bert baker02/12/2019 07:06:17
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1491 forum posts
305 photos

And the most important bit will be the correct type of battery checker.

Don’t use a lipo tester

Get a dedicated Nimh tester one that will load test the battery pack

I favour the Fusion one

Nigel R02/12/2019 09:38:42
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3176 forum posts
487 photos

change the switch, a rotten switch means complete radio failure with inevitable result

battery pack, either nimh 4 cell eneloop low discharge

**LINK**

or the vapex low discharge nimh 4 cell

**LINK**

or a 6.6V life type pack

**LINK**

find out what servos you have first - some will not like the higher voltage of a life battery

a nimh pack needs a nimh charger, a life pack needs a life charger.

many chargers can do both - if you have something capable of charging big lipos they will often have a nimh option.

Peter Beeney02/12/2019 14:39:53
1568 forum posts
59 photos

My choice would be a simple 2 cell LiFe, usually 700 or 1000 milliamp hour size; and not forgetting the mandatory (for me, anyway) on board Rx battery voltage checker to go with it.These two should be joined at the hip. Personally I think this is a superb piece of safety kit, not only is it very accurate when performing it’s main function of faithfully following the battery voltage, i.e. down among the reds where you really need it but also by default it might also give you first indications of other possible model traps too. If everything is in apple pie order when you constantly stir the sticks, on the ground of course, the second led should stay firmly lit. It’ll be the second led because a LiFe quickly falls a snifter from it’s fully charged voltage; and then just stays there. If the leds run up and down a bit then that may need a quick look, if it keeps hitting the red, as one did that I saw recently, then definitely dive in. That one was the battery plug, but the model was still flying perfectly. Also not forgetting to check the unit itself as well in the event of a mystery, a lesson learnt early in a working life a long time ago.

Just for interest, again way back in the days of Futaba M kit, I was tasked with with finding a trainer that could be used constantly all day long. At first I thought that the receiver battery, a 4 cell 500mAh nicad, the one and only standard in those days, would fail so I made sure I had spares and they could be changed easily. In the event the Rx pack ran all day without even blinking but the Tx lump only managed about 3 hours. This was 2 4 cell 500mAh packs in series, hard wired in so they couldn’t be changed and no fast charging either back then; so proceedings then came came to a rather frustrating halt. I solved it by drilling a hole in the plastic side, fitting a jack and wiring it so that I could use a 9.6V 2.5Ah Makita drill battery with the requisite wander lead soldered to it and carried in a little pouch on my belt supplied by ‘er indoors. As it happened this actually worked better than I ever expected, I could just pull the plug for any ground work and plug back in when flying. This was the Master Tx for a buddy system and the first sign that the battery was getting low occurred when the model fell into a tight spin when on the buddy box. All the control surfaces went to the end stops. Full control fortunately came back on releasing the button.

Looking back now, was this some result of unexpected consequences, an early form of unintended failsafe perhaps…

Halcyon days…

PB

Edited By Peter Beeney on 02/12/2019 14:41:49

Steve J02/12/2019 15:11:10
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1645 forum posts
49 photos

4 cell Eneloop 2000 or 2 cell LiFe. The latter only if all components are good to 7V (which most will be).

Posted by David Davis on 02/12/2019 06:50:56:

6v, five cells, if using a Spektrum radio.

The great Spektrum brownout myth goes on.

Paul Marsh02/12/2019 18:14:29
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3744 forum posts
1070 photos
:

6v, five cells, if using a Spektrum radio.

The great Spektrum brownout myth goes on.

No, not really, I use 6v on all protocols now, mainly as the servos are more faster (if they are ok to use at 6v) and add a margin of safety.

Normally I use a good 2500mah NiMh low discharge battery on most models,, and 2s Life on large models, or where power is required.

Even Sub C packs, I use 6v where weight is required on the nose, as these are great for high currents, where AAs aren't.

ken anderson.02/12/2019 19:47:50
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8481 forum posts
773 photos

hello Richard and welcome to the forum...loads of replies for you...I would also recommend you go with a 2000 m/amp ...when I started the norm(not much choice) was a 500/600mah NiCad...so the 2000 jobs will be fine..

ken anderson ne..1..nimh dept.

Richard Elvin 102/12/2019 23:13:19
11 forum posts

Well that has given me a lot to get my head round !!yes Thanks to all for your swift replies. Just a bit more info on the plane, I am pretty sure that is at least 10 years old and is currently fitted with 5 Hirec HS-300 servo's and a switch harness. My current Tx is a Spektrum DX6i and a Spektrum AR6200 will be the the Rx of choice. The plane has been sat in an ISO container for a long time so I think for peace of mind I will replace the old servo's, can any one recommend a suitable equivalent to the Hirec's ? Please excuse my ignorance in this matter as I have just returned to the hobby after a small ?? break of 55 years!!. Back in the day I only flew C/L, FAI Team Race, Rat Race, Combat and Stunt, I had never flown an RC plane until this Spring when one of my friends walked into my garage with an elec powered WOT 4 under his arm and said " were going flying!! " I had immense fun over the Summer on a buddy box, the WOT 4 is no more alas ( I didn't crash it, my mentor did!! )

So, basically, what I know about the technical side of RC you could write on the proverbial fag packet, so a vertical learning curve at the moment and I shall spend some time going through all the links provided. Once again thank you all for your replies and I will post some pics of the finished a/c when completed.

Richard.

Martin Harris02/12/2019 23:13:32
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8968 forum posts
221 photos

Just don't go for a cheap and cheerful 2000mAh AA pack - getting that much capacity in a small package can be at the expense of reliability and voltage stability under load.

Keith Miles 203/12/2019 03:21:55
198 forum posts
6 photos

Richard, my four pence worth!

Unless you already have a dedicated Lipo charger, go with Eneloop (i.e. low self discharge) NiMH! These are still readily available with the fairly standard plug fitted for the receiver connection. 4.8v is a pretty common fit unless you are using servos that need 6v. Most receivers that I know of should be fine on 4.8v. Many servos will also operate happily either at 4.8 or 6 volts.

As for battery capacity,and as an example, after 8 exuberant fifteen minute flights from a 46 powered Wot4 with five standard size analogue servos and a 4.8v/1000mah Rx pack I find that I never use more than 50% of the charge and with a remaining healthy voltage!

As Martin suggests, you DON'T, therefore, need 2000mah and, although it is probably not usually an issue in practice the higher internal resistance of higher capacity packs for a given cell size (AA, in this case), reduces maximum current and can cause a relatively greater volt drop under load. That said, I would simply say why fit what you don't need? And, of course, depending on the charger capability, the higher capacity could take a lot longer to charge!

Lipos do have many advantages (and are a virtual MUST for most electric powered models!) greater power relative to weight and much faster charging for example, but If you do wish to use Lipo, in addition to the dedicated Lipo charger you will also need to spend about 8 quid, at least, on a 6v regulator (e.g. Etronix 5A 6V) for the 7.4volt Lipo AND then probably do a little bit of snipping and soldering of wiring in order to connect the regulator between the switch and the receiver.

So, in summary, and not knowing your experience, much depends on your experience, what items you already have and what your future ambitions are!

Oh, and as always, how much money you are willing to spend in the short or long term!

smiley

P.S. Apologies,Richard, if you are already aware but Lipos come with numerous types of connectors so if buying one for powering the receiver/radio gear make sure that it is a receiver battery i.e. one with the correct type of plug on it for connecting to the switch input lead!

P.P.S. Reading through all the other posts again, I can only say that I have used 4.8volt NiMh (and the earlier NiCds) for years without problems, likewise 1000mah capacity. Perfectly adequate for your average 4/5 servo model especially a relatively tame and low performance 50-60 in span trainer.. As for added "safety" and monitoring features, nothing wrong with that, or technological progress, but lack of it has never given me nightmares and I do wonder if some of us over complicate things unnecessarily sometimes! No offence intended!

smiley

 

Edited By Keith Miles 2 on 03/12/2019 03:37:11

Edited By Keith Miles 2 on 03/12/2019 04:06:07

cymaz03/12/2019 04:34:29
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8817 forum posts
1195 photos
Posted by David Davis on 02/12/2019 06:50:56:

+1 for a 4.8v Eneloop if using Futaba equipment, that's four cells,or 6v, five cells, if using a Spektrum radio. 1600-2000 maH should do fine.

Where did you get that switch from Cymaz?

Edited By David Davis on 02/12/2019 06:52:21

Either from Wheelspin Models or Etronix . They’re about £15

David Davis03/12/2019 07:46:10
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3472 forum posts
622 photos
Posted by cymaz on 03/12/2019 04:34:29:
Posted by David Davis on 02/12/2019 06:50:56:

+1 for a 4.8v Eneloop if using Futaba equipment, that's four cells,or 6v, five cells, if using a Spektrum radio. 1600-2000 maH should do fine.

Where did you get that switch from Cymaz?

Edited By David Davis on 02/12/2019 06:52:21

Either from Wheelspin Models or Etronix . They’re about £15

Thanks for the info Cymaz, it'll look great on my Big Guff!

Richard, as for servos, you won't go wrong with Hitec 311s in this model.

Peter Miller03/12/2019 08:45:52
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10331 forum posts
1231 photos
10 articles

Hitec 311s from me too. and a 5 cell Eneloop pack. as most people have said.

Another good investment is an onboard battery checker. It has a row of lights which tell you how the battery is doing. Cheap at about a fiver for two

**LINK**

Edited By Peter Miller on 03/12/2019 08:46:51

Cuban803/12/2019 09:21:41
2810 forum posts
1 photos

Done this to death in other posts, but in any case - yes the little LED voltage indicators are an essential bit of kit to give a heads up to a failing battery, have them on all my models and have shown up dodgy cells on a number of occasions, latest one only a few weeks ago in an underperforming 5 cell Nimh.

On batteries, I have a couple of questions to pose to everyone........can you honestly say what the C rating of your battery pack is? ...................

.........and do you have any idea as to your model's power requirements (for simplicity that'll be max current) in a worse case scenario?

Answer no to any of the above and you're asking for trouble.

Peter Christy03/12/2019 09:24:22
1619 forum posts

1) I've been using Spektrum receivers since they first came out, all running on 4-cells, and have never experienced a "brown-out". Unless the servos are guaranteed up to 7 volts, stick to 4-cells. Receivers are generally safe to higher voltages, its the servos that are the issue.

I recommend the 2000mAH Eneloops. The higher capacity ones (2500mAH) tend to have a higher internal resistance and are more prone to voltage drops under load. If using a lot of powerful servos go for sub-C cells instead of AAs. Vapextec are also available, but I have had a Vapextec cell fail. I have yet to have an Eneloop fail.

LiFes are excellent as long as the servos are guaranteed safe at 7 volts (check manufacturers spec, not word of mouth!).

2) Servos. The ones you have may be fine. Check that they all move at the correct speed (is one or more faster or slower than the rest?) and then check for rough spots. This is done by moving them slowly from one extreme to the other while looking for any sign of jittering. If they run smoothly and at a consistent speed, you should be good to go.

3) Replace the switch harness. Use a good, high quality item. I've always used the JR high power ones, but these are no longer available. Futaba do a similar one. The one suggested by Cymaz looks good, but I have no first-hand experience of it.

If you choose a Futaba or JR lead, do NOT use the ones with a charge socket built into the switch. These are notoriously unreliable. Use the ones with a separate fly-lead for charging.

Follow the above rules, and true happiness will follow! laugh

--

Pete

Nigel R03/12/2019 09:58:41
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3176 forum posts
487 photos

"although it is probably not usually an issue in practice the higher internal resistance of higher capacity packs for a given cell size (AA, in this case)"

I've posted this before I think, but to the best of my knowledge, the internal resistance of a 2000mAh Eneloop is comparable to that of a 600mAh NiCad.

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