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Average current draw

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John Wagg09/11/2019 17:18:39
60 forum posts
10 photos

I have a battery charger/discharger.

Does anyone have an idea of what would be be be an average current draw for a receiver battery. I have a couple of batteries that I want to test but can only set a constant current draw.

At the moment I have set 200 mA but is this enough to give a representative of battery life time ?

Frank Skilbeck09/11/2019 17:38:41
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4664 forum posts
101 photos

Your receiver will be less than that, but it's the servos that consume the power as they are doing the work, average current will depend on the servos and how much work they are doing. A 1/4 scale glider will use less mah than a 1/4 scale 3D aerobatic model (if flown properly wink)

SIMON CRAGG09/11/2019 18:24:21
552 forum posts
5 photos

I did some experiments on the subject prior to changing to Life rx packs.

Not at all scientific but a 10 minute flight=

Vintage 3 channel = 80ma

Low wing aerobatic = 120ma

Basic 3D = 150ma

Full house / flaps / retracts = Max 200ma

All run on 1100mah Life packs.

Hope this helps.

John Wagg09/11/2019 18:37:55
60 forum posts
10 photos

Thanks guys. Yes I meant including servos.

So my 200 mA would seem to be reasonable test. ?

Getting abut 2 hours for each. One is an old 500mA Ni-Cad and the other a poorly 800mA Ni-mH.

Cheers.

Simon Chaddock09/11/2019 18:54:49
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5672 forum posts
3011 photos

John

Just remember that whilst the average current draw may be measured in ma the servo peak current can be more than 10 times as much.

Small batteries suffer voltage drop more than big ones. Receivers tend to be more voltage sensitive than servos and the loss of a receiver for just a second (not all recover than fast!) at the wrong time can be serious.

John Wagg09/11/2019 19:07:15
60 forum posts
10 photos

Noted Simon, Thanks.

The Ni-Cad is from about 1994 and the Ni-mH is fairly new but got cooked on a fast charge, Might use the Ni-mH but not the Ni-cad.

Currently (pun intended blush) the Ni-cad does over 2 hours but not done a full test on the Ni-mH yet.

Cheers

Phil Green09/11/2019 19:09:00
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1576 forum posts
318 photos
Posted by Simon Chaddock on 09/11/2019 18:54:49:

John

Just remember that whilst the average current draw may be measured in ma the servo peak current can be more than 10 times as much.

Small batteries suffer voltage drop more than big ones. Receivers tend to be more voltage sensitive than servos and the loss of a receiver for just a second (not all recover than fast!) at the wrong time can be serious.

At situation best resolved by a low ESR pack, not by adding another equally poor cell in series
Cheers
Phil
www.4cells-are-enough.com

SIMON CRAGG09/11/2019 19:40:38
552 forum posts
5 photos
Posted by John Wagg on 09/11/2019 19:07:15:

Noted Simon, Thanks.

The Ni-Cad is from about 1994 and the Ni-mH is fairly new but got cooked on a fast charge, Might use the Ni-mH but not the Ni-cad.

Currently (pun intended blush) the Ni-cad does over 2 hours but not done a full test on the Ni-mH yet.

Cheers

John, I would seriously have a look at Life packs. There are lots of good videos etc. available. I ditched all my NIMH packs years ago, and have never looked back. There is a load of rubbish talked about them, but as an average club level flyer, I would not use anything else!.

John Wagg09/11/2019 20:04:35
60 forum posts
10 photos

Simon, I'm not sure about Life packs as to being able to trickle charge or fast charge properly.

With the NimH's I can trickle charge with some impunity and get reasonable safety margins for flying.

Always open to new ideas and education though.

Just returning to RC and I am more used to ni-cads as being the staple source back in the 70s,80s & 90s.

Steve J09/11/2019 20:38:01
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1819 forum posts
51 photos

Posted by Phil Green on 09/11/2019 19:09:00:

www.4cells-are-enough.com

+1

John Wagg09/11/2019 20:42:30
60 forum posts
10 photos
Posted by Steve J on 09/11/2019 20:38:01:

Posted by Phil Green on 09/11/2019 19:09:00:

www.4cells-are-enough.com

+1

Sorry but no "link" and done a search as well.

Thanks.

Steve J09/11/2019 20:43:38
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1819 forum posts
51 photos
Posted by John Wagg on 09/11/2019 18:37:55:

One is an old 500mA Ni-Cad and the other a poorly 800mA Ni-mH.

Take your packs down the recycling centre.

Buy a couple of 4 cell Eneloop 2000 packs or 2 cell LiFePO4 packs (the latter only if the rest of your gear will handle 7V).

If you don't already have one, buy a decent charger that will peak charge NiMH's and understands LiPo and LiFePO4 batteries.

Steve J09/11/2019 20:45:27
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1819 forum posts
51 photos
Posted by John Wagg on 09/11/2019 20:42:30:
Posted by Steve J on 09/11/2019 20:38:01:

Posted by Phil Green on 09/11/2019 19:09:00:

www.4cells-are-enough.com

+1

Sorry but no "link" and done a search as well.

www.4cells-are-enough.com is a joke.

Gary Manuel09/11/2019 21:02:09
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2253 forum posts
1548 photos
Posted by Steve J on 09/11/2019 20:45:27:
Posted by John Wagg on 09/11/2019 20:42:30:
Posted by Steve J on 09/11/2019 20:38:01:

Posted by Phil Green on 09/11/2019 19:09:00:

www.4cells-are-enough.com

+1

Sorry but no "link" and done a search as well.

www.4cells-are-enough.com is a joke.

You're not kidding. Low on stock and outrageous prices.

John Wagg09/11/2019 21:05:45
60 forum posts
10 photos
Posted by Steve J on 09/11/2019 20:45:27:
Posted by John Wagg on 09/11/2019 20:42:30:
Posted by Steve J on 09/11/2019 20:38:01:

Posted by Phil Green on 09/11/2019 19:09:00:

www.4cells-are-enough.com

+1

Sorry but no "link" and done a search as well.

www.4cells-are-enough.com is a joke.

About the number I have left working LoL.

https://www.rcgroups.com/forums/showthread.php?2863122-A123-LiFe-performance-as-Receiver-Battery-Packs

Just reading through the above post and not convinced yet. Seems a bit over-complicated just for a couple of hours flying. My usual max' flying time would be a couple of hours slope soaring or I.C. power flying at the field.

Martin Harris10/11/2019 00:24:55
avatar
9257 forum posts
245 photos
Posted by John Wagg on 09/11/2019 19:07:15:

Noted Simon, Thanks.

The Ni-Cad is from about 1994 and the Ni-mH is fairly new but got cooked on a fast charge, Might use the Ni-mH but not the Ni-cad.

Currently (pun intended blush) the Ni-cad does over 2 hours but not done a full test on the Ni-mH yet.

Cheers

1994 NiCd giving in excess of 4/5 of its rated capacity? Bring back (good quality) NiCds...

I'd be happier using that battery (after a black wire corrosion check) than a new budget NiMH although I favour LiFe where my servos allow them.

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