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Help with info on Lipo batteries

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LYKA23/09/2016 14:10:23
89 forum posts

I am a bit ignorant when it comes to electrical flight,I am stuck in the Stone Age. My question is I want to get the Dynam ME 262 and it recommends a 4 cell 4000 mAh battery to fly it ( I get that because it has 2 motors).I have a load of 4s 3200mAh batteries (25C ) will these be OK to fly it or should I splash out and get some 4s 4000 batteries.( more expense).Failing that is the Dynam Tempest a better bet to go for and save me buying loads of batteries

chris larkins23/09/2016 14:37:03
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212 forum posts
151 photos

The 3200mAh batteries would probably work ok...........but the endurance would probably be just 3 mins or so. Ducted fan models have a high current draw and even with the recommended battery flights of 4-5 mins are the norm, which is why many people fit batteries that are much larger than recommended and accept the weight penalty, in addition fitted to an EDF a 25C battery would only give average performance at full throttle and a battery with a higher 'C' rating would give better performance.

As to the model it all depends how much you want the ME262, if you don't want to buy new batteries stick to the Tempest, if you really want the ME262 get some new batteries with a 4000-5000 mAh capacity and a rating of at least 30C

Edited By chris larkins on 23/09/2016 14:37:26

gangster23/09/2016 14:48:04
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1030 forum posts
29 photos

I agree with Chris there. I am not familiar with the model but believe it is capable of drawing well over 100 amps with the set up it has. 3200 batteries would give a very short flight at the best of times and it's compounded by the fact that 25c rating would be woefully inadequate and the power would drop off rapidly. 30 c minimum for 4000 and 30c for 4000. Lovely looking model though Must admit I am going off electric flight due to the variety of batteries needed if you choose a range of models. Seems the same gallon of glow fuel work for a 20 to 120 and beyond

Simon Chaddock23/09/2016 15:39:13
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5716 forum posts
3034 photos

LYKA

Just to help a bit

Lets say the Me 262 tries to draw 100A at full power.

For a 3200mAh (3.2 Ah) battery that would be drawing 100/3.2 = 31.25C. In other words it would be discharging at a higher rate than the 25C that battery was intended to provide and this of course assumes the battery manufacturer claims are realistic in the first place!

In practise the maximum current a LiPo can deliver is limited by how hot it gets doing it. LiPo do not like getting too hot.

The heat generated comes from an internal voltage drop so at 100A your battery would not be delivering its nominal 14.8V but perhaps 12V or even less so at full throttle the actual power will be significantly lower than might be expected..

It follows that the end result of using a smaller & lower C rated battery than is recommended is not only shorter flight times and less power but also a much shortened battery life.wink 2

Edited By Simon Chaddock on 23/09/2016 15:39:40

Cuban823/09/2016 17:42:07
2959 forum posts
1 photos

Dynam website quotes 4S 14.8V 5000mAh 60C LiPo. Seems a tad more realistic given the X2 70mm fans in the model. My Durafly Vampire which has a 70mm fan, draws around 40A at full wallop, but thankfully only requires WOT for takeoff - about half to two thirds after that. I run a 3000 4S 30C which only gets moderately warm after a five minute flight, so I'd guess that the current is in the region of 20-30A

Personally, I'm surprised they went with a 4S setup in the 262............6S would have been much more efficient.

 

 

Edited By Cuban8 on 23/09/2016 17:52:55

Ian10123/09/2016 18:44:18
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226 forum posts
323 photos

My lad has one. It has only had 3 flights so far but looks fantastic in the air and nice to fly. It is not too scale with its bigger wing tips, but makes it a lot less prone to tip stalling. I think the Freewing version is more scale, looks better but more money and more tip-stally! Anyway, he runs 4s 4500mah 45-90C Nano Tech batteries. 4 minutes max (need to be on the ground really at 4 mins) flying in a scale like manner.

We also changed the retracts because Dynam retracts are the most useless things on the planet!

malcolm woodcock 115/06/2017 16:44:14
403 forum posts

Don't know if this is the right place for my query but the other day I was using a HobbyKing Eco Six AC/DC charger to charge a 2200 mAh 3S1P battery and I had a fire in the balance board. It wasn't even in the 3S part of the board it was in the 4S socket which I wasn't using. Now I keep getting 'Battery error' message come up even though I'm using a different balance board. Has anybody else had this happen to them and is there a 'cure' for the charger or is bin material?

Denis Watkins15/06/2017 17:44:20
4449 forum posts
113 photos

Malcolm, this comment is not to do with the make of the charger, but applies to any make of charger.

Battery error, can refer to the supply

So if you charge from a external battery connected to your charger, then this supply could be low.

Check the supply, and the supply leads, and check for internal fuse on the circuit diagram or instructions, as an AC/DC charger is fused, and this blown fuse would affect the supply, then try again

If this fails, then replace the charger, as they are not expensive

Edited By Denis Watkins on 15/06/2017 17:47:42

malcolm woodcock 115/06/2017 22:08:43
403 forum posts

Many thanks Denis, I think it must be a internal fuse as I was on AC power at the time.

Nigel R16/06/2017 08:18:47
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3916 forum posts
678 photos

" and I had a fire in the balance board."

So under normal use, the charger caught fire?

" is there a 'cure' for the charger"

Depends on what caused the fire. It is almost certainly not worth repairing IMO.

Personally, I would recommend a different brand.

All I will say is, it's one thing for a cheap motor or ESC to burn out in the air and take out a model, another thing for a mains supplied charger to overbake your lipos and set your garage on fire.

malcolm woodcock 116/06/2017 08:45:52
403 forum posts

Thanks for your reply Nigel. The charger didn't catch fire, it's the kind that has a plug in balance board and I was charging a 3S1P but it was under the 5S socket that the fire started not the charger at all but it managed to make the charger defunct. Didn't know if this has ever happened to anybody else.

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