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Is LiFe passing me by?

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Andy Green16/05/2013 13:21:00
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2279 forum posts
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Had a flying mate come round the other day, and commented that all my Rx flight packs are NiMh.

He uses LiFe for all flight packs, but he couldn't offer any real reason why.

I tried to argue that my 2600mha sub C pack was better than his 800mah Life, but de couldn't get it. SO maybe its me

So am I missing out on something here, are they safer / longer lasting / more robust?

I am a bit anal with my flight packs, and after a flying session any packs do get a full discharge / charge cycle, and I either have an onboard battery monitor or telemetry to keep an eye on my cells during the day.

Andy

Olly P16/05/2013 13:30:42
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3215 forum posts
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Just different thats all. NiMh are fine, as are LiFe - I certainly wouldn't replace them just for the sake of it.

When I am looking for new batteries anyway in future products I will consider LiFe, along with LiPo and NiMH, depending on what I need at the time.

NigelH16/05/2013 14:38:04
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I'm considering this at the moment. I just don't know if I can feel comfortable about my Hitec 5485HBs and 85MGs seeing 7.2 volts. I know that NiMHs also put out more than 6 volts but I've read that they settle down quickly once a load has been applied.

Nev Haycox16/05/2013 14:39:02
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327 forum posts
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Hi Andy,

I have one LiFe battery to my name. I bought it with the intention of using it in my electric powered Zlin instead of a SBEC, however, the worry of the 7.2 volts it generates put me off as all my servos are rated at 6 volts max.

I would be interested to know the thoughts of people in the know as to whether this is ok or not.

Nev.

Edited By Racing Snake on 16/05/2013 14:39:49

simon burch16/05/2013 14:57:32
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Li-fe packs don't hold that 7.2 for very long. They drop down to their working voltage of 6.6volts pretty much soon after you wiggle the sticks. Only thing you need to be careful of is they will hold that voltage pretty stable until the point where they will just drop off. Battery testers are pretty useless, so it's a case of having a few flights, charging them back up and seeing how much you've used.

One of the great things is the ability to charge them very quickly. Most of my Ni-Mh have gone bad over the winter, so like my heli's my planks now have Li-Fe packs to replace them (they are also quite cheap!!). Another nice thing is that quite a few come with twin leads so you can have a bit of redundancy in the system.

I used to have voltage regulators and all sorts in my heli's, all points of potential failure. These have all gone now, its just a case of plugging in the Li-Fe direct. Not had any problems with servos, even ones rated at 6v (which most of mine are).

Personally, I would put the question back, what are the benefits of staying with Ni-Mh ?? I don't charge my planks in advance anymore, I just top up the Li-Fe pack at the field.

Regards,

Simon

NigelH16/05/2013 15:17:00
891 forum posts
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Could you charge a pack fully and then discharge it down to 6.6 volts with a bulbor something ? Would that be a reliable way of knowing that you're not exceeding that voltage ?

NigelH16/05/2013 15:22:19
891 forum posts
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Posted by simon burch on 16/05/2013 14:57:32:

Another nice thing is that quite a few come with twin leads so you can have a bit of redundancy in the system.

Which ones available over here come with twin leads ? I've not seen any myself.

I've seen one today rated at 3000mAh, discharge at 60A but with the connector described as only 3A. Without another lead, the discharge rating seems irrelevant.

Roger Bird16/05/2013 15:22:55
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93 forum posts
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Not sure if this the right thread and I'm probably the last person in the world to know.

I have just purchased some lithium batteries, as far as I am aware the pro's and cons are as follows :-

The batteries are AA/AAA size.

They are 1.5 volt.

They are advertised as lasting 15 times longer than a conventional battery.

They cost £4 - 39 for a pack of four.

They weigh 65 g per pack of 4, as opposed to 110 g for 4 x NIMH.

They are single use only, not rechargable. I assume they must be disposed of in an appropriate manner.

I have no affiliation with the manufacturer or supplier. I obtained mine from this link but I'm sure there are many others.

Bob Cotsford16/05/2013 15:26:13
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8261 forum posts
454 photos

I've been running 2S LiFe packs unregulated for a couple of years on Futaba, JR, Hitec, E-Max, Corona, TowerPro and a few no-name brand servos without burning out a single one. These are in models from .40 powered 5lb'ers to 1.20 powered 10lb'ers.

I use the soft cell packs and find them smaller and lighter than Nixx packs, they don't self-discharge to any degree so I'm happy using smaller capacity packs (1100 is favourite at the moment), they fast charge (up to 5C even on cheap packs) and I'm happy charging them in the models (unlike LiPo).

As my NiMh packs expire I just replace them with LiFe.

I do seem to be writing-off a few NiMH packs this spring. They all show a lack of capacity over a 5 cycle test. Must be because of the long winter and neglecting the maintenance charges. My LiFes are ok thoughsmiley

Biggles' Elder Brother - Moderator16/05/2013 16:02:57
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15748 forum posts
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Andy,

  1. does your existing kit work?
  2. are you dissatisfied with what they do in some way?

If you answered "yes" to question 1 and "no" to question 2 - then whats the problem?

BEB

Andy Green16/05/2013 16:40:38
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2279 forum posts
67 photos
2 articles

Hi BEB

Yep existing NiMH work fine and satified. There is no problem, just wondered if there was something I was missing.

I've just bought one for my Extawot to see what they are all about

A

John Hickson16/05/2013 17:13:45
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222 forum posts
1 photos

I connect up all my servos to a servo tester set to automatic, add some "ballast" to the control surfaces to simulate flight loads and time it. That way all I have to guesstimate is what my RX's will draw when working - easy enough to measure with a meter in series.

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