Rx Lipo - Futaba

[David Drew]

Hi all,

I'm looking for a 3s lipo to into my Futaba 7C 2.4ghz.

I have had a look at the UK internet shops but the only one I can find is from HK.

I may want some more lipos anyway so HobbyKing may be my best option, but meanwhile if I can get one in the UK quickly that would be better.

Any ideas?

[cjcj1949]

Is there a special size that you need? You might find a pack made from the new Nimhs ( Sanyo eneloop for instance) that hold their charge as long as lipos a better option. Lipos are usually too high in volts and will invalidate your guarantee. I think their safe in our country especially in the Winter, as do lots of others. A LiFe pack will have a lower voltage like the one below
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Chris

[David Drew]

It' has to be the same size as, or smaller than, a 4 + 4 cell NiMh pack.

My two Tx packs are nearing the end of their life & I was talking to a flyer yesterday who uses a 3s in his Spektrum with no problems.

I hear what you say about the voltage - I have to say that that does worry me.

[Andy from Sandy]

I don't know how the low voltage alarm works but if it is just looking for 8.8 volts then if the alarm ever went off and you were using Li-Pos they would for all purposes be useless.

If you don't want to use Sanyo eneloops then possibly look at the Li-Fe as already stated the voltage will be better matched. The only problem with those cells is they give the same voltage out until they are flat and then basically stop outputting so you have to waatch how long the tx has been on for.

[wayne123]

What you need is the LRP VTEC Tx lipo packs, I have had one in my spectrum DX7 and my JR DSX9 for over 12 months now and I have had no problems with them at all, in fact you will me surprised how long you can use your TX before it needs a charge, mine are 3s 2700mAh packs but I see you can get 3000's now, have a google for LRP VTEC lipos.

[SRH990]

I've been using a 2600mAh 3S lipo in my Futaba 10CG since I bought it, well over a year ago. As it's got 3 timers I rest the master timer after charging the battery and after 9hrs of use the battery is still only just under 50% discharged and putting a 12.6V pack in has never caused a problem. As it's a lipo topping up the charge isn't a problem so I tend to charge when the pack hits around 11V or so.

If the higher voltage is a concern then the Enerloop or equivalent nimhs are a good bet as they also have high capacity and a very low self discharge rate.

[David Drew]

Hi Steve,

You missed a great day Sunday. Weather was perfect

I have an Eneloop Rx pack and whilst it keeps it's charge longer than a normal NiMh it has also started to drop voltage quickly in use. Getting tired I think.

I want to go lipo if I can. I have some spre 3s so I might try soldering on some thin Futaba leads to the main output cables.

It's dark....nothing else to do.................on the other hand,........... Hi Honey

[Mark_T]

I have an Eneloop Rx pack and whilst it keeps it's charge longer than a normal NiMh it has also started to drop voltage quickly in use. Getting tired I think.

Not sure if we are talking at cross purposes since you mentioned RX in the title then asked about a TX pack, but if you really are using Eneloops in an RX pack then I'm not surprised if it isn't standing up to this very well.

The Eneloops are well suited to TX use where the current drain is low and slow, they will not work well in an RX pack where the current drain is much higher.

[David Drew]

Not sure if we are talking at cross purposes since you mentioned RX in the title then asked about a TX pack, but if you really are using Eneloops in an RX pack then I'm not surprised if it isn't standing up to this very well.

The Eneloops are well suited to TX use where the current drain is low and slow, they will not work well in an RX pack where the current drain is much higher.

Mark,

What I meant was that I use an Enelop in an RX pack & have my doubts (before the cold weather) about using an equivalent in a Tx.

Think I'll try both a lipo & an Eneloop

Thanks

[Mark_T]

What I meant was that I use an Enelop in an RX pack & have my doubts (before the cold weather) about using an equivalent in a Tx.

Got it.

Personally I wouldn't use the Eneloops in the RX pack, no AA cell is great at handling high current drain and these are less suited than 'normal' NiMH.

So I wouldn't extrapolate from their performance in an RX pack and worry about a TX pack.

A LiPo on the other hand as you know is very well suited to high current drain and less suited to remaining full or close to full for long periods of time so makes a great flight pack and a less great TX pack

[David Drew]

I think the biggest issue with Nimh & NiCd is memory effect. I know NiMh are supposed to be better but topping them up, unless really discharged, still causes a loss of discharge / capacity eventually. I suspect that is what has happened to my Rx pack

Why are batts never simple????

[Mark_T]

I think the biggest issue with Nimh & NiCd is memory effect. I know NiMh are supposed to be better but topping them up, unless really discharged, still causes a loss of discharge / capacity eventually. I suspect that is what has happened to my Rx pack

The fix for the 'voltage suppression' problem is the same in NiMH as it is in NiCad, just an occasional deep discharge cycle.

Public safety warning that I know is not needed for the vast majority of people - Do *not* try this with a LiPo !!

I agree though that nothing is simple when it comes to batteries.

[SRH990]

I think the biggest issue with Nimh & NiCd is memory effect. I know NiMh are supposed to be better but topping them up, unless really discharged, still causes a loss of discharge / capacity eventually. I suspect that is what has happened to my Rx pack

Why are batts never simple????

If you have a charger that will cycle nimhs then carry out a couple of discharge - charge cycles, this will tell you the packs actual usable capacity, if necessary then carry out a few more cycles which, as Mark_T says, could well wake them up a bit, although the sub-zero temperatures aren't helping any battery chemistry out at the moment.

It was my son's & grandson's christening on Sunday so couldn't make it, believe me, I'd rather have been with you in the cold

[Andy from Sandy]

After checking around all rechargeable batteries benefit from trickle charging. This allows all the cells to equalise similar to the balancing of Li-Pos. Using fastish charging methods on Ni-Mh batteries results in the cells getting out of balance. It is beneficial to slowly charge these cells over many hours. The memory effect can be reversed but it can several days on a very low charge rate.

A feature of the CellPro PL8 is to go into trickle charge mode after the charger detects the Ni-XX or Pb battery is charged.

[David Drew]

If you have a charger that will cycle nimhs then carry out a couple of discharge - charge cycles, this will tell you the packs actual usable capacity, if necessary then carry out a few more cycles which, as Mark_T says, could well wake them up a bit, although the sub-zero temperatures aren't helping any battery chemistry out at the moment.

It was my son's & grandson's christening on Sunday so couldn't make it, believe me, I'd rather have been with you in the cold

I think I'll have a go at reviving the packs, but I still like the idea of a lipo. Something to talk about next Sunday

Cold????? It was sweltering at 2 deg C and very sunny. Shades deployed. Lee was on fire with his 3D. A fabulous day's flying