Li-po's

[Mouldy]

Thanks for the above!

On further research I found a review on the Flight Power site for the plane I have, happy days! Small quotes shown below although there is some corruption in the txt. Also the motor changes from an S early in the txt to an L further down!:-

" The KatanaS 50e is available in two forms, with or without motor. I chose to have the motor deal, resoning that if the motor was good enough for Sebastiano Silvestri, it was bound to be good enough for me. The motor supplied is the Hacker A50-14S. This is a large outrunner type motor, which is radial mounted, and turns a 16x8 APC electric propeller using a 5s FlightPower EVO 25 Lipo (more on this later). The motor is easy to mount using the supplied pre drilled firewall and the supplied radial mount.

As mentioned previously, the motor used is the Hacker A50-14L. This is a “.60” size replacement, producing approximately 1250watts (a shade under two horsepower). The ESC is a new Hacker X70-SB-Pro, a 70amp esc with a new switching BEC, which provides enough power to power up to 6 standard size servos. This is then combined with a new FlightPower EVO25 5s1p 3700mAh to complete the same FlightPower / Hacker combination that Sebastiano uses in championship competitions.

First flight brought no surprises, with the model tracking well in both slow and fast flight. Nothing too strenuous was done on the first fight, just large smooth aerobatics and some basic 3D. After 12 minutes of varied flying testing the power setup, I called landing. Putting the pack on charge showed that, with 12 minutes of smooth flying, 3200mAh was put back into the pack. This just shows how far electric models have come, ballistic power for 12 minutes, something we could only have dreamed of only a few years ago."

So in the short term at least a couple of 5s1p 3700's will do. Ill pick up a watt meter as you have suggested and then I can play around with prop sizes.

This thread has been extremely useful to me though, please dont feel that Im ignoring your advice! Part of the problem is, (as mentioned before), I hadnt relalised the cost of the batteries! Should of I guess but there you go! 

Im sure Ill have some more questions shortly!!!!!

[Tim Mackey]

Glad you found it useful, and as I said in one of my latter posts, 5S with propping to 50A should be sufficient IF you can keep the weight down...

I notice they did not say what the AUW was, but obviously using a 5S pack will be lighter than a 6S

Both  of these variants are only rated at 40A continuous, so be aware of that when fitting props, again, although they say 16 X 8 I would still meter it to be safe.

Strictly speaking, at 40A with a 5s pack - you will be inputting around 925 watts NOT as stated 1250. To get that the pack will need to be holding 25 V - Impossible with a 5s even a F/P . Therefore I can only imagine that they are quoting short peak bursts at a higher Amperage ( IE full throttle ) somewhere around 68Amps !! The motor is rated ABSOLUTE max of 50 amp....so I reckon that they are quoting the Potential Max Wattage which would need at least a 6S pack, rather than what they actually got with a 5S. % s will give MAXIMUM 18.5V under load, and with the prop set to pull MAXIMUM motor current allowed of 50A this is only 953 Watts...and even then in very short bursts only - max 5 Seconds.

[Mouldy]

All read with interest!

You are right of course to suggest that getting packs to suit an existing charger is ar$e about face! However I have a car to build and have got distracted with a hobby that I left some time ago and have now rekindled!!! Funds need to head more toward the car at the moment, and if I get 6s packs, which as you have pointed out are expensive,(!), Ill need then to spend even more to charge em!! My fault for getting carried away and getting a bigger model!! As and when funds allow Ill move up.

Keeping the wieght down however Ill have to use the BEC option which would appear to support up to 6 servo's according to more research! Earlier though you suggest not to use the BEC. What problems would likely to occur if I use it then?  

[Tim Mackey]

I think in hindsight that the hacker ( top class gear incidentally )will be OK, it is a good quality regulator, whereas some of the lesser ESC BECs use a poorer design of regulator.

One of the main issues with using any sort of BEC - either built into the ESC or standalone, is that when using large voltages from big batteries, the regulator has a LOT of work to do to drop the voltage sufficiently for the radio, this causes overheating and other problems for lesser regulators, and many ESCs will NOT allow useage on more than 3 or 4 cell LiPo packs.

With a built in BEC, this could of course destroy the actual ESC itself, as well as cause complete radio failure ! With expensive and fast /big models, many peeps prefer to use a seperate small battery for the RC....but as you rightly say....this equals more weight

Another option with your batteries which I have deployed in days past, is to use 2 X 3s packs connected with a Y harness to give 6S. These can then be split up for charging as 3S packs, which most chargers are capable of. Of course it means a longer wait between refills....but it is an option.

[Mouldy]

Happy days!

Regarding your last paragraph, 2 X 3s packs are a cheaper option then a 1 x 6s pack. EG FP 6s 3700 pack is £150 where as an FP 3s 2500 pack is £60. So quite a lot more mah for £30 less.

whats the catch? Other then longer to 're-fill'!! 

[Tim Mackey]

Ahh, NO my friend.    2 x 3s 2500 packs in series will still only be 2500ma. Tis the volts which increase in series NOT the capacity.

Your 3700 pack is much bigger capacity 50% bigger in fact. 

[Mouldy]

Doh!! Of course. Already read that somewhere on here, in fact I think it was one of your postings!!

Might have found a good source for FP packs, if everything goes to plan Ill post up the seller!!! Watch this space! 

[Tim Mackey]

I will be very surprised if they are able to discount them, F/P like to keep their premium image and accompanying pricepoint.

I would seriously look at the Dualsky stuff that Als hobbies have - Nathan Farrel Jones swears by 'em and he is not easily pleased with batteries I can tell you ! 

[Mouldy]

decisions decisions!!

There was a little bit of GMD, (good mush discount!), to be had, but not enough to worry about.

Can get a Dualsky 5S at a whopping 6.6A for £180. Tempting! 

[Tim Mackey]

Now that would hold voltage very well, and give good duration - check the weight though - higher capacity ususally means high density and therfore weight.

[Mouldy]

Cant find any details on weight, the Dualsky site only lists packs upto 5A. The 5S 5A pack weighs in at 612g. The FP 5S 3.7A weighs in at 478g

[Tim Mackey]

Hmmm think if the funds will stretch I would choose the F/P.

[Mouldy]

......and the FP 6S 3.7A is 562g.

The Dualsky packs only come in the larger sizes from Al's. At least they are the only ones I can find suitable for the application required.

So FP it is then! Right wheres the nearest bank to rob?

[Tim Mackey]

Remeber your limited to the 5s pack at present 'cos of your charger

PS these are also a good battery, and favour quite well with the FP on price and only a few grams more.

http://www.westlondonmodels.com/product1072/ThunderPower-TP3850-5SXL/

[Myron Beaumont]

Blimey !  & I thought the Welsh language was the only thing foreigners like me couldn't understand ! ????????  

[Mouldy]

ah well,

Im fluent in English, Welsh, Russian, French and with some help from Timbo Li-po too!

[Tim Mackey]

chwerthin

[Mouldy]

Iawn da 'm ddyn!

[Myron Beaumont]

Bonsoir Mouldy    Comment ca va .Timbo parle en LIPO  .Mois je parle Francais et aussi Anglais .Bienvenue ! Je suppose que vous aimez l'aeromodellisme  .Mois non plus .

Ici Myron qu'on appel Grumpy . sur cette site  

[Mouldy]

Je suis sain! Remercier pour demandant! Aussie? pardon Je fais pas comprenons!!

[Tim Mackey]

Bloody show offs

[Mouldy]

OK, kit has arrived!!

 On reading the instructions, (yeah I know that its a girls option but I've been away for a long time and know very little about electric setups!!), recommended battery is 5S 3300 or 5S 3700. The latter for duration and precision and the former for unlimited 3D. I guess this has something to do with the battery weight. So thats the decision made then. Ill go for one of each!

 Recommended props for these packs and the Hacker A50-14S and the X70 SBEC Pro ESC are either 16X8 or 16X10, although as I have been told I will still get a watt meter!

 Apparently the weight is 2.25 RTF although this would not appear to include the battery, so how the hell that can be RTF is a little beyond me!!!

Motor is a beastie!!!

[Mouldy]

More advice needed!

The motor and ESC do not have any connectors. Are 4mm gold bullets able to take the 50 or so Amps? Or do I need to fit something different? 

[Mouldy]

Seemed to have answered my last question, 4mm connectors would appear to have a rating of 80A.

Next question!   I have come across bags for charging Li-Po's in made by Duremax. Good idea? Waste of time? Anyone else use em? 

[Tim Mackey]

Yep 4mm gold caged connectors will be fine.

I did make up a concrete bunker years ago for LiPo charging, but now dont bother with it, as I prettty well always charge 'em under supervision, and if I do a field charge, they sit out on the grass well away from anything /one.

I guess the "Lipo sack" can't be NOT recommended really......especially if you are not very familiar with the procedures.