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Arising Star Power Issue


Simon UK
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Simon I would persevere with the A123's for a while. They do turn out very cost effective in the long run. We fly many 40 sized models on 6S A123's. 

Try adding a cell. This will of course increase current and power available. But that will not necessarily reduce flight times. This is because you will cruise at a slightly lower throttle setting.

If 6S is successful but 1P gives too short a flight time, then do try 6S2P. This setup will hold voltage better at the expense of weight (and of course cost).

I've not read every post above, But I think you mentioned that you are keeping the cells balanced?  The other things these cells seem to thrive on, is the fastest charge you can possibly manage (up to 10A that is).

Make sure all your wiring is nice and fat, and that no connectors are getting warm at all. (A sure sign of a poor connection). 

Good luck and have fun
Chris
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Argh! Chris - lol now you have put the spanner back in the works (so to speak). I must admit i was really upset at my failure with the a123's, i will aquire another cell and see what difference it makes.
 
When you say connectors are you refering to my Deans plugs? or the connectors between the cells - which i am pretty sure do get hot! 
 
Yes i was ballance charging my pack - due mainly to my charger being capable of only 5 amp charging (which drops the more cells in the pack). I was planning on getting a more suitable chargewr though if i could get the A123's to function for me.
 
Main problem i have with the A123's now is not in fitting them in as 2 packs but in removing them for charging purposes, i am aware that i can charge them in situ, but i do not know how to wire them to have a seperate charging plug - any help here?
 
Cheers
Simon
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Sorry Simon...

Any wiring or connections really shouldn't be getting hot. 
A slightly warming battery its self is OK, but any hots spots are signs of electrical resistance. Which are wasting power, a possible point of failure and can be potentially dangerous.

I tend to charge in situ without balancing. After say 10 charges I will take them out to balance. But that is with a pack I am very confident is balanced well. I never balance if I
charge at the flying field.

Chris


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Just another thought Simon, although I'm not sure how much you want to spend experimenting?  

If you are expecting to go down the 2P route, how about trying 5S2P and raising the prop size a little to cause more power to be drawn?  
You'll need to check if the motor will take more current.
Going up to 2P will raise the full throttle voltage too, as each pack will then only be delivering half the amps. (see the graph posted earlier)
 
Just another idea..
Chris
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Have a monster under carriage from my Red Zephyr, think i will try it on the Star and see what my prop clearance is like.
 
I think the 2P route is the only way to go with the a123's, i would like 10 minute flights (or as close as pos) and i can't see me achieving that 1P.
 
What ever i do Chris the battery pack has to be able to be used with my Cub aswell as the Star. I think i will take the pack apart and add a cell first before i do anything else. If nothing else it will give me a chance to clean up some of my wiring.
 
In an ideal world i would like to use A123's exclusively in .40 and larger planes, i do not mind Lipo's in my small park flyers but cost will get excessive in large models depending on how many recharges i get from a pack.
 
Thanks again for the help
Simon
 
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  • 1 month later...
Just a bit of an update on the Arising Star
 
I tried my new 6s1p A123 pack on Saturday, i set my timer for a conservative 4:30 minutes and took off. Great news as the plane could fly on 1/3rd throttle and when i landed after time was up, the pack only took 730 mah to re-fill to capacity. Yipee! I have now set my Timer for 8 minutes and i should have plenty of juice in the battery pack for extra go around if needed.
 
Thanks for the advice guys
 
 
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Blimey it depends what you mean by cheapish?
 
Make sure you work out the power required to charge 6S at 10A. Some chargers rated at 10A only manage it at low cell counts. It's something over 200W. Obviuously make sure 
 
There's quite a range at hobbyking that fit the bill.
I know Timbo has tested at least a couple of theirs. 
 
I'm just looking to buy one at the moment. I'm looking at an iCharger 208B as it does 20A, 350W and 8S liPo and 10S A123. They have lower cost less powerful ones in the same range too.
 
You seem to have to chose power/cell count etc etc against price.  so you should be able to find something that fits your particular bill. 
 
Many UK outlets have chargers that are LiFe capable these days too. 
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I dont normally endorse particular products - recommending is one thing, suggesting that an item is perfectly suited to the job in hand is another. I did a review of the older version of the iCharger 1010B unit a couple years back, and although it performed admirably at first, serious firmware issues have caused me to be less enthusiastic lately. I also have the 208B and this too has suffered with problems. The main concern is the complete lack of UK supplier ( unless things have changed in the last few months ) and therefore any problems necessitate returning the unit to China - something which I have now done 4 times in all between the two units. They are now both performing correctly, and are very capable chargers....... but I cant honestly recommend them just yet.
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Hmmm not ideal then Timbo, i have a Turnigy accucel 6 at the moment but it cap's out at about 3 amps for 6 A123 cells. Which leaves me not taking advantage of the batteries as you are well aware.
 
As i am not asking for an endorsement :P but some advice is there a Hoby King or Giant Cod charger you would buy yourself (if limited cash was in the equation).
 
I have no problem plodding away at 45-50 minute recharges until i get a new one, so if there is an all singing all dancing must have charger i could save for a wee while and plump for that if it was highly recommended.
 
Cheers
Simon
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Having just been browsing Robs site ( Giant Cod ) earlier today, I notice that he is now stocking the IC chargers !
In that case, I might perhaps suggest you try the new 208B, as at least then if there are issues, returns / refunds will be whole lot easier.
This is the only charger I know of that comes even close to proper high power capacity at a sensible price.
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Simon, how electrically/electronically confident are you?
 
I built a few chargers, and the one I still use all the time is set up purely for 6S and starts a charge at 10A dropping to about 9A for most of it.
 
However it does no balancing.
It is a slightly modified Laptop PSU 
 
NOTE: I would only consider this if you really knew what you were taking on.
There are dangerous currents around and these units are fairly easy to destroy.
That would of course waste some of that precious cash.
And it's best to use a wattmeter with it which could be more expense if you don't have one. (Which of course you should if yr doing electric flight )
 
Of couse if anyone tried this, I cannot be held responsible and you would take full responsibility....
  
 
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OK I've had a play.
It seems I was an early adopter of some of this technology, before it all worked properly. Now we seem to be in the generation where it is all sorted. That makes it just plain useful, instead of frustrating. 
 
208B 
The instructions are good, but on a CD. I might print these out.
Interesting features are:-
Brushed motor supply for running in..   not sure I'll use that.
Foam cutting supply for a hot wire.. maybe??
Measure battery and cell internal resistance.  Should be useful to watch the change in batteries over time.
 
In charger mode, it all seems very straightforward, following the same menu structure as most charger seen these days.
I particularly like how easy it is to change lithium battery types, say from LiPo to LiFe, that was quite convoluted in previous chargers.
 
One issue with previous chargers was when charging high voltage (high series cell count) batteries was that to boost the voltage, very high currents had to be drawn. This is a law of physics, but can now be mitigated with this one, by using two supply batteries in series thus reducing supply current. In fact it will take a supply voltage up to 32V. (It's a shame that isn't 3x12V...)
 
Having a charge capability of 20A I now have to decide what I want to set for A123's. Up to now, everything has just been set to flat out!
 
Other battery types look just as easy to set up, and there's some detailed options available if you really need to tweak. 
 
It's nice to have some "logview" software that actually works reliably too watching all the cell voltages as they charge requires a quality anorak.. but the option is there. I just wish the default didn't squash all the traves up at the top of the screen.
 
I've not investigated charge memories yet, but again, could be useful.
Overall it seems to be a top class charger. Let's hope I dont have any of the quality issues Timbo reported.. 
 
Now, must go, there's a funfighter P51 Miss America, good weather and a little free time calling all at the same time. Quite rare these days.
 
Cheers
Chris 
 
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