BEC question?
 

I hope this isn't a stupid questin? I was wondering if I could use a bec such as http://www.lowpricerc.com/product_in...products_id=34 with a 1300 11.1 Lipo to power the electronics on my glow plane....and would it give me longer life than the 5cell 1400 nimh i am using now....I know charging would be quicker as I can't seem to charge my NiMh over .5 amps...I just didn't know if the higher voltage would just be wasted by the bec???

RE: BEC question?
 

Definitely not a stupid question. However, going with the higher voltage pack isn't going to give you any longer run times, and here is why. Your original pack is rated at 1400 Mah and the pack that you want to go is is only rated at 1300 Mah. Comparing the two packs with both putting out approximately 5 volts (4.8 for your original pack and 5 volts adjusted on the new pack) your original pack has the higher capacity as it can supply 1400 Mah. In addition, by adding the BEC you are adding one more thing that can go wrong in the system. If you are looking to increase your flight times go with a pack with a higher capacity, not higher voltage

Ken

RE: BEC question?
 

With an analog BEC you are throwing away excess current to drop the voltage to the required levels.

It is unlikely with this combination, that you'll get additional run times with a 1300 11.1v 3S LiPo pack versus a 1400mAh NiMH pack, provided that both are in good condition.

If the latter is aging, while the former is relatively new, then yes you may.

Now if you were using a switching BEC ( aka a UBEC ) it is entirely possible that you may indeed get better run times, as a switching BEC may not place as high of a load on the battery.

However I'll go with UBECs or BECs only when there is a clear advantage to doing so...

e.g. I can either cut weight, or install a much HIGHER capacity pack for the same weight penalty...

So I may opt for a 3000mAh 7.4v LiPo pack to power the electronics using either a UBEC or Regulator, knowing that I'm only adding the equivalent to a 1400mAh NiCD pack in terms of weight.

In your shoes, I'd just buy another bigger battery pack...

e.g. one of these at a fantastic price: [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXVHY4&P=7]3000mAh 6v pack ( click me! )[/link]

RE: BEC question?
 

Ken
I think you may be missing somthing although it may be me that doesn't understand. I thought a battery mah rating was at its rated voltage. So wouldn't a 1000 mah 12 volt battery have twice the stored enegry as a 1000 mah 6 volt battery?

I think by the voltage being regulated down to almost half would effectively increase the mah available.I'm sure the method/efficiency of regulation would bea factor. I think watt hours would be a more accurate way to measure the total stored energy in a pack.

RE: BEC question?
 

Something I alluded to above...

Analog BEC throw away energy as heat, but a switching BEC may do as you said.


I do disagree with Ken on the complexity issue...

Modelers have no qualms about throwing in relatively complex circutry, receivers, power boxes, etc. into their planes all the time.

Why then single out the lowly BEC as a point of faiilure when there are so many other things ready to do that task?

I've had more failures with dying cells, bad switches, etc. than I've ever had with a BEC... currently ZERO BEC failures, even with the cheapies.

RE: BEC question?
 

Thanks for the great info, Now out of curiosity what amperage should I be charging my 1400MAH NiMh, I have always used a wall charger (trickle), I now have a acucell 6 which works great, but I am having a hard time figuring out how to fast charge my reciever packs,,,

Thanks again...Dave

RE: BEC question?
 

Opjose,
 I have no problems with usings BEC's and I don't think they are overly complex for normal usage. However, in the context of the Beginner's Forum I do feel they are an added complexity that beginners simply don't need. There is enough going on when learning and the KISS statement comes into play.

Ken</p>

RE: BEC question?
 

Thorn,
For maximum life a NiMh battery should be charged at 10% or C/10 of capacity.
In your case charge at 140 mAh.
If you need to fast charge, slower is still better.
Try to stay at capacity unless your battery specifically states it may be charged faster.
Good Luck,
KW_Counter

RE: BEC question?
 

That I don't disagree with at all... hence the advice to just buy a new and bigger pack....

Especially since in his case, he's not gaining anything by going to the BEC combination.