Airborne batteries

[Earl Haury]

Bob

NiMH & Li are both viable and offer advantages over NiCad in capacity, maintenance, and weight. 

The internal impedance of the present day NiMH results in slightly more voltage drop for a given current than NiCad (or Li), but the price / capacity / weight value is hard to beat. Mechanical durability is as good as NiCad. I use a Sanyo 1650 mah 5 cell pack (5 cells to minimize the volt drop effect) with a regulator ) <$20 &142 gr. I've logged more than 1000 flights on these with no problems (generally renew the pack annually). I use the same cells in my xmtr. Slow charging is no problem except that the higher capacity takes longer if they're discharged fully. The advantages over Li are cost and the acceptance of fast charging. Some peak detect fast chargers don't do well with NiMH, I've found the Sirius Pro to be excellent.

However, I am changing to Li (the hard case of the Li-ion makes them a bit more mechanically durable than LiPo). Low impedance provides minimal voltage drop at high current loads. The real advantage is the weight / capacity ratio, a 2400 mah Li-ion weighs less than 100 gr. with even less weight for LiPo. The disadvantages are that a volt reg is necessary, their inability to accept fast charging, and higher cost. I use the NMP charger from Central (Jim Oddino designs are reliable). 


Earl




  ----- Original Message ----- 
  From: Bob Richards 
  To: discussion at nsrca.org 
  Sent: Thursday, October 06, 2005 7:40 AM
  Subject: Airborne batteries


  Guys,

  I'm needing to replace several nicad airborne packs for my radios (as well as a couple of transmitter packs). I'm wondering what has changed in the technology in the past 8 years. 

  NiMh packs had just hit the market about 10 years ago, and as I recall it seemed that they did not stand up well to vibration - several inflight failures being reported. Seemed they were ok for transmitters. Has that changed?

  I know Li-ion and Li-poly are now available, but what type of charging apparatus am I looking at investing in? I also think I need to use a regulator with these?

  I don't presently have a fast field charger and would like to have one, is there one that covers all the above bases?

  Thanks in advance,

  Bob Richards.
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