2 cell Lithium polymers as your receiver pack?

[JOddino]

See my comments after each paragraph.

----- Original Message ----- 
From: "Adam Glatt" <adam.g at sasktel.net>
To: <discussion at nsrca.org>
Sent: Friday, November 21, 2003 4:25 PM
Subject: Re: 2 cell Lithium polymers as your receiver pack?


>
> If you run all or mostly digitals expect ~150mah per flight.

Find out what your plane draws.  Don't take anything for granted.
>
> Never heard of a regulator over heating.  Due to bad combination of
> hard-mounted pipe and DZ and weak fuselage I was drawing 225mah per
> flight most of this year on a 7.4v ThunderPower 1950mah pack with a 4.8v
> regulator (with a heatsink), never had any problems.

Regulators can overheat if they dissipate too much power.  When they do they
shut down.  Understand your system requirements and add a heat sink if
necessary.
>
> If you charge them at too high voltage (i.e. in nicd mode, or any
> non-lithium charge mode) they will expand, and if they expand enough
> they will vent and stink and be toxic and possibly cause a fire, as by
> this point they are very hot.

Use a charger designed for your pack and you will have no problems.
>
> Good: more capacity at lighter weight (though in the 1100mah range the
> constant weight of the regulator overcomes the weight/mah of the lipoly
> vs the nicd... so only existant at higher capacities). No self discharge.
>
> Bad: dangerous and quick to be turn to garbage if mis-charged, more $$,
> requires a more expensive charger.

Price will come down.  Cells cost less than $3.00 in quantity.  Chargers can
be very inexpensive.
>
> If anything, the Lipoly is good for more charges (atleast the Thunder
> Power ones are).

In the end I believe we will change batteries based on time, not number of
cycles.
>
> Lipolys only offer a clear advantage when they power the motor.  In
> everything else our batteries are already light, and you really have to
> weigh the pros and cons.  Though I should point out that in the >
> ~1500mah range, the NiCds do become quite heavy and the lipolys offer a
> real weight saving. If you want NiCds and lots (12 flights on a charge)
> of flying you have to go with a smaller capacity and more than one pack.
>
> BTW, Thunder Power is already producing batteries that make the one
> Shulman used in Poland look like old news =>
>
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