[Elecraft] Re: Battery use with QRP rigs - page updated - NiMH info added

[John Harper]

I've just updated my battery page again, adding a discharge curve (at 300 
mA) from an 8-cell pack of AA NiNH batteries sent to me by VE3NFK who has 
the same analyzer I do. And NN4CW is sending me a couple of *very* tiny LiPo 
batteries to test that he uses in the Spartan Sprint contests with excellent 
results. Thanks to both of you for your contribution.

I've gotten a ton of email regarding battery operation w/QRP since making my 
initial post a few days ago. Several folks are doing some interesting 
experiments involving high-farad capacitors, DC-DC converters & batteries 
with solar cells.

In a previous post, there is a link to
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2335

The price and capacity of this battery made me wonder what the "catch" was 
since I recently paid $30 more for a slightly smaller battery:
http://www.aeromicro.com/Catalog/thunder_power_pro_lite_3-cell_2100_mah_li-po_pack_4479728.htm

When/If shopping for a LiPo battery keep in mind that batteries of identical 
capacities (mAh ratings) can have drastically different discharge ratings. 
The battery in the first link has a max discharge rating of 2.5 amps (1C). 
The more expensive battery is rated at 31 amps continuous, 50 amps peak. 
With our QRP rigs, we will probably never draw 2.5 amps from a battery, so 
is there any reason to use the more expensive battery? The main difference 
between these two batteries is that the smaller rated battery will have more 
of a voltage drop during transmit than the 31-amp battery. This is the 
effect that some folks who are experimenting with large capacitors on the 
outputs of their batteries are compensating for, with excellent results in 
higher output power over simply using the batteries alone.

As it is, I have more than one reason to have the higher-rated battery (R/C 
electric planes), but if I was going to use the battery strictly for QRP, 
I'd probably go with the less expensive one (and then wonder what tangible 
benefits there may be from the other one!) and then start experimenting with 
these caps.
http://www.maxwell.com/ultracapacitors/index.html

John Harper AE5X
Portable QRP: http://www.ae5x.com