[aprssig] Solar Powered Digi's.

Scott Miller scott at opentrac.org
Tue Dec 4 14:56:51 EST 2007

Disconnecting the display backlight makes a big difference for some 
mobiles.  My DR-112 seems to have taken the initiative and disabled the 
backlight itself, in fact.  =]

Obviously the power control option on a Tracker2 isn't going to work for 
a digi that's got to listen all the time, but it works great for remote 
weather stations.


Mark Earle wrote:
> John Ronan wrote:
>> On 4 Dec 2007, at 18:53, Phillip B. Pacier wrote:
>>> I had a solar powered digi up for five years (W7RBV-2).  I have since 
>>> transferred ownership of the digi and it is no longer solar powered, 
>>> but what what information are you looking for?
>> Typical "Rules of thumb" I guess for battery/panel sizing.
>> I was thinking of a OT2 and maybe a FT-1500 or some other dedicated 2m 
>> Radio.  The OT2 will also broadcast battery voltage as telemetry for me.
>> Its not something we've done before.. so avoiding any 'gotchas' would 
>> help.
>> Apparently, the 'average' Sun hours per day over here is about 3.75.  
>> So I was going to go for a rough figure of TX'ing 20% of the time, and 
>> try and size the battery so that it never gets discharged below 80% on 
>> that figure.  And then I guess, size the panel so that it could 
>> recharge the battery from roughly 80% discharge on a 3.5 hour day of 
>> sun.  Does that sound reasonable?
>> Regards
>> John
> Those are reasonable numbers, but no synthesized radio.
> They are not optimized for stand by.
> Let's say you transmit 20% of the time. That's 288 minutes of 
> transmitter time, or, say at 2a 288 x 2a = 576 amp-minutes or 9.6 
> amp-hours.
> Now then. 100 ma (0.1 amp) of stand-by for 1152 minutes
> 1152 x .1 = 115.2 amp-minutes, or 1.92 amp-hours.
> Oops. The 1500 shows .3 amp squelched. More while receiving.
> So 1152 x .3 = 345.6 amp-minutes or 5.76 amp-hours.
> Of course, there will be receiving time and the current there is 0.6a 
> for that radio.
> So you are looking at a power budget of 7.68 or so amp-hours/day.
> Notice that the standby time is a significant part of your power budget. 
> You would want to find a transceiver which can draw much less current.
> Use a crystal radio, and remove or disable / disconnect the audio 
> portion of the receiver - you just need to buffer discriminator audio. 
> You could get the standby requirement down to on the order of 0.05 a vs 
> 0.30 a. Save you a lot of energy.
> Just some thoughts.

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