Home Made 600Wh Energy Station

Tired of being stressed during the setup of my telescope because of thinking about not having enough battery to take a correct amount of poses, I decided to design a powerfull and energy efficient battery box.
I had two main ideas:

1. Using a car battery
2. Using a 19V converter to power the laptop without using the 220V power suply for efficiency

So, my box has a 12V output for the telescope, a 19V output for the laptop (a Dell X1) and also a 220V output that I do not plan to use regularly, but that may help one day (for example if I forgot to recharge the camera...).

This power station is made of wood around a 12V-50Ah car battery and switches, voltmeter and plugs coming from an old plastic car start booster. The 220V converter is a classic cigar lighter plugged 75W one. But the most interesting part is my 8$ DC-DC boost converter found on e-bay! This little module can convert the 12V output to a higher volatge up to 32V. It's very useful to power a laptop that generally requires a 19V DC input.

the connections

12V 50Ah car battery

The dc-dc boost converter, tuned at 19V

Well, is it really efficient?

The answer is definetely YES!

The problem with my old car start booster and the 220V adapter was that the battery could only add 1 hour of extra power to the laptop, due to the bad efficiency of the 12V (battery) -> 220V (car converter) -> 19V  (laptop power supply) conversion.

I decided to make a few measurements to check if the 19V converter was really efficient. To do so, I plugged an ammeter between the battery and the input of the whole circuit to measure exactely what is consumed when using the 220V converter plus laptop power supply or the 19V converter, to compare. Here are the results:

With no load [1]
	220V:	0.28 A
	19V:	0.06 A
With laptop charging [2]
	220V:	5.44 A
	19V:	4.56 A
With laptop charged [3]
	220V:	2.30 A
	19V:	1.8 A

[1]: Just the converter powered on, nothing plugged
[2]: When the battery of the laptop is at about 80%. I noticed that the laptop charges the battery with pulses. The indicated value is during a pulse. 
[3]: Here, the laptop has it's battery removed or at 100% (the two have been tested, same result) 
During the tests, the laptop had it's screen light at 100% and a guiding software opened (but with no camera).


Then, I powered the telescope (Orion Sirius EQ-G), turned the light of the laptop to the minimum, plugged the guiding camera on the laptop and started a guiding software and took another set of measurements:

	Laptop on 19V	No other load
Scope moving (2 axis) [1]:	2.3 - 3 A	1.2 - 1.7 A
Scope following :	1.98 A	0.55 A

[1]: the higher value is obtained by applying an opposite force to the axis rotation (the scope was not mounted on the mount) 

So, I can conclude that:

• The 220V converter + PS loses about 30% of energy, compared to the DC-DC booster! Furthermore, it consumes 3.4W even if nothing is plugged (compared to 0.72 for the DC-DC booster)!

• If I plan to use 80% max of my battery (for not decharging it completely), I can power my telescope and my laptop during about 40 Ah/ 2.2 A = 18 hours! (2.2 is an estimation of the mean consumption, laptop on, scope following most of the time but moving sometimes). 

Now, I can take my time to set up my telescope and autoguiding system, with no stress!

Venus et Lune au Mak 90

Il y a 3 semaines, petite soirée sous la lune, pas de grande ambition, petit téléscope Mak90 et finalement de bien belles choses tout de même!

Zoom sur la lune au SW Mak90/1250 et camera iNova PLB-C2, le 30/04/2012 au Pic de l'Huile (73)

Phase de Venus au SW Mak 90/1250 et camera iNova PLB-C2, le 30/04/2012 au Pic de l'Huile (73)

Ce petit Maksutov très compact que j'ai acheté pour faire de l'autoguidage et pour l'observation occasionnelle est bien sympathique :-)

Astrobin

Un site de stockage de photos d'astro super!

http://astrobin.com/users/bzizou/

Ce qu'il y a de plus génial, c'est qu'il repère automatiquement les objets qui sont visibles sur les photos (comme picasa reconnais les visages!). Il a même trouvé une galaxie que je n'avais pas vue sur ma photo de l'amas de la vierge que j'avais publié ici et pour laquelle j'avais passé des heures à repérer les objets!