Telescope Reviews: PortaPOWER! Inverter, batteries or Jumpstarter?

Jon,

You're going to need a fairly robust setup to power all of that.

Mount 12v .5-1amp
Mallincam 12v .5amp
Dew strips 12v 2amp
Speco 110v 45w
DV VCR 110v ?w (my hard disk based DVR is rated at 50w so I'll use that for the calculations)
Laptop 110v 70-90w (I'd stay with the original 110v adapter on the laptop since you're going to have to get an inverter for the other two 110v products anyway ... the alternative it to buy a 12v converter/adapter for the laptop but since this project is already going to get a little pricey I wouldn't bother).

Depending on the rating of your VCR it looks like you'll need about 180w of 110v, so using the 50% extra rule figure on a 300w inverter. The 180w 110v requirement plus the ~3 amps @ 12v for the mount/MC/dew strips means that for a normal night's use I'd say about 150amp/hour total capacity will be required (180w @12v = 15amp/hour + 3 amp/hour for the other 12v stuff ... that means 18amp/hour x 8 hours = 144amp/hour). This calculation leads to an almost totally discharged battery ... not a good thing, so either less run time or more battery capacity will likely be needed. I haven't factored in the inefficiency of the inverter but I also used the maximum 90w for the laptop, which it won't draw anything close to. The laptop will be likely around 60-70w in continuous use plus if it's internal battery is already charged then that number will drop way way down. As with any electrical capacity calculation you go with the worst case and then add a little fudge factor.

Deep cycle batteries are likely the way to go here, and wet cells are the more popular but AGMs (glass mat) batteries are less maintenance and more flexible but are also almost twice the price of the traditional wet cells. I think two ~75amp/hour batteries or one big honking (technical term) 150amp/hour unit and a good charger are the way to go. Mount them in a plastic tool case that has wheels and a long handle (think luggage wheelie or boxes on a dolly type of setup).

As for the inverter ... the modified sine wave units are now pretty good but since you're driving two units that are going to affect the image quality I think I'd go pure sine wave (hey it's only your money

). With the requirement for nice clean 110v power I'd watch out of the all in one battery/inverter packages. I've seen some very tempting all in one units that even come packaged with the wheels and the handle ... the problem is that you just don't know what your getting in terms of the individual components.

As for the mount and Mallincam, I'd just tap off of the 12v battery supply for a few 12v outputs (also don't forget the dew strips and controller).

So it would end up something like this ...

150amp/hour 12v deep cycle battery, preferably the AGM type.
Good quality battery charger
300 pure sine wave inverter for the Speco monitor, Mini-DV VCR, and Laptop
2 or 3 12v taps off of the battery for the mount, Mallincam, and dew controller/strips
Case to house all this, plus wheels and a long handle (you don't want to be carrying this puppy around).

The 12v taps could be those cigarette lighter style sockets (link) so you can use the stock power connections, but you will have to at least build a new power cable for the Mallincam.

--------------------
Mark

C11, C6, APM/TMB115, and AT80ED
Tandem mount CGE and CG-5A, WO EZ-Touch and AT Voyager
25x100s, 8x56s, T-Mount Light, and Mark 1 eyeballs
Modded 350D, SPC900, Mallincam

Edited by mclewis1 (06/05/08 06:09 PM)