I just acquired ....

ZeroID (Brent) · #1 17-01-2012, 08:12 PM

Some 12v 7AH batteries ... about 5 of them in good nick.
They just did a full maintenence of the big 20 KW APC UPS at work.
It uses 8 x 12v batteries(13.2V actually ) to make up 100 v modules and they replaced the lot, about 12 modules.
So I pulled one open, tested the 8, only one dud at 11.1 v and grabbed 5 of the best all over 13.2 v each for a portable power supply for the mount, fans etc.
Parallel them up for ~ 35 Amp Hours. Should keep things humming for a while.
I'll work up a design and build and post pics\instructions for any interested people. Might try and grab a few more.

ZeroID (Brent) · #2 18-01-2012, 07:35 AM

Plan is to buy a suitable chilly bin (esky to you Aussies ). Fit the batteries inside along with an inbuilt trickle charger. Fit 12V output connectors for the mount, fans, lights etc. Provide a selectable 3-6-9 volt supply outlet from an inbuilt car power adapter ( Dick Smith special ) for fan speed control or any other voltage sensitive device. Switched and fused output connectors. Might find another battery if it fits with the case.

The idea is to use the unit at the home pier as well because it will deliver 13 volts + rather than the well regulated but 12 volt limited supply I currently have for the mount. I've had no problems so far with this but I have yet to load it fully with accessories and a battery driven system will also be safe from power dropouts etc rare though they may be over here. ( More likely me tripping over the cable causing grief

).

Add Volt and Amp meters on top to monitor it all. Was thinking of adding a solar panel as well but cost and value do not add up and I don't do remote enough to be a problem. At the home pier I would use it plugged into the AC. Also makes for a nice waterproof (dew) tidy system that should be easily transportable.

Any thing I've missed

I have most of the electrical bits at home already.

kinetic (Steve) · #3 18-01-2012, 07:52 AM

Quote:

Originally Posted by ZeroID

Any thing I've missed

Yes Brent, just be REALLY careful with all that capacity in case of a short,
if you parallel them all up.
Make sure there is no way a lead or terminal can come adrift in the dark
or if tipped over in the car in transit etc.
Sounds like a great project

Steve

ZeroID (Brent) · #4 18-01-2012, 08:41 AM

Cheers Steve for the warning. I'm an Electrical Tech, limited rego and very safety conscious. Had enough scares in my early days to keep me cautious.
I've been using a modified 400 watt PC Power Supply to drive my gear. Delivers about 10 Amps at 5 V, 5 Amps at 12V, very smooth and quite small for it's output. Simple resistor mod to trick the PS into thinking it's got a load connected and away she goes.

I'm a great believer in using already available resources.

What diversion ? It's all good

traveller (Bo) · #5 18-01-2012, 09:09 AM

I am sure you thought of this Brent but a few ventilation holes in the esky/chilli bin would help also.

DavidTrap (David) · #6 18-01-2012, 01:16 PM

I'm use a completely 12V system at my dark sky setup. Much quieter - no generator, or fans from power supplies and I'm not worried about dew getting in to 240V equipment.

I run the laptop via a Jaycar 12-19V adapter and everything else is natively 12V (mount, CCD, Dew heaters, robofocus, lightbox, water pump).

My batteries are second hand, some salvaged from a motor scooter repair shop. The current draw isn't high, so older batteries seem to be suitable. I've recently rewired the setup to include fixed links and polarised plugs to reduce the risk of sparks in the darkness.

All the best.

DT

ZeroID (Brent) · #7 19-01-2012, 11:52 AM

Cheers Bo, David, good points to remember.
Actually just realised I have an APC travel adapter which takes anything from 12v to 240 v AC or DC and puts out a selectable 12 to 21 volt output for laptop power. And laptop has it's own battery as well of course. have to think this through a bit more. A slightly bigger Esky might be needed, back to the drawing board.