Project: BattBox – A DIY Powertank

A quick scour of Amazon reveals that your average Celestron Powertank, a portable battery box for astronomers, varies in price from around £50 for a 7ah model, through to £130 for a 17ah model, to £150 for a Lithium Ferrite beasty.

Blimey, astro manufacturers know how to hit astronomers right in the bank balance! SCREW THAT. I’ll do it DirtyAstro style!

Total cost for this version: £120

Build time: an hour

Tools: Drill, hack saw / oscillating multitool / dremel

Weight:  Down to choice of battery. For this one, lots!

Shopping List

NB: *Links below updated late-2018 to something-similarly-available seeing as wire and switches were from the now-defunct Maplin…


Strap it all together, wire it all up and you have what should last an entire weekend from a full charge of 12v goodness, fully switched and fused.

See attached pics!

Wiring is effectively thus: red on battery [+] to FUSE to POWER pole of switch. ACC pole of switch to + terminal on cigarette socket / USB socket accessory we want to switch. Black from battery [-] to GROUND pole of switch. Black from battery [-] to – terminal on cigarette socket accessory.

Repeat for remaining switch & socket.

For the final pushbutton and voltmeter, red [+] on battery to FUSE to + pole on pushbutton. – pole of push button to + pole of voltmeter. – pole of voltmeter to black [-] on battery.

Just follow the wiring in the Rat’s Nest pix below and the above should make sense.


Rat’s nest…

IMG_0848.JPGBottom left, momentary switch for centre voltmeter. Top left, on/off switch for left hand cigarette socket. Top right, on/off switch for righthand USB sockets.


Other end of rat’s nest… (the two black wires disappearing off down beside the battery are the quick connector for my maintenance charger)


Voltmeter… on a 2A fuse


Momentary switch on rear for voltmeter… hold for a reading.


Left hand switch is power on/off for left hand locking cigarette socket, on a 10A fuse.


And Right hand switch is power on / off for right hand pair of USB sockets, on a 5A fuse