Simple portable power supply for Skywatcher Alt-Az mount

[Jove]

To advanced astro_DIYers this little project will seem trivial, but it fixes something that was bugging me for ages

My main problem was that my Skywatcher tracking mount requires a 12V DC power supply. I can use either a mains adapter or an 8xAA powerpack. The former tethers me to the house, and I don't much like running cables across the garden when there is a lot of dew. Rechargable AA cells are OKish, but only give a few hours worth of charge. Non-rechargables work better but cost a fortune.

So, I went to Maplins and bought:

a 4.2Ah sealed lead acid battery

a connector to fit the SW mount power in socket

a cable to connect the two

crimp on connectors

a charger for the lead-acid cell

Assembly was literally: bare the wire cables and crimp on the connectors that slide onto the battery terminals, plug teh connector into the other end of the wire and plug that into the mount.

I wasn't sure it would work - I've tried using one of those portable car jumpstarter packs before and found that the current was really variable, and that the charging process took ages. This battery gives a good constant current and charges fully in a few hours - much better than the 24h+ for bigger car battery size cells. I've done about 5 hours observing with it and it's not flat yet - I reckon I should be able to get 8h or more since the mains adapter supplies a max of 500mA. Compared to car-battery cells this unit is small (no more that a 10cm x 10cm x 10cm cube) and light (maybe 1kg?).

I'm hoping this set up will meet my mount power supply needs - for now I am pretty happy with it.

[crashtestdummy]

i purchased a motorcycle battery to do the same thing but after a trip to maplins on saturday ive seen the sealed lead acid batteries and considering changing tack but not wanting to have wasted £30 on a battery that i cant use so may make it work anyway.

[knobby]

Or .. http://stargazerslounge.com/index.php?/topic/158114-Charging-10-1.2v-nimh-in-series?

But I think I like yours better !

Got any pics ?

[Gina]

I think a sealed lead acid battery is definitely the way to go for a portable system. I couldn't see any mention of which model of mount you're using but I have an NEQ6 which takes around 1A when slewing at full speed in both axes at a time and drops to 0.5A when tracking. It takes 0.3A when switched on but not tracking. Anyway, it sounds like you have chosen a very suitable size of battery - you want a good power margin but not too much weight to cart about

I have a permanent setup and run from a 13.8v mains PSU with a power distribution box on my pier. It has a digital ammeter so that I can check current consumption.

[gooseholla]

I purchased a portable battery charger for £35, does the job fine.