December, er, Observing and LiFePO4 Battery Pack

[Captain Scarlet]

This is part (anti-)observation report from December, and part “First Light” account of my new Celestron Powertank Lithium Pro LiFePO4 battery pack.

I was in SW Ireland for Christmas and the New Year, where it’s much darker than where I live near London, and it’s where I keep most of my nice astronomy stuff. As ever, I was careful to record the results of my observing through the fortnight before I forgot it:

 

Thick layers of cloud. every.single.night.

 

Also at that time I received, courtesy of Santa, the Celestron Powertank. Obviously, I had no chance to test the battery pack whilst there.

This last weekend, though, in the UK, I did finally have time and, it seemed, the right conditions to give this thing its “first light”. Unfortunately, as soon as sufficient darkness arrived on both Saturday and Sunday evenings, so did the clouds and I couldn’t properly get past the 1^st alignment star in the initialization routine on either Saturday or Sunday night. Nonetheless, Sunday evening around 6:15pm I did just about get Rigel through cloud as my first alignment star, and by I guessing where Polaris was through impenetrable cloud, the SynScan told me “Alignment Successful”. We-Heh! So I set it to “GoTo” Mars, left it to track, and went inside to get the evening’s chicken on to roast. So far, so good: the power supply appeared to be working fine, the measured voltage reported both by the SynScan and a separate multi-meter showed a tad over 13V.

About an hour later I nipped outside to check it was still tracking, to find it had switched itself off! How annoying! It had been fully charged. The manual says under the USB charging section: “The charger automatically shuts off when the load drops below 100mA for 1 hour” – it seems that this holds for 12V telescope powering too, so if you want to observe, say, Jupiter for more than an hour at a time, beware!

Also, the manual (see link below) suggests that the box when new contains a cigarette-lighter-plug=>telescope_plug, AND ALSO A CHARGING-PORT=>TELESCOPE_PLUG, meaning that one can power a telescope with a lead from the _charging port_ to the scope. I don’t recall there being a lead like that when I got it (The box itself is in Ireland so I can’t immediately check). It does mean that it has 2 useful 12V outlets, though, which I hadn’t appreciated.

A link to the manual: https://s3.amazonaws.com/celestron-site-support-files/support_files/18768_PowerTank_Lithium_Pro_Manual_5lang_Web.pdf

Cheers, Magnus

[happy-kat]

Have you got the double power tank or the single?

I have the single one and it does not have the cig lighter socket.

[Captain Scarlet]

it's this one, which I think is the double:

 

[happy-kat]

I've used mine left tracking for over an hour fine as far as I can think through I can't say with 100% certainly as I don't do long sessions.

What mount are you using the battery with?

My battery came with the tip positive cable which is perfect for my mount. You'll have to raise missing bits with your supplier I think.

[Captain Scarlet]

The mount in this case is the SupaTrak one that comes with the SkyMax 127, I'm not sure how much it draws when tracking-only but it wouldn't surprise me if it was less than 100mA, at 12V making it less than 1.2W . I'll have to do more experimentation...

As for that cable, it's quite likely I noticed the Celestron mount plug at one end and mentally dismissed it as I don't have a Celestron mount.

Ultimately this battery will be used on my AZ-EQ6 and SkyMax 180 and/or SW 300p in Ireland.

Magnus

PS not sure how my initial post got its weird difficult-to-read font and spacing. I copy/pasted it from Outlook which is where I drafted it, and I haven't been able to edit it to make it look "normal". If a friendly mod would like to edit it and normalise the "look", I wouldn't complain...

[happy-kat]

I tend to copy text to notepad before copying again into a post it strips the formatting.

I use a skywatcher virtuoso mount which handly had the same power socket fitting.

@Stu perhaps you can help please  have you found the power from the battery (I saw one on your tripod leg) stops powering after an hour if it is just tracking (not slewing) ?

[happy-kat]

Sorry you appear to not have had a reply.

[Captain Scarlet]

Not to worry, thanks for your responses. I'll continue trying to pin it down, my guess is the current for tracking-only on that mount brings it below that 100mA threshhold, I might see if I can measure it. It could also be a glitchv SynScan. I'll see if I can reproduce it this weekend...

Cheers, Magnus

[happy-kat]

When I next get a clear night I'll make a note of timing what time I leave it tracking to what time I then interrupt to see if it was over an hour. Virtuoso with synscan v3 handset and 7ah tank like yours.