Which 12v Power Supply Tank?

[arg0naut]

Will need to think about portable 12v power supply at some point. Do I go with Celestrons or does anybody know of other options ie. car battery jump starters/power tanks.

[Veracocha]

I have the Maplin 4 in 1 £39.99 jobbie. Works a treat with my Celestron Nexstar 127 Mak. The outlet connector also fits the mount without having to search for a cable (tip positive)

[arg0naut]

Sorry, should have stated my requirements. I have a CPC 800 and will probably go down the heated dew shield route aswell.

[red dwalf]

i was in aldi yesterday and noticed they have there power tanks back in stock, look good quailty with 2 cigar outlets, think thet were around £40

[Nillchill]

I've looked at the aldi supplies they also have a USB power slot built in.

I bought an Aldi unit a few years back , lasted me approx 2 years, did the work I needed during that time

[shepsboss]

Hi, I purchased 'Jump start with air compressor' from Aldi on Monday. £34.99, it has 2x 12vDC sockets with overload protection, maintenance free 12v / 17.2 Ah battery. 5v usb socket etc and 3 years warranty! Exeter branch had loads of them. I have not yet decided on my telescope but the final choice will be go-to so I could not resist a cheap power pack. Good luck.

[spacebloke]

I've got the celestron tank and it's great, i've had no issues at all with it.

[Horus]

I,ve bought the £29 Maplins and it's the 17Ah version.. http://mobile.maplin.co.uk/module.aspx?moduleno=383992

[m.tweedy]

if you have the money bearing in mind you mentioned dew control

Numax 75AH Sealed Leisure Battery | GO Outdoors

12V CAR ELECTRICAL LIGHTER SOCKET WITH BATTERY CLAMPS on eBay (end time 23-Feb-11 21:36:40 GMT) you may need to put an inline fuze in place to protect your mount

here is a link from a previous discussion on batteries that may help

http://stargazerslounge.com/diy-astronomer/95646-105ah-powertank.html

[samir_ansari]

sorry for the silly question but how would you go about connecting the jumpstart powerpacks from maplin to your mount? I'm guessing it would just be a case of clamping the red and black crocodile clips on to the ones that came with the mount, or are there adaptors involved that I am missing out?

Thanks!

Samir

[Veracocha]

There is a cigarette lighter type connector that attaches to the side of the power tank which plugs directly into the mount.

[Horus]

No you don't use the jump start leads! You use a cigar lighter lead that fits you mount. The power pack as cigar lighter plug

[samir_ansari]

hahah thank god I asked first! I am obviously very new to all this

Thanks guys

[Horus]

Don't worry , ask away

[samir_ansari]

Ok one more - sorry arg0naut I didn't mean to hijack your thread but I guess this is all relative.

I essentially wanted to power a standard laptop, my mount and my DSLR through AC with one of these sealed batteries (either the maplin or aldi one). Would this be too much for it?

[mikeknowle]

I've used a Maplin one for a long time....cheap as chips (£14-ish), located inside an anti-dew forcefield device (i.e. an upturned plastic bucket).

[samir_ansari]

so is there anyway I could power my laptop through a cheapish battery?

[Merlin66]

I've been using a collection of 20Ah gel cell batteries ( and an electronic charger) for the last five years - works 100% and very cost effective in the long run.

For laptops you can get a car transformer 12V to say 18V (whatever your laptop needs) so it runs of a battery. Unfortunately some laptops, when recharging the internal battery can pull lots of power...

[obscura]

I got a mains 12v @ 5A from Modern Astronomy for £28. So you could get 2 @ £56 nad have dew heaters etc seperate from the scope's desires.

[Skylook123]

There are almost as many answers as power supplies, so some ground rules might thin down the options.

First, the philosophical situation. Many of us use the jump start battery form of supply. This usually has an auto battery in a utility case of some sort, with power outlets and jumper cables, perhaps even a beacon light, air compressor, even a radio in the Celestron/Orion units. Quite the orchestra, when the need is basically a bass drum. The battery in the units, being an auto type, is designed for high current short burst need, followed by quick recharging. Is that what we do? Well, we do low draw, long continuous use. This has a tendency of limited life, compared to a perfect choice of a golf cart, wheel chair, or marine use deep discharge unit that tolerates being pulled way down and recharged. Jump start units have thinner plates, and they can degrade faster than deep discharge units when in regular use. But then, many of us use the jump starts because, well, it's convenient to buy a box that does our task without our needing to be an electrical engineer or fabricator. The purists say marine/deep discharge, while most of us shrug our shoulders and use what is easily available.

Philosophy aside, the first consideration is the power draw. Mount alone, maybe half an amp for tracking, close to 2 amps for bigger units on GOTO, especially if not perfectly balanced. Now, throw the lappy at it. Unless you take an hour or two of initial setup pains with the laptop, it can draw in excess of 3 amps while it purrs along while we ignore it when we are at the eyepiece. For my setup, I went into the desktop setup and created a new theme I call ASTRO. I saved the daytime profile as NORMAL so I can switch between them. Then I changed all the color options on ASTRO to dark red and black. I opened the power settings and screen saver and made the screen go dark at 2 minutes of no input. And I used the function settings on the keyboard to set the intensity at the very minimum possible. Just this action changed my maximum useage time on battery from nearly 2 hours to almost 6 hours. The screen and the hard disk accesses are the big power draw, so cutting down the screen intensity provides gobs of extra time on battery. I also bought a spare laptop battery, so now I have over 10 hours of computer battery available and I don't need to plug into my astronomy battery at all.

But, suppose one does use the astro battery for the laptop, as well as the mount, as well as dew control, and imaging, (guide camera, guide software, imaging camera, and on and on). Now we might be talking 5 amps or more of draw. Our Celestron pack is 17 AH, or 12 AH for newer units, and others of the same type run around 18 to 20 AH capacity. This is capacity, not accessible capacity. Jump starts especially should not be drawn below 50 percent capacity or the plates start to sulfate, and can even crumble, if exercised to extreme. And it gets worse if it is not immediately recharged to full after a night of use, no matter how little capacity was used. So, now our generic 18 amp-hour has become 9 amp-hour of reliable access. Any wonder why our first tries at imaging we are stunned when the whole kit shuts down after only two hours? Yes, size matters. Thus, we need to have a realistic assessment of our demands, and a realistic assessment of our capabilties.

Now, we have a moderately wild guess of our needs, and we take the pledge not to think our 18 AH battery has an 18 AH reservoir for us. How will we treat our unit? We know from the technology that the lead plates do not like being in a discharged environment; it's a chemistry thing. The more discharged the worse they do, to the point that it is possible to physically damage the unit if taken down to the point where the brownout occurs on the equipment. The power supply when fresh and recharged will put out well over 13 V, and gradually decay to the vicinity of 12V or a little below. But if it gets close to 11V, some of these are permanently damaged and the equipment powered by the unit certainly doesn't like it. So, we promise to be aware of our useage and not go below about 50 percent of the rated capacity. How do we bring it back to full?

I have a real distrust of the so-called wall wart that comes with the Celestron units for recharging. I actually have three different jump start supplies, and they each have a different charging scheme. The Celestron wall unit is notorious for poor reliability. Not all turn bad, but enough to consider an alternative. For one thing, they are continuous power, in the neighborhood of 0.8 amp. If we followed our self-imposed rule of 50% maximum drain, why, that means nearly 10 hours of charging. Not bad, if we only get suitable weather on occasion. BUT, they are constant current, so suppose we only used 10%? When the battery gets fully charged, the continuous current input will start to boil the electrolyte, or otherwise damage the unit. We must watch it carefully! The failure mode of the wall charger is to reduce the voltage of the output so that it no longer pushes the juice up the hill into the battery. So we think it's been charged long enough, and we go and damage a battery because it wasn't full. I have heard of one unit fail "hot" and kill a battery this way, too. One of my other supplies has a wall wart of only 0.5 amp. That's nearly a day for 9 amps! Please don't let me forget it. Finally, the lights on the Celestron/Orion Power Tanks are very misleading. At times the Fully Charged light and the Charging light will both be on. This is because the charging circuit is poorly calibrated for these lights. Remember that the 12V battery is not fully charged until it gets to well over 13V, but that light comes on at 12V. The fact that it is still taking a charge is why the Charging light remains on. Best practice is to keep it on the charger until the Charging light goes off. Another source of premature death of these units.

Many of us use a different charging solution, such as Battery Defender or my favorite, a Canadian unit called the Soneil 1206s. These units don't just trickle in a low current. They will sense the condition and start in the 3-6 amp range, helping to condition the battery as well as charge it. Plus, they taper down at the end and actually can be left on the battery indefinitely, sensing the charging need and keeping it ready to use. But how to apply it to the Power Tank?

There are several methods. The Celestron unit is unique among the jump starts I've seen in that the jumper cables are always "hot", or on. So, for these units, the front panel switch is OFF, and the output of the charger is connected to the jumper cables. The CHARGE setting on the front switch is only for the wall wart socket. An alternative some folks use is to get a double ended cigar plug line and run one end into a motor vehicle utility or cigar lighter socket, or build a cigar plug ended cable with aligator clips or othe connection to the charger. Plug the cigar connector into the equivalent socke on the Power Tank, leave the switch OFF, and pump the juice in. Either way, more efficient and more reliable than the wall unit.

My other two units are the reverse configuration; the jumper cables are cold unless switched on, but always able to charege through the socket on the unit. So, for these two, I still connect my Soneil charger to the jumper cables, but I need to remember to turn the jumper cable switch to ON to charge the battery. And remember to turn it off when done: I once went to a public outreach after two weeks of non-use, and found that after charging I had left the jumper switch on, depleting the battery. I always bring two, so no harm.

In conclusion, I'd advise to first learn your demand, then limit your demand where possible, then choose the method you think fits your needs whether a jump start or deep discharge, and always treat your power supply kindly; it will return the favor.

[Herbig]

Very comprehensive summary Jim.

Regards

Pete

[Horus]

Let say that's the best review I've seen on Power Tanks Jim , well done ive learnt some things .

[metz]

well jim that was enlighting blimey good read

[mrmoo]

Very useful information, bookmarked. Thanks Jim.

[Truly55]

I've used a Maplin one for a long time....cheap as chips (£14-ish), located inside an anti-dew forcefield device (i.e. an upturned plastic bucket).

Very funny. :). Back on topic I bought a Celestron power tank when I bought my Celestron scope. I just figured that I would feel better running something from the same company especially if there was a warranty issue. The daft thing is that the tanks are probably all the same but for different company stickers. Besides there would be no way of checking that I was using someone elses power tank if I did have a warranty issue with the scope, tripod, etc.