Power tanks

[IanL]

Anyone recommend any power tanks for running the EQ6pro.
I used to have the celestron power tank and only found that it is dead as a donut after a year and a half. So I refuse to buy another one in case it does the same after the same time period.
Anyone suggest other brands.

Cheers
Ian

[Robert9]

Go to Super-Cheap Autos and pick up a "Jump Start" for under $100. make sure it has a cigarette-lighter receptacle on the side into which you can plug your EQ6. I have a 17VA / 900A peak unit which gives me a couple of nights viewing before needing a recharge. Thoght it is better for the battery that it is not fully discharged before recharging as they are not designed for deep cycling. The units are equipped with intelligent chargers which ensure you don't overcharge, so you can leave them on the charger when not in use. Larger units are available.

Alternatively, you can get replacement batteries for around $60 from Dick Smith and one of these might be suitable for your Power Tank.

Robert

[astronut]

Ian,
Any of the offerings mentioned are really not suitable for your application.
They are mainly used for a one at a time "jump start" not a night long drain.
I recommend that you use "Deep Cycle Batteries" They have a thicker plate than the other types and are suited to the type of power requirements needed by astronomers.
They do cost more, but the trade off is a constant and longer lasting battery.
At M.A.S we have a number of members using this setup, and they swear by it's reliability.:thumbsup:

[acropolite]

Ian, the main reason all powertank type supplies don't last is because they have Sealed Lead Acid batteries which are not suited to deep and repeated discharge.
As John suggests you will get better service life from deep cycle batteries which have a different chemical composition to allow for repetative deep discharge. The single most important factor in battery life is the time interval between discharging and subsequent recharge, all lead acid batteries should be charged immediately following discharge if possible any more than a few days and the battery starts to sulphate.

[Robert9]

John,
I have to disagree with you. A 17AHr battery is quite happy delivering power at the 10% rate ie 1.7A, and can do so over a period of a few hours. Now, I don't know what the drain would be on the battery while running the EQ6, but I would guess that it does not exceed 1A. Furthermore, the high current is only being drawn while the motors are running, which only happens in short bursts while sky-hopping. The power drawn while tracking I feel, would be very much less than this, so I can't see that a standard battery should be at such risk. The great proviso is, as was said, that they are not left in a discharged state for any extended period of time due to the risk of sulphating the plates.
My thoughts are that if Ian's battery in his power tank died prematurely, he may have just had a baddy, or alternatively, he didn't keep it charged.
Robert

[Kal]

Even if you don't use the powertank, you still need to recharge it every month. If you don't and you leave it sitting idle it will slowly drain and die.

[astronut]

Robert,
I'm happy to say that we're both right:)
If only used as you've said, the standard battery will probably work just fine, but.......................and there's always a but, if the unit is used in anything but mild temp's the battery doesn't last as long as a Deep cycle one.
Batteries don't like the cold, the thicker plated ones (D.C) hang onto their charge a lot better.
The other matter is that I'm sure (rather quickly) that other power hungry units will be added to the batteries drain (heaters, etc) these will all work better and longer on the D.C batt.:)

[Robert9]

John,
Fair enough comment. The DC (deep-cycle) batts. as you say are certainly a better unit.
I don't know where Ian is located. It may be that he sits out in the 0 to 5C nights on top of some mountain or in the Alice in mid-winter and yes, under these conditions the old lead-acid gives a poorer performance, but I don't think a DC goes any better than a standard under these conditions, as the performance is chemistry related rather than dependent upon the thickness or otherwise of the plates.
If other equipment is to be used, there are heavier duty "jump-starts" available, eg 25 AHr. A dew-heater will use at the most 1A (unless its a very large scope - my 6" uses only about 0.6A). What else is there? A lap-top? Maybe, although these tend to have a battery with a reasonable operation time.
I think the real answer lies in the correct useage and maintenance of the battery. Not discharging it beyond 50 - 75% capacity nor allowing it to stay discharged for an extended time. For a 25AHr battery therefore, the maximum discharge should be say 15AHr. At the max. discharge rate of 10%, (ie 2.5A continuous) this represents 6 hours of operation. Should be plenty.
Then recharge the next day. The intelligent charger built into the "jump-start" or power-tank, should handle this comfortably within the time available before the next night's viewing.

Robert

[chrisp9au]

G'day Astronut/John,

Would you be able to post details, maybe with a picture, of the typical setup used by your M.A.S members? Or maybe you could PM me?
I rather think the DC battery setup would be the best option, but not being the 'technical type' would appreciate a guide or some tips on setting up a portable rig.

Thanks :thumbsup:
Chris