12v portable power supply

[guggle]

Hi everyone,

I just wanted to get an idea of what people use for a 12v power supply. I've got a NEQ6 Pro and I have a 240v adapter to use while I am at home, but there's a wetlands area nearby home with very good open areas but, obviously, no power.

I know I can use a car battery, but they're pretty heavy and I am looking for something a little bit more portable.

Any ideas?

Cheers, Michael.

[Shano592]

I use a 7-cell car battery from supercheap. They aren't particularly heavy, and will run all week!

I think they are about $60 or thereabouts.

For 230v, just grab an AC converter for under $100, plug in a power board, and you are set!

EDIT: For portability, you could always make a cart or sled...

[Merlin66]

For the past seven years I've been using a series of 20Ah gel cell batteries for all my gear. If they are looked after (using a triple stage charger) they will almost last forever. Mine are now over 7 years old and still as good as new!

[guggle]

Hi Ken,

Your set up sounds interesting. Would you please explain a little more about it, e.g. how many batteries make up your power supply, we did you get them from, etc?

Many thanks, Michael.

[Merlin66]

I have three 20Ah gel cell batteries - the type used in Golf Buggies and mobility scooters. I bought at least one of them from a place in McIntyre Rd Sunshine, the others from ELDO in Heidelberg.
I fitted a 12V socket to each.
I'll check the make and model of the charger for you but it gives initially a hi charge to a flat battery, then a slower medium charge and finally a trickle charge - you can leave the battery connected forever without overcharging!
One for the mount, one for the camera and one backup.
Seriously, one of the best investments I've made.

[Allan_L]

This is what I use.
Some May Say overkill, but if you are running a GoTo mount and several dew heaters at a remote site, excess is good.

[Astro_Bot]

Not me. I have two Repco battery boxes with a ~55Ah AGM deep cycle battery in each, and each fitted with a second cig. lighter socket. One runs the mount and dew heaters and the other runs the laptop and electronics. I can go anywhere*. :thumbsup:



* Of course, I don't actually go anywhere in reality. I'm really quite lazy when it comes to doing the things I planned to do ......

[Merlin66]

The only real issue with those bigger batteries is that they are SO heavy...definitely "Luggable" or trolley mount?...
At least with the physically smaller 20Ah they are much easier to handle, store and use.
Just my 2c

[Astro_Bot]

Heavy, but not so as to be a problem - about 16kg each, so no heavier than the NEQ6 head, and easier to carry since the boxes have carry handles (I upgraded the lid securing strap to dual 300kg metal-buckled straps from Bunnings, rather than trust the flimsy plastic-buckled thing they came with).

[Marios]

I also have the Neq6, I went down the AGM deep cycle battery path and got all the other bits and pieces from Jaycar. I put the battery into a tradie type lunch bag that had a plastic ice box lining.

The 35ah runs both my mount, laptop, red light all night no problem. The Full river range allows you to discharge the batter by up to 80% before it cuts out, so keep this in mind some cheaper ones only allow you to only utilize 65 -70% before the cut off. So to much power is better than not enough.!

Also keep in mind spend a little extra and get a 4 stage charger so that you can leave the battery connected constantly in a ready stand by mode.

Here is my Rig. http://imageshack.com/a/img812/6297/55d9.jpg

http://www.allpurposebatteries.com.au/product_info.php?cPath=11_31&products_id=31

http://www.allpurposebatteries.com.au/product_info.php?cPath=4&products_id=121

http://www.jaycar.com.au/productView.asp?ID=PP2007

[guggle]

Hi Marios,

Thanks for the photos and links! Ball park..how much did this setup cost?

[Regulus]

Michael, I have a 12V7Amp for the LXD75 mount. I have noticed these 'Century' brand batteries in Supercheap Autos and so probably other auto parts places stock them. It's about 20x12x7cm. They had a range from 2Amp on up to 500.
Very manageable weight and the price is very reasonable (under $40 all up).
The lead was a cigarette lighter lead that I removed the CLighter from and attached two terminal sleeves, that are again from a car shop, since they are a standard car wiring joiner.
I will post a pic tomorrow.

Trevor

[Larryp]

Michael, you can buy deep cycle AGM batteries of various capacities on Ebay quite cheaply.

[Marios]

Call it $280.

[guggle]

Hi Trevor,

How long do you get out of your setup? I'd be interested in seeing you photo(s).

Thanks, Michael.

[Regulus]

Michael - had net problems the last few days so am a bit slow getting back here.

This is the middle of the range but there are larger amperage's without being unduly heavy or unwieldy in size.
i think this one can be had for under $40, and shopping around, probably $30.
U can see the kind of contact sleeve used. They come in packs of about 10 male and female and in various sizes. About $5-7.
The lead is a taken from a short car cigarette lead about a metre long with the C-Lighter end removed and was $4.95 from a Leading Edge electronics shop.

I cannot give a definite running time as yet but so far, for an LXD75 that usually comes with a power pack holding 8 D-Cell batts, i expect at least an all night performance.
Bear in mind that I am not running a camera or netbook etc from this set-up and would expect to go to a power tank arrangement to do so - like one of the 12V500Amp car starter types.
Since my netbook battery is adequate to a nights viewing/imaging there was no need to take the extra weight.
Hope this helps - Trevor

[The_bluester]

I have been using a cheapo jump starter pack for the last couple of years. When it was new it would comfortably run my CPC925 all night without any issues (But without any dew control) but it's capacity is falling away now. It was a cheapie though. I have also been using a spare car battery. It literally is a spacer one so I am not too concerned about eventually killing it with over dishcharging.

I am thinking that something like what Allan has is of interest. PLenty of capacity to run a visual scope and dew heaters all night and then plenty more again.

[Astro_Bot]

Apologies if you already know this, but those starter packs aren't deep cycle - they're typically designed for sparse usage and 5-10% discharge, similar to a car battery, though I'm guessing that the starter packs are likely to use the cheapest and nastiest battery available.

Deep cycle batteries are designed for around 50% discharge (though some manufacturers claim 80% - I personally have trouble believing that), and if re-charged promptly, should (IIRC) manage 600+ charge-discharge cycles before losing noticeable capacity.

The main difference is in the plate construction - deep cycle batteries have heavier, solid plates with alloy components to stabilise them (with the effect of reducing maximum current), whereas high-current (car/starter pack) batteries use a lighter, honeycomb plates that maximise surface area but will suffer more rapid degradation if discharged deeply.

I sized my batteries for 8-hour sessions running worst case loads (where I calculated that discharge would not exceed 53% in one and 48% in the other). Alternatively, I can run average loads for two average nights in succession. Maybe it's overkill, but I'm confident of achieving 10+ year life (as they're sealed AGM batteries and I'm fastidious about re-charging).

Now excuse me while I go and re-arrange my sock drawer. :screwy: :)

[Marios]

So basically Michael it all depends what you want to do now and in the near future. Take note of your mounts power consumption 2A at max draw, laptops about 3 - 4A max draw, DEW heaters about 3 - 5A MAx Draw.

You wont draw 2A from your NEQ6 unless you are slewing at top speed so really draw is at most times less than 1A when tracking a object at rate 3. Write off 40% of the batterys claimed capacity as not usuable ie. 12AH becomes a 8AH. Then you get a true expectation of the available power in Amps per hour. Go atleast a 12AH AGM Battery for just pure observational use of your telescope.

Good luck :thumbsup:

[MrB]

Confirmed. At least for the ones I saw, obviously I can't speak for all of the various 'starter packs' out there.

When I was managing a Jaycar store we would get one or two customers a week chasing a replacement battery for their starter pack.
All of the old batteries were about half the weight of the equivalent sized replacement.

[Marios]

Generally SLI type batterys in those things good for a burst of energy to jump start and not much else. If you dont charge them regularly they die a quick death.

[guggle]

Yesterday I spoke to someone at Battery World. He suggested a 12v 7AH AGM battery for around $39 (I think the brand was Panasonic) or 9AH for about $10 more plus $29 for a charger. At this stage I don't have any other accessories other than the fan at the bottom of my scope and probably won't get any more for a while, so I think I'll settle for the 9amp battery.

Thanks everyone for your input, it's great to get some good advice!

By the way, I mentioned the fan at the bottom of the scope. I asked what it was for when I bought it, but I've forgotten the reason. Would someone please refresh my memory..

Cheers, Michael.

[raymo]

Your primary mirror needs to be at or very near ambient temperature
to perform properly, so you should put the scope outside an hour or
so before you start viewing. The fan cools the mirror, so you don't
have to wait so long for the mirror to equalise. Until it equalises you will see some turbulence in your view, which is warmth from the mirror
rising up inside the scope.
raymo

[guggle]

Thanks!

[Astro_Bot]

Forgive the information dump ... :)


Power drawn by the fan will depend on size and design, but assuming it's a typical 80mm fan, it'll be around 3W. The NEQ6 in sidereal tracking draws 11W (I've measured it) and 22W at max slew speed, so that's 14W total for the majority of the time assuming the fan remains on. At 12VDC that's equivalent to 1.17A. I'll assume you're happy to go a bit over 50% depth-of-discharge for a battery you intend to replace maybe in a couple of years, so let's say 60% is the limit. With a 9Ah battery, to not exceed 60% discharge at 1.17A, you'll get around 5 hours usage*, less if you slew a lot.

For an AGM battery you should use a charger with AGM mode (they need different voltages). A 3-stage smart charger is recommended - bulk, absorption and float being the three stages. The charger should be sized for the Ah capacity of the battery to maximise life and not overheat the battery, though the acceptable range is fairly accommodating and opinions vary somewhat. The battery manufacturer should state the maximum initial current and (hopefully) afix it to the battery - do not exceed this. In the absence of this info, the rule of thumb is: charger rating (maximum current) = 0.3C, so for a 9Ah battery, the charger should have a rating of no more than 3A. However, AGM batteries are usually more tolerant of a higher initial current, and also going a bit smaller doesn't hurt too much.

* A note on capacity:

Typically, the manufacturer labels the battery with the C/20 capacity - that means when the battery discharges at a current of 1/20th it's capacity (which will take 20 hours). E.g. a "40Ah" battery only has 40Ah capacity when discharged at 2 Amps. Discharge faster and the capacity dwindles.

For a 9Ah battery, C/20 is 0.45A. Your equipment will draw more than twice this current, so the useful capacity will be less than 9Ah, which in turn, will shorten the run time. I don't know the specifics of the battery you're considering, but a rough guess would be a useful capacity reduction of 15-20% and a run-time reduction to 4 hours.

[guggle]

No problem at all!! Thanks for the info! :thumbsup:

[pfitzgerald]

I've been thinking of a portable supply also. Does anyone have any thoughts/knowledge about one of these? I'm thinking that I'd be able to run my HEQ5-Pro, two Kendrick dew heaters and the Orion Autoguider camera off this in one go.

PS I'm not trying to HJ the thread, but thought it would be better to add here, rather than start a new thread. :-)

http://www.ebay.com.au/itm/Matson-MA44AH-44Ah-12V-Portable-Power-Supply-Camping-Power-Fridge-/111099345438?pt=AU_Car_Parts_Access ories&hash=item19de097a1e

Matson MA44AH 44Ah 12V Portable Power Supply, Camping Power, Fridge




Output Voltage: 12V DC & 5 Volt DC (USB)
Type of battery: 2 x 22Ah high quality SLA batteries
Dimensions: 260mm x 285mm x 255mm
Weight: 16kg
Output Media: 1x accessory (cigarette lighter) 12v, 15A socket, 1x merit 12v, 15A socket, 1 x 5v 2A USB port, 1x 50amp Anderson plug
Protection: 2 x On/Off switch with LED indicators, 2x 15A manual resetable circuit breakers
Digital voltage display: Battery voltage, current draw, charging current
LED for: charging status, low voltage, fully charged
Charging option: 12v DC charger, max 15A

[guggle]

WOW! That's some serious power! A bit pricey for what I want now, but it might be useful down the track as I start to add gear. I also have considered the Celestron Power Tank (http://www.celestron.com/astronomy/celestron-powertank-12v-power-supply.html) which can be bought from Australian Geographic for about $200.

P.S. If you make a mistake in a post, you can edit it, rather that repost it. ;)

[pfitzgerald]

I actually double posted - unintentionally, and found that I couldn't delete the whole thing.

I'm currently using a Celestron Power Tank with my school's telescope. Initially I used it for running an EQ5 mount, but now use it for the dew heater only. When used for just running the scope I comfortably got four-five hours out of it if I ensured that it was fully charged before I started. I did notice that after several months of use its performance was starting to drop off a bit, but since running on mains power at home I haven't tried it on the mount for quite some time.

Paul

[Marios]

Dont bother mate you are paying for the nice box and connecitons, plus the battery is a SLA not a Deep cycle AGM which is best for your application. You can get a 55AH AGM with a power tank box and you would be be better off. http://www.ebay.com.au/itm/AQUATRACK-LARGE-POWER-BATTERY-BOX-SOCKET-12V-CONDITION-TESTER-Boat-Caravan-4x4-/190712548749?_trksid=p2054897.l4276

[pfitzgerald]

Thanks for that Marios I'll look into it. :)

[Marios]

Those power tanks are waste of monet cheap SLA battery's that dont last the test of time. I strongly suggest you dont use the wall charger if you get a power surge on the mains it will fry youre board. There have been a few threads on tha thappening to people, stay with a battery for the scopes primary source.

[Marios]

Chargers can be expensive make sure there AGM rated but you dont need a high powered one even 1 .25 amp Charger is good enough jus tmeans will take longer to charge generally over night.

[Astro_Bot]

That's the same box I have (I have 2). They're a tad cheaper at Repco (RRP $75 last time I looked and sometimes on sale for ~$50, which is what I paid). They may also be available at other stores.

[pfitzgerald]

Thanks Guys - So I'm looking at:

One of these,
http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=190712548749&fromMakeTrack=true&ssPageName=VIP:watchlink:top:en

One of these,
http://www.ebay.com.au/itm/12V-55AH-super-heavy-duty-AGM-SLA-deep-cycle-Battery-/181195721237?pt=AU_Sport_Scooters_A ccessories&hash=item2a301b4a15

And one of these
http://www.ebay.com.au/itm/PROJECTA-PC400-12-VOLT-4AMP-BATTERY-CHARGER-6-STAGE-AUTOMATIC-GEL-AGM-SLA-12V-/281199805734?pt=AU_Car_Parts_Access ories&hash=item4178d08526

Would that be right? It will also need cables/adapters to the three bits of kit yes?

Paul

[Larryp]

Hi Paul
I think you can do much better than that price for the battery. There are sellers who market batteries that are more than 12 months old but are still new and unused, at big discounts, and these batteries are fine-I have been using 40Ah AGMs that I bought for $50.00 each, and they are fine

[Astro_Bot]

Mainly, that's true - 1.25A would be fine for a 9Ah battery, or even larger.

But there's a technicality that's probably worth mentioning - lower rated chargers (that supply a low initial/maximum current) won't de-sulphate the battery as well as higher current chargers (though there are other factors such as age, temperature that come into play). For maximum life, the rating of the charger should be no less than 1/20th the nominal battery capacity.

If you only have one battery, there's no issue - just choose a suitable charger. Difficulties may arise if you use one charger for batteries of different capacity - then you'll have to pick a "happy medium" for your charger.

[Astro_Bot]

I concur with Laurie that the price for the battery is excessive - you can do much better - shop around.

[The_bluester]

Yeah, I know that stuff. I bought it as it it was available and cheap and it has done the job for a couple of years so I have no complaints.