Which power supply for a mobile astronomer?

[Delboy_Hog]

Hi Folks,
 
I was hoping to get your views on a suitable power solution for when I pack my kit up and take it all out away from home.  I’ve been working with the little Skywatcher 7Ah power tank for the last few years, and it’s served me very well indeed.  However, I acquired a new mount a little while back, an HEQ5, which seems to take a lot more power than the little old Synscan AZ goto.  I’m spending a bit more time travelling to dark sites to escape the local light pollution, and so when I’m under dark skies and the conditions are good, I don’t want to be limited to the couple of hours of power that the little power tank gives me on the HEQ5 when I’ve got the dew straps going too.
 
Ideally I’d like to be able to power both the HEQ5 and the Synscan AZ goto – one for imaging, and the other for observing while the camera is clicking away.  That potentially means 2 mounts and 2-3 dew straps on the go too.  In the interests of future-proofing, it would be handy if the power supply could keep a laptop going too, in case I decide to invest in a CCD camera.
 
I don’t think the larger 17Ah power tank would quite cut it on a long cold night with all of the kit going, so I guess it’d be between the leisure batteries, where it’s easy to pick up a 50+Ah battery for £50, and the more expensive tracer batteries as sold by First Light Optics.  Size / weight wouldn’t be too critical for me, though being portable and safe (when sat in a car / tent) would be.  It would also help if it was ‘plug and play’ like the power tank I have now, as wiring and the like makes me a bit nervous!!
 
Does anyone have any views or experiences that would help with making the final decision?
 
Many thanks for any help you can offer.
 
Derek

[Davey-T]

If you're not fussed about the expense then a big Tracer battery is good but as you say there is no facility to connect anything just one cig' socket or a couple of terminals.

Two mounts and dew bands won't require anything huge but depending on its power consumption a laptop is another matter.

I use a 40ah Tracer LifePo battery that runs my setup all night with no problems but is fitted inside a jumpstarter case in place of the original battery so has USB sockets and built in light.

Dave

[kendg]

Look into using a small portable generator.  A 2000 watt one should be just great. While is will be bigger than a large battery/inverter it probably won't weigh as much.

Works like a charm for me and it wasn't a whole lot more than using batteries and inverter.

Plus you'll be really popular when you let others plug into it too

[Delboy_Hog]

Thanks Dave.  That mod you made to the Tracer sounds really handy!

Thanks Ken.  I hadn't thought about that as an option - off to do a bit of researching to see what I can find out!

[AlistairW]

Out of interest - is the generator particularly noisy ?

It's the power drain of the laptop (for imaging) that has always concerned me. I can get a cheap inverter etc ... but sounds like I would need a large amp hour battery ( heavy one ) to keep up.

Alistair

[dannybgoode]

I've just ordered one of these puppies. Looks fine for now but may change the battery at some point to a slow discharge leisure one. 

http://www.eurocarparts.com/ecp/p/car-accessories/car-accessories-products/emergency-and-breakdown/booster-pack/?529771111&0&cc5_824

Luckily my laptop has a very long battery life so don't really need to worry about that but I do have an inverter if necessary for a top up. 

[Waldemar]

Add up the maximum power consumption of all the equipment you are going to use in Amps, multiply that with twice the time you need it to work for example when using lead-acid batteries, or 1,2 times with LiPO4 batteries

2 mounts using 0,5 Amps average each (depends on slewing times), two dewheaters 1,5 Amps each, 1 camera with cooling  2,5 Amps, 1 laptop 60 Watts average = 5 amps  total 11,5 Amps per hour.
If you want to be able to use it for example 3 nights of 6 hours in a row, that is 18 hours, the powerconsumption will be 11,5 Amps x 18 hours = 207 Ah. Of course those figures vary with the equipment used.
if using LiPO4  batteries, 250 Ah  would be sufficient to run that setup, but with leadacid batteries you will need about 400 Ah, because of the voltage drop during discharging.

So as you can see this is going to be an expensive venture...
The remark to use a silent portable generator is smart. Your total power consumption will be about 150 Watts (never run a generator above 70% of it's capacity) so you will need at least a 250 Watts. I think the smallest ones are about 500 Watts,
so you are good with those. Not expensive on Amazon either.  If as suggested you like to do your fellow astronomers a favour, or want some extra for a little coffeemaker, the sky is the limit off course...

[BRUN]

do you not think you could wire up your own power box ?

im making one at the moment, my 22Ah battery cost me £35, plywood was spare out my shed, then probably £10-15 on connectors etc

[Waldemar]

Sure you can... all that is needed is some knowhow about electrics and soldering skills, nothing special.

My comment was about the needed power to run a setup for some executive nights.

With the mentioned set up, including cooled camera and laptop, you can run for 1,5 hours at the most with a 22ah battery
keeping it warm with a plywood casing does make a difference in those cold winternights.

[BRUN]

sorry not you Waldemar, i meant the OP

[cjdawson]

I use a 70Ah leisure battery from Halfords.  It's quite heavy, but the up side is that there should more than enough power to run two scopes, laptop, dew strips, cameras and more.

Here's what mine looks like.

[Delboy_Hog]

18 hours ago, AlistairW said:

Out of interest - is the generator particularly noisy?

That's a good question - it's pretty rare that there's anyone else around where I go out on a night, but if it's relatively quiet so that no-one can accuse me of disturbing the peace when I've got it fired up and running, then this would certainly be a good option. 

 

10 hours ago, Waldemar said:

Add up the maximum power consumption of all the equipment you are going to use in Amps, multiply that with twice the time you need it to work for example when using lead-acid batteries, or 1,2 times with LiPO4 batteries...

Thanks for setting out the sums so clearly Waldemar, that's really helpful, especially taking the laptop / camera etc into consideration as well.  So on that basis, I'd need to go a bit bigger than I was probably thinking, to be on the safe side.

9 hours ago, Waldemar said:

or want some extra for a little coffeemaker...

That's genius!  I've lost count of the times where I've drained my thermos flask of coffee within a couple of hours and then wish I had a bit more on me to keep me awake for the journey home! 

 

9 hours ago, BRUN said:

Do you not think you could wire up your own power box?

Not at the moment BRUN, don't have the skills, knowledge or equipment to do it (safely!), though I might be tempted to do a bit of research, as it sounds like a really good way of customising to get exactly what would be useful.

 

8 hours ago, cjdawson said:

I use a 70Ah leisure battery from Halfords.  It's quite heavy, but the up side is that there should more than enough power to run two scopes, laptop, dew strips, cameras and more.

Here's what mine looks like.

Thanks CJ, helpful to see it in context.  I think I'd probably be ok with the weight, and the amount of power you get for the price is excellent compared to some of the Tracers etc that are available.  Hmmm, options options...

 

[AKB]

23 hours ago, kendg said:

Look into using a small portable generator.  A 2000 watt one should be just great. While is will be bigger than a large battery/inverter it probably won't weigh as much.

If noise was the problem, then for a price (although not TOO much these days) a hydrogen fuel cell could be the answer? 

[kendg]

20 minutes ago, AKB said:

If noise was the problem, then for a price (although not TOO much these days) a hydrogen fuel cell could be the answer? 

The Evopower ones look pretty quiet too. Also seem to be a bit cheaper on Amazon UK

https://www.amazon.co.uk/Evopower-EVO20i-Suitcase-Inverter-Generator/dp/B00J7LKV0M/ref=sr_1_36?s=outdoors&ie=UTF8&qid=1484677580&sr=1-36&keywords=generator

[Waldemar]

Maybe we should ask Elon Musk to wrap his head around this one... 

[Waldemar]

1 hour ago, Delboy_Hog said:

11 hours ago, BRUN said:

Do you not think you could wire up your own power box?

Not at the moment BRUN, don't have the skills, knowledge or equipment to do it (safely!), though I might be tempted to do a bit of research, as it sounds like a really good way of customising to get exactly what would be useful.

 

For DC the oinly thing you need to know is that RED is plus and BLACK is minus. For the cable to use it depends on the amps that will run through it, but you can safely use 1.5 mm wiring for 7,5 to 10 Amps. continously for the main powerlead. From there you can go with 0,5 to 1,0 mm for the separate applications. You will need a soldering tool, though, preferably with a small pointy tip. After having you fingers burned a couple of times you will get the hang of it.

If you want to master it, remember that the soldered connections should be shiny, if not, they are not okay and you have to do them again. A third hand is a very handy tool for this kind of work.  Keeps the parts still and spares your fingers  :-)
And... use multicore soldering tin, but not too much.

It is really sattisfying to make things your own... exact length and the amount of connections you need.  RCA connectors are very nice to make a powerhub with.

[wookie1965]

10 hours ago, cjdawson said:

I use a 70Ah leisure battery from Halfords.  It's quite heavy, but the up side is that there should more than enough power to run two scopes, laptop, dew strips, cameras and more.

Here's what mine looks like.

I love this when funds become available I will be buying all the bits for one.

[Stu]

It will always be batteries for me. Regardless of how quiet a generator is, as close to total silence is how I like my observing, far more relaxing. I use a 22Ah Tracer battery which I am very happy with.

[Delboy_Hog]

35 minutes ago, Waldemar said:

It is really sattisfying to make things your own...

Thanks for the tips in your message   My father-in-law is a bit of handy man and I've seen him soldering things before - I think he'd probably quite enjoy the challenge of helping me to figure it all out, and as you say, I love that satisfaction of having worked on something yourself.  Perhaps my (slightly late) new years' resolution should be to get stuck into this little project!

[Delboy_Hog]

8 minutes ago, Stu said:

It will always be batteries for me. Regardless of how quiet a generator is, as close to total silence is how I like my observing, far more relaxing. I use a 22Ah Tracer battery which I am very happy with.

I see that Stu, definitely.  Part of my love for this crazy hobby is the peace and quiet, so it would have to be pretty quiet for me I think, if I was to go down this route.

How has the Tracer been for you so far?

[RayD]

Couple of tips if soldering:

• Make sure you use pre-fluxed solder (needed to let the solder flow correctly
• Make sure all the surfaces are nice and clean
• Make sure you have a soldering iron of the correct wattage.  This is really important if soldering plastic fittings as too cold means you need to hold the iron on the work longer and the plastic can start to melt.  Irons are available in wattage, so get one which will get your solder and work nice and hot quite quickly
• Cool the work quickly if soldering plastic plugs.  Keep a small damp cloth close by and just dab to cool

If soldering you would normally use some heat shrink tubing to cover the joint.  Make sure you run the tubing right up the wire before soldering as the wire can get warm and shrink the tube before you want it to.

Have fun building your box, it is really rewarding, and you can make it just how you like it 

[Stu]

10 minutes ago, Delboy_Hog said:

I see that Stu, definitely.  Part of my love for this crazy hobby is the peace and quiet, so it would have to be pretty quiet for me I think, if I was to go down this route.

How has the Tracer been for you so far?

The Tracers are expensive but worthwhile in my experience. They hold their charge for a long time without needing recharging, and just seem to deliver to their rated capacity very well. I have a 110 Ah leisure battery which rarely gets used now, mainly because it is so heavy and needs regular charging.

[Delboy_Hog]

Thanks Ray - I really am quite tempted by this now...

[RayD]

1 minute ago, Delboy_Hog said:

Thanks Ray - I really am quite tempted by this now...

It's a doddle Derek, but just make sure you get a decent powered iron.  Something like this one from Amazon at 60w is ideal for small jobs, and will also be hot enough to shrink the heat shrink tubing.

Don't forget to do a little thread with pics if you go ahead.

[Waldemar]

4 minutes ago, Stu said:

The Tracers are expensive but worthwhile in my experience. They hold their charge for a long time without needing recharging, and just seem to deliver to their rated capacity very well. I have a 110 Ah leisure battery which rarely gets used now, mainly because it is so heavy and needs regular charging.

Absolutely agreed. The Tracer (LiPO4) not only hold their charge very well, but the discharging curve is very flat. A normal lead/acid battery goes below 12v  very fast.