Astrocookie Posted June 6, 2013 Share Posted June 6, 2013 Hi. I'm thinking of building a field power supply with a leisure battery to power everything. What sort of Ah battery would you suggest. I would like to power my laptop with a 12 targus step up unit. 70W. I'm stepping down the 12 to 6 for my motors. Low current skywatcher dual axis eq5 jobbies! Everything else is via USB on the laptop! Oh. And I might mod the Dslr to eliminate the battery. I'm thinking around 45Ah. Anyone's thoughts appreciated. Gracias Paul Link to comment Share on other sites More sharing options...
Brantuk Posted June 6, 2013 Share Posted June 6, 2013 Check out local caravan and camping stores Paul - you can get 110ah leisure batterys for around £90-£110 or 85ah for a bit less. Enough in either of those to last all night and more. Link to comment Share on other sites More sharing options...
xanthic Posted June 6, 2013 Share Posted June 6, 2013 I'm not sure I'd remove the dslr battery. You don't want to get any ground loops. Discreet power supplies would be my preference. Happy to bow to superior knowledge though! Link to comment Share on other sites More sharing options...
Astrocookie Posted June 6, 2013 Author Share Posted June 6, 2013 Check out local caravan and camping stores Paul - you can get 110ah leisure batterys for around £90-£110 or 85ah for a bit less. Enough in either of those to last all night and more. Cheers Kim. I think I can get sealed lead acid batteries hugely discounted but not sure if I can get in 100 Ah. They may do a 75Ah. Do you reckon that'll do the job? Link to comment Share on other sites More sharing options...
Astrocookie Posted June 6, 2013 Author Share Posted June 6, 2013 I'm not sure I'd remove the dslr battery. You don't want to get any ground loops. Discreet power supplies would be my preference. Happy to bow to superior knowledge though! Cheers Leigh Good thinking. I have a Duracell replacement for my 300D and to be fair it's not ran out on me on an evening yet so perhaps 'if it ain't broke....' Are ground loops a big problem with battery supplies. I figured as long as I common 0v I would be Ok. I will most likely use Dc to dc converters for the step down. Paul Link to comment Share on other sites More sharing options...
Brantuk Posted June 6, 2013 Share Posted June 6, 2013 75ah should cover most rigs - mounts and cameras don't draw a lot - but do the numbers on your heat bands to get an accurate figure for how long the total draw will last - then halve it to account for temperature drops and battery run down. I'd be surprised if you didn't get 8hrs all in two nights in a row. Link to comment Share on other sites More sharing options...
xanthic Posted June 6, 2013 Share Posted June 6, 2013 I think you can get problems when you interconnect kit with each other, laptop to mount etc and get voltage variation. I've got a decent explanation in a book of mine. I'll copy it out and post it up later. Link to comment Share on other sites More sharing options...
Perkil8r Posted June 6, 2013 Share Posted June 6, 2013 In my experience removing the camera battery is a very wise move. The heat from the battery pack causes amp glow on longer exposures and generally heats up the camera causing noise and hot pixels. There are some tutorials on the web for converting the old battery to a wired version. I bought mine of Astromiser and it has been worth every penny x 1000% Do bear in mind you might need to add some dew prevention so allow for extra drain on the power source too. Link to comment Share on other sites More sharing options...
dawson Posted June 7, 2013 Share Posted June 7, 2013 Mike Does a battery grip greatly reduce the heat from the battery(batteries) from the sensor? http://blog.martinbaileyphotography.com/wp-content/uploads/2012/06/MBP_Canon_BG-E11_Battery_Grip_20120602_7449.jpg James Link to comment Share on other sites More sharing options...
Perkil8r Posted June 7, 2013 Share Posted June 7, 2013 To be honest I have no idea. I would think it will help, but it's still going to add to the heat in the camera I would have thought. If you can get rid of the battery all together it can only help, not only from a heat perspective but also from the weight point of view. The more weight hanging off the end of the focuser the more the chances of droop on the focuser tube and also of slippage if the focuser is pointing up or down. Link to comment Share on other sites More sharing options...
xanthic Posted June 7, 2013 Share Posted June 7, 2013 This thread on CN gives some decent advice on DC grounding. I did a lot of trawling and still find conflicting information on it though. http://www.cloudynights.com/ubbthreads/showflat.php/Cat/1,2,3,4,5,8/Number/3044153/page/318/view/collapsed/sb/5/o/all/fpart/1/vc/1 Link to comment Share on other sites More sharing options...
Astrocookie Posted June 8, 2013 Author Share Posted June 8, 2013 This thread on CN gives some decent advice on DC grounding. I did a lot of trawling and still find conflicting information on it though. http://www.cloudynights.com/ubbthreads/showflat.php/Cat/1,2,3,4,5,8/Number/3044153/page/318/view/collapsed/sb/5/o/all/fpart/1/vc/1 Thanks for the research Leigh. Everything is going to be tied to the negative terminal on the battery and this will be the only power source so fingers crossed. Cheers Paul Link to comment Share on other sites More sharing options...
xanthic Posted June 10, 2013 Share Posted June 10, 2013 Let me know how you get on. I'm in the market for a power source too. Link to comment Share on other sites More sharing options...
Astrocookie Posted June 12, 2013 Author Share Posted June 12, 2013 Multicell have a leisure battery for £ 50.00 Its an 85Ah weighs about 20Kg The 70Ah I was originally interested in is more expensive than the higher capacity =, so no brainer. Going to fabricate a metal frame with painted plywood sides. Got sidetracked by building a cable hub to reduce the amount of dangling cables on my rig! Link to comment Share on other sites More sharing options...
catman161 Posted June 12, 2013 Share Posted June 12, 2013 Have you not thought about wiring the leisure battery into one of these off eBay? http://bit.ly/11YufKi It's what I use and is very durable and heavy duty. Can't fault it. Highly recommended. I did a thread on mine, I'll see if I can find the link. The box takes anything up to 110ah batteries. Link to comment Share on other sites More sharing options...
catman161 Posted June 12, 2013 Share Posted June 12, 2013 Here's the link to my original post. I have a 3 female socket adaptor plugged into the single female plug socket that comes as standard when you purchase the box. That powers my mount and all my dew prevention kit. Haven't looked into inverterS to power laptop but probably doable. I like how compact the box is for ease of putting in boot of car along with all other gear and getting going. http://www.eastmidlandsstargazers.org.uk/topic/3444-battery-box/#entry38085 Link to comment Share on other sites More sharing options...
Astrocookie Posted June 13, 2013 Author Share Posted June 13, 2013 That looks proper that does :-) Trouble is it would almost double the cost. I have the necessary bits and pieces for construction and connectivity. Plus, I wouldn't get to spend hours in the shed :-) Link to comment Share on other sites More sharing options...
catman161 Posted June 13, 2013 Share Posted June 13, 2013 I got the battery for free and then it was £50 for the box. Pretty good IMO Link to comment Share on other sites More sharing options...
Guest Steve Posted June 14, 2013 Share Posted June 14, 2013 As an alternative for a box how about a wheeled tool chest like this or cheaper: http://www.ebay.co.uk/itm/Stanley-Wheeled-Professional-Mobile-Tool-Chest-Box-Heavy-Duty-1-92-902-/310496533401?pt=UK_Garage_Equipment_Tools_Tool_Boxes_Storage&hash=item484b091b99 I keep my scope bits in the chest and when it is set up I put the battery inside so it is safe and insulated from the elements. I haven't done anything fancy for connections, but it would be feasible to add all the standard connector sockets and meters to the box lid. Just a thought! Link to comment Share on other sites More sharing options...
Al.Grant Posted September 11, 2013 Share Posted September 11, 2013 Just been reading through this thread after a quick forum search ..... I'm looking at getting a mobile power supply sorted out before the dark night really draw in (and hopefully get to get to the dark sky sites at long last!) I have an opportunity to get my leisure batteries at 'trade' price from a friend and want to get a good idea of what to ask him to get. I think it's probably worth checking the prices of gel batteries (he's already said he can get those). Obviously I'll need to power my mount (HEQ5), but ideally I also want to try running the laptop. Looking to the future there will probably be a ccd camera included in there somewhere. At the moment I don't plan on adding dew heaters ..... the vixen VC200L is supposed to be very resistant to dewing, but only time will tell on that one! So far I think an 85ah or maybe a 110ah should do the job, but if the price is right I may see if I can get 2 batteries and run the laptop from it's own battery. This may also give me the flexibility to move the laptop away from the mount if I need to retreat to somewhere a little warmer (car/tent etc). Would I be better going for 2 x 85ah gel batteries, or a single larger battery ? Thanks Link to comment Share on other sites More sharing options...
dawson Posted September 11, 2013 Share Posted September 11, 2013 Cn you get rid of a laptop and use a computing device which uses less energy (i'm not very clever wih these things but i believe those tablets consume much less energy, then you'd be good with an 85 battery for mount and dew bands. Sheila and stephen are the best people to speak to, i think between them they could power half of the east midlands Link to comment Share on other sites More sharing options...
Sheila Posted September 11, 2013 Share Posted September 11, 2013 personally i would not go less than 110 ah and one battery is easier than lugging 2. others seem to have smaller ones but i just like to be on the safe side. if it clear on a dark night from 7 pm to 6 am think 85ah might struggle Link to comment Share on other sites More sharing options...
Guest Tweedledum Posted September 11, 2013 Share Posted September 11, 2013 Hi There, The best way to calculate the battery size is to work out how much power you are going to draw from the battery. The calculation on the drain on the 85ah battery is :-- 100W @ 12 Volts = 8.333 ampere. An 85 AH battery would supply 100W for a little more than 10 hours. Link to comment Share on other sites More sharing options...
Sheila Posted September 11, 2013 Share Posted September 11, 2013 Hi There, The best way to calculate the battery size is to work out how much power you are going to draw from the battery. The calculation on the drain on the 85ah battery is :-- 100W @ 12 Volts = 8.333 ampere. An 85 AH battery would supply 100W for a little more than 10 hours. that is OK for normal batteries but when the battery is at -5 or -10 in a field in belper, i can assure you it does not last anywhere near that long. cold does not help optimum running of the battery it can reduce the time down by up to 40% depending on temperature Link to comment Share on other sites More sharing options...
xanthic Posted September 11, 2013 Share Posted September 11, 2013 You could also get ground loop issues if running off two batteries Link to comment Share on other sites More sharing options...
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