DC battery to power laptop etc

[jman17]

Hi,


I want to use a 12Volt DC Battery to power a SkyWatcher Star Adventurer, laptop and DSLR for astrophotography and am wondering if anyone can advise me on the best products to buy and any pitfalls to watch out for. I am looking for a setup that can power a GOTO mount like the HEQ5 too with the capacity to run other reasonable equipment I might buy for astrophotography in the future as well. I plan to use a DC Power adapter to power the laptop and a DC coupler running into a dummy battery for my Canon 450D. I want to use a good, efficient surge protection system as well, but I am not sure of what to get for this. I heard I can use an inverter with this built in but that this is not as efficient. I know that I would need to watch out for the recommended voltage and amps rating for my gear. Would anyone be able to advise me on the best way to go about this, what to buy and from where?


Thanks,
jman17

[LostInSp_ce]

Hi jman, is this a portable setup for offsite use? If so a Marine Deep Cycle Battery which can be found at any boat store will do the job. The no maintenance ones cost more, but it's one less thing to think about. When calculating your total amps remember to do it for the entire night and not just one hour (e.g. 10Ah is 80A for 8hrs). Something else to consider when choosing a battery is size and weight. They're not light and are awkward things to carry around in the dark.

[OzEclipse]

If you look at a laptop charger, they are usually rated quite high, eg an apple magsafe charge is 160W. But this is only when recharging the laptop battery. If you plug in a fully charged laptop, the power consumption will be much less. If you plug in a laptop with a flat battery, that battery will suck the power out of your car battery.

Most mounts use around 0.2 - 1A when tracking and about 2-4A when slewing.

The HEQ5 power supply is rated at 2A so presumably it uses 2A for slew and considerably less to track.

The active cooling on astro cameras typically use lots of power, more than the drive system. Dew heaters can also chew up the power.

A standard cheap small car battery should run your HEQ5 or SW Star Aventurer, fully charged laptop and other accessories for one or possibly more nights. I use a smaller (lighter) car battery to do this so I am not lugging a big deep cycle marine battery. The marine battery will give much more power, the small battery will be easier to handle.

I can run a Takahashi EM200 (basically an EQ6) plus other accessories from a small 260CCA Supercheap Auto battery that cost around $120 has a built in handle and is pretty easy to shift into position under the scope each session. I don't power my laptop and I run sky safari off an ipad and a skyfi. One charge of the car battery lasts at least 2 nights.

A deep cycle marine battery will run your setup for a week but will be very heavy to move around. You have to choose what's right for you.

Joe

[PKay]

This is what I have set up.
It will drive 2 laptops, EQ6, camera cooler and clock for about 12 hours.
I have battery and inverter mounted in the van and I run a 10m cable loom to the rig.

Century N70T 100aHR Deep cycle battery. Very heavy, that's why it stays in the van.
2kW pure sine wave inverter.
Also have large 160W solar panel on the roof.

The 12v cable needs to be at least 6mm because of voltage drop (essential).
USB extensions must be powered.

I don't think this system is overkill. I had tried using a small car battery and it failed halfway though the night.
Better to make the system 100% reliable.

[LostInSp_ce]

A couple of other things I should have also mentioned is that Deep Cycle batteries are designed to provide a steady amount of current over a long period of time so they don't surge as much as car batteries do. They can be deeply discharged over and over (car batteries don't handle this well) and the marine ones are designed to be bashed around in boats without leaking. If you're clumsy like me then this adds a level of comfort in case you accidentally drop it or tip it over when transporting it in the car.

[that_guy]

I've been looking at some dc laptop adapters for my own deep cycle battery. There are some available on jaycar and officeworks that MAY work. some quick googling shows that it might be more preferable to using an inverter as its more efficient to use dc power outride instead of converting dc to ac back to dc again.
Jaycar 150W DC Adapter (https://www.jaycar.com.au/150w-car-laptop-power-supply/p/MP3472)
Officeworks (https://www.officeworks.com.au/shop/officeworks/p/targus-laptop-car-charger-and-usb-fast-charging-port-taapd046au)

[RobF]

I've used a couple of the Jaycar ones for last 5 years with 3 laptops with no worries.

[jman17]

Hi,

Thanks for the advice. It's for my use both at home and offsite. I think that for my situation that a lighter battery that I can easily lift would be a lot better, but I would like to get some advice on surge protection. What surge protection is recommended for a DC 12V battery if not using an inverter with it? I don't want to take chances with my gear but don't want to have to buy a very heavy battery to use with an inverter unless I have to. What would you recommend for this? DIY is really not an option for me. I know that I can get a DC Power Adapter for example with surge protection but how effective would this be and would more levels of protection be recommended?

jman17

[Wavytone]

I use a 12AH sealed lead acid battery (like a motorscooter one) from Batteryworld in Chatswood. They also fitted it with a female socket (mount plugs into this directly) and provided the right battery charger (wall wart type). The reason I chose the 12AH is the rated current output (4A) needed by my mount when slewing - the AZEQ6 motors may stall when supplied from smaller batteries.

If you really need an inverter to power the laptop a “beercan” type will do.

The primary protection needed with batteries is short-circuit protection otherwise they can explode catastrophically and the contents are very hazardous (acid). This can be as simple as an inline fuse or small circuit breaker, though the latter is more complicated (a box, plugs and sockets).

[jimmyh1555]

I use two 12v sealed batteries paralled together. One is an old battery (7A-h) from my NBN unit, the other is a cheapo 7A-h one from Jaycar - ie total 14 A-h. Stickey taped together and as long as I charge them after each night, they seem to be ok. Don't kbow if they will be man enough though when I start long imaging sessions. I will probably then just get a small car battery from the service station. No big deal really. What is all this talk about an inverter? My observatory is at bottom of garden - no mains power down there.....:D

[raymo]

I don't know if you were joking or not Jimmy, but if you want/need to run
a 240v device, then you're going to need an inverter, or 20 12v batteries in series:lol::lol::lol:. For long sessions an inverter is invaluable for running
a laptop, and also my 240v adaptor for my Canon DSLR.
raymo

[jimmyh1555]

I am not joking, Raymo, my HEQ5 runs on 12v. My laptop runs on its own battery. I know what an inverter is. I dont need mains power to run my imaging set-up. I really do not intend to take more than 2 hours to take one photo.

[raymo]

Fair enough James, but rest assured that many imagers are out there
for a lot longer than 2hrs, me for one. I have to take advantage of clear skies when they occur. My laptop's battery lasts 1hr 20m, useless, and I use mains power to run my camera to prevent battery heat problems.
raymo

[Chris.B]

If you want light weight and plenty of capacity and current you want a Lithium battery. They are half the weight and can be drained to 10% with no damage. But they come at a price and require a special charger.
Otherwise go an AGM deep cycle battery. Remember SLA type batteries should only be discharged to 50% of the rated capacity. if you wish to have them last more than 500 cycles.
The output voltage is not constant either unlike Lithium.

[jman17]

Hi,

I have been looking for an AGM DC 12 Volt battery and a store has offered me a 38ah Fusion Gel battery. How would a Gel battery compare to an AGM battery for astrophotography? I know that I would need a special charger.

jman17

[Merlin66]

I regularly use a couple of 20Ah gel cell batteries (now over eight years old and still going strong) with DC to DC converters. I have a 12v to 15v to handle the HEQ5pro and another for the laptop. No issues, no drama.

[RobF]

Glen you can over-ride the Windows power settings to force the laptop to "performance mode". However using (decent sized) batteries with a DC-DC converter that shouldn't be an issue - the laptop "thinks" it is on mains power the whole time - again, providing the batteries are up to the tasks of holding decent voltage all night.

[jman17]

Hi,

Thanks for the help. While looking around for a higher ah Gel battery I found this 60ah Victron AGM Super Cycle battery. http://www.forbesbatteries.com/12V-60Ah-AGM-Super-Cycle-Batt-M5-p/bat412060081.htm I couldn't find much info on the quality of Victron AGM batteries at all online after a lot of searching and was wondering if anyone can give me feedback on their quality? It is a Super Cycle AGM and apparently suited to high current discharging and I am unsure of how well it would suit my needs for astrophotography. It does have a 2 year warranty as well.

Thanks for any feedback,
jman17

[RobF]

You don't need high current discharge rates. Most important thing is the "deep cycle" capability to be ok drained to 30% or lower and ok if recharged reasonably quickly - that and being able to do so over and over. Can't see anything in the specs to say it wouldn't be ok, as long as you can get a decent multi-stage charger that suits it.

I've bought these sorts of things in the past. Your link seems a decent battery for similar pricing.
http://www.ebay.com.au/itm/12V-50AH-GEL-DEEP-CYCLE-BATTERY-GOLF-BUGGY-CARAVAN-4WD-DUAL-SYSTEM-CBG12V50AH-/281203595209?hash=item41790a57c9
(http://www.ebay.com.au/itm/12V-50AH-GEL-DEEP-CYCLE-BATTERY-GOLF-BUGGY-CARAVAN-4WD-DUAL-SYSTEM-CBG12V50AH-/281203595209?hash=item41790a57c9)

[jman17]

Hi,

After getting the advice I ended up buying a Fusion 50ah AGM in a battery box for a power supply. Thanks for the help.

jman17

[RobF]

Hope it does the job reliably for years to come.