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Cigarette lighter to AC power inverter with mount?

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#1 Jon Rista

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Posted 24 February 2014 - 09:40 PM

I have a quick question about powering my mount (and, really, my DSLR and laptop) out at dark sky sites. I know that the most common solution is to use a high capacity battery, but I have a 75W BESTEK AC power inverter that plugs into my car's cigarette lighter. I was thinking about buying a more powerful one to power my equipment out in the field (I do not believe 75W is enough to power everything)...but I am curious if anyone has done this before.

I've heard the power signal from these things isn't necessarily the cleanest, however since the power is being converted to direct current for all of the devices anyway (they all have their own DC power bricks that plug into AC outlets), I am curious if that even matters.

Does anyone have any experience using a car AC power inverter with their mount? Are they effective?

#2 JMW

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Posted 24 February 2014 - 09:57 PM

I would recommend getting a good deep cycle battery for power and leave your car battery for starting your car when it is time to go. I prefer to avoid AC power inverters and find DC-DC solutions that can work directly from the battery.

I have Canon DSLR 12 volt power supply. Orion now sells one that is pretty affordable. There usually are 12 volt versions for laptops.

#3 CharlesW

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Posted 24 February 2014 - 10:05 PM

As you know, you don't have to kill your car battery, you just have to run it down enough so it doesn't start your car. Not a problem if the AAA truck can get to you. But, I use an $80 deep cycle from Costco and a $150, 400w inverter from Frys. I keep the battery charged at home with a Noco Genius from Amazon.

#4 Jon Rista

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Posted 24 February 2014 - 11:12 PM

Hmm. Good point about running the battery down too low.

How would something like this do, then?

http://www.amazon.co...dp/B000GPV2Q...

400watts, has both AC and DC outlets, two each. That's handy. The only concern I have for most of these types of pre-packaged battery utilities is the 18Ah life...not sure that's enough to handle the mount, camera and laptop (mainly the laptop). I know deep cycle marine batteries are usually recommended...many of those have 40, 90, even 200 Ah capacities.

#5 T1R2

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Posted 24 February 2014 - 11:24 PM

your correct Jon, the 18amphr is not going to be enough, with all that eqp. think about at least a 50+amphr, get the most your back and wallet will allow.

#6 SkipW

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Posted 24 February 2014 - 11:32 PM

As you know, you don't have to kill your car battery, you just have to run it down enough so it doesn't start your car. Not a problem if the AAA truck can get to you. But, I use an $80 deep cycle from Costco and a $150, 400w inverter from Frys. I keep the battery charged at home with a Noco Genius from Amazon.

"Not a problem if the AAA truck can get to you"... don't forget: "and you have phone coverage", and "and the phone works."

But wait! Even if AAA can't get there, not all is lost. Here are some more options:

1) If you're with a group, two words: jumper cables. Know how to use them; this is also useful even in real life - beats waiting for AAA. They really should teach this in Driver's Ed, along with how to change a flat tire.

2) Buy an inexpensive jump-start pack. Keep it charged up. If you use the car battery to power the equipment, start the car using the jump-start pack in a pinch if you have to - that's what it's designed for.

3) Drive a car with a stick shift (after learning to drive a stick if necessary) and park facing downhill (after learning to "bump start" it).

... just trying to help. :)

Seriously, though, I have used the $40 7-Ah jump-start pack bought to power the telescope to start cars with dead batteries, and I do usually park facing downgrade when observing (and have a manual transmission [whether it's a long enough run to actually work is an open question - it might be - but I'm never alone there, so see 1)]).

#7 Jon Rista

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Posted 24 February 2014 - 11:37 PM

So, I guess the answer really is to pick up a deep cell marine battery with 50+ Ah, a power inverter, and keep the equipment powered separately from the car. Well, that's more expensive than I was hoping, but I'd rather not have to get my car going at a running start. ;)

#8 Chuckwagon

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Posted 25 February 2014 - 01:19 AM

I chose to get multiple batteries. I have two 22ah batteries that I use 1 each to power my laptop and mount. Then I have an 11ah battery that I can use for backup to one of the others, or a second mount, camera, whatever. Each one alone ends up being easy to handle, much lighter than a 55ah battery by itself. So portability does not suffer. And I'm not sharing a single battery with a heavy load. That matters, because as the load goes up, the capacity goes down, and you are more likely to dip into the expended range where battery life is affected.

Also, some components do not play well together. I would never run an inverter, or a dew heater, or high speed motor, etc. on the same battery I'm running my mount with; too noisy, spikey draw and too much chance for odd behaviors. Planning to keep the draw on your battery(ies) from going below half their rated ah capacity will help get the longest life out of them as well. So careful planning of the various loads you will power, the length of time you will power them, and how deeply that will discharge your batteries is a good idea.

Also keep in mind how long it will take to recharge, if you hope to do multi night sessions. A 55ah battery, discharged 50%, on a 3amp charger, will take around 12 hours to charge. This is one area where a DIY project can really be fun, and useful. Matching the right charger, with the right battery, and the right connectors for your use can be an educational exercise. :)

Cheers,
Charles

#9 JMW

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Posted 25 February 2014 - 11:51 AM

For multiple nights of imaging I bring my 5x8 astronomy cargo trailer. It has a 220 amp-hour of 6 volt deep cycles in series feed by 240 watts of solar panels using a MPPT 15 amp charge controller. Under full sun the battery are usually back to 100% by noon.

For stand alone batteries I like 35 amp-hour AGM batteries. They are compact and provide better value than the astronomy related power pack setups. I also use 3 or 7 amp-hour gels batteries for keeping my Sky Commander or Argo Navis feed with 12 volts in the cold weather when the screen heaters are on. I use use Battery Minder plus smart charge controllers for my stand alone batteries. This allow me to keep them plugged into the chargers all the time so they are ready to be used. My chargers have SAE quick connect plugs to mate to the fuse protected batteries. I use 3 socket Cigarette style adapters that also have SAE connectors for mating to the batteries.

#10 Jon Rista

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Posted 25 February 2014 - 02:40 PM

JMW, sounds like you are a true dark sky hunter! I don't suspect I'll be hauling out a 5x8 any time soon, but I do like the idea of having multiple batteries.

My laptop draws 120W DC power, or 176W AC power with it's adapter brick. I think it's going to need it's own power supply. The mount and camera together draw about 40W of power, but since the camera uses an AC power adapter, I'd use that on the same battery as the laptop (only another 13W). I think I'll just pick up a couple of deep cycle batteries with enough power to last a night.

#11 shawnhar

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Posted 25 February 2014 - 03:02 PM

I use a 160ah deep cycle marine I got at the auto parts store for less than 100 bucks. I actually use 2 now, I run a cheap 100w inverter to power my laptop with a separate battery, my guide camera gets interference if I run the cheap inverter off the same battery. (it works but I can guide on much dimmer stars if the inverter is not running on the same battery)
You should run the mount straight off the batter without an inverter as that is just wasting power.
I also just got a 12v stepdown for like 12 bucks on ebay to run the camera, will be cutting the cord of the ac adapter and wiring straight to the 12v battery.

#12 bseltzer

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Posted 25 February 2014 - 09:01 PM

Jon,

Do I understand that you're looking to go from DC to AC via an inverter and then back to DC to power your mount, computer, etc.? I'm no EE by any stretch of the wildest imagination, but it seems to me that's an inefficient way to go. At each stage of the conversion, you're loosing power to heat, etc. The other thing is car batteries are 'starter' type batteries. They're intended to deliver a hefty jolt to a starter motor for short periods of time. They don't tolerate power draws over the long term well, and if discharged beyond a certain point, they may fail to take a full recharge. Not good.

I'd stick with a full DC solution as has been suggested utilizing a good deep cycle battery with rated at 60 - 80 Ah as a minimum.

#13 Jon Rista

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Posted 25 February 2014 - 09:49 PM

I do understand that there are conversion inefficiencies. Problem is my laptop is a good six years old now, and I'm not sure I can find a direct DC power connector for it. I've looked, and maybe I'm just not using the right search terms, but I haven't found any direct DC power cables that can provide the kind of power I need. It's a large Sony Vaio, 18.4" screen, and it's current AC adapter provides 19.5V 6.4amp power. I've found some "universal" laptop power connectors that plug directly into a cigarette lighter (I'd just cut off the plug and wire the cables directly if I got one), however the most amperage I've seen is around 4 amps. I guess I could scrounge up some cabling myself and wire the necessary sony connector onto the computer side...but I'm not an electrician, and I don't want to fry the thing.

Regarding direct DC connections for Canon cameras, I've found some, and they seem to be surprisingly expensive. Orion seems to have the cheapest one at around $110, I found a few others before that one that were well over $200. I have a real hard time paying that kind of money for something that should be pretty strait forward. I've found AC battery adapters for my 7D for as little as 10 bucks, and I purchased one for $22. Spending so much more for a 12V DC connection...eh, tough sell, even if there are some inefficiencies in conversion.

As for the mount, I'll be going DC direct for sure. The mount only draws 2amps, so a smaller battery around 22Ah should be fine.

#14 bseltzer

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Posted 26 February 2014 - 12:24 PM

For your laptop, try searching for this "Sony VAIO VPC-Z21TGX Car Adapter" The ones I found were rated at 90+ Watts and were priced around $20 - $40. It would surprise me if it needs more than 4 amps even if it is 7 years old.

I don't know enough about DSLR's in general and Canons in particular to offer any options there.

#15 rmollise

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Posted 26 February 2014 - 01:25 PM

I have a quick question about powering my mount (and, really, my DSLR and laptop) out at dark sky sites. I know that the most common solution is to use a high capacity battery, but I have a 75W BESTEK AC power inverter that plugs into my car's cigarette lighter. I was thinking about buying a more powerful one to power my equipment out in the field (I do not believe 75W is enough to power everything)...but I am curious if anyone has done this before.

I've heard the power signal from these things isn't necessarily the cleanest, however since the power is being converted to direct current for all of the devices anyway (they all have their own DC power bricks that plug into AC outlets), I am curious if that even matters.

Does anyone have any experience using a car AC power inverter with their mount? Are they effective?


Power cleanliness is not really a factor with modern (non vibrator, that is) inverters. And especially not with a laptop, since what you are doing is charging the battery, which is running the computer. The problem is efficiency. An inverter will suck down your battery in a right quick hurry. I wouldn't run from my car unless I had a buddy along to jump me off at the end of the evening. ;)

Best bet? Run anything that can be run on DC from DC. Use an external battery, not your car battery, and use an inverter only when you MUST have AC.

I do run my laptop from an inverter. What I do is charge the laptop fully before leaving home to ensure max runtime. It is plugged into a little inverter I got from harbor freight, which is plugged into a jump start battery. That will run the PC all night, and has been a decent solution for me for years. ;)

#16 Jon Rista

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Posted 26 February 2014 - 01:41 PM

I've looked at the Sony VAIO Car Adapters before. They seem to provide the 19.5V, but only 4.7 amps. The old VGN-AW190 that I have is one of Sony's largest laptops. I bought it at the time to do programming on a contract job, and it had a nice, huge 18.4" 1920x1080 screen, and a pretty powerful processor. It's old enough now that it's processor draws more power for less "power" than anything on the market today (especially the Haswell stuff.) I don't know if there is a 19.5V adapter out there that can deliver the necessary amperage for my laptop.

Rod, I would use the laptop's battery, however it stopped charging properly about a year ago. I generally drained and charged it full each use, but it still ended up encountering a memory problem. I get about 7 minutes battery use time before the laptop simply powers off. A replacement battery for this laptop is $160, and I'd rather spend that money on something else.

#17 Hilmi

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Posted 26 February 2014 - 04:01 PM

My mount is powered by a hamster on a mini treadmill. He doesn't mind I treat him with high calorie chocolate bars for his efforts.

On a more serious note, that's why I love my polarie. 4 AA batteries keep me going all night! I carry enough batteries to last me a week on each trip

#18 Phillip Easton

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Posted 26 February 2014 - 10:11 PM

My mount is powered by a hamster on a mini treadmill. He doesn't mind I treat him with high calorie chocolate bars for his efforts.


Don't you get little pellets in the gears? Would think that would cause high non-periodic error. Hard to guide out ;)

#19 Hilmi

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Posted 27 February 2014 - 01:30 AM

It's not pellets, its dry lubricant. Better than the high end bicycle teflon spray on dry lubricant






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