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Bruce N
member


Reged: 04/01/13

Running the CPC off my car battery new
      #5992179 - 07/26/13 11:18 PM

How long can I run my cpc 800 off my car battery from the cigarette lighter jack without draining the battery?

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Stacy
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Reged: 09/15/02

Loc: Seattle, WA
Re: Running the CPC off my car battery new [Re: Bruce N]
      #5992189 - 07/26/13 11:31 PM

Quote:

How long can I run my cpc 800 off my car battery from the cigarette lighter jack without draining the battery?




Hi Bruce.

The answer to that question depends on the type and condition of your car battery. However, you should be able to use your scope for a few nights without any problems. Always smart to charge between sessions if possible. Why do you ask?

Stacy


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Digital Don
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Reged: 01/20/04

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Re: Running the CPC off my car battery new [Re: Bruce N]
      #5992287 - 07/27/13 12:53 AM

Quote:

How long can I run my cpc 800 off my car battery from the cigarette lighter jack without draining the battery?




Even though Stacy's answer may be accurate, I think the real question you should ask is "How will get home if I can't start my car?"

If you observe with friends who could jump start your car in an emergency, no problem. If you observe alone, it's really not prudent to run a telescope and it's ancillary equipment from your car battery.

You might consider buying a 'jump start battery' to run the scope. They are relatively inexpensive, rechargeable, and can power a scope and anti-dew equipment for a number of hours.

Don


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Bruce N
member


Reged: 04/01/13

Re: Running the CPC off my car battery new [Re: Digital Don]
      #5992300 - 07/27/13 01:04 AM

Yes, that is the question. I've just not wanted to spend the $50 bucks to buy a jump start battery. But thanks. I'll buy one tomorrow.

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rigelsys
Vendor (Rigel Systems)


Reged: 08/22/06

Re: Running the CPC off my car battery [Re: Bruce N]
      #5993981 - 07/28/13 12:57 AM

$38 at harbor freight

http://www.harborfreight.com/12-volt-jump-start-and-power-supply-38391.html?c...

plus you might be able to get another 20% off


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David Knisely
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Reged: 04/19/04

Loc: southeastern Nebraska
Re: Running the CPC off my car battery new [Re: Bruce N]
      #5994005 - 07/28/13 01:21 AM

It would work OK if it was a brief one-time deal, but there is a problem with doing this long-term. Car starter batteries are intended to provide a brief high-current burst of electricity for the starter motor, and not to provide a constant low-current output (although they are quite capable of doing this occasionally). Their plates tend to be rather thin, and under a low constant current draw, the plates can have their lead flake off. This can (if carried on long and frequently enough) eventually damage the plates and reduce or kill off the battery's ability to provide that big burst of power needed to start the car, potentially leaving you stranded. This is one reason why it is recommended that some external battery system (preferably deep-cycle batteries) be used for powering scopes and other electronic hardware in the field. Clear skies to you.

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Stacy
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Reged: 09/15/02

Loc: Seattle, WA
Re: Running the CPC off my car battery new [Re: David Knisely]
      #5994073 - 07/28/13 02:34 AM

Quote:

It would work OK if it was a brief one-time deal, but there is a problem with doing this long-term. Car starter batteries are intended to provide a brief high-current burst of electricity for the starter motor, and not to provide a constant low-current output (although they are quite capable of doing this occasionally). Their plates tend to be rather thin, and under a low constant current draw, the plates can have their lead flake off. This can (if carried on long and frequently enough) eventually damage the plates and reduce or kill off the battery's ability to provide that big burst of power needed to start the car, potentially leaving you stranded. This is one reason why it is recommended that some external battery system (preferably deep-cycle batteries) be used for powering scopes and other electronic hardware in the field. Clear skies to you.




I have been using a jump start / power supply / air compressor type battery from Costco. It seems it's capacity is far more than the "power tanks" I own from Celestron and others. I wonder what type of batteries are in those?

I know what you mean about auto batteries . I have 4 6-volt golf cart battteries (also from Costco) wired in series and parallel to provide 12v DC power for my rv. I know they are designed to provide a continous power supply and be able to discharge up to 50% or so on a regular basis.

Stacy


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David Knisely
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Reged: 04/19/04

Loc: southeastern Nebraska
Re: Running the CPC off my car battery new [Re: Stacy]
      #5994134 - 07/28/13 04:28 AM

Quote:

Quote:

It would work OK if it was a brief one-time deal, but there is a problem with doing this long-term. Car starter batteries are intended to provide a brief high-current burst of electricity for the starter motor, and not to provide a constant low-current output (although they are quite capable of doing this occasionally). Their plates tend to be rather thin, and under a low constant current draw, the plates can have their lead flake off. This can (if carried on long and frequently enough) eventually damage the plates and reduce or kill off the battery's ability to provide that big burst of power needed to start the car, potentially leaving you stranded. This is one reason why it is recommended that some external battery system (preferably deep-cycle batteries) be used for powering scopes and other electronic hardware in the field. Clear skies to you.




I have been using a jump start / power supply / air compressor type battery from Costco. It seems it's capacity is far more than the "power tanks" I own from Celestron and others. I wonder what type of batteries are in those?

I know what you mean about auto batteries . I have 4 6-volt golf cart battteries (also from Costco) wired in series and parallel to provide 12v DC power for my rv. I know they are designed to provide a continous power supply and be able to discharge up to 50% or so on a regular basis.

Stacy




Some are standard lead-acid (often sealed) while other are AGM (absorbed glass mat). However, most tend to be more in the "starter" style of battery rather than deep-cycle. Clear skies to you.


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cn register 5
scholastic sledgehammer


Reged: 12/26/12

Re: Running the CPC off my car battery new [Re: David Knisely]
      #5994185 - 07/28/13 06:11 AM

I think the predictions of doom running a mount off a car battery are a little over done.

The CPC on it's own takes about 0.5A when tracking, that's 6W, about the same as one interior light.

I don't think that will kill a car battery in a night unless the battery is already on it's last legs. But if you add all the extra paraphernalia - dew heaters, CCD cameras, laptops in particular - then that's more of a problem.

I ran a NS11GPS and a laptop through an inverter off the car battery for the duration of the transit of Mercury a few years ago and it wasn't a problem.

More of a problem will be tripping over the long trailing lead, that's a good reason to get a power supply that can be hidden under the tripod.

Chris


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Stacy
Star Partyer
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Reged: 09/15/02

Loc: Seattle, WA
Re: Running the CPC off my car battery new [Re: cn register 5]
      #5995257 - 07/28/13 06:16 PM

Quote:

I think the predictions of doom running a mount off a car battery are a little over done.




Uh huh, sure. And just how do we know you are not the monster?


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cn register 5
scholastic sledgehammer


Reged: 12/26/12

Re: Running the CPC off my car battery new [Re: Stacy]
      #5996955 - 07/29/13 04:42 PM

Do you have something rational to contribute, or are you just being rude?

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brianb11213
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Re: Running the CPC off my car battery new [Re: cn register 5]
      #5996980 - 07/29/13 05:02 PM

Quote:

The CPC on it's own takes about 0.5A when tracking



Maybe yours does. My CPC1100 draws 2.5A at 12V (substantially more when slewing). Add 3.5A for a dew control strap at the objective and 1A for a dew control strap for the eyepiece for a total draw of around 7A. This is entirely consistent with my 70AH deep cycle battery not lasting a whole night except during the short, warm nights of summer.


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cn register 5
scholastic sledgehammer


Reged: 12/26/12

Re: Running the CPC off my car battery new [Re: brianb11213]
      #5997054 - 07/29/13 05:59 PM

2.5A at 12V is 30W. That's enough for something to be getting hot. Have you measured it? With a meter? My measurements of scope power use are far less than this.

4.5A for heaters? Seriously? Are you not concerned about the scope catching fire?

I did exclude dew heaters, Laptops, Coffee makers, aircon and so on, just the scope.

Chris


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Stacy
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Reged: 09/15/02

Loc: Seattle, WA
Re: Running the CPC off my car battery new [Re: cn register 5]
      #5997171 - 07/29/13 07:22 PM

It's much safer to get a dedicated battery. I have actually used my scope battery to start the rv once or twice when I let the starter battery go dead after a week in the woods.

That's when the monster strikes! When your car won't start!!! (Sorry, thought everybody knew that)


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David Knisely
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Reged: 04/19/04

Loc: southeastern Nebraska
Re: Running the CPC off my car battery new [Re: cn register 5]
      #5998768 - 07/30/13 04:49 PM

cn register5 wrote:

Quote:

I think the predictions of doom running a mount off a car battery are a little over done.




I was not predicting any "doom", but only providing a reason why it is not an outstanding idea to use the vehicle's starting battery for long-term low current draw use. I too have occasionally used my vehicle's battery to power my NexStar 9.25GPS for a couple of hours (current drain between 0.5 and one amp except during slewing), but this is only when there is no other option. I have two other portable battery systems which I normally use for the telescope and my laptop because I don't want to stress the van's battery too much. One problem many vehicle owners have is that they do not pay enough attention to the age or maintenance of their vehicle batteries. In those cases, long term use of a low-current application can shorten vehicle battery life or potentially kill off enough of that high current capacity to make that battery unable to power the vehicle's starter motor properly. This can be a real problem under cold winter observing conditions as battery capacity is already reduced by the temperature. While it might be unlikely that the use of the vehicle's battery to power a single scope will completely kill the battery, it is at least somewhat possible that an inattentive observer who neglected to keep their vehicle battery up to snuff might end up stuck out in the middle of nowhere unable to start their vehicle even though that battery was moments before happily powering their telescope. This is what I am cautioning against. Clear skies to you.


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rigelsys
Vendor (Rigel Systems)


Reged: 08/22/06

Re: Running the CPC off my car battery new [Re: cn register 5]
      #5998867 - 07/30/13 05:59 PM

CPC is spec'd at 12 VDC-1.5A (Tip positive)

Celestron's recommended AC-DC wall wart is 2.5A

My experiences is with age and cold and lubrication stiffening, 2x that is required to keep the voltage up so the computer doesn't reset when slewing.

And it makes a dandy hand warmer

Edited by rigelsys (07/30/13 06:01 PM)


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cn register 5
scholastic sledgehammer


Reged: 12/26/12

Re: Running the CPC off my car battery new [Re: rigelsys]
      #5998911 - 07/30/13 06:36 PM

This is a load of FUD. Have you actually measured the current drain?

The reason for the high peak current specification is obvious to anyone who understands how DC motors operate and has nothing to do with the average current. The average current is what matters for battery life.

Still, It won't wreck the mount. Carrying vast amounts of unnecessary batteries around won't do any harm, other than to your bank balance and your back.

You don't have to believe me. You can measure the current. Meters are easily available for a few pounds and you can measure what current your scope takes.

Astronomy is supposed to be a science, why not do some?

Chris


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RTLR 12
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Reged: 12/04/08

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Re: Running the CPC off my car battery new [Re: cn register 5]
      #5998930 - 07/30/13 06:49 PM

Quote:

Astronomy is supposed to be a science, why not do some?




Anyone ever try to run their mount on potato batteries?

Stan


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rboeAdministrator

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Reged: 03/16/02

Loc: Phx, AZ
Re: Running the CPC off my car battery new [Re: RTLR 12]
      #5999306 - 07/30/13 11:45 PM

I've run my NS11 several times with my car battery. Switched to the Starizona battery pack; which will not last a Messier Marathon. Almost though.

I have since started using a Lithium Ion Fe battery I bought for a motorcycle. I've only used it for a few hours at a time so I have never come close to tapping it out. Expensive but seems to have gobs more power than the Starizona.


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rigelsys
Vendor (Rigel Systems)


Reged: 08/22/06

Re: Running the CPC off my car battery new [Re: cn register 5]
      #6000492 - 07/31/13 07:47 PM

Quote:

This is a load of FUD. Have you actually measured the current drain?

The reason for the high peak current specification is obvious to anyone who understands how DC motors operate and has nothing to do with the average current. The average current is what matters for battery life.

Still, It won't wreck the mount. Carrying vast amounts of unnecessary batteries around won't do any harm, other than to your bank balance and your back.

You don't have to believe me. You can measure the current. Meters are easily available for a few pounds and you can measure what current your scope takes.

Astronomy is supposed to be a science, why not do some?

Chris




Fact not FUD. Stepper motors are not DC motors. Stepper pulse currents are as high as 1A, depending upon load.

I've had to upgrade the AC/DC power supplies on a fleet of 10x 8" nexstars over the last 10 years due to lubrication stiffening causing current draw to gradually increase with age which causes handsets to crash (pulling down the voltage). You know, actual experimentation in the field, not arm chair science... tho you might try Ohms law. V=IR... assume V = 12V, look up R for typical stepper specs, solve for I... Higher current, more torque. Am in the habit of running steppers at currents that make them nice tea warmers.

Edited by rigelsys (07/31/13 07:56 PM)


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