battery packs

Hello, I was curious if anybody has an opinion on the celestron 12v battery packs?
Is there something better ? they run $75 for the slightly more powerful.
I have dew heater straps for starters, then maybe another item.
Thanks

Those battery packs you see from Celestron and others (and from your local Walmart and Kmart Auto section) are, deep down inside, a $15-30 battery, readily available on the internet, with some interesting connectors and lots of casing.

If what you want is cost and weight effective power, I would suggest you google "SLA 12 volt battery" You will find any one of a thousand suppliers. These are what are used inside the power packs you are asking about.

While you are there, buy yourself a separate batery charger designed for these things ($8-15). I should say, though, that you may already have one or more of them around the house.

THen go down to your local Radio Shack, auto parts store, electronics warehouse, whatever, and buy yourself a cord, or whatever connectors you want, and make up your outlet arrangement.

You will have the functional equivalent of the power pack for half the price, less weight, and smaller form.

(Now, whether they will be sufficient for your uses, that will depend on how much elecctricity you use. I simply do not have experience with dew, so cannot advise you there. )

Alex

Brian Pope said:

Hello, I was curious if anybody has an opinion on the celestron 12v battery packs?
Is there something better ? they run $75 for the slightly more powerful.
I have dew heater straps for starters, then maybe another item.
Thanks

Brian,

Whether you buy or build, the key item to consider is how much power you will need to make it through your typical viewing session. Batteries are rated in terms of Amp-hours. The battery inside the Celestron Power Tank is typically a 17 to 20 amp hour rating battery.

The math is simple. If you only pull one amp at 12 volts, then you will have 17 to 20 hours of power available max. If you pull 2 amps, you'll have 8.5 to 10 hours of power, and at 4 amps you'll only make it 4.25 to 5 hours. These are theoretical maximums, and if you want your battery to remain healthy you will not want to completely discharge it. Also be aware that as the battery discharges the output voltage sags. Some electronics may malfunction, motors will stall, etc. when the voltage drops below 12VDC.

As Alex states, cheaper batteries are available and are the same class that come in the Celestron and similar "power tank" setups. These are typically sealed, lead acid batteries and are not rated for repeated deep cycle use. There are more expensive Gel based AGM batteries that are rated for repeated deep cycle discharge. They tend to have a longer life cycle.

The best small battery charger setup I've used is the Deltran Battery Tender. For a single battery, the Battery Tender Plus model is rated for continuous, long term connection even when the battery is in long term storage. The plus model cycles the charge voltage over time to "stir" the electrlyte and thus insure the battery does not sulfate. It keeps them healthy for years. I use them for batteries in Tractors, ATVs, an RV, and a boat.

One thing to always remember, you are not suppose to completely drain a battery of any type. So when you see a rating of 15 amp hours, think of using only 20-30% of that or you will hurt the battery in most cases. But under no circumstance should you drop below 12v with any battery.

I have one of the Celestron units. I got it from a friend with a dead battery. I bought a replacement battery for about $15 and replaced it. It works fine but is only good for a single mount for a night before you have to recharge it. The more you slew, the faster it runs down.

The good thing about one of these units or others like it is the availability of different voltages for running things. This can be handy.

But the best way to power is to get a Deep Cycle Marine style battery that is quite heavy and has a lot of power. Then you can run for multiple nights if needed or run other things besides the mount. I bought two from WalMart for about $70-80 each and they have a lot of power and will take some running down without damage. It is heavy to carry but it has a carry handle and 1/4" wing nuts and posts to allow you to put things on it like a multiple cigarette lighter plug. They sell one there with 2-3 receptacles and all you have to do is cut off the male end and put the wires on the terminals or put eyelet connectors on the wires if you like a nice neat solution.

Hi Brian,
All good advice. Prior to the remote setup I'd go to the field for several days and power was always an issue. I drained the car battery in the field more than once and needed to do something different. Here is an image of a DIY 3-bank setup with charger power-supply and both "visual" voltage monitoring and "computer" voltage and current monitoring. It is very heavy 75pounds, used AGM deep cycle sealed batteries, but worked. Three banks with 21 amp hours each. One bank for cameras, one for computers, and the third for mount and focus.

Best,
Dave

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When I go out to a remote dark site I tend to stay for several nights so I use 100A AGM batteries designed for commercial UPS applications. I charge during the day with a 150 watt solar panel. The batteries power the scope, CCDs, computers and all the other stuff we use while imaging. The charge regulator has a handy display which shows voltage and amperage while charging or discharging. I have a second panel for the "Moonlight Manor". I have spent as long as 10 nights "boondocking" at TSP, RMSS, ESP and trips to the middle of nowhere. The large AGM batteries are not cheap and heavy but it sure beats a dead battery when you are 50 miles from a power plug and they are cheaper and quieter and less hassel than a generator.

John
CCD-Freak

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Never forget that cold takes away from a batteries capacity. So if it is very cold, you have to compensate.

I have a motorhome with a generator that I use to charge the battery during the day. I run a regular charger and run it for 1-1.5 hours as needed. I have done this a few times without a problem. But I carry two batteries as well as a power cord from the cab batteries that I can run out to the mount and computer. IF you are out for days you have to be prepared for any situation or you will end up having a problem that will shut you down. 8)

Thank you all for replying, some great things out there and appreciate the knowledge input. For starters, I am going to go with the deep marine route, and put some of those nicely crafted case setups for future possible remote use.