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17ah or 8ah power tank?


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Hi, I know this question has been asked before however now I want to read it I can't find it! Ok so I have a Skywatcher Power Tank 17ah version which is now dead as a Dodo - see my previous post regarding flashing lights! (not in the sky on the power tank). Therefore I am faced with replacing the battery or replacing the tank. Replacing the battery (assuming this is a simple job for a novice) will cost about £50 and a new tank 8ah will cost about £60 (a new 17ah will cost about £120). Can anyone tell me if the 8ah would be enough for an evenings viewing or do we really need the 17ah. This tank seems large and cumbersome and therefore if you can get away with something smaller for about 3 hours viewing then I would be happy. Any comments would be appreciated. The tank will be running an EQ5 mount with goto etc to give you an idea of what its powering.

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Forget the branded tanks they are Waaaayyyy!!!! overpriced. You can get a power pack from maplins for £40 3-in-1 Portable Jumpstarter : Jump Starters : Maplin Electronics But they are often on offer for much less (around £25). Or you can buy a "leisure battery" which is designed for the drawing of a low load over time and will last much longer in the long run - even if a little more expensive to start with.

To work out what you need simply add the amps from each item you use eg Mount=2Amps, Dew heater = 1 Amp. Total +3 amps. A battery of 40 Amp=hours will run this for 40/3 = approx 13 hours BUT you should only run a battery down by about half so this is realistically 7-8 hours.

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Hunters Wholesalers alarms & Security, have 17Ah Power-sonic SLA batteries which are excellent and have a long shelf life after charging at £31.07 inclusive of VAT, there will be a delivery charge on top of course :)

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Bit of advice on jumper packs, some of the cheaper models are rubbish. They are not meant for sustained useage and just to boost a car battery if it's 'nearly' flat. Having been through quite a lot of these in the motor trade I can tell you a lot of them have poor to dangerous chargers that I have seen last days before just failing or they have actually got so hot they melted. The batteries inside these units are often nowhere near the Ah stated we tested 20Ah at 5 often. Not all are bad but usually the ones that are junk look similar and you may see them in Aldi, Lidl and other 'cheap' stores as well as some supermarkets.

They are pretty much like this one in the attached pic but probably a different label. I have one in my garage that anyone can have for free, it was working last time I looked but that's no guarantee lol.

post-32952-133877752134_thumb.jpg

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  • 3 years later...

I would recommend replacing the battery in your existing power tank. My 17ah Celestron one got wrecked in heavy dew and I got a new 20ah battery from these guys: https://www.tayna.co.uk/ I just had to make sure the dimensions allowed it to fit in the tank. And it's a piece of cake to wire up.

Wheelchair and golf trolley batteries are pretty good at the lower ah ratings (designed for heavier duty than a mount demands). I can slew and track all night for a good 6-8hrs (though most of my sessions tend to be around 4hrs - except in summertime). :)

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Well you can open up the old power tank and simply measure it's dimensions - there's usually type and dimensions against most of their products on their website. If in doubt you can give them a call - they're pretty knowledgeable and give very helpful advice. :)

(I just got a simple lead acid mobility scooter one for my tank - also a golf one for a dob fan.)

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