Battery Problems.

[lonebod]

I got one of the Skywatcher 7A powertanks about 9 months go. It's been fine for me as I only ever manage a couple of hours observation time.

In the last month I've noticed the length of time i get power from the powertank has reduce dramatically and I now only get about 30 minutes.

Has anyone has similar experiences? Any one got any advice on if i can fix it?

[Scott]

that's not good is it, even taking into account the cold weather being more of a drain. What are you running off the battery? lastly, would this be covered by a warrentee? I have no idea what a warrentee would cover on a battery. I guess you could try and keep the battery warm to try and get more out of it but I'm not sure it would solve your problems

[russ.will]

Unfortunately, these power tanks are based on a cheapo lead-acid battery, which isn't suited to the role of continually being drained and then charged up. This dramatically shortens the life of the battery. Whether or not this one is faulty, you'd be better off in the long run replacing the battery with a gel golf cart/trolley battery which is designed for that sort of duty cycle. It might be an idea to see if you can fit a higher capacity battery in there whilst you're at it, as 7Ah is a bare minimum. I use one of these and it always outlasts me!

I'd also note that the GOTO Dobs are very heavy and don't half use some juice in slewing. Assuming your encoders are up to snuff, I'd make a habit of pushing the scope to the correct part of the sky and just letting the GOTO do the last bit and tracking.

Russell

[ronin]

I go with Russ the battery is not a match to the use.

If they drain they get "damaged" and so hold less charge. The problem is that "drained" is not when they supply too little to drive the scope it is when about half the capacity is used. So they are driving your scope but reducing their life at the same time.

Unfortunately we tend to stand outside and stop using them when they stop supplying sufficent power, at that time the damage is done.

Standing doing nothing will discharge them also, so drained and a new one eventually required.

[brantuk]

I used to run my 12" goto dob from a 17ah power tank. I only used the power for "near object" finding and centering after moving it manually near to what I was looking for, and then tracking. It was good for a 4 hour session even in the cold - but always needed recharging. I'd have big doubts about using a 7ah one. More amp hours is the answer to your problem - an 80ah leisure battery will cost as many pounds from a caravan center shop, and will last all night. Hth