Skywatcher/celestron power tanks

[brrttpaul]

Are they any good?. Im sure I read somewhere could even be my own post lol that they are a bad investment. On the other hand I know nothing about electricity wattage amps volts etc im hopeless with it so know I would fail miserably at making one. A third option would be to find someone local that could do it for me I suppose which takes me onto batteries. On FL there are smaller batteries that say they hold the same capacity as a normal lead battery would these be any good or would I need a leisure battery?

[JonC]

I looked at getting one to run my Meade ETX and keep my tablet charged. The 17ah model costs £100ish, you can buy the actual battery bit for about £30, maybe £10 on cables. I have a good car battery charger so use that to keep a battery  topped up, have read that the powertank charger isn't great and will not prolong the battery life. AT the moment I use a smaller battery for mobility.

[brrttpaul]

All I will need it for would be the HEQ5 mount , a laptop eventually and probably the hitecastro focuser, one of the boys in work mentioned a golf car battery but as I said Im useless on it. Saying that now there is a battery factory up by me I may pop in and pick their brains maybe they could make one up at a small charge

[Pyrodave]

Not sure how good the celestron /skywatcher powertanks are but I've gone through 3 of the automotive type power packs in the past .

I now use an 85 amp hr leisure battery and keep it topped up with my optimate  battery conditioner and have never run out of power since .

The trouble with the smaller powertanks is if you let them drain completely they never recover properly

[ronin]

The problem is that the battery is not really correct for slow long drainage.

In a car they give a high power kick to start the engine turning and all the other bits, then the alternator takes over and recharges the battery.

In a power tank we perform a long slow drain, and the battery is not then recharged.

The plates in the battery get "damaged" from the slow discharge and hold less charge. We tend to use a power tank until it will not run the equipment any more, that is again bad for the battery itself. In a car they do not get near being even half drained in normal use.

The battery "design" is wrong for the use we put them to and we ignore this and carry on using them. So they get a short life. If everything is going fine, clear night, good sky, equipment humming away happily. pleasant weather are you going to look at your watch after 2 hours and pack away or are you going to sit back and carry on for another 2 or 3 hours? Remembering that immediatly after the first 2 hours you are then damaging the battery on your power tank - which looks perfectly happy and content.

There are deep cycle batteries that are more suited, they are usually a bit more costly, there are I believe what is used in golf trolly's, they need a different charger. If I recall Maplins do one and they also do a solar trickle charger for them. There are others Lithium based also again not overly costly.

[JonC]

The problem with golf trolley battery's is that its a size not a construction type, so many of the cheap ones are not deep cycle, they are just small. This might be a good option for modest power draw

http://www.hardwarexpress.co.uk/12v-20ah-vrla-deep-cycle-battery-2921-p.asp