Short battery life (or something else??)

[Stridor]

Managed about 2 hrs of viewing last night after charging up my `Skywatcher 17aH power tank for most of the day when the Light on my EQ6 started flashing. I was also using a Dew tape around the scope, but that is something I tend to do 50% of the time anyway; I could have run an extension cable from the garage to keep things running but was somewhat surprised it only lasted barely 2hrs this time. Anybody have any thoughts; does this sound normal or could something suddenly be amiss? 

[Northern Soul man]

Hi Strider, sounds like the power tank has let you down there mate.  The lead acid batteries in the power tanks seem to need to be kept well charged when not in use,  I usually charge mine after every use, I just leave it on a motorcycle battery optimiser - this trickle charges the unit and keeps it topped up, so you can leave it plugged in and connected for long periods of time.

The power tanks don't like to be left off charge for long periods of time - this damages the internal structure when you come to re - charge, the optimiser/trickle chargers just keep them "topped up" with charge - some place a load on the battery and then cycle through a charge/load/charge routine - may be worth you getting one of these Martin as the batteries become sulphated over long periods when the battery is just left on the shelf, some of these chargers may promise to try and recover the battery to a useable state, but usually the battery is beyond saving - could be time for a new power tank, or most people opt for a leisure battery - these seem to handle the deep cycle routines that us Astronomers put them through.

Let us know how you get on - if one of your friends has one of these chargers - maybe you can borrow and see if you can recover the powertank.

The scope usually draws around an amp or two per hour and the dew heaters (for the larger apertures) can draw around 4 - 5 amps per hour - so the 17 Ah should be good for around 3 - 4 hours max.

Paul. 

[Stridor]

Hi Strider, sounds like the power tank has let you down there mate.  The lead acid batteries in the power tanks seem to need to be kept well charged when not in use,  I usually charge mine after every use, I just leave it on a motorcycle battery optimiser - this trickle charges the unit and keeps it topped up, so you can leave it plugged in and connected for long periods of time.

The power tanks don't like to be left off charge for long periods of time - this damages the internal structure when you come to re - charge, the optimiser/trickle chargers just keep them "topped up" with charge - some place a load on the battery and then cycle through a charge/load/charge routine - may be worth you getting one of these Martin as the batteries become sulphated over long periods when the battery is just left on the shelf, some of these chargers may promise to try and recover the battery to a useable state, but usually the battery is beyond saving - could be time for a new power tank, or most people opt for a leisure battery - these seem to handle the deep cycle routines that us Astronomers put them through.

Let us know how you get on - if one of your friends has one of these chargers - maybe you can borrow and see if you can recover the powertank.

The scope usually draws around an amp or two per hour and the dew heaters (for the larger apertures) can draw around 4 - 5 amps per hour - so the 17 Ah should be good for around 3 - 4 hours max.

Paul. 

Hi Paul

Thanks for that info; I had a feeling a `leisure battery` would have been the way to go in the first place.  I must admit, I never charge up the unit after use, only on the day of using it next; I will have a go at keeping it topped up and see what happens.

Martin

[ronin]

The other thing is when a lead acid battery is drained by 50% then it does not retain charge as much at subsequent charges. So the ability of the battery to run anything slowly (or rapidly) decreases.