Skywatcher/Celestron 7ah/17ah Power Tanks

[TK IAIN]

Howdy Folks.

Just a quick query if you have the time.

Just dropped my Skywatcher 17ah Power Tank (in the garage and a ladder had fallen over on it and it's now completely gubbed bar the radio).

So!Need to get a new one for my Meade LX90 ACF and was wondering if the smaller 7ah model would be of any use rather than a few more pennies on it's big brother.

Just seeing what the more experienced astronmomers think.

[umadog]

It depends on you. Calculate the number of amps your gear is drawing. This information is generally listed in spec sheets, etc. Make sure you count dew heater strips. If you're drawing 1 amp total then the 7 ah battery will last about 7 hours. So it depends how long you use it for and how much stuff you need to power.

These are deep cycle batteries and are designed to power devices that draw fairly low currents and to be run down significantly before being re-charged. However you probably don't want to be running it down too close to empty since doing so may reduce the lifetime. Consequently, you should err on the larger side and plan for the possibility that you will need it for longer and/or will need to power more stuff. The battery will last longer that way.

To save money, I don't buy power tanks but only the deep cycle batteries. You get more capacity for less money this way. All you need is an adapter like this: http://ecx.images-amazon.com/images/I/41OIT3IUIPL._SL500_AA300_.jpg

[ggreene1]

I thought I could save myself some cash by building my own. It has a 12 volt / 7ah rechargeable battery and I charge it with my battery tender from my motorcycle. I have a Celestron 8SE SCT. I have used it several times in a row without recharging it for a total of probably at least 3+ hours. Here a link to a couple of pictures...

http://gordongreene.com/photogallery/displayimage.php?album=77&pid=3060#top_display_media

[LukeSkywatcher]

I have the Celestron 7Ah pack (2 of them). I use them on my 8SE. They are expensive because of the brand name. I got them free with my 8SE.

Basically non-branded 7Ah will be fine.

I believe that Maplins sell excellent packs dirt cheap and they are 14Ah(?)

[ggreene1]

I never did any calculations on load for my telescope. I thought worst case scenario I could add another battery in parallel. I have plenty of room in the small toolbox I built it in. I bought my battery from an online battery company for about $24 as I recall. I almost bought a power tank, but decided to build it from scratch for 1/2 the price. The reason it worked for me is that I had the battery conditioner to charge the battery.

[glowjet]

Just in case you are anticipating buying a separate SLA battery, Battery Masters are quite reasonable, they do the Power-Sonic range which are of excellent quality and have a long shelf life without recharging, not like some others which need to be charged on a regular basis. Last time I looked the 7 A/h was something in the region of £13 and the 17 A/h £34

John.

[garethmob]

Maplins have a 7ah battery with a single cigar port for £24.99 you could just get a multi plug for it then

Sent from my iPhone using Tapatalk

[eekeek]

...

To save money, I don't buy power tanks but only the deep cycle batteries. You get more capacity for less money this way. All you need is an adapter like this: http://ecx.images-amazon.com/images/I/41OIT3IUIPL._SL500_AA300_.jpg

ruff!

Do you need fuses with these? Also, have I got this right? If I attached another lead at the battery for dew strips etc., that would be in parallel so the voltage is the same you are only adding to the total draw on the battery?

[todd8137]

you need something like 30/40 ah will last all night as power levels drop the mount will suffer

[glowjet]

ruff!

Do you need fuses with these? Also, have I got this right? If I attached another lead at the battery for dew strips etc., that would be in parallel so the voltage is the same you are only adding to the total draw on the battery?

You really do need to fuse each circuit to just above the max current you will use, if you do not and there is a hefty car fuse that has been left in the system, you are likely to fry your equipment. The glass fuse in the car lighter plugs can be changed, by in most instances, unscrewing the the silver tip, the Glass fuse is spring loaded and will drop out. You need to measure your total current consumption with everything plugged in, then you can budget for a large battery or split the supplies in two and use two power sources, your choice

John.

[Steve Ward]

Go for the most Ah you can afford , I went for the 7Ah with my HEQ5Pro and is fine until those properly cold winter nights when you want a long session outside , rarely got more than 3 1/2 hrs out of it .

Got a mains fed P.S. now , no more worries when out all night.

[TK IAIN]

Thanks for all the pointers folks and it is very much appreciated.

Think I'll be going for another 17ah model once I get the cash together.

Iain