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Don't know how to build a powertank? neither did I


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Hi Everyone :smiley:,

Like alot of people on this forum and in the amateur astro community as a whole I think that a large AH powertank is the way to go.

So, I looked througout the forums for ideas, but couldn't find anything that told me what exactly I needed and exactly how to build it.

I thought the best thing to do is just to ask someone. so, I got into contact with Mark (sgl member Lardy) for advise on this project.

He gave me a full parts list and a diagram for how to put it together.

Not knowing anything at all about electronics, I asked that he make it more of an 'idiots guide to building a powertank'.

I then layed out all of the parts as labelled in the diagram.





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Right, next part - The build!

First off was to drill the holes for the cigarette sockets and isolator switch. This was done with a 29mm boring bit (I bought a cheap one on ebay for about £1.70 inc delivery).

When the box arrived it already had some dense foam inside. Initially I thought about removing this this to provide more space. Luckily the space between the foam fitted the battery perfect so I left it.

The first step was to prepare and attach the wire. I decided to do the negative side first.

Please bear in mind that I have never tinned wire and soldered before so it looks a little rough.

Picture number 4 show the 17.5amp wire (labelled 'heavy wire in the written diagram). this wire was 'tinned', where you cover the wire in solder to improve the connection (at least that's what I think it's for).

The wire is looped round the battery connection through the battery connector and the cover and into the terminal.

This is the only 17.5amp black wire (negative) used.

Picture 5 shows the 8amp wire during the preperation stage. The wire is tinned and soldered to the spade connector. Then the spade cover goes over and then the heat shrink. I don't have a heat gun so I used a hair dryer to seal the heat shrink.

One end of the wire goes into the terminal block and the other into one of the cigarette sockets.

Picture 6 is the illustrates the powertank once all the negative connections have been completed.

Back later, with how I connected the isolator switch and the positive connections.





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Hi again, back with the final couple of posts.

Right.... So at the moment the negative side of the powertank is complete, I can move on to the posotive side.

Because safety was a concern of mine I wanted to fit an isolator switch, this means I can cut the power whenever I want. It also allows me to isolate one socket and use that purely for charging whilst the rest of the tank is unpowered.

Pictures 7,8 and 9 shows the first section of wiring (battery to isolator switch and charging socket).

The 17.5amp wire goes from the battery, through the battery connector and cover, this then attaches to a 10mm ring connector.

The ring connector is going to be fitted to one end of the isolator switch. Also coming from the ring connector is some of the 8amp wire, which will be connected to the charging socket via a spade connector.

Don't forget to tin all of the wire first. please make sure you make sure the wire is correct length first (something I forgot to do myself. This meant I had to solder two pieces together and seal them with heat shrink.

Picture 9 shows the tank with these wires connected.





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Final part now.

Now it's time to connect the isolator switch to the fuse box.

I forgot to take a picture of this but it's basically the thicker 17.5amp wire with a 10mm ring connector one end and a 6mm ring connector the other. (remember to put the loose heat shrink over the wire beforehand as it won't fit over once you've soldered the ring connectors on).

I'm sure there are lots of fuse boxes out there and I don't know (at all) the difference between them. This one was recomended to me, so this is the one I've got. It is a 6 way fuse box with leds, these light up so you can tell which fuse has blown.

They take standard blade fuses and are connected via spade connectors.

Originally I had planned to use 2 3amp fuses and 1 4amp fuse for my mount. Unfortunately the 4amp fuse was too thick to fit the fuse box so I went with all 3amp ones. I'm not sure whether they are all made like that or if I just got a dodgy fuse.

This final part of the build is fairly simple, I just cut 3 of the 8amp wire and solderd spade connectors to each end (again, not forgetting to out the spade connector cover on before).

Pictures 10 and 11 show the wire pre and post heat shrink (please forgive the quality of soldering as I've never done it before).

Well that's it, finished! :grin:

Pictures 12,13 and 14 show the finished powertank (I forgot to put the cover on the fuse box :embarassed:)

As you can tell it's quite a bit bigger than the 7ah celestron one.

So looking back was this build a success and am I glad I took the leap and did it?


I know nothing at all about electronics, I have never soldered before and my general diy skills are comical!

But with some help from people on this forum I have managed it and I hope this thread inspires people to try and make there own.

I'd like to give a special thanks to Mark (lardy) for all of his help and patience throughout this project.

Oh yeah...... Forgot to mention....... It works! I tried each socket with my Heq5 pro (not out in the field yet). The led light is solid with no flickering even at maximum slew rate.

Cheers for reading, and please ask if you have any question (not technical ones though :huh: ).







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Hi Stuart,

Looks ok and you will have enough power for weeks!

Only note of caution...The battery looks like an unsealed open-cycle type, used for cars, caravans, camping etc so it will release explosive hydrogen gas during charging!

You will have to make sure you leave the lid open during charging or you might blow yourself up!

The other problem will be corrosion of the electrical connectors, again due to gasses released during charging.

A series of say four 10mm holes drilled along the bottom and top edges of both short sides of the box will ventilate the box sufficiently to prevent hydrogen build-up.

The other option would be to replace the battery with a sealed closed-cycle gel type, this is the type of cell usually found in the commercial power tank, but an equivalent capacity battery to the one you have would cost more than a hundred pounds, a few ventilation holes work out a lot cheaper!

We use similar battery-in-the-box solutions to power medical equipment used away from mains supplies but with an inverter built in as well for 12vDC to 230vAC.

In our battery boxes the manufacturers usually build in a 12v fan to force air through the box during charging since the inverter modules tend to inhibit good air-flow.



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very nice build mate, happy for you.try and get some silocone grease to cover the battery terminals or at least some petrolium jelly, also have you seen how bright your leds are with dark adapted eyes in case they are to bright. one last touch you could add, i bought a lovely voltage display in red led so you can see how much power you have left in your tank, cost about a fiver on ebay, would be a nice touch,you can find my tank in this section if you want to have a look,just to say it again nice job

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