Battery Box for Imaging setup

[kirkster501]

Hey guys, i am thinking of building a 100A battery box from a Leisure battery. It'd be a nice job made from wood with better connectors than cigar plugs and would be fused etc

From this box I'd be powering Mount, CCD, FW, and PC (after PC battery discharged). I'd also build an inverter into the battery box

Can anyone foresee any issues with such a system please (other than it being heavy ) For instance I read somewhere that CCD's don't like to "share" a power supply?

Thanks, Steve

[ollypenrice]

It's a good idea and, potentially, a time saver. I had a German guest a while back who had done something like this. All his electronics were in alloy cases which he didn't need to open because their contents were wired to sockets on the outside of the cases. He had labelled looms which simply plugged into the outside of the cases. Very organized and very effective. A little insulation might be good for the battery as well and would add a bit of bulk but little weight.

While havng a separate supply for the mount is supposed to be a good idea I doubt that many mobile imagers go that far. From the earlier post it might be an idea to run guider, imaging camera and F/W independently back to the battery terminals, though, to avoid risk of new noise.

Be very careful about polarity with the mount. (What scares me to death in my observatory is the 24 volt power supply for the Tak mount. It uses the same connector as 12 volt. An accident waiting to happen...)

Olly

[russellhq]

It's a good idea and, potentially, a time saver. I had a German guest a while back who had done something like this. All his electronics were in alloy cases which he didn't need to open because their contents were wired to sockets on the outside of the cases. He had labelled looms which simply plugged into the outside of the cases. Very organized and very effective. A little insulation might be good for the battery as well and would add a bit of bulk but little weight.

While havng a separate supply for the mount is supposed to be a good idea I doubt that many mobile imagers go that far. From the earlier post it might be an idea to run guider, imaging camera and F/W independently back to the battery terminals, though, to avoid risk of new noise.

Be very careful about polarity with the mount. (What scares me to death in my observatory is the 24 volt power supply for the Tak mount. It uses the same connector as 12 volt. An accident waiting to happen...)

Olly

Sounds very German

[Wolfgangwand]

Steve , what size inverter are you planing on using / ratings ?

[tferrari]

I built mine using a rigid plastic rolling toolbox with 2 wheels. It holds 2 75AH batteries, 12V distribution panel (separate fuse for each output), 1500W sine wave AC inverter, dew controller, USB hub. All of my cabling from the mount runs back to this box and I have a single 30 foot USB cable that comes out of it to my PC so I can operate it from a distance if necessary. Works like a charm.

It's heavy and bulky, and I often run it with only 1 deep-cycle battery unless im going on a road trip without access to power for a while to help with weight issue.

It is quite cluttered but I only open it to turn the AC inverter on. Perhaps some more cable management is in order.

Setup time is practically nothing now as my cable bundle has all the perfect length of cables without any snagging or pulling. When I'm done, i just unplug from the mount, throw the bundles into the box, turn off a power switch. I can store some odds and ends in the box too when moving my mobile setup around.

I've seen some better designs, but a better design wouldn't change how poor the skies in this area are anyways.

[Russe]

Naw, I don't think I can do that... I need an electrician friend...

When is someone going to open up an eBay shop with these batteries???!!!

[tferrari]

It's terribly easy to wire if you have some basic experience with electricity and a soldering iron. If you're looking for prebuilt boxes (or at least some ideas), look at the power packs on Kendrick Astro's website.

[Russe]

It's terribly easy to wire if you have some basic experience with electricity and a soldering iron. If you're looking for prebuilt boxes (or at least some ideas), look at the power packs on Kendrick Astro's website.

There's the trouble. "Basic experience" is lacking. Lol!

Mechanically I'm fine. Electricity is beyond me...

[Macavity]

I think there is justified concern with some CCD cameras re. operational voltage. I was also getting a certain amount of "barring" on a Watec Video camera when run off the common / general observatory supply. (Much of this introduced by a deep cycle charger kicking in occasionally!) The over-voltage typical of the deep-cycle battery (~13.5V) had insufficient headroom to stabilise at 12V, so I have a pair of up-converting Laptop supplies. One delivering 19V to a netbook / laptop. The other set to 15V, reduced / stabilised / filtered to 12V by classic 7812 circuitry - As a dedicated camera supply.

I just feel happier with a (relatively) expensive camera requiring "12V +/- 10%" getting something close to that. A bit more convincing than the (sometime) sightly wooley documentation advice to avoid connecting the camera until the supply voltage has dropped slightly from freshly charged values.

I haven't actually built a "Sarcophagus" for the battery. In observatory context, less necessary? Voltage distribution is via die-cast boxes, busbars, fuses, switches, sockets, bulkhead feed-throughs etc. Have thrown in a couple of red LED DVM modules to monitor voltage / current (across a 20A shunt)... You name it? The "mission control" fantasy?

[starnut]

There's the trouble. "Basic experience" is lacking. Lol!

Mechanically I'm fine. Electricity is beyond me...

I built this and know sod all about electricity and dew heaters

http://stargazerslounge.com/topic/176399-12-volt-power-supply-distributer/

[Oddsocks]

Hi Steve,

I keep meaning to write a post about the dangers of using a 12V DC to 230V AC inverter in combination with low voltage equipment but I fear my skill with plain language is not strong enough to explain clearly.

I had the awful experience of having to administer CPR to a camper on the next pitch to mine who had been electrocuted using one and went into cardiac arrest half way up a Cumbrian fell side, no mobile phone signal, pouring with rain and five miles from the nearest village, it took fifty minutes before help arrived and four of us took turns at CPR but the outcome was grim, the casualty wasn't found for quite some time, being past midnight and dark no one was around to react immediately.

So what is it that makes a mains inverter dangerous?

Apart from the obvious danger of dew formation on the power sockets, this can be avoided by boxing the inverter, but this wasn't what had electrocuted our neighbouring camper, he had been in the tent and dry, cradling a laptop in one hand, running the laptop AC/DC converter off the mains inverter and it is assumed he either accidentally knocked or touched the negative battery terminal crocodile clip with his free hand.

The subsequent inquest showed that the inverter was working to it's normal specification and wasn't damaged but there existed an AC voltage difference equivalent of half the inverters output, 115V AC between the laptop and the battery terminals.

A technical expert pointed out at the inquest into the accident that the term 220 AC, 230 AC or 115V AC etc is a bit misleading as well since these are an RMS (route mean square) value, something used in electrical engineering to give an equivalent "power" rating to an AC waveform that has a similar "power" that would be produced by a pure DC source.

In the inverter the 230V AC output had a peak voltage of 339V AC and between the laptop and the negative battery terminal there existed a peak voltage of 162V AC.

This applies in the home too, the 240V AC in that wall socket has a peak voltage of 339V AC in the U.K.

Given the damp conditions that night this was enough to stop the victims heart even though he was young and quite fit.

Various countries around the world, most notably Australia, have been trying to improve the safety of DC/AC inverters following a surge in deaths and injuries amongst campers and hobby sailors in recent years.

So far international agreement has been slow to materialise.

At the accident inquest the maker/importer of the inverter absolved responsibility by referring to the instruction leaflet that came with the inverter stating the inverter must only be used with a grounding rod or permanent earth and that in certain situations where the connected equipment had an earth to neutral connection then there could exist a dangerous voltage between the connected equipment earth and the battery terminals.

Unfortunately, the evidence is overwhelming that a lot of people, and anecdotally most men, don't read instruction manuals but "put them aside" to be read later when necessary.

On the campsite we stayed at there were no earthing rods provided and it wasn't a legal requirement.

None of the other witnesses at the inquest had known that this inherent danger existed with AC inverters even though several had similar inverters,

The representative from the manufacturer/importer stated that the AC inverters were never intended for use by campers in such a way, they were intended to be permanently fitted to caravans or boats where the battery was isolated away from the power circuits but this was not in their literature.

This was the case with the laptop power converter, it had a connection from the earth pin of the AC/DC power converter lead to the common zero volt line going to the laptop.

This meant that the magnesium alloy frame and the chassis of the laptop had a voltage difference of 162 V between it and the battery terminals.

Apart from the safety implications of using an inverter under such conditions what about the danger to the equipment?

Clearly if you connected your mount and camera directly to the battery and then powered your laptop from the inverter, now you go to plug in that serial port or USB connector to the mount or camera, there could be a voltage difference of 162V AC.

You could easily destroy the mount or camera electronics as well as receiving a shock if you held onto the camera or mount with one hand while plugging in the lead with the other.

For astronomy imaging DC to AC inverters can cause interference which shows up as random web-like or "Hum-Bar" noise patterns in the image, particularly the cheapest so called "modified" sine wave inverters.

For "electrically quiet" operation the pure sine wave inverters are the most suitable but they cost two or three times as much for the same output.

Obviously it would be better if no astronomer (or camper) actually used an AC inverter, for laptops and other small electronic devices you can buy a DC to DC universal travel adaptor which have no dangerous high voltage AC present.

Here is a link to a universal travel adaptor at Maplins that works with a 12V DC input as well as a 120V AC to 240V AC input so powering that laptop in the field becomes much safer:

http://www.maplin.co...or-plugs-341898

If you really must use a DC to AC inverter then the ONLY safe way is to power everthing off the AC inverter, mount, laptop, camera, heaters etc etc, all must be powered via their appropriate AC to DC converters and nothing other than the AC inverters connectors may be connected to the battery, the battery terminals and all cabling have to be made so that neither you or anything else can touch the 12 DC wires and at the same time touch any of the connected equipment.

This has the downside of very high battery drain due to the losses in double conversion process.

I do hope that someone better able than I at getting the technical description across will write a post about the dangers of using AC inverters and it is pinned to the top of the getting started forums.

I never want to have to go through that experience again, no one should be killed or injured in pursuit of a fairly benign hobby like ours.

Do yourselves a favour, leave AC inverters in caravans or boats where they belong, as First Officer Spock would have it "Live Long and Prosper"

William.

[kirkster501]

Thans for an excellent commentary William. Most interesting. The only reason I need an inverted AC supply - 240V provided by the inbuilt inverter on a jump start battery pack from Maplins - is to provide the 240V input to my electroluminescent flats panel. Everything else I can power with 12vDC. The flats panel transformer requires 240V, provided by the tranformer they supplied with the panel and the output - i.e. the voltage fed into the panel itself is 90V AC. I built the EL panel into a wooden frame and the xformer is mounted on the back of the flat panel with a mains lead that hangs of and plugs into the battery pack inverter.

Is there some means to provide 12v from the battery - as per the normal cigar lighter - to some device that then provided the required 12vDC to 90vAC so that the only trailing lead is 12vDC? That would negate thd need for an invertor competely.....

Steve.

[Macavity]

The current requirements must be fairly minimal? There seem to be quite a few 12V to 90V A.C. "EL Inverters" on the market - Usually in small, sealed plastic boxes. Most to illuminate lighting cable / strip, but some capable of illuminating A5... A4 panels? Such (EL things) are used by PC case modders (mea culpa once!) so must be fairly child / idiot-proof? LOL. Far safer than the canonical 300W AC inverter, whatever?

[Oddsocks]

Hi Steve,

Glad you liked the post, sadly the issue has become a bit of a bete noir of mine since the accident, makes me cringe whenever I see somebody posting that they are going to integrate an AC inverter into a battery box.

Here is a link to a sealed 12V to 90V E.L. flat panel power supply for $15, should do what you want.

I have an E.L. panel in my obs' but sometimes struggle with frequency banding in the flats so I'm going to make a white light LED panel over the next month or two.

This would be my second attempt, the first used 30 of each red, green and blue LED's in a matrix with two diffusers spaced 10cm apart, and it worked well for the L-RGB filters but was less efficient with the narrow band OIII.

Now that the wide band white LED's are so cheap I thought it was time for another go.

William.

[Oddsocks]

Sorry Steve, that link I "tried" to give you was shipping to the US only.

Blame it on the Pinot Grigio that I had too much of with Sunday Lunch.

Here is another shipping to the UK from China for £1.81 !

http://www.ebay.co.uk/itm/12V-DC-to-AC-Inverter-for-EL-Lamp-Wire-Electroluminescent-3M-Meters-/230836323429?pt=UK_Home_Garden_Night_Lights_Fairy_Lights&hash=item35beeac465

There's quite a few on e-bay once you search under the term "electroluminescent"

William.

[Oddsocks]

And here's another EL power module from RS for a bigger 12x12cm panel for ~ £25 ex vat but you would need to make up the connector leads yourself.

http://uk.rs-online....erters/2678863/

NOTE: the RS web page says this power module is for 30cm² panels but the data sheet says it will power up to 160cm².

[Oddsocks]

Finally, here's a E.L. panel power supply from Hong Kong that will power an A4 sized sheet for ~ $5

http://www.ebay.co.u...=item35c9860775

Regards,

[kirkster501]

Thanks for the links. Seems a lot of them don't power a A4 sheet though. It might be worth giving the last link you posed a try.

For now I am imaging from back garden so have access to mains via extension cable with RCD to power the flats panel.