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Portable 12v Power Box


julian489289
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Thinking of building a power box with 5-6 cigarette type sockets, couple of USB sockets, volt meter and a deep cycle marine battery. With this in mind, I have a couple of queries well more than a couple really:
-What ah for the battery? Looking to power the mount HEQ5, three dew bands, DSLR & electronic focusser. Also my laptop through a coupler which increases the voltage to 19.5v which I already have.
-Is there an alternative to the cigarette style plugs & sockets? I get fed up with cigarette plugs getting loose within the socket and having to power everything down and start again??
-Would you have to regulate the 12v battery supply to the sockets to prevent damage to the equipment?
-What is the best charger, a trickle charger?
Hope someone can give me some help

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To calculate what Ah battery you will need you need to know the current draw of all your equipment.  You can then approximate how long a battery will last from a full charge

A 12Ah battery will supply 12amps for 1 hour, 6 amps for 2 hours, 3 amps for 4 hours and so on.  The time will be shorter than this due to loses

I use screw lock audio connectors for my equipment available from Maplins  http://www.maplin.co.uk/p/maplin-2-way-audio-locking-connector-chassis-plug-fm50e

A battery is self regulating.  If all your equipment can handle up to 14.5 Volts which they usually can if designed to connect to a 12V battery.  12V is listed as the nominal voltage.  14.5 is max voltage when fully charged but very quickly drops under load.  If any equipment uses less voltage ie. 5V you will need to drop the voltage.  A switched mode regulator is more efficient but some stuff doesn't like PWM power.  A linear regulator is clean but loses alot of power in heat to drop the voltage

Any charger designed for the type of battery will do.  My solar kit uses an MPPT charger.  My bike uses an Optimate

Edited by MarkyD
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Thanks Mark, so the audio connectors will be fine for 12v supply,  I take it you just connect up two corresponding pins?

How would I calculate the amp requirement for each of my peripherals, Canon DSLR, dew bands, focusser and guide cam?  :hmh:

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The connectors are rated at 5Amp so will be OK.  For the current draw take the wattage of the dew bands and divide by 12 to get the current

I(amps) = W(watts)/V(volts)

ie.  for a 20Watt band

I = 20/12

I = 1.67Amps at 100% power

The canon, and guide cam will take little current so allow 0.5A for each as a safety net.  The manufacturer may have the specs for the focuser.  Worst case is when stalled as this will ramp up the current momentarily.  The HEQ5 specs say 12V 2Amp so allow 3amp to be safe.

I would also add a few amps on top for future additions

Edited by MarkyD
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The bigger the battery in amp hour (Ah) the longer your sessions will be. Consider the equation with ALL of your equipment working together. If you don't use all of your gear, then you'll get a little longer. Remember, the bigger the battery, the dearer it will be, and the heavier it will be. @MarkyD has given you the calculation above to help with battery selection.

Cigarette sockets are not the ideal as they tend to be rather loose in the socket, and can cause power drop-outs. Remember also that weatherproof sockets are'nt weatherproof when the socket is open.

Buck converters are cheap (about£2 each!) allowing you to drop voltages safely, but if they fail, then the full 12v will pass through (from what I've read). Have a look at my project below. I've used 2 of these in mine, and on the one that will be used for my DSLR, I have built a very simply circuit that is after the converter, which only allows 9v to the camera should the buck fail. Should that fail, then the voltage stops and cannot pass. 

 In regards to chargers, this is the one I use for all of my SLA leisure Deep Cycle batteries, and can be left connected permanently http://www.ebay.co.uk/itm/Sakura-Car-Van-4x4-Bike-12v-6v-5-3A-Automatic-Intelligent-Smart-Battery-Charger-/301663140633?hash=item463c863b19:g:askAAOSwmtJXa-11 

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On 08/03/2017 at 08:40, MarkyD said:

A 12Ah battery will supply 12amps for 1 hour, 6 amps for 2 hours, 3 amps for 4 hours and so on.

The other thing to bear in mind is that even with deep cycle batteries they shouldn't be discharged below 50% for optimum lifespan, and never below ~80%. So once you've worked out your power draw, and how long you expect an imaging session to be, double the number of amp hours!

 

I found one of these useful for my power box build - http://www.ebay.co.uk/itm/12V-Car-4-2A-Dual-USB-Charger-Socket-Adapter-Voltage-Voltmeter-Motorcycle-Orange/252673267574?_trksid=p2045573.c100508.m3226&_trkparms=aid%3D555017%26algo%3DPL.CASSINI%26ao%3D1%26asc%3D20160706105120%26meid%3Deaf894c2adcc4f52b846e34180baabcd%26pid%3D100508%26rk%3D1%26rkt%3D1%26

Solves your USB power and voltmeter in a single device.

 

If you're planning on using dew strips, you can use a PWM controller. I prefer the ones with the dial on a flying lead for ease of mounting - e.g. http://www.ebay.co.uk/itm/UK-New-12V-36V-3A-DC-Motor-Speed-Regulator-Controller-Switch-Control-PWM-HHO-RC-/152095041000

 

It's advisable to have a circuit breaker close to the positive battery terminal, just in case there's a short somewhere, I used one of these - http://www.ebay.co.uk/itm/20-100A-Car-Audio-Inline-Circuit-Breaker-Fuse-Holder-12v-24v-System-Protection-/221846538313

I also fused the individual sockets etc with a blade fuse box - e.g. http://www.ebay.co.uk/itm/12V-24V-10-Way-Blade-Fuse-Box-Holder-LED-Warning-Light-Kit-Car-Race-Rally-Marine-/201624907701

 

So in my case, positive terminal --> 30a circuit breaker --> fuse box --> sockets/PWM/USB --> service connector block -> negative terminal.

I used 6mm cable between the battery and fuse box/connector block and 1.5mm cable for the individual socket circuits between the fuse box and connector block.

 

Of course you could just use something like this, but it's better to do things safely!

Edited by Bagnaj97
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I used these PWM's, and once you take them apart, you end up with exactly the same thing as you posted above http://www.ebay.co.uk/itm/PWM-Dimmer-Controller-LED-Light-Lamp-Strip-Adjustable-Brightness-12V-24V-8A-FT-/111865802969?hash=item1a0bb8b0d9:g:WNEAAOSwKtlWihRN 

30 Amp is massive, are you powering an oven? :) I agree with having a main fuse as soon as the power comes from the battery, and then having every circuit have separate fuses rated just above the expected draw.  My main fuse is 5 amp, but I expect to rise to 7.5 amp perhaps.

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I use a Trojan 24-AGM for my equipment. At 53 pounds, it's a heavyweight. But, it can last a weekend for me without worry about charging.

I have 2 - 12 volt cigarette type sockets attached to it, as well as my AGM charger clipped on. One socket is for my mount, exclusively. The other goes up and branches to my 1. CCD camera's cooling, 2. Focuser and filter wheel controllers, 3. USB hub power supply, and 4. My voltage converter for 12 VDC to 5 VDC for my mini Stick computer.

Each of the 12 volt plugs have a 5 amp fast blow glass fuse in them. So my mounts battery connection is just 2 plugs.

I would rather deal with the 53 pound sealed AGM battery, than to want for power late at night in the cold and dark. I house it in a plastic battery box, which has enough room to also store my 350 watt inverter to run my laptop if wanted. I have a Voltage/Amperage meter en-route to install in the amply arched top of my battery box. That will give me the ability to glance down and see how my battery is doing without using my multi-meter.

Fortunately for me, I don't need dew heaters. So I don't suffer the huge drain they can put on your system. Typically, I will use 10% of my batteries capacity in an evening.

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On 12/03/2017 at 01:12, Daz69 said:

30 Amp is massive, are you powering an oven? :) I agree with having a main fuse as soon as the power comes from the battery, and then having every circuit have separate fuses rated just above the expected draw.

I won't be drawing anywhere near 30 amps, the idea of the 30 amp breaker was simply to prevent the cable being the fuse in the event of a short. I suspect a short across the 6mm battery cable would get "slightly" warm, followed swiftly by fireworks. Realistically it's hard to imagine a scenario where the 30 amp breaker would ever trip - any problems are far more likely to be in the individual fused circuits and the blade fuses should blow first - I'm just being extra cautious.

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  • 2 weeks later...

Well I eventually got around to making the power box to run my equipment in the field. Two 5v USB and five waterproof 12v marine sockets with a couple of LEDs to illuminate the area when setting up and dismantling. 85 ah 12v deep cycle leisure battery to power the box.  :icon_biggrin:

 

PB1.jpg

PB2.jpg

PB3.jpg

PB4.jpg

PB5.jpg

PB6.jpg

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You need to remove the red bung pronto.   Why didn't you run the all of the Negative cables to the battery terminal rather than have a floating join with the screw.  They also look like 40A fuses (Orange) and I would have run a thicker cable from the Battery + to the fuse box

Other than that it looks nice and easy to use :)

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Yea, looks great - nice strong box, room for any additions - good stuff  :icon_biggrin:

and I would worry about that floating cable, short twix pos & neg could be interesting, some sort of cover on battery terminals may be a nice touch.  What fuses do you have in the 12v marine plugs. 

Edited by Mick J
added note on floating cable
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Thought it looked neater to run one cable to the battery, the floating screw is to be fixed to the side wall and covered with a foam top to keep all cables separate.

The fuse from the positive supply is 10a fast blow and the fuses in the fuse box are each rated at 5a.  Also all marine style cigarette plugs have 5a fast blow fuses in as welll.  Hopefully if any issue one of them will pop before my equipment will get damaged.

I do have terminal covers but they weren't on when the photo was taken, most obvious statement of the century!! :happy7:

Thanks guys

 

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Here's some pics of the power box that I built a couple of years back. It's not small, but it does the job fantastically.

 

I've got 4 marine style 12 sockts on the front, and 4 USB sockets too.

On the side is a port for expansion, my idea was to be able to add a second battery, but it's not really needed. Also I have put jumper terminals to allow me to connect it up for charging.

5793a1bc356b8_Photo23-07-2016162038.thumb.jpg.b2d9dc0101fcad611aa945176c0bd5a3.jpg5793a12b190a2_Photo23-07-2016162047(1).thumb.jpg.2da205ed13e7c8bfb045a18e5ea72610.jpg

 

On the side, I have a volt meter and ammeter, with a switch.  In addition, there's an XLR socket, this is what I use to connect power to my telescope.  The socket has a lock on it, so there's little chance of it unplugging by accident.

5793a09a8c7c1_Photo23-07-2016162044.thumb.jpg.6bdbcdb9af6b180dc620f823d1782ad3.jpg

The box is itself is from the JCB Site system, was available at B&Q.  In addition to the box I have a number of cases, which all stack neatly on top.  Makes carting the stuff about really easy.

5793a02f28693_Photo23-07-2016171411.thumb.jpg.a308aab03c375ab324769f7f8c8e1c51.jpg

 

Inside the box, I added a 300W inverter.  For those rare times when 240V is needed.  I don't normally need that though.

57939fc02781a_Photo23-07-2016162031.thumb.jpg.be433dfab28f3afc7b6d4b3f0a4f9531.jpg

 

Everything is fused.  I've each socket has a 10 Amp fuse, the USB sockets have 5 Amp fuses.  I think the red one is a 20 amp for the external battery.   The wiring itself is rated for 50 Amp. The crimps are rated for 10 Amp each.  In total I don't think I've ever pulled more than 10 amps with everthing plugged in and working.  The electrical tape is there for extra protextion from short circuits.  Can't be too careful ;-)

5793a24fc5821_Photo23-07-2016162113.thumb.jpg.d7b20b65393defbb418725c100169bf8.jpg

 

The XLR socket has a cable that connects to this box.  It contains my dew heater controllers, and also the 12v and 6v feeds that go to the scope.  I'm thinking about adding an 8V feed to power a DSLR at some point.

post-46378-0-39090200-1442697463_thumb.jpg

 

That box in turns connect to this one, which distributes the power out to the devices.

post-46378-0-73712900-1445198186_thumb.jpg

 

 

The reason I chose that modular design is to allow things to be split down better.  There's only one cable that needs to travel from the scope to the control box.  The control box, lets me adjust the dew heaters without touching the scope no vibration if I adjust during imaging.

Having the control box connect to a seperate battery means that I can power the setup from a completely different power supply.   I recently bought a caravan, so rather than power the scope from it's own battery there's nothing stopping me from powering the telescope from the caravans 12v or even the 240v electric hook up :)

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  • 2 weeks later...
On 3/23/2017 at 12:32, MarkyD said:

The 100V - 10A looks to be the very same I have now, to me, MarkyD.

I like having the dual function in a single small meter. Currently, (Um, no pun intended), my AVX, and all the trimmings, hover around 0.98 - 1.09 amps in action. With the Stick computer added in (wireless operation) that bumps up to 1 1/2 - almost 2 amps of current.

I just returned from a holiday where I had to revert to my USB cable to the mount from my laptop. I could not operate wirelessly as I do not have a portable router... yet.  My laptop was plugged in, so not a part of the equation.

I'm wondering if anyone makes a percentage meter that can be used? Seems that 80% is the magical number for deep cycle batteries. Ever hear of such an animal?

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On ‎21‎/‎03‎/‎2017 at 21:44, julian489289 said:

Well I eventually got around to making the power box to run my equipment in the field. Two 5v USB and five waterproof 12v marine sockets with a couple of LEDs to illuminate the area when setting up and dismantling. 85 ah 12v deep cycle leisure battery to power the box.  :icon_biggrin:

 

PB1.jpg

PB2.jpg

PB3.jpg

PB4.jpg

PB5.jpg

PB6.jpg

hi that's a great box where did you get it from

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  • 3 weeks later...
On 25 April 2017 at 20:08, julian489289 said:

http://www.ebay.co.uk/itm/371796972652

 

This is the link to Ebay Neil  - Wham heavy duty Bambox.  Very sturdy box, I am pleased with it.

Thanks for the link about the same price as a battery box

if it's not too cheeky of me could you puts links up for the other components that you used so I could work a price out to make one myself 

you used a 85ah battery I was thinking about 75ah where did you get the battery from many thanks

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