I’ve been meaning to write this for a while, but a year ago I had a some gear failure on the 12V side while camping. We use 12V for all our refrigeration, lights, water pump and phone charging. Fortunately we had power near by so all was not lost at the time.
But it led me to create something hopefully a bit more reliable and useful. The root cause of my issue was the following:
- Cigarette connections corrode easily and are “loose”. Apparently rated for 10A, I would personally not use them for anything more than 1A. If I have to use them I’d get good quality ones.
- I had a DC-DC converter for my laptop (http://www.sidewinder.com.au/page210.html). Both the cigarette lighter connections and the DC-DC converter got really hot. Here’s what it looks like. It is rated at 90W, but I think it’s more like 30W. So this is rubbish even though it comes with a great number of connectors:
This box has the following features:
- 4x20A Anderson plugs for 12V output
- 2x10A Hella (Merit) sockets for 12V output
- 2x10A Cigarette sockets for 12V output
- 2×2 USB charger sockets (5V, 2.1A rated).
- 2xAnderson plugs.with 10A/19.5V output (around 200W total power) and has a switch. 2 laptops can be connected concurrently.
- 1x50A Anderson plug output.
- 50A rated current and voltage readout. A switch enables the meter.
- 12V Anderson plug input to power the whole thing.
These are all protected with 10 regular blade fuses and 2 thermal fuses at various ratings.
The 12V feed comes via an MPPT regulator which takes power from a solar panel, but could come from any 12V source.
The internals are shown below. The 50A shunt resister, the blade fuses and the DC-DC converter take up most of the space and made the wiring a little complicated:
The DC-DC converter needed to be pulled apart and attached to the chassis. The heat-sink is on the bottom. A side view is below:
Why power laptops with a DC-DC converter? I personally hate 240V inverters as I don’t have it safely mounted, so 12DC->19.5VDC is the way to go for powering a laptop and much safer 🙂 It has the bonus of not wasting energy through a 2nd inverter (which is your laptop power supply).
I did try powering my laptop(s) through 12VDC directly, but it appears they need the extra voltage. You can see what a laptop requires by looking at the label on the laptop power supply and they all appear to be around 19.5V. So looking for a good converter was challenging but I eventually found one.
I cut the DC side of the laptop power cable and put Anderson plugs on both sides. This enables me to directly connect my laptop to this box or to use the regular mains supply.
Here’s a pickie of the box in action. I’ve got a laptop powered via the box with a wi-fi connection to a 4G dongle that is in one of the USB ports. 2 LED light strips, 1 fridge, 1 water pump and a smartphone complete the connections. My laptop is playing music from my NAS at home while 120km away 🙂
For reference I’ve got as many parts listed below:
- The all important case: Bud Industries AN-1308 (http://www.budind.com/view/Die+Cast+Aluminum+Enclosure/NEMA+4).
- Blue Sea 1011 Cigarette sockets
- Blue Sea 1016 Dual 5V USB sockets
- Narva 82104 – Merit/Hella sockets
- Anderson 50A plugs (available everywhere).
- 19mm 12V latching On/Off Push Button
- DC-DC boost converter: http://www.aliexpress.com/item/Free-shipping-DC-DC-600W-DC-IN-10-60V-OUT-12-80V-Boost-Converter-Step-up/671569832.html
- 50A meter: http://www.aliexpress.com/item/DC-Two-color-display-LED-Volt-Amp-Meter-2in1-DC-0-100V-50A-Red-Blue-Voltmeter/932058277.html
- Most of the other bits such as the blade fuse holder, thermal fuses, the DC-DC switch etc were from Jaycar.
- All the heavy current cabling uses 6AWG with 8AWG used for the lower current paths.
The chassis is the earth on the load side of the shunt resistor. This made the wiring much simpler but if the chassis is connected to say the car or the trailer, then the current readings will be incorrect.
The Anderson plugs holes were drilled out with a regular drill and attached directly to the side of the case which had the right amount of height to attach the plugs.
This box has been on two camping trips now without any issues. I did modify it to add an extra USB dual-charger. With 3 smart phones, two tablets and a USB powered bluetooth sound system we didn’t have enough ports.
And no we don’t camp. We glamp 🙂