The Surimi INVERTER (230AC Power Supply From 12V Battery).

The Surimi INVERTER is a quite powerful portable 120/240V AC supply using a simple 12V DC power source such as an RC battery (drone or such), or laptop battery.

This can run a sewing machine or a standard 60W soldering iron, for example, depending on how powerful the DC battery is (capacity, maximum discharge rate, ...).

Important Note: The "surimi box" is a very fragile design (FOR PROTOTYPING ONLY), so once the whole stuff's working properly, consider transferring all the inner components in a way stronger and better insulated casing.

CAUTION:

The "240 AC 60W, or so" output of the inverter circuit can be quite armful so wear gloves as soon as the battery has been connected to it.

DISCLAMER:

This project is for learning and prototyping purpose, do not use it as is!

Invented by Golgauth

To achieve this to work, you will need a few hand tools:

• cutting pliers
• stripping pliers
• soldering iron with some flux/rosin, low temperature stain and a few thermo-retractable sheath
• cross screw driver

As well as a few components:

• a very good quality surimi box
• the inverter circuit board itself (we won't be reinventing the wheel here, see the specs of the one I am using below).
• a BMS (battery management system, applying for 3S (3 serial) Li-Ion batteries, to protect the battery pack while charging/discharging it
• a 12V DC fan (here using a 4020 salvaged from an old GPU card)
• classic 2.1mm x 5.5mm female panel mount DC jack connector
• regular switch
• regular 120/240V AC outlet
• a few salvaged wires (that can handle quite some amps (~18 AWG), grabbed from an old microwaves oven, in my case)

Drilling the holes:

• Drill a few holes for allowing air flow
• Make a squared hole for the switch (theoretically 18x12mm)
• Make a circular one for the fan (here diameter is 40mm)
• Another one for the 240V AC outlet (here diameter is 55mm)
• And a last one for the 12V input plug (diameter 11mm here)

• Remove everything around the cells themselves (accept 4 wires: Positive and negative main wires + the 2 smaller one in between which we will use with the BMS)
• Remove also the thermal sensors
• Then pack the cells such that they can fit in the surimi box

Note: Here, I was able to superpose them without any additional work. If this is more complicated, you will have to individualize the cells and rewire/solder them together with long enough wires to obtain a suitable pack shape.

Fix the AC outlet according to its design.

Just take good care of insulating the eventual screws properly.

• Solder two wires to the plug before installing
• Taking care of the insulation
• Place it on the case

• Solder two wires on the switch (same process as with the DC plug)
• Place it on the case

Important Note: For the next steps, I'll be connecting things together with spring caps (electrical cable connectors with spring inserted nuts), instead of soldering because "surimi box" is a very fragile design (FOR PROTOTYPING ONLY) and I want things to be reversible such that I can reuse all the inner components in a way stronger and better insulated casing.

• Connect the positive wire of the battery to the BMS "B+" pad
• Connect the negative wire of the battery to the BMS "B-" pad
• Connect the thin (here white) wire (negative pin of the B+ battery cell) to the BMS "B2" pad
• Connect the thin (here green) wire (positive pin of the B- battery cell) to the BMS "B1" pad
• Check all the voltages (especially, you should have around 12V between the B+ and B- pads). If not, intermediate voltages, and reverse some polarities!

Note: 3S BMS can also be salvaged from RC middle-sized drones, wireless vacuum, ...

See picture's legend.

The fan must be positioned after the switch, such that it does run only when needed.

• Cut of the original plug of the fan and strip the wires
• Connect it to the Inverter's input (red on '+', black on '-')

• Attach the fan to the case
• Place the battery pack (taking care of fixing firmly and insulating while manipulating - yellow tape on wire tips)
• Add a separator (sheet of MDF here)
• Place the inverter board
• Connect the later to the AC outlet
• Connect the switch (neutral position) to the inverter '-' DC input pin
• Connect the three '-' together (DC input/output, battery 'P-' and switch) - Blue cap here
• Connect the three '+' together (DC input/output, battery 'P+' and inverter board input) - brown cap here
• Fix the BMS board apart, and well insulated from the rest
• Check if every wire is connected to somewhere
• Rearrange the wires (shortening, fixing) until you get a clean work (very unlike mine, which is a great mess, I have to concede !!) and also until you can close the box without obstructing the fan!

Give it a try, with CAUTION:

• Be very aware of the maximum ratings (Cf. data sheet) of your particular inverter board!! (mainly the maximum peak amps your battery pack can deliver AND the maximum wattage the inverter is made for. Also the ratings of the BMS cares a lot)
• Careful with the limitations, thus the kind of stuffs we can run on this tiny box.
• Controlling the temperature inside the box while working (specially in summer time). ##Overheating of the inverter board as well as the batteries.
• Start with smaller, low demanding application like a small light, then a 15W soledring iron, an raise until you get a good idea of the limits...
• Buy an industrial, secured system, for more demanding / heavy duty applications.

NOTE: The inverter board used in this Instructable is rated at max 100W (and is not the best design for the price) and the laptop battery is initially rated at 65Wh and around 5A continuous discharge at max. (an mine is old, an thus way beyond that). Be aware of that! You can run a 30W soldering iron, a 50W sewing machine, or 12W LED bulb light. But not a driller, for sure! Use power tools battery cells and more powerful inverter board for more...