How to make your own voltage stabilizer


New Member
Sep 3, 2016
Civic EK4 sedan
Hi guys. I would like to share my experience building a voltage stabilizer for my old Civic. The purpose of this device, as with all automotive voltage stabilizers, is to reduce electrical noise and distortions within the vehicle. Electrical noise comes from distributor, alternator, automatic transmission solenoids, certain relays etc.

Okay, back to the main story. Firstly, after figuring out the space available under the bonnet and taking the measurements, I design the circuit using a circuit design software called Proteus ISIS. You can download and use some other free circuit design software like Eagle PCB. The schematic is really simple. Basically, all the capacitors have to be connected in parallel.

The only suitable place I can find is between the battery and intake manifold. I want to have around 100,000uF of total capacitance. After researching on the internet, I found out that in order for the voltage stabilizer to 'absorb' or dampen many types of electrical noises within the car, it is also important to reduce the ESR (equivalent series resistance) so that the currents from the electrical noise can easily flow in and out of the device. So in this case, instead of using some big capacitors like the 50,000uF monsters, I use many smaller ones.

3D view of the design:

It turns out I can only fit 14 units of 4700uF 35V caps and 11 units of 2200uF 35V caps within the space available. The total capacitance is 90,000uF, pretty close to my target. Next, I use a rapid prototyping CnC machine to fabricate the printed circuit board (PCB). You can use the toner transfer technique and normal etching method if you don't have the CnC machine, no big deal. Alternatively, you can also use strip boards, although I wouldn't recommend this as the gaps between copper strips are pretty close. This can increase the conductivity between + and - terminals of the caps quite a bit.

The completed bare board:

The caps are then soldered:

I put a 20 amp fuse for protection:

Hot glue is applied between the caps to make them more rigid. Engine vibrations can make solder joints crack.

The main copper tracks are soldered with extra layer of lead to lower the resistance and improve current carrying capacity:

I made up the casing using some wood planks. Hopefully the low heat conductivity of wood will increase the life of the capacitors. Living under the bonnet sure will suck the life out of them.

I drill some holes for the PCB stand and put some industrial resin there to support it. The resin looks somewhat familiar, haha!

After the + and - wires are soldered, the board is put into the wooden box.


After the connectors are put to the wire ends, I use some heat shrink tube to secure them. That's it!