Under the Choko Tree By Nevin Sweeney

A Tale of Two Regulators

For those who don’t know, the whole point of a regulator is to prevent the batteries of your 12 volt power system being overcharged by your solar panels (or whatever you are using to charge them). When I first built my system I did not have a regulator, I had read that if you are charging at less than 10% of your battery storage capacity (ie below 44 amps for a 440amphour battery) you didn’t need one. It turns out this is rubbish and after seriously decreasing the life of a brand new battery bank it turned out a regulator was something I should invest in.

For the top battery bank (powering the lights) I bought myself a STECA 30 amp photovoltaic regulator, it cost several hundred dollars but seemed pretty much what I was looking for. I installed it and while it worked well, the place where you insert the wires from the panels and to the batteries was a connector block designed for wire about 3 - 4mm thick, but I used wire 6mm thick. This meant that I wasn’t able to get all the wire into the connection block and over time the end of the wire got a bit ratty with little bits of frayed copper wire all over the place. The more I tried to push it in, the rattier it got and evidently the less wire was available to transfer the current.

It got to the point where the wire would occasionally fall out and the system would stop charging. This is where the remote voltmeter in the kitchen earned its keep and allowed me to see there was a problem. Anyway I had come up with a fix but had not implemented it when disaster struck. Due to a lot of amps going through not much wire the increased resistance caused the regulator to heat up, then make expensive smells, then cease to work. Yes, my friends I had burned something in my regulator out due to stupidity.

My options were –

  • Try and repair the old regulator. (my son-in-law is the electronic wiz, not me!)
  • Just connect the wires and leave the regulator out of the loop as it were (and risk harm to the batteries.
  • Buy a new one.
  • Do without 12 volt lights (95% of our house lights are 12 volt!)

Soooo, buy a new one it is!

Unfortunately to replace the one I had fried with an equivalent was several hundred dollars, but for under a hundred I could get a new regulator that would do the job – a Powertech Super Solar Charge controller (it was, after all, SUPER, so how could I go wrong?) It also had spade lugs for attaching wires from the panels and the batteries. This meant I could solder on a spade lug and not have to worry about things overheating. Winner!

Powertech Regulator from the bottom showing spade lugs

A slight diversion at this point… The Steca regulator works by sensing the charge of the batteries and then allowing power from the panels to flow into the batteries, cutting back slowly as the batteries approach full charge. This approach worked very well. After reading the instructions on the power tech, it appears that it acts like a switch, switching current from the panels on when the batteries are below a certain DC voltage (13 volts) and then switch it off when it hits around the 14 volt mark, allowing the surface change on the plates to be absorbed, dropping the voltage below 13 volts and switching on the panels again. Makes sense to me.

Unfortunately in practice, not so much. As soon as the new regulator went in the battery voltage drop at night (as we used the lights) was much sharper than with the Steca regulator, even if we only used a couple of lights. The system was working but not as well as it had so it looked like I needed to revisit my options and have a go at fixing the original regulator. Fortunately this did not prove as much as an issue as I thought it would be.

Guts of the Steca regulator showing burned terminal block

Now that I had access to it (after removing it from the system and could open it up) I found that the plastic terminal block connector for the positive side of the solar panel output had just melted due to the heat from the poor connection, hence the expensive smells. I was able to replace the burned out section by cutting that bit off and inserting a new section cut off another terminal block (bought from the hardware for the purpose), but that still left me with the problem of fitting the wire into the connection block.

Banana plug without ferrule

As alluded to previously I did have a fix. I got hold of some Gold Locking Banana Plugs, (from Jaycar Electronics) two with red rings, two with black rings. I have no idea what their official use is but they accept the 8mm wire easily in one end and allow it to be secured with two grub screws. The only issue is that there is a ferrule on the outside of the plug which makes it a bit wide to go into the connection block on the regulator without touching its neighbour. It is not necessary for my use so I just unscrewed it and left it off.

The pin out the other end can then be easily fitted into the connector block in the regulator and secured with the fitted screw, allowing sufficient power transfer so that they don’t even get warm, let alone hot.

Steca back in operation - with banana plugs!

So, this system is now in full working order and I still have the Powertech regulator in backup in case I do something similarly stupid in the future.

 

 

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