Have a instant/tankless water heater/geyser in our home. It's powered by one Alkaline D battery (so 1.5v). During winters it lasts only 1 month (because of water usage). The company guy who installed the geyser also wired up a DC power port with the battery box, but provided a 3V 2a power supply. I asked him if it will work fine since its 1.5v higher, he assured me it would.

Last week, after going through 3 batteries, I finally hooked up the power supply. Although, it seems to be working fine but the ignition is much much more rapid now i.e. the clicking noise when water heater lights up. With battery it used to be around 2 sparks per second, now its like a machine gun going off (may 8-10 sparks per second).

Was wondering whether in the long term it would damage the circuit/pcb of the water heater. So tried finding a 1.5 power supply but apparently those aren't being made at all, minimum is 3v (I guess that's why they just handed me a 3v supply?). Was reading on a forum that I can use a regular diode in series and that would drop the voltage by about 0.7 volts. So 2 should drop it down to 1.6v (which is exactly the voltage on a brand new D battery.

Does that sound good? Any downsides? Alternatives are getting rechargeable Nimh D batteries and a charger for them OR getting one of the lithium D batteries - but their reviews are all over the place, so not sure how long are those gonna last.

 

Try putting two diodes in series with the 3V supply to drop it down.

 

Try putting two diodes in series with the 3V supply to drop it down.

As he himself suggested.

Yes, that should work.

 

Been there and done that and yes it works. BUT the diodes current rating must be adequate for the application. Also, the fact that the igniter clicks faster may not be an issue at all. Try and measure the actual voltage of that supply when the igniter is sparking.
Some of those little supplies have very poor regulation, others have no regulation.

 

I'm going to guess here since in Australia we don't actually have this sort of stuff.
I would imagine that the normal operation would be to run the heater off mains power for the 3v. The battery is just there in case the mains fails.
If you run it this way the battery will probably last months.

 

I'm going to guess here since in Australia we don't actually have this sort of stuff.
I would imagine that the normal operation would be to run the heater off mains power for the 3v. The battery is just there in case the mains fails.
If you run it this way the battery will probably last months.

Its actually designed to run off of D-size battery, they added DC input socket as an afterthought and I want to use mains power to run it primarily (mainly to save on D battery purchases). I will experiment with Diodes as soon as I get a new adapter and will share post an update.

 

It did take a few moments to see that the one battery cell was for the igniter.
Once again I suggest measuring the actual voltage from that "3 volt " supply, because it is probably not regulated. The no-load voltage will probably be a bit higher..
For mosy of the unregulated supplies the rated voltage is only at the rated current.