24VAC solenoid control from LIPO battery?

Thread Starter

babweupatree

Joined Jul 22, 2017
17
Hi there, I don't know if this is a totally mad idea but would be be possible to control a 24VAC solenoid from a single lithium cell by using a boost converter and making a square sine wave output to control the solenoid state? Solenoid is 370mA inrush, 210mA holding current.
 

Thread Starter

babweupatree

Joined Jul 22, 2017
17
Thank you for the reply crutschow, I want to use an 18650 3500mA lithium cell and maximum time the valve will be operated is an hour at a time (between charges - want to use solar to charge the cell).
 

MisterBill2

Joined Jan 23, 2018
9,843
An AC solenoid will often operate off of a much lower DC voltage. WE ran the 24 volt AC gas valve solenoid from a 12 volt trailer battery for several days during a nasty winter power outage. It was a boiler system with no pumps and so all it took was the gas valve to get heat.
But the single lithium cell can only deliver about 3.5 volts or so, and with a 100% efficient voltage multiplier the draw would be 5 x that 220 mA holding current, about 2.1 amps, with the 100% efficient converter. More like 2.5 amps with a believable inverter. So one hour is about the best you could get.
So you need a step-up swithching power supply, good for up to 350 mA.
 

MisterBill2

Joined Jan 23, 2018
9,843
Given the stated voltage and current it seems that any alternate coil would still require at least 1.25 watts. That would be a significant part of the battery capacity. AND, quite probably there are not low voltage DC coils available for most valves.
 

Thread Starter

babweupatree

Joined Jul 22, 2017
17
Thank you guys apologies for the late response. It is indeed a solenoid valve and only available in 24VDC. My thinking was to set up a small solar panel to keep the LIPO battery charged and only run the valve during the daytime (which is how it needs to work anyway, given my current power setup which is completely off grid).
 

MisterBill2

Joined Jan 23, 2018
9,843
The driver circuit could be a boost type switching supply that does not need excellent regulation. Solenoids will usually hold in with quite a bit less current than they need to hold in. And there are valve driver circuits that drop the voltage very oon after switching on. The bigger challenge will be getting a full charge from the solar cell.
 

Thread Starter

babweupatree

Joined Jul 22, 2017
17
Thanks MaxHeadRoom I have already looked for DC versions but they are very expensive.

MisterBill2 - thanks I am going to try and do it with a 3500 mAh cell and see if the panel does the job. Just need to source the parts first.
 
Top