Hello all.
I'm not sure how to word this or even what to call such a device...
I'm looking for a power supply that will self-adjust.
My application would be a 64vdc battery system. That system also charges at roughly 70-72vdc.
I'd like to put a monitoring device on this battery system but the monitoring device is meant for 24vdc systems that are roughly 28v while charging.
The monitoring device gets its power from being connected to the 24v battery.
So the power supply that may not even exist would need to be 24v output when 64v input and scale appropriately so that when the input is 72v the output is 28v.
Adjustable power supplies certainly exist, and some are capable of computer control.
So the power supply that may not even exist would need to be 24v output when 64v input
That would be called a voltage regulator, and models are commonly available in any desirable output voltage (fixed or adjustable) and certain ranges of output current.
Right but will it automatically adjust? I've seen fixed and adjustable power supplies but the only adjustable ones i've seen have to be adjusted with a screw driver manually.
would need to be 24v output when 64v input and scale appropriately so that when the input is 72v the output is 28v.
This is possible, but please explain the requirement. It is very hard to imagine a situation where such an adjustment is either desirable or necessary.
The monitor is from a company called Ayantra, they dont really have a link to the product. They are mainly used to monitor the status of standby generators.
On a generator, the monitor tells you the battery voltage. Static and running. By doing so, the monitor will alert you to low battery voltage situations or even failed battery charging alternators. Or a properly working system.
The monitor has an onboard battery but does connect to the generator battery for power/charging the onboard battery/battery sensing
A simple voltage divider will scale the 64V -> 24V and 72V -> 28V if ± 5% is acceptable. Then a transistor emitter follower current buffer sourced from the 64-72V could supply the 24V for the monitoring device as long as its current requirements were not too high.
current is pretty small. I'm pretty sure that the monitor uses its onboard battery (a 5vdc lipo) for most of its work and just uses the 24v battery as a charging source.
If I understand correctly the monitor is intended for use on a 24 volt nominal battery. (12 cell lead acid I presume.) You want to monitor a 64 volt (nominal) battery, which would be a 32 cell lead acid battery.
The monitor senses the battery voltage but also uses the battery as a power supply.
So you need a power supply that will emulate the 24 volt battery state of charge but is actuall representing the 64 volt battery.
The circuit @EmilyJane has provided will work. A better circuit could use a potentiometer to fine tune the voltage divider. An even better solution would use an op-amp to provide better linearity and stability.
Note that if you are not using a lead acid battery the monitor will not work correctly.
Devices like that can't be picky about the power supply voltage. I'm quite sure that if you actually research the power requirements, you will find that a wide range of input voltages is acceptable.
Write to the company and ask for the data sheet or manual. No responsible company sells such equipment without documentation.
