12V Battery Box: to regulate or not to regulate...

[jespy]

Hi all,

 

I'm looking to DIY my next battery box seeing as my iOptron powerweight has a dead cell (a replacement of which is ludicrously expensive).

 

I've done my research and know my shopping list! However, there seems to be very little info online about people adding 12V regulators into the circuit. I know deep cycle lead-acid batteries shouldn't be run much below 12V anyway, but I'm wondering whether there is a benefit to the mount in pinning the supply from the battery at a fixed 12V. 

 

This is the regulator I was looking at: https://www.amazon.co.uk/Voltage-Stabilizer-Regulator-Protector-Protection/dp/B08BRN3R5Y/

 

Thanks in advance

Tom 

[Dr_Ju_ju]

For regulators to provide a reliable steady output voltage, you have to make sure that the source voltage is at least 3 volts above the nominal output voltage, to ensure the internal circuitry works correctly.

So if your source power supply is below, at least 15v, I wouldn't bother, and may well provide an additional drain on the source, limiting 'running' time.

[jespy]

1 minute ago, Dr_Ju_ju said:

For regulators to provide a reliable steady output voltage, you have to make sure that the source voltage is at least 3 volts above the nominal output voltage, to ensure the internal circuitry works correctly.

So if your source power supply is below, at least 15v, I wouldn't bother, and may well provide an additional drain on the source, limiting 'running' time.

That's what I'd thought originally re the +3V, however looking through the datasheet it seems that this buck/boost sits happily in the 10V - 13V range to regulate at 12V. Granted you'd always lose some of your running time, but I'm way over capacity as is! 

 

So there is no benefit to running a mount from a regulated 12V source compared to 11.5 - 12.6?

 

Cheers

[Dr_Ju_ju]

Buck converters work on the basis of using an internal oscillator that generates a nominal 'high' voltage frequency, which, when then rectified & regulated, produces a steady state output voltage up to the nominal rated current output, (as long as the source can supply this current) but will drop off if this is exceeded. 

So by using one, you will at least guarantee that the output stays constant, but by the nature that it works, it may be 'noisier' with switching artefacts imposed on the voltage rail, which may then have knock on effects of the equipment being powered. 

[pete_l]

The electronics inside the mount will contain its own regulators to supply the 5 Volts or 3.3 Volts (or whatever low voltage the internals work at) that it needs. The only components that will "see" the input voltage will be the motors.

As such any switching noise on the input should be pretty harmless - as long as you are using a supply that is designed to power equipment, rather than simply charge a battery.
Having said that it is my personal belief that many, many "unexplained" faults with mounts are due to dodgy power supplies. Either ones that drop below their lower limit due to instantaneous high demands (such as when the motors first spin up) or power supplies that do strange things with their electrical Earth - common connections.

And those problems that aren't electrical, are more than likely to be from mechanically unsound connectors.

 

[Carbon Brush]

Don't forget the DC/DC convertor is not going to be 100% efficient.
If you have a lead acid battery that has far more capacity than you need, no problem.

For work I sometimes buy DC/DC convertors and to get good performance pay a lot more money per watt than the Amazon offering.
Even then manufacturers often recommend additional filter components.

The car environment is electrically very noisy so I would not expect this device to be especially good in this respect..

The comments about voltage spikes, electrical noise, etc are relevant.
A lot of astronomy kit is not designed to handle transients and noise - that costs money.

Home astro kit is generally quite tolerant of variation in the 12V supply level, so just run it direct.
When I say direct. Don't forget fusing or circuit breakers.

HTH, David.